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H/V Vega
12-09-2009, 05:05 AM
G'day,

I am the skipper of a 120 year old Historical Vessel that keeps herself alive and sailing by delivering Medical teams and medical supplies to isolated Island communities. Many of these islands have not seen a nurse, much less a doctor for 20 years. We specialize in child immunization and general health as well as public health education. Why I am here is simple, well maybe for you lot, most of our medications require refrigeration. Some in fridges and others in freezers. When our old system started to die one of our sponsors was kind enough to send us a load of "just what you need" for a new installation. That is two freezers and a fridge. The second freezer is because everyone enjoys a cold one at the end of a long hot day, right? Also it is not really a good idea to do as we were doing and store medical supplies along side food.

Well as the story unwinds we have three Danfoss DB50F compressors with the 12 VDC / 220 VAc electronics packages and a mountain of other bits and bobs. We had the new units made up to drawings with built in Eutectic plates. That took forever, isolated places are not known for harboring rocket scientists, filled them with the suggested mix and called in the local freezer man to install the lot. Well wonders the chiller works! The freezers how ever never freeze the plates and just will not get below 4-5 degrees C. From 27 G till 10 C they go down at about 2.5 degrees per hour then from 10C until about 5C it's 1 degree per hour. After that the whole thing stalls.

The freezer man at first said we did not need the Danfoss TN2 valves and accumulators but insisted that a coil ( looking like a spring) of very small pipe was enough. HUmph! Well that doesn't work at all. Any one feel like being our "remote advisor? The guy is willing, but his experience is very limited... best I can say is he solders nicely and is very careful about insulation. I have a good technical background so if someone will explain what we should do I will guide this guy through it.

Best regards

Shane

Gary
12-09-2009, 05:20 AM
Maybe this will help get you started:

http://www.refrigeration-engineer.com/forums/showthread.php?t=19701

nike123
12-09-2009, 06:12 AM
The freezer man at first said we did not need the Danfoss TN2 valves and accumulators but insisted that a coil ( looking like a spring) of very small pipe was enough. HUmph! Well that doesn't work at all. Any one feel like being our "remote advisor? The guy is willing, but his experience is very limited... best I can say is he solders nicely and is very careful about insulation. I have a good technical background so if someone will explain what we should do I will guide this guy through it.

Best regards

Shane

That DB50F is probably BD50F! Are you sure with model numbers!
If you wish to make freezer with that BD50F, that freezer will be small (about 200l) because that compressor has around 50W capacity at -25/45°C working temperatures (-18°C in freezer, 35°C ambient).
You say that compressor is came with all electronics. Is it maybe BD150F?

That TN2 is actually TXV (http://en.wikipedia.org/wiki/Thermal_expansion_valve)!
That coil is capillary tube (http://www.overclockers.com.au/wiki/Phase-Change#Capillary_Tube)!

Both have function of metering refrigerant in system.
Capillary tube is used in small systems while TXV is used in larger systems.



If you want us to help you, you should supply us with all information's about what components you have (make, model number) with pictures of parts and pictures of place where equipment will be positioned.
Also person who will make assembly need to be qualified to work with refrigerants and brazing equipment and must have all necessary tools to make that.

Since you don't have enough posts to insert photos or links to them, best is to upload your photos to imageshack (http://imageshack.us/) or flickr (http://www.flickr.com/) or any other photo sharing site and post here link but without any http//www. part of link.

shooter
12-09-2009, 08:28 AM
this freezer man can be discarded as a waste of time, he is good in consumer freezers but this is a little bigger.

we like to have more info from you obvious.
like a schematic how everything is connected.
on provision stores i use a pressure regulator:
as the provision only has one compressor running and one standby and to prevent freezing up of the cooler this pressure regulator keeps the pressure of the cooler up. When any of the coolers or freezers is asking for cold (the expansion valve is open) the compressor runs because the pressure is rising.
on the compressor is obviously a pressure regulator that will stop the compressor as soon as the pressure is low enough . in your case the pressure is set too high so just turn the knob down to 1 bar. this way the comprerssor will keep running until around -15 Celsius. do not go below 0. You will notice the compressors will get rather hot. Keep an eye on them. If head temp goes over 120 C a fan will be needed to cool it down.
And you will need these tn2 valves as a simple restriction can only be used in a single evaporator setup.

H/V Vega
12-09-2009, 11:42 AM
Thanks for the feed back. I agree the "Freezer Guy" is a dead loss but he is the best available here in the 4th world and right now. He does braze well and is neat in his work just isn't tuned up to custom stuff or design... he only "fixes" them usually. That's why I was getting a bit frustrated. The two freezer units are not large. One is about 120 Liters and the other about 90 liters. The eutectic plates are built in and wrap around the whole box ( both cases) about 1/3 the way down the sides. They both have 12 individual lines from a common manifold with half going clock wise and the other half counter clockwise inside the plates. They are well spaced and well supported. The boxes are narrow and deep. Here is a list of what I was sent to work with.

2 X Danfoss BD50F compressors
2 X Danfoss 101N0500 electronics packages ( 12/24 Vdc & 220 Vac)
2 X Eliwell IC 901 thermostat / control units 12Vdc ( although the actual units say IC 961 on them)
4 X temp sensors for above
2 X Danfoss TN2 TEV
2 X Danfoss 00 orifices for above
2 X 2lb receivers with pressure relief valves and regulators
2 x Site gauges with fittings
2 X drier/filter units For 1/4 ton capacity

I didn't put all this before to avoid jamming up my notice.

Again thanks for the help it really is appreciated

nike123
12-09-2009, 01:00 PM
this freezer man can be discarded as a waste of time, he is good in consumer freezers but this is a little bigger.



Big and small are relative terms!
50W refrigeration capacity compressor is small in my eyes!;)

nike123
12-09-2009, 01:03 PM
Thanks for the feed back. I agree the "Freezer Guy" is a dead loss but he is the best available here in the 4th world and right now. He does braze well and is neat in his work just isn't tuned up to custom stuff or design... he only "fixes" them usually. That's why I was getting a bit frustrated. The two freezer units are not large. One is about 120 Liters and the other about 90 liters. The eutectic plates are built in and wrap around the whole box ( both cases) about 1/3 the way down the sides. They both have 12 individual lines from a common manifold with half going clock wise and the other half counter clockwise inside the plates. They are well spaced and well supported. The boxes are narrow and deep. Here is a list of what I was sent to work with.


Pictures tells lot more than words!
What are evaporators and condensers make and model#


2 X Danfoss BD50F compressors
2 X Danfoss 101N0500 electronics packages ( 12/24 Vdc & 220 Vac)
2 X Eliwell IC 901 thermostat / control units 12Vdc ( although the actual units say IC 961 on them)
4 X temp sensors for above
2 X Danfoss TN2 TEV
2 X Danfoss 00 orifices for above
2 X 2lb receivers with pressure relief valves and regulators
2 x Site gauges with fittings
2 X drier/filter units For 1/4 ton capacity

I didn't put all this before to avoid jamming up my notice.

Again thanks for the help it really is appreciatedDo you have any schematic to start with?

H/V Vega
13-09-2009, 12:54 AM
G'day,

After I posted that last I realized that I had not mentioned the condensers. There us one unit that has been partitioned into two segments each with its own fan. The compartments are separated so no "feed-back" I will try to make a drawing of how it is rigged up now and post it. The evaporators are eutectic plates as I mentioned above they are 12 wraps of 3/16" copper tubing evenly spaced and well supported. Half go clockwise around the box and the other half go counter clock wise from and to manifolds. The eutectic solution is ethylene glycol at about 35% with distilled water.

One question that is coming up is "do we need to keep the capillary tube coils when the Danfoss TN2 TXV valves are installed?" My island rocket scientist says "Me never see no have that"

Sorry for all the dumb questions. I know you lads are pros at this and I am not even an amateur, but these freezer are important for a lot of people and it's not as if I can run down to the local shop and have a chat about it. In fact there is no local shop !

Thanks again

Shane

nike123
13-09-2009, 07:05 AM
One question that is coming up is "do we need to keep the capillary tube coils when the Danfoss TN2 TXV valves are installed?" My island rocket scientist says "Me never see no have that"



I would not install that valve either. Its capacity with that orifice is about 10 times that of compressor and it will never be able to control evaporator satisfactory. As your "freezer guy" is already pointed, capillary tube is right option in your case. It appears that he know thing or two.

Did I mention photos?;)

That condenser probably has make and model#!

It is not clear (to me) is that asembled in way that every freezer is separate refrigeration circuit with its own compressor and condenser (but together with other condenser on one common frame) or as one system with two evaporators and two compressor and two condensers (on same refrigeration circuit).


Did I mention photos! I don't believe that no one there have digital photo camera.;)

H/V Vega
13-09-2009, 07:36 AM
Thanks Nike123,

`We can't find any make or model n the condenser that was assembled before the parts box was sent to us It seems to have started life as a singe unit then had its tubes cut so that now it serves for two separate compressors. In the box were also two size OX orifices perhaps those would be better? These units are required to run for long periods on battery power alone so if I understand rightly the idea was that these valves made the whole unit more efficient.

Yes each freezer is an individual unit with its own compressor et al. The logic behind that is should one fail we do not loose a whole batch of vaccines or other medical supplies. We are often months away from even the most basic of "city" facilities working in places where the only power is what we make. There are still many communities where they simply have no power at all.

I would love to send you photos, although the space is very tight and it would be had to see, but I am communicating with you via SSB radio link to a dedicated email server that does not allow me to send attachments. Just plain text. It doesn't really like me being on the web like this.

H/V Vega
13-09-2009, 08:13 AM
Thanks Nike123,

`We can't find any make or model n the condenser that was assembled before the parts box was sent to us It seems to have started life as a singe unit then had its tubes cut so that now it serves for two separate compressors. In the box were also two size OX orifices perhaps those would be better? These units are required to run for long periods on battery power alone so if I understand rightly the idea was that these valves made the whole unit more efficient.

Yes each freezer is an individual unit with its own compressor et al. The logic behind that is should one fail we do not loose a whole batch of vaccines or other medical supplies. We are often months away from even the most basic of "city" facilities working in places where the only power is what we make. There are still many communities where they simply have no power at all.

I would love to send you photos, although the space is very tight and it would be had to see, but I am communicating with you via SSB radio link to a dedicated email server that does not allow me to send attachments. Just plain text. It doesn't really like me being on the web like this.

H/V Vega
13-09-2009, 08:15 AM
Thanks Nike123,

`We can't find any make or model n the condenser that was assembled before the parts box was sent to us It seems to have started life as a singe unit then had its tubes cut so that now it serves for two separate compressors. In the box were also two size OX orifices perhaps those would be better? These units are required to run for long periods on battery power alone so if I understand rightly the idea was that these valves made the whole unit more efficient.

Yes each freezer is an individual unit with its own compressor et al. The logic behind that is should one fail we do not loose a whole batch of vaccines or other medical supplies. We are often months away from even the most basic of "city" facilities working in places where the only power is what we make. There are still many communities where they simply have no power at all.

I would love to send you photos, although the space is very tight and it would be had to see, but I am communicating with you via SSB radio link to a dedicated email server that does not allow me to send attachments. Just plain text. It doesn't really like me being on the web like this.It takes ages just to send a reply sometimes.

nike123
13-09-2009, 08:33 AM
Thanks Nike123,

`We can't find any make or model n the condenser that was assembled before the parts box was sent to us It seems to have started life as a singe unit then had its tubes cut so that now it serves for two separate compressors. In the box were also two size OX orifices perhaps those would be better? These units are required to run for long periods on battery power alone so if I understand rightly the idea was that these valves made the whole unit more efficient.

Yes each freezer is an individual unit with its own compressor et al. The logic behind that is should one fail we do not loose a whole batch of vaccines or other medical supplies. We are often months away from even the most basic of "city" facilities working in places where the only power is what we make. There are still many communities where they simply have no power at all.

I would love to send you photos, although the space is very tight and it would be had to see, but I am communicating with you via SSB radio link to a dedicated email server that does not allow me to send attachments. Just plain text. It doesn't really like me being on the web like this.It takes ages just to send a reply sometimes.


OK, I see now!

Then we should switch to experimenting mode (and hope for best) since lot of data to proper dimensioning is unavailable and you don't have much options with parts and spares. If that "freezer guy" time is cheap!

In that case I would install that TN2 with 0X orifice in place of that capillary tube on one system and see what happens.
When capillary is out it should be measured for internal diameter and length in order that if TN2 valve doesn't work (which I expect), we knew what is capillary dimensions, and, if needed, to modify that according to compressor capacity.

It could be useful to get data about current box temperatures and suction pressure and temperature of suction line at about 20 cm before compressor for both systems.
Also, ask him if temperature of filter (before capillary tube) is higher than ambient air temperature or at ambient temperature.

H/V Vega
13-09-2009, 09:21 AM
OK yes his time is not really expensive at all. In fact I think he is having fun at something new. We had to bring him from the "Big" island to do this job so he is eating and sleeping well and very happy to be here. The guy is not dumb just has not had the chances to learn all the technical bits and bobs.

We just measured the tube he had in place and it was 8 feet long and .31 mm ID sorry about mixing metric but he only knows metric measures. Just to recap with that tube in place from +27 degrees to about +10 degrees C the drop in the box was 2.5 degrees per hour then from +10 degrees C to about +5 C it was at 1 degree per hour after that it stalled at 4-5 degrees. He also has another tube we can use that is .28 mm . Right now he is trying the TVX valves with the 00 orifice but that is not working at all it seems. We get heat going into the condenser and very cool coming out but no cooling to the box. Next plan is to try the OX orifices.

nike123
13-09-2009, 10:10 AM
We just measured the tube he had in place and it was 8 feet long and .31 mm ID sorry about mixing metric but he only knows metric measures.

You probably mean 0.031in ID!

8 feet is 96 inches. That lenght is suitable for compressor of about 90W capacity (almost double refrigerant flow)
Capillary length for 0.031 ID (according to Danfoss software and if we take in account compressor capacity of 55W at -25°C evaporation and 45°C condensation temperatures and 5°C line temperature at compressor suction (30°C total superheat)) should be 269 inches, which mean almost 3 times longer.
Since that is almost 3 times longer that what you have now, it is clear why you have such high temperatures in boxes because there is not enough restriction in capillary.

Since capillary should be between 5 and 15 feet long I suggest that capillary should be 120 inch 0.026 in ID (0.028 is not standard dimension and it is probably wrong).

As I said, it is best to make modification and experiments on one box and then, when that is sorted, make other box same as that sorted box. Double less hassling.

Proceed with fitting that TN2 on one system but with 0X orifice and if that doesn't help change capillary with length I suggested.
Tell guy to charge refrigerant slowly in order to not overcharge system and to stop charging immediately when suction line of compressor starts to cool down to about 5-10°C. Then let time to system work for few hours and make notes of temperatures and pressures I asked before.


It could be useful to get data about current box temperatures and suction pressure and temperature of suction line at about 20 cm before compressor for both systems.
Also, ask him if temperature of filter (before capillary tube) is higher than ambient air temperature or at ambient temperature.

Peter_1
13-09-2009, 04:11 PM
50 W can never be regulated with a TN nor a TUA valve. You have to do it anyhow with the right capillary tube.
Nike is right on spot with the length, I have 7.54 m of 0.031 (which is ways to long) or 3.8 m of 0.028 or 2.28 m of 0.025.

Is your 'tech' using the right gas (R134a) in the system?

I'm with Nike, 50 W is not that much, I doubt you can handle the heat infiltration apart from the solidification of the ice.

You could also install an AEV instead of an TEV so that you can play a little bit with the refrigerant flow.

You could increase capacity of the freezer compressor when you run your liquid line of the freezer first through the cold box.

Try to condense as low as possible to increase compressor capacity. Can't you use seawater to condense? Installing a copper coil outside the ship.

Bridge your thermostat contact and use the probe of the EWPC961 (set to decimal point) to measure temperatures if you don't have an accurate thermometer.

shooter
13-09-2009, 04:38 PM
obvious one more copper in seawater that works great for about a week.

H/V Vega
14-09-2009, 09:43 AM
Thanks we are trying Nike's suggestions now will give an update in the morning. Using 120 " of .026 tube. I really would not like to use the sea water for cooling for many reasons like growth in the cooling hoses and a load of others. I know it sounds great and must work a champ for somebody, but for us it was just a constant problem. Air cooled has never really given us any problems. We take the air from the bilges so it is nice and cool.

Peter_1
14-09-2009, 12:37 PM
obvious one more copper in seawater that works great for about a week.

Why you think this will last only one week?
They find copper coins from era's ago in the sea.
I visited once in Canada the artifacts of the Titanic. Amongst those were in copper.
We use copper tubes in our eutectic plates and the oldest are +/- 25 years old.
You have to update your way of thinking about copper. Read once the free downloadable book on www.copper.org.

Peter_1
14-09-2009, 10:55 PM
....I really would not like to use the sea water for cooling for many reasons like growth in the cooling hoses and a load of others. ....
I meant, condenser direct in the water. When I worked on container boats in the harbor of Antwerp - a long time ago - and on the fishing vessels in Ostend, Seabruges, all condensers were seawater cooled.

H/V Vega
15-09-2009, 01:09 AM
G'Day all,

First , thanks for all the help it really is appreciated.

Here is the latest up date. We replaced the TEV and receiver on one of the units with 120" (3 meter) of .026 mm cap tube and have cooling again. Sadly he did it on the larger box ( about 120 liters) so it is taking a while to cool down. Left it over night and still have no freezing on the solution. He was a bit excited and switched the cooling lines so now I have freezer one feeding freezer two. Interesting situation where I have no idea what the actual temp is in the box right now. Later today will try to get them back to the right configuration again. He sleeps in the village on shore so must await the canoe to bring him out this morning. I know I could switch the probes but that would mess up all the electronics and power switching on AC & DC panels etc so best wait. Right now the base of the cap tube is at room temp and the top has ice on it. Now that something is happening again I will ask him for the presures Nike ask for as soon as he pitches up. Going into the condenser is very warm but coming out is at room temp perhaps a bit under that. Should it not be getting cold enough in the boxes what should we start looking at next? Looks like this is turning into a real lick the finger and look for the wind project. I have another 4 days here then we are off to another island. That will be a 4 day trip so would be best to have this solved before then if possible. I cannot see him working at sea on this.

Magoo
15-09-2009, 03:20 AM
Some one must have a capillary tube size and length solution to balance compressor to load relationship, so the local fridge can do the job.
Speak up now, or for ever hold you peice.
Magoo

Chef
15-09-2009, 05:08 AM
The BD50 is going to struggle with a 120L box size for a freezer unless you have 4" or even better 6" of insulation. You may find the box is just too large and the heat inflow is more than your system can cope with, 60 or 80L box size would be much better.

I am running a BD35 at 3500RPM through 2.8metres of 0.026" cap tube and it works fine and freezes down to -15C but box size is just 60L. With the bigger BD50 running at 3500RPM you would need a 0.026" tube of about 1.8metres or a 0.031" tube of about 3.0 to 3.5 metres long. If you put a tube in that is too long you will see very high discharge pressures (more than 220PSI) and your compressor might trip on overload protection that's built into the BD50.

To fully understand the system you have and its performance it would be usefull to have the discharge pressure and the suction pressure from the engineers gauges when it is running at its coldest operating condition you can get and also the maximum discharge pressure you see when starting the system from warm i.e. from room temperature.

Also when you charge the system you should add gas untill you get a continous shhhh sound in the evaporator about 10 or 15 minutes after start up from warm and then adjust the gas charge to keep the shhh sound continuous as it cools down, a little bit at a time. When the system is as cold as it gets the plate should start to freeze on the surface and the optimum will be when all the plate is frosted but the return line to the compressor is not frosted. If the return does frost then remove a little gas at a time until the return line does not frost - wait 5 minutes for it to balance before adjusting it again.

The eutectic plate will take a long time to freeze its solution and may be it take from 3 to 8 hours before all the fluid is frozen. Another system I am running takes 4 hours to freeze the plates from the startup at warm and then only 30 minutes to get back down to temperature when it starts to cycle on the thermostat so you may need to give it a long time for its first cool down.

Also understand your SSB pactor issue and how difficult it is to post here using it - another solution may be text exchanges only - I would be happy yo post them for you.
Chef

H/V Vega
15-09-2009, 06:59 AM
Thanks for the guidance.

The boxes have 6" of closed cell polyurethane under them and an average of 6" around the sides. Tops have an average of 4" and the lids are 4" combination wood and insolation. Between the boxes the insolation is a bit thinner averaging about 3".

The resistors I was sent should have the units running at about 3,250 RPM according to the chart that came with the units. Right now we have 3 meters of 0026 cap tube Over the past 2 hours the smaller box has dropped from 28 C to 16 C and the larger that was running over night but shut down for 4 hours this morning dropped 1 C in one hour from +4 to +3.

Small Unit current temp +15 C
Pressure 175 PSI
Suction 20 PSI

Large Unit Current temp +3 C
Pressure 175 PSI
Suction 5 PSI

Trying to tune the return lines to between +5-10 C now. Will keep you posted.

H/V Vega
15-09-2009, 07:09 AM
I do love this Pactor much better than the Iridium for sure but just try it with three grinders and a belt sander all going at the same time :o{(

H/V Vega
15-09-2009, 08:55 AM
Up Date at 14:30 my time which was :30 mins after the last post I had

Small Box +2 C
Large Box +11 C

At 15:30

Small Box +1 C
Large Box +7 C

The rate of cooling is slowing some what but still going down.

H/V Vega
15-09-2009, 08:56 AM
Sorry I managed to reverse the small and large box numbers

nike123
15-09-2009, 10:24 AM
Trying to tune the return lines to between +5-10 C now. Will keep you posted.


What was ambient temperature (condenser air in) when you measured pressures?

You could use Eliwell sensor to measure temperature of air and pipes. When measuring pipes, wrap sensor and pipe with insulation and make sure good contact is between pipe an sensor metal (wrap it with cable tie).

When measuring, please make all measurements of one system in time, in short period of time (few minutes but alow 1-2 minute to sensor reach stable reading) and post folowing data:

Box temperature
Pressures
Temp. of pipe leaving box
Temp. of pipe 10" before compressor
Temp. of air entering condenser
Temp. of air leaving condenser
Temp. of pipe leaving condenser

nike123
15-09-2009, 10:48 AM
Trying to tune the return lines to between +5-10 C now. Will keep you posted.

Return line could be somewhat hotter during pull down.
You should check that during pull down it is not cooler than cca 5°C.
If it is cooler than remove some charge.

Chef
15-09-2009, 10:56 AM
OK so the insulation is very good and so you may be fine with both box sizes, you may not get to -20C but -10 or -15C seems possible.

The discharge pressure of 175 seems too high (would expect to see about 150PSI) and the cap tube at 3 metres is way too long for a 0.026" size. That is the length they supply for the BD35 running at 2500RPM so you need to get the tube shorter, say to 1.8m or even 2m but no more.

Can you describe the evaporator in as much detail as possible. The length of the pipes - are they all equal as you say you have 12 pipes of 3/16" on a header with 6 going clockwise and the rest anti clock?

From the inlet - do the pipes spiral upward or downward - and how is the end connected - in a manifold as well? The length is quite important though.

Also any info on the condenser - its size, fans, any thing you can describe. Are the units in the big and small box the same?

So without the grinders can you hear the evaporater - is it constant shhh or is it intermittent.

Its tough to diagnose the system without pics and details but the words will have to do fine.

Any info will help so run your hand over all the parts and describe the temperatures you feel and how long you can hold onto the item for - say for 65C its about 3 or 4 seconds, it will help.

Maybe you should think about Thuraya instead of the Iridium as it works at GPRS speeds on downloads, about 40 times the Iridium data rate but it depends where you are, PNG is covered and so is Solomon. Where are you?

Chef

nike123
15-09-2009, 11:04 AM
OK so the insulation is very good and so you may be fine with both box sizes, you may not get to -20C but -10 or -15C seems possible.

The discharge pressure of 175 seems too high (would expect to see about 150PSI) and the cap tube at 3 metres is way too long for a 0.026" size. That is the length they supply for the BD35 running at 2500RPM so you need to get the tube shorter, say to 1.8m or even 2m but no more.



We do not have condenser air in temperature to say if this is high or not.

Chef, what is your input data for capillary dimensioning?
I find it pretty odd that capillary dimension from Danfoss software is that much different, if you calculated with same input data as I am.

I know you using your software, but that much difference is ...

nike123
15-09-2009, 11:43 AM
Hi H/V Vega!
I found that capillary tube 0.028 is also produced and that you probably have that tube instead of 0.026 I suggested.
Factor for correction of length is then 1.38
But do not change anything until we see measurements winch will tell us if present should be shortened as Chef suggest.
BTW, he is much better with capillary tubes than me!:D
I am TXV fan.;)





Since capillary should be between 5 and 15 feet long I suggest that capillary should be 120 inch 0.026 in ID (0.028 is not standard dimension and it is probably wrong).

Chef
15-09-2009, 01:35 PM
We do not have condenser air in temperature to say if this is high or not.

Chef, what is your input data for capillary dimensioning?
I find it pretty odd that capillary dimension from Danfoss software is that much different, if you calculated with same input data as I am.

I know you using your software, but that much difference is ...

Nike - The Danfoss program (may) be a long way out as discussed in previous threads. It never matches any other sources so care must be taken using it. My first point is that I am using a BD35 with 2.8m of 0.026 so a BD50 must be shorter and as it has a greater mass flow rate and so the tube has to be shorter. I understand the tube is very sensitive to inlet conditions but in the end the range they have to operate over is so large that the final conditions dictate the best tube length. This is always longer than a practical tube length because of startup loads and discharge pressures in the pull down phase.
If its too long it will suffocate the system but if it is too short it will always work (with a loss of efficiency as the system gets really cold)

Your quite right that we do not know the ambient temperature but we might safely assume it is about 30C in this area as this is where I currently live, maybe a bit more in the day on a hot one but close enough to make a first guess.

The 0.028" is produced but it is rare and maybe not commonly available in the outer islands?

Chef

H/V Vega
16-09-2009, 05:02 AM
Let me try and answer the questions first then I have some times and temps for you to look at. Ambient air to condenser is about 27- 30 C, The evaporators are built into the body of the box protruding into them. They are 4-cm thick and both are 20 cm high. All of the pipes were cut to the same length sometimes we had to bend small curves into the ones that came up long but always keeping the length the same. From the inlet the pipes go down into the boxes and then regroup at a second manifold for the return line. Manifolds and all connections are outside the boxes. Tubing length for the small boxes were measured at 195 cm each for a total of 23.5 meters. For the large box tubes were measured at 2.42 meters each for a total of 29 meters. They were spaces roughly 3 cm from each other in a zig zag pattern from top to bottom. Space from the walls was average 1.5 cm. there are flow spaces for the eutectic fluid at top and bottom all around. The small box holds about 15 liters of fluid and the large box holds about 20 liters minus about 15% for expansion. The compressor units for both the big and small boxes are both the same. The condenser seems to be doing quite well as heat goes in but the outlet side is a bit cooler than room temp. Freezer guy here says if anything they may be a touch too big but are OK for here. We are in the Solomon Islands right now.

OK then here are the test temps from the Eli temp sets for each unit after we put the 3 meter tubes in yesterday.

Time Large box Small Box
10:30 & 28
12:30 & 22
1:30 3 16 Larger box had been running over night and was already cooled down
2:30 2 11
3:30 1 7
4:30 0 4
5:30 0 1
6:30 -1 -1
7:30 -2 -2
8:30 -3 -3
9:30 -3 -5 here the small box temp control cut it off
12:00 -5 -4 Large box temp control cut it off

6:am -5 -3 Reset set points to -10C
10:30 -5 -8
11:30 -6 -9

H/V Vega
16-09-2009, 05:24 AM
Just did presure readings and the large box has
Temp -7C
Suction 5
HP 175

Small Box has
Temp-9C
Suction 5
HP 175

All of my temp readings are from the Eli controlers the probes are about 15% down from the top and on the furthest side away from the coolant inlet to the plates. That should be the warmest point in the boxes. The only other temp probe we have is an outdoor thing in a wooden base which I doubt is very accurate.

Chef
16-09-2009, 06:18 AM
The temps seem to be coming down nicely but very slowly, although that is expected as your trying to freeze 20L of water as well as cool the box itself down. It looks as though you have working system and now need to fine tune it to reduce the power consumption and get the best cooling effeciency.

The discharge pressure does seem to be quite high and as you say the outlet of the condensor is at room temperature (there about) it seems you have some excess liquid holding up in the last part of the condensor. This can happens if the cap tube is too long and I still think that 2metres would be better.

What kind of fans do you have on the condensor?

Checking the size of your ezporator at the moment and will let you know soon.

Do you need the technical manuals for the compressor or do you have them?

Chef

Chef
16-09-2009, 06:47 AM
The evaporater has a volume of about 0.2 to 0.25 litres and as you have a maximum charge of 300grams for the BD50 it seems safe to frost the evaporater to the exit point but if you can weigh the refrigerant in and use no more than 300 gram it would be better. If you put too much refrigreant in then it can ruin the compressor when you start it up from warm.

The BD50 has a cooling power of 160watts at -5C, 124w at -10C, 95w at -15C an 72w at -20C so the cooling power drops quickly as it gets colder and will seem to go slower and slower as the box temp falls. Once the heat flow in matches the cooling performance this will be the maximum cold you an achieve.

If you set the thermostat to say -10C and then when it gets to temp and starts to cycle on and of by the controller - time the period the compressor stays off and time the on period till it trips again. From this we can find out what the heat leakage is into your box and then find out what the lowest temperature you can expect to achieve.

Chef

nike123
16-09-2009, 07:28 AM
When I change input data to more realistic according to your last measurements, I got this result:
Input data:

Evaporation temperature -26°C
Condensation temperature 40°C
Return gas temperature 5°C
Compressor capacity at above conditions 62W
Capillary tube length:
0.026" ID = 72 in (1,82 m)
0.028" ID = 100 in (2,54 m)

Do as Chef suggested and shorten capillary to about 2 meters.
I would do that on only one system and see what is happening.
I expect that condensation pressure then should be around 160 psig if outdoor is 27-30°C, and that suction remains same.
Pipe temperatures as I asked before would be of much help to fine tune this system.
You could easily use Eliwell probe on extension cord to gather these temperatures.

P.S.

It seems that we have some confusion about unit of measure of capillary tube!
You stated earlier that you have capillary tube of 0.31 and 0.28 internal diameter in millimeter unit of measure.
Is that correct or you mistakenly giving us capillary tube of 0.031 and 0.028 internal diameter in inch unit of measure.
Capillary tubing is rarely produced with inner diameter smaller than 0.6 mm and therefore I think you giving us inch dimensions.

Chef
16-09-2009, 08:28 AM
Nike - The idea of changing just one system is a good one - would be nice to see the comparisons and your numbers are just like mine so nice to know.

Hope H/V Vega gets away on time for her sail as it all looks a very important and worthy cause. (They have a nice website)

Chef

mad fridgie
16-09-2009, 09:38 AM
15 liters of fluid and the large box holds about 20 liters minus about 15% for expansion.
Is this fluid , one which is suspose to freeze? if so this could give the effect that your capacity has reached equalibrium, when infact it is removing latent heat from the fluid. I would hate for you to make a change when you are making great improvements.

H/V Vega
17-09-2009, 01:12 AM
Thanks for all the help. I had to send the freezer guy off on the weekly boat last night and will be packing up this circus today so we can get off to the next place. It looks like our program is being put on hold so the money can be used for the latest flu scare. ( FYI all the doctors we talk to are wondering what the hype is all about. This is an old well known flu that has been around for ever. Was the first to be typed hence the H1N1. In any case most think it is just anther "Bird Flu" hype so the drug companies can get richer.) If we do stop then we will be sailing to Bali for some refitting and then see what happens next. I hope this thread stays alive so we can continue with the fine tuning as soon as I can find another freezer guy. Again thanks a lot for the help. As to our website it is hopelessly out of date we hope to update it soon with all we have been doing these past few years.

H/V Vega
29-09-2009, 01:02 AM
Sorry to have been away so long we have been busy and also had a few miles to make. The latest reports are:

The freezers are staying about the same. They get to about -10-12 and stay there without using too much power. The chiller has become a problem though. Just before he left my freezer man changed the chiller cap coil to 2 meters of the .026 tube ( it was 0.031 before and working not that badly) saying if it was good for the freezers then the chiller would just cool down that much faster. :o{( well so much for that bright idea. It is taking a lot longer to cool and running more than twice the time as before. I maybe able to have him back for a day or two so would like ideas on what to do if I can manage to get him again.

Best regards and thanks again for sharing all of your knowledge and experience.

Magoo
29-09-2009, 03:29 AM
Hi H/V vega,
sounds like you are between a rock and a hard spot.
All problems stem from capillary, internal diameter and length are so critical. When your man re-apperars tell him to cut 0.25 metres off it and start again, otherwise the compressor is going to overheat and die.
magoo

Chef
29-09-2009, 07:34 AM
H/V Vega - Hope the sail was a nice one.

Do you have any gauges you can measure the discharge pressure with?

Also is the chiller plate frosted partly, over half or nearly all of it just before it cycles off? It may be best to determine if you have the correct charge in the system before changing it.

We were talking before about the cap being 1.8 to 2m long and so Magoo's idea of lopping off .25m seems OK but I doubt it will go from cycles of 'twice as long' to normal. Something else is probably wrong.

Walk your hand over the system and describe the temps at various places.

Have you ever been to Bali before? Serengoon? May 08?

Chef

H/V Vega
30-09-2009, 03:54 AM
G'Day,

Yes I have gauges but not exactly sure where to connect them. The chiller plate gets about 90% frosted over before shutting down. The liquid in that one is distilled water. I spoke to the freezer man and he says he put 2.5 meters of the 0.026 in that one. Sounds a bit long to me from what the discussion has been here for the freezers.

nike123
30-09-2009, 04:55 AM
G'Day,

Yes I have gauges but not exactly sure where to connect them. The chiller plate gets about 90% frosted over before shutting down. The liquid in that one is distilled water. I spoke to the freezer man and he says he put 2.5 meters of the 0.026 in that one. Sounds a bit long to me from what the discussion has been here for the freezers.
It is not same thing as with freezers. You have diferent capacity at higher temperature (90 w) and you need less superheat. 0,026 of 2.5 lenght is too much restriction.
I would change that capillary back to 0.031 of 1.6m length if compressor is same model as with freezers.
What was length of old capillary?

H/V Vega
19-11-2009, 04:10 AM
Greetings all. After a lot of shifting and shuffling we are now in Langkawi, Malaysia until the 2nd December (perhaps someone knows a good freezer man here?) when we go into the boat yard in Kantang Thailand. So great time to continue the saga of the errant freezers and chiller. I did change the cap tube to 0.031 at 1.6 meters as suggested above just before we set out. It works a bit better but still does not freeze down the eutectic plate completely. The freezers stay at -3 and -7 max no matter how long I run them so I have set them at those temps for now to save power and wear / tear on the compressor. Needless to say that is not at all freezing the eutectic solution (-15). Any ideas what to try next other than buying ice at the local shop?

Chef
19-11-2009, 12:18 PM
Vega - read your PM's - Private Messages for some help in your new location.

Chef

H/V Vega
15-01-2010, 03:18 AM
Well Hail to the Chef! We managed to meet up with Chef back in November ( sorry have been out of range and off the net for a while now) and I must admit that man does know his business and is the first person I have met who could explain what he was doing and exactly why. I learned more from him in an hour than in months of looking over shoulders and asking questions of the others.

OK in the boat yard we were very lucky to find a young man fresh from the technical school who was able and willing to dig in and make it work. First thing we did was change the cap coils, filter driers, and sight gauges then vacuum the systems on both ends for several hours, as Chef had advised us to do. True enough some of our major leaks were in those sight gauges Chef, but the real leak was in the flare going to one of the filter driers. When the lad gave it a shake the pipe blew right out of its fitting. I must admit the man was dedicated in chasing the many leaks he managed to find, and fix. We now have a sealed system ( says he knocking on wood) The main trick now is getting the gas right. Sometimes he would re-gas and the freezer would go rapidly down to -13-14C others and it would strain for -10-11C. He said the difference is so slight that it is had to know when it is right. I am keeping the tops of the receivers just cooler than room temp as a guide but that is not a very technical way to do it. In any case once again, Hail to the Chef and thanks a lot for all the help. Now if I can just get this mess fine tuned what a wonder life will be.

Chef
15-01-2010, 11:30 AM
The main trick now is getting the gas right. Sometimes he would re-gas and the freezer would go rapidly down to -13-14C others and it would strain for -10-11C. He said the difference is so slight that it is had to know when it is right. I am keeping the tops of the receivers just cooler than room temp as a guide but that is not a very technical way to do it..

Vega - Nice to hear things are working out a bit better and it sounds as if you had a really great technician to sort out the bugs.

As for the charging - well as you have a very large suction line receiver you could even charge the system (only when it is right down to temperature) until the inlet to the suction accumulators (receivers) gets quite cold - say about 10 to 15C - not frosted but nice and wet. That would be the max charge for the system and probably the best performance. Pretty sure it will be just a quick puff of gas and then watch it and then later maybe another quick puff and wait, maybe an hour or more to see if it has changed the temperature of the inlet pipe. By now you should have a feeling for how a puff of gas drops the temperature. Dont rush it as the system has to cool down all stuff in the freezer and plates solution etc.

If it ices up its got too much gas!

Very glad to help in any way we can and I am pretty sure we saw you ghosting past Phi Phi Don the other day?

Guess you were in the yard for Xmas - no fun at all really - we blew our genset on Xmas day so it was spanners and gaskets instead of presents.

I would be interested to hear what tube you finally chose ie diameter and length?

Chef

H/V Vega
15-01-2010, 01:36 PM
He is fresh out of the technical school and trying hard to make a name for himself. He spent a lot of time chasing leaks and then trying to get things right for us. A really great find he was. Now it seems we have no more leaks in the system. The cap coil was exactly what you had recomended in your email. we did not try shortening it, which may have made a difference, as he was just so busy trying to find the other silly problems. Will try slowly upping the gas as you suggest and keep you posted.

That could well have been us passing Phi Phi Don the other day if I remember we had the square sail out and were enjoying the peace of a run with it, or if it was the next day then it was topsails and all doing 8 knots close reaching on about 12 of wind. Yeppers it was the yard for us over the holidays but well worth it as we got so many things we wanted to do done. It is amazing we are at last getting the boat where we want her and seeing the end of the big projects. Sorry about the genset if we can help let me know.

H/V Vega
16-01-2010, 03:24 AM
Good day Chef,

Just a quick question about the small chiller. It has been acting a bit funny since the boat yard and rather slow to cool down ( running a lot) the pressures he has it at are about 150 and 5 which I remember your telling me was too high. Do you happen to remember what those pressures should be?

Chef
17-01-2010, 05:29 AM
I cant remember what the pressures were before but 150 over 5 is not out of line. It would be nice to see the Dx in the range of 140 to 155 and the Sx from 5 to 10. Ideal would be around 145 over 7 but that will depend on what temperature the box is and as its a chiller I am assuming the plate is at about -5C.

As it has been regassed you should wait till its at steady state and then see where the frost extends to on the evaporator plate. It may go over the whole plate so place your hand on the entry to the evap and see how long it takes to remove the frost and do this in the middle and at the exit end. If the frost melts really quite quick at the exit end compared to the entrance end you may be short of gas a little. Difficult to give hard and fast guidelines on this method as it is system and hand specific. Let your hand warm up in between though or use it to keep your beer cold. As your techy said its very sensitve to just a small amount of gas and so try not to take the gauges on and off too often till it is about right as the gas from the system to fill the gauge lines will upset the system each time you connect them.

As it is a built system you wont know what the critical charge is and so you cannot weigh in the gas but after a while you will be able to feel the lines at various places to give you a feeling of how it works, each of the 3 systems will be slightly different though.

Did the strange vibration on the coil go away?

Chef

H/V Vega
20-01-2010, 05:54 AM
Well has taken me days to get loged in again. Had it nailed at 145 / 7 for 2 days the plates get cold but do not freeze even with it running constantly. You should hear the complaints from my poor batteries....Today I dropped it to 135/6-5 will try and see if that is better. Since we know it works I am assuming it will just be a matter of mucking around slowly until I hit the right combination.... or not &:o)
As to the coils they shut right up when the new ones went in so you must have been right about it going super sonic and creating shock waves. Slowly this is becoming a working system.....I hope!

H/V Vega
08-04-2010, 11:35 AM
Well it has taken a long time to get back in here but the report is good. After a lot of very careful whiffs at last the system settled down. I only get -11-12C on the small one, -7-8C on the large one and the chiller is doing just fine. We are thinking about making the boxes a bit smaller as Chef suggested. The idea is to fill the bottom with a few sheets of sealed cell Poly foam, just to reduce the space. The chiller is OK as it is. Any idas how much we should shoot for in the reduction? 2nd question there is a small possibility we can get 1 of the 90 bd compressors that would go on the large freezer. Would that make sense Chef and any ideas if it would be worth while? Thanks again for all your great help.

constantine
15-04-2010, 06:35 AM
G'day,

I am the skipper of a 120 year old Historical Vessel that keeps herself alive and sailing by delivering Medical teams and medical supplies to isolated Island communities. Many of these islands have not seen a nurse, much less a doctor for 20 years. We specialize in child immunization and general health as well as public health education. Why I am here is simple, well maybe for you lot, most of our medications require refrigeration. Some in fridges and others in freezers. When our old system started to die one of our sponsors was kind enough to send us a load of "just what you need" for a new installation. That is two freezers and a fridge. The second freezer is because everyone enjoys a cold one at the end of a long hot day, right? Also it is not really a good idea to do as we were doing and store medical supplies along side food.

Well as the story unwinds we have three Danfoss DB50F compressors with the 12 VDC / 220 VAc electronics packages and a mountain of other bits and bobs. We had the new units made up to drawings with built in Eutectic plates. That took forever, isolated places are not known for harboring rocket scientists, filled them with the suggested mix and called in the local freezer man to install the lot. Well wonders the chiller works! The freezers how ever never freeze the plates and just will not get below 4-5 degrees C. From 27 G till 10 C they go down at about 2.5 degrees per hour then from 10C until about 5C it's 1 degree per hour. After that the whole thing stalls.

The freezer man at first said we did not need the Danfoss TN2 valves and accumulators but insisted that a coil ( looking like a spring) of very small pipe was enough. HUmph! Well that doesn't work at all. Any one feel like being our "remote advisor? The guy is willing, but his experience is very limited... best I can say is he solders nicely and is very careful about insulation. I have a good technical background so if someone will explain what we should do I will guide this guy through it.

Best regards

Shane
hi vega,i would first of all check the refrigerant charge then the electronic controls to see for any unwarranted shortcycles on the system.

Chef
15-04-2010, 07:40 AM
Well it has taken a long time to get back in here but the report is good. After a lot of very careful whiffs at last the system settled down. I only get -11-12C on the small one, -7-8C on the large one and the chiller is doing just fine. We are thinking about making the boxes a bit smaller as Chef suggested. The idea is to fill the bottom with a few sheets of sealed cell Poly foam, just to reduce the space. The chiller is OK as it is. Any idas how much we should shoot for in the reduction? 2nd question there is a small possibility we can get 1 of the 90 bd compressors that would go on the large freezer. Would that make sense Chef and any ideas if it would be worth while? Thanks again for all your great help.

Missed your post earlier. There may a few things to try before you opt for a bigger BD90.

First check all the seals to make sure you have no air leaking in and through the system, this is normally shown by a large and quick frosting of the plates with a quick build up of ice. If it lasts 2 weeks between de-icing it is OK otherwise you may need to focus on the door seals. Also de-icing weekly is a good procedure on these systems. Just remove the gear, point a spare fan into the box and it is done in 5 mins.

Second you should check if you have a drain line from the box's, this is to help drain away liquid from the box (if you get any) but sometimes they just let cold air pour out and warm air creep in by the seals. Sometimes a loop in this vent line (in a warm area ie bilge) will trap some water and stop it from dumping cold - otherwise stick a plastic plug in it till you de-ice.

Next try a sheet of say 1" non hygroscopic foam on the bottom of the freezer - a good fit is preferred but as you have SS solid interior the cold will still travel along the metalwork but worth a try as it is easy to do at no cost. Note the difference with the same goods loaded and then try 2", you will soon see if this going to work.

Last try a top cover - keep your goods at least 3" below the underpart of the top of the freezer and then place a nicely cut to shape foam pad (again 1") on top of all the goods, this works quite well and may not get you much more cold but it will hold for longer.

With all this done you may see a couple of degrees or more?

As to putting in a BD90 - well that would have to be checked to see if it matches your evaporator, the condenser and you will need a new cap tube (thats a bugger) so it should be a last ditch attempt really.

What RPM are you running the BD50 at? This could be important in future work?

Best

Chef

H/V Vega
16-04-2010, 02:11 AM
Hi Chef,

Well thanks again for the wise assistance. Most of what you mention you had mentioned before so those are things already done ( we take your advice quite seriously) Will look for foam today to try filling the bottom up a bit. I think starting with 2" will not hurt at all as those two units are quite deep. Not much problem with frosting up. It is lasting several weeks more like a month between defrosting. A build up of about 1/2 " on the plates is when Meggi attacks it. Seals are good no signs of leaking there. We have the "top covers" in place and find them quite useful when taking things in and out to seal the top when they need to be open for a while, for what ever reason. The BD50's are set at about 3,250 according to the resistor values. That had more to do with available resistors than desires. I did replace the cooling fans with more powerful units and that seemed to help a little. Oh well the saga continues. Perhaps one year these things will settle down and I can put away the gas bottle and gages for a while. Thanks again for all the help.

Chef
16-04-2010, 06:52 AM
Can you see the resistors and if so what are the colour bands, worth checking this out first as again its an easy option.

2" sounds fine and it will be interesting to see the results.

Chef