High Liquid Line Temperature

This is probably me just being paranoid, but I´ll check anyway. :)

Went to a look at an Infrico bottle cooler today ( same as this http://www.infrico.es/funcs/muestrai...imo&tamMax=300 ) which wasn´t getting to temp. Found the compressor wasn´t pumping and condenser fan motor wasn´t working. Replaced both and the drier. Started to charge it (R134a) got the suction to around 20psi and decided to leave it for 10 minutes to settle, came back and liquid line was hot to touch. Suction pressure was 40 psi. Now I was thinking of possible problems,

a) I´ve got the wrong fan motor
b) It´s a crap design for the condenser, so there may be nothing wrong with it.
c) I´ve screwed the charge up

If it was undercharged then I could have a high liquid line temperature, no? But if it was undercharged I should have a low suction pressure, or so I would think. If it was over charged, then the liquid line would be cold or ambient temp?

The fan motor is difficult to prove, the old motor has very limited information (Trial TAS24B-019 230v50-HZ). The one they gave me in the wholesalers is the same physical size (rotor and motor) and again has limited data on it, but it is a different manufacturer.

The condenser design is rubbish. The condenser lays vertical and fan is located at the back blowing air through to the front. Imagine a normal condenser on a fridge with a cross flow fan fitted on the top blowing through the coil to the bottom, then lay this over 90º. The top side (which would be the air on side normally) is open.

The air off the condenser was 60ºc. The ambient air was 22ºc as was the cabinet temperature. Gas is R134a. There´s no service valves except for the one at the compressor (suction).

I don´t think the condenser is getting rid of the heat. Would somebody like to disprove everything I just said and tell me something completely different? :P

i posted a thread calld "appears short of refrigerent" nike gave a good answer witch may help, you sorr i dont know how to create a link too it

I will quote this PDF!

Attachment 2673

Quote:

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For system charge and performance evaluation we must take temperatures across the
entire system before we can effectively evaluate any part of the system. What we are
saying is, every single component within the refrigeration circuit is dependant upon the
other components within that system. For that reason it is recommended you take
readings from the system in order for any system you want to analyze. I will explain the
reasons behind the reading and sequence as you read on. While doing so, I will use
acronyms and discuss locations which are outlined on the included diagram. If you are
new to the trade, becoming familiar with the following acronyms is highly recommended
as you will heat and read them throughout your career.
Acronyms:
Comp = Compressor
Cond = Condenser
MD = Metering device
Evap = Evaporator
DT = Delta Temperature (indicating a CHANGE within the same medium)
TD = Temperature Difference (indicating a temperature difference in TWO mediums)
SCT = Saturated Condensing Temperature
SC = Sub Cooling
LL = Liquid Line
SH = Superheat
SST = Saturated Suction Temperature
Readings:
Air entering condenser
Air leaving condenser
Condensing saturation temperature
Liquid line at outlet of receiver / condenser
Liquid line at inlet of metering device
Air entering evaporator
Air leaving evaporator
Evaporator saturation temperature
Suction line temperature at the evaporator
Suction line temperature at the compressor
Compressor voltage and amperage
Systems using vapor compression refrigeration fundamentally all work the same. Since
they all work the same, when evaluating the system the criteria and procedures should be
the same. To effectively determine and evaluate the net refrigeration effect of the system
you must consider all the factors that influence the system. We also must do so in an
orderly manner that follows a sense of flow and logic just as the system operates. As the
compressor pumps the refrigerant, it is the logical point to begin and follow the same
flow that the system maintains.
The compressor pumps the refrigerant to the discharge line. Since no useful information
can be gained as far as system performance is concerned, pressures and temperatures in
this line are relatively unimportant. Do not misunderstand, a proper operating range exist
for this line, however, it reacts to other components opposed to impacts other
components. The usual concerns are proper line size or with the few components that
might be installed in it like a muffler or oil separator which wile rare, could develop a
restriction.
At the condenser we are concerned with far more than just sub cooling. We must consider
mediums, the air and the refrigerant. Since the air removes the heat from the refrigerant,
we must first prove proper airflow. In optimum conditions by design for entering and
leaving air DT should be 15 to 20 degrees. If the DT is greater than 30, no matter what the
SEER rating the unit may have, it is being asked to perform outside its design parameters.
When the DT is 30 or above reduced BTU capacity and artificially high head pressures
result. Because both situations would result in improper flow rate and sub cooling we
must correct this before we can proceed. Common causes, dirt, fan speed, improper fan
blade, failing motor or capacitor.
Next we need the SCT. It is also imperative that we have the temperature within design
parameters If we are in a low ambient condition we will not have the proper pressure
differential to push enough refrigerant through the metering device. Metering devices are
size by pressure drop and flow rate (tonnage). This requires we bring the SCT to 100 °F.
This simulates a 70 to 75°F day where most systems are designed to begin operation.
Even systems that are designed for low ambient have components to bring it into this
range.
Our next step is to determine our SC. SC is required, however, many technicians have a
tendency to misinterpret SC. The SC is only one portion of the system evaluation and can
NOT be used as the sole source for charging or system evaluation. Requirements for SC
vary only a little and to gain a better understanding of the need one must consider the
metering device. The required SC is the difference created by pressure drop through the
Cond, LL components and the LL itself plus 1 additional degree SC and the metering
device will flow at the correct rate. NOTE: this is in regards to the metering device only
not the system. The operation of a refrigeration system needs to be efficient, increasing
the SC a little can significantly increase the efficiency without affecting input power a lot
and improves overall performance of the system. SC of 10 to 15 degrees is a normal
range.
If manufacture specifications are known to have a higher SC, by all means follow their
guidelines as it will peak the efficiency of the unit. If you do not have the information,
the unit will operate and operate well in the 10 to 15 degree range.
Next we must evaluate the LL. The LL needs to be evaluated as a working part of the
system beyond just a transporter of the liquid. Since there are often accessories in the
liquid line including the LL filter drier, we must find a way to determine performance.
The LL leaving the Cond or receiver will not give up much heat prior to the metering
device. This is in relationship to the velocity of the liquid traveling through the line and
the TD of the line to ambient conditions. Assuming no change in ambient conditions,
there should be no more than a 2°F change in the liquid line between the service and
about 6” from the metering device. The 6” is to eliminate any conductive heat transfer
that might take place from the cool side of the metering device.
Next we evaluate the evaporator. Yes, I know we skipped the metering device at this
point. There is no individualized part that the metering device performs in the system. It
is dependant upon the rest of the system since it is effectively just a hole or a valve.
The DT at the evap represents system wide performance. It must not go too low or it will
not remove enough BTU’s from the conditioned space. It also must not be too high. If the
DT is too high, we are not moving enough air over the evaporator. Not moving enough air
over the evap results in not enough BTU’s is being absorbed into the refrigerant. This
changes the density of the return vapor and lowers the temperatures. In air conditioning
we need the evaporator to be below the dew point for humidity control; however, we
must not drop the temperature below 30°F where frost will begin to form. If frost begins
to form, air flow is reduced further and the coil will quickly begin to ice. If the coil ices,
we have a very good chance liquid will pass through the evaporator and suction line
possibly resulting in catastrophic compressor failure.
A DT of 30°F will result in evaporator freezing. A DT of 25°F is likely to frost and freeze
if the unit is operated in lower ambient conditions such as happens overnight in the spring
and fall. We know the typical air conditioning coil is designed for a 40°F temp and a
55°F leaving air temp. That indicates a TD of 15°F between the air and refrigerant. If you
have a 70°F return air and you are maintaining a 25°F DT, that would be a discharge
temp of 45°F. This would give you a coil temp of 30 at which point frost would begin to
form and freeze up is quite possible. For those reasons we need to maintain a DT of 15 to
20 degrees across the evap.
Next we must evaluate the superheat produced by the system. We take SH in two
locations for two reasons. One is to evaluate how much refrigerant is in the evaporator;
the other is to be sure we do not send excessive or inefficient superheat to the
compressor. Evap SH can and does vary and levels ranging from 4 to 20 are not
uncommon. Most air conditioning systems fall into the 8 to15 degree ranges at the coil.
Remember the reason for SH is to prevent liquid from returning to the compressor, no
other purpose. Most compressors are designed to work properly with 25 to 30°F SH
entering the suction valve. One should measure system SH about 6” from the compressor
to prevent conductive heat transfer from the compressor. On residential equipment,
measuring the superheat at the service valves if the unit does not have an accumulator or
excessive suction line before the valve. The superheat reading at the suction service valve
normally is less than 20°F when operating at design conditions.
The compressor amperage and voltage must be taken to determine if the compressor is
handling the load correctly.

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Kindly check the refrigerant pressure at suction and discharge if both are high then it is confirmed overcharge

do you mean the condenser lays horizontal or flat under the base of the cabinet ? sounds like the fan is not going the right way or not blowing enough air over the condenser,other thing to check ,is it definatley R134A and not R600 stamped on the cabinet, that would give those symtoms:eek:

Definitely R134a. The label inside the cabinet says R134a, the old compressor (danfoss FR8.5G) says R134a and the new compressor (same as the old one) says R134a. I double checked all these yesterday.

After pondering over this all night, I too think it´s got to be something to do with the fan. I have the old fan with me now and I just ran it to see which way it goes, it is the same direction as the new fan.

Like I said in my original post. The only point of reference for pressure that I have is the suction stub on the compressor. Is this the true suction pressure, or could this be affected if the compressor gets hot? So I can´t take a lot of the normal stuff like sub cooling, because I have nothing to reference it from.

The condenser lays horizontal underneath the cabnet, with the fan just sticking out in to the compressor section. It makes it difficult to get a precise measurement of temperatures for this reason.

I´m going to go to site now and put the old fan back on. If I run it with the old fan and the system runs normal then I know it´s the new fan I bought. If the problem persists then i will remove the refrigerant and braze a stub on the discharge line, so I have another reference point to work with.

Thanks for the help. I will report my findings later.

just weigh in the gas job done

I think the problem is solved. I put the old fan back on and discharge didn´t get hot. So I put the new fan on and noticed it was slightly different. On the new fan, the outlet is rectangular but on the old fan it is still rectangular but has an extra bit at the top edge that is angled up (like a kind of v-shape). So I put this on the new fan and got the same results. So looking good. It´s a little short of gas which I will rectify tomorrow, so it´s either got a leak or it was the fan or both.

We´ll see tomorrow. Attached is a picture to show the condenser for those that didnt understand what I meant. You can see flip up bit on the top side nearest the fan.
http://img5.imageshack.us/img5/3885/image05ex6.th.jpg

Quote:

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Originally Posted by airefresco

The air off the condenser was 60ºc. The ambient air was 22ºc...

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60 - 22 = 38K/68F condenser delta-T.

The cond delta-T should be no more than 20K/35F... and this would be for a low efficiency system. Today's higher efficiency systems should have more like 14K/25F max.

High cond delta-T can ONLY be caused by insufficient condenser airflow.

did you change the fan motor or the motor/blade assembly?

i wonder if the new motor spins the same way but the new blade has a reverse curve?

Quote:

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Originally Posted by nike123

I will quote this PDF!

Attachment 2673

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Good quote, Nike... written by one of my customers. Makes me proud. :D

Quote:

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Originally Posted by airefresco

I think the problem is solved. I put the old fan back on and discharge didn´t get hot. So I put the new fan on and noticed it was slightly different. On the new fan, the outlet is rectangular but on the old fan it is still rectangular but has an extra bit at the top edge that is angled up (like a kind of v-shape). So I put this on the new fan and got the same results. So looking good. It´s a little short of gas which I will rectify tomorrow, so it´s either got a leak or it was the fan or both.

We´ll see tomorrow. Attached is a picture to show the condenser for those that didnt understand what I meant. You can see flip up bit on the top side nearest the fan.
http://img5.imageshack.us/img5/3885/image05ex6.th.jpg

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Tell me precise dimensions (A,B,C) of your original fan and make and full model number of replacemant fan.
http://farm4.static.flickr.com/3404/...15fbe5_o_d.png

Quote:

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Originally Posted by Gary

Good quote, Nike... written by one of my customers. Makes me proud. :D

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Yep, I liked this approach to explanation about how should we examine system performance.

Quote:

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Originally Posted by nike123

Yep, I liked this approach to explanation about how should we examine system performance.

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Overall, he explained it very well. I would offer one small clarification, however:

If the superheat is low then the subcooling will be low. Therefore, first check for high SC, then check for high or low SH, then check for low SC... and depending on the particular system, low SC may not in fact indicate a problem.

Quote:

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Originally Posted by Gary

Overall, he explained it very well. I would offer one small clarification, however:

If the superheat is low then the subcooling will be low. Therefore, first check for high SC, then check for high or low SH, then check for low SC... and depending on the particular system, low SC may not in fact indicate a problem.

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Thank you for that.

Quote:

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Originally Posted by piersons_man

did you change the fan motor or the motor/blade assembly?

i wonder if the new motor spins the same way but the new blade has a reverse curve?

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The whole fan assemble (motor, blade and casing.) Although now I have the old casing with the new fan motor and blade. They are both look the same and are the same physical dimensions. The only phyical difference is the v-shape metal piece and the electrical terminals are in different positions. Other than that they look the same.

Quote:

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Originally Posted by Gary

60 - 22 = 38K/68F condenser delta-T.

The cond delta-T should be no more than 20K/35F... and this would be for a low efficiency system. Today's higher efficiency systems should have more like 14K/25F max.

High cond delta-T can ONLY be caused by insufficient condenser airflow.

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Thanks for that Gary. After much consideration last night, I came to the conclusion that it must be the fan or possible the actual condenser (blocked, dirt etc). So it´s good to know that someone with your knowledge agrees. Thanks

@Nike123 - The document you posted earlier is now part of my van, along with Gary´s notes. For dimensions and model nº, I will get them when I return to site tomorrow. Thanks for your input.

Back to square one :(

It had a leak, one of my brazes too, which makes things worse. I fixed that and went round it with the leak detector, just to be sure there were no more leaks, and all seems ok in that department.

Vacced it out and recharged. Worked brilliantly for 10 minutes, the box temp came down to 17ºc and stayed there (started at 22ºc), then liquid line started to get hot again and the suction pressure started to rise. I think it must be something to do with the new fan.

Some model numbers. The fridge is a Infrico EV 350 PT. I found a PDF on the Infrico site It says on there the fan should be a TURB.TANG.QLZ06/0024/3030, which I found http://www.ebmpapst.com/en/products/...php?pID=53517#. The picture is different than the old fan that was on the fridge. The motor section is on the other side and looks nothing like the one on the picture.

The new fan doesn´t really make things much simpler the only sticker on that says, Emmevi/Milano. COD 116601 230v/50Hz. My Invoice says TGO60/1 180-30. Which is listed on the Emmevi site as a model number.
http://www.emmevi-fans.com/catalog.a...10412&ID=89717. If anybody has any data on these fans, I would be most grateful if you could share it, so I can compare the two.

Many Thanks,
Paul

Again... in order to determine what's wrong we need more information.

I don´t really know what more I can tell you Gary. Everything was the same as in my original post (to within a degree or two). Like I have said it´s only possible to take a pressure reading from the suction stub on the compressor, which I believe may not even be a true reading anyway, surely this must be affected by the heat from the compressor?

As for information on the fridge or fans. I have been searching google for hours, and not really come up with much more than what I have posted already.

One thing I should add, just as a side note, is that condenser section is really badly designed. Under the doors of the fridge is a grille (you can see on the photo on the first post). The condenser sits behind this grille about 10cm I would say. It´s only about 25-30cm wide, but it sits right behind the controller. So in effect 1/3 of the coil outlet is blocked, maybe a little more. If they had positioned the controller more to the left, then condenser would have a much clearer path. All this is irrelevant anyway, as it used to work fine before the fan died, and there are hundreds like this working.

EDIT: Found some more info on the fans. The New Fan is a 31w motor with an air flow of 180m3/h. The old fan is a 33w motor and airflow 170m3/h. So the new fan should be get more air across the coil?

Quote:

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Originally Posted by airefresco

Everything was the same as in my original post (to within a degree or two).

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So... you are saying that the air leaving the condenser is 60C?... or are you just guessing instead of taking measurements?

Quote:

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Originally Posted by airefresco

I don´t really know what more I can tell you Gary. Everything was the same as in my original post (to within a degree or two). Like I have said it´s only possible to take a pressure reading from the suction stub on the compressor, which I believe may not even be a true reading anyway, surely this must be affected by the heat from the compressor?

As for information on the fridge or fans. I have been searching google for hours, and not really come up with much more than what I have posted already.

One thing I should add, just as a side note, is that condenser section is really badly designed. Under the doors of the fridge is a grille (you can see on the photo on the first post). The condenser sits behind this grille about 10cm I would say. It´s only about 25-30cm wide, but it sits right behind the controller. So in effect 1/3 of the coil outlet is blocked, maybe a little more. If they had positioned the controller more to the left, then condenser would have a much clearer path. All this is irrelevant anyway, as it used to work fine before the fan died, and there are hundreds like this working.

EDIT: Found some more info on the fans. The New Fan is a 31w motor with an air flow of 180m3/h. The old fan is a 33w motor and airflow 170m3/h. So the new fan should be get more air across the coil?

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Did your motor turns in right direction?

Yes, I checked and both motors (old and new) spin in the same direction, which I assume is the correct, judging by the dust patterns on the condenser.

The air off can only be taken at the outlet grille which is on the front of the fridge, which i know is not a good measurement but it´s the best you can do with the configuration.

I´ve ran out of options now. I´m pretty convinced that the fan and airflow is good as it can be. I let the fridge run to see how well it works, and it does actually work quite well, just the liquid line being so hot that worries me. After a few modifications to condenser section, i managed to get the air leaving the front grille at 48ºc, which is still a little high for my liking, but better.

After 1 hour (with approx 100 bottles in the cooler) the cabinet temp came down to 11.2ºc from 22ºc, and was still falling. I´m going to go back tomorrow and see how it´s doing. If it´s not getting down to temp, then I will rethink the condenser configuration or a bigger fan then the original.

Is the new compressor identical to the old compressor?

Earlier I stated that high cond delta-T can only be caused by insufficient airflow. I may now have to eat my words. The other thing that can cause high cond delta-T is oversized compressor. Since compressors rarely grow, the original statement is true for most systems.

So we are still waiting for a line temperature when the unit is down to temperature.

These high temperatures are when it is under excess pull-down load ?

Yes to both of you. The compressor is exactly the same, identical in fact. A Danfoss FR8.5G.

That´s my thinking too Brian, see what the line temperature is like when it´s got close to, or at, temperature. Maybe it´s struggling now because it´s under load, which really rubbish, considering it´s a bottle cooler, it has one purpose in life, to cool bottles. We´ll see tomorrow.

Quote:

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Originally Posted by airefresco

EDIT: Found some more info on the fans. The New Fan is a 31w motor with an air flow of 180m3/h. The old fan is a 33w motor and airflow 170m3/h. So the new fan should be get more air across the coil?

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From your data, I have calculated that your achieved air flow is about 60m^3/h.
Either you mounted cross flow fan in wrong direction or 2/3 of your air doesn't go thru condenser.

Quote:

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Originally Posted by nike123

From your data, I have calculated that your achieved air flow is about 60m^3/h.
Either you mounted cross flow fan in wrong direction or 2/3 of your air doesn't go thru condenser.

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... or part of the hot air is recirculating.

I think that is more likely to be the case Gary. Placing a piece of card across the top of the coil, forcing the air to go through the whole coil, seems to improved things.

Temp measurements... we need temp measurements.

If you mean air off/on then it´s pretty tricky to get precise measurements. The way the whole thing is constructed you can´t get access to the condenser when it´s in position. The best you can do is measure the air the grilles at the front of the fridge, but that´s not really accurate because there is a gap between the condenser and that grille. It´s hard to explain what I mean.

The reason for the card was to try and force the air to the grille to
a) Get rid of the air away from the condenser and prevent recirculation
b) give me a better chance of getting a precise measurement.

The air off was 48ºc after about 10 minutes (maybe a little longer) of running. It was 60ºc when I first started this, so that is an improvement, whether or not the condenser is any cooler I don´t know, but the fridge is working better now, so I think it must be. The ambient was 22ºc by the way, so that 26k dT across the condenser, which is still a little high, but more reasonable than it was and it had a lot of bottles to cool too.

Is that some old model, since present Infrico bottle coolers doesn't have that condenser cooled with cross flow fans. They all have some axial fans and they call it "INFRICOOL® System of ventilated condensation".
Check this!
Is it possible that someone has changed that condenser with not original spare?

I noticed that too Nike. I found the manual for the actual bottle cooler and it is the same type of condenser, fan, etc. It seems to be the only model with this configuration though, so perhaps this is a common problem and they changed the design with the later models. I think this model is from around 2003.

http://www.infrico.com/infrico/ES/de...efrigerado.pdf Page 4 of this PDF is what I am dealing with.

Quote:

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Originally Posted by airefresco

I noticed that too Nike. I found the manual for the actual bottle cooler and it is the same type of condenser, fan, etc. It seems to be the only model with this configuration though, so perhaps this is a common problem and they changed the design with the later models. I think this model is from around 2003.

www.infrico.com/infrico/ES/descarga.php?file=../recambios/17_expositor%20vertical%20refrigerado.pdf Page 4 of this PDF is what I am dealing with.

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I see now.
From what I see, it could be that cross flow fan is in elevated height space and condenser is in low height space in bottom of cooler and that you need somehow to partition (with some foam or simmilar) that two spaces in order to got "proper" air circulation and avoid hot air recirculation.

Attachment 2689

Possibly a fan could be added behind the discharge grille to help pull the air through the condenser?

Thanks Nike. If I understand your drawing correctly, that is exactly what I have done with the card, the air now has to pass through the coil and shouldn´t circulate.

I've just been to check it, the first time since Saturday and it was at 5.2ºc (setpoint is 5ºc), then liquid line was a little warm but not as bad as it was. I didn´t take any measurements, as I was just passing, so I called in to see how it was doing. The client says it has been between 5-6ºc since Saturday, so looks good.

I´ve advised the client to stock the fridge slowly, i.e. don´t fill it full of warm bottles, as I think the condenser struggles under load.

Thanks to everybody who has helped me.

While it may be working, keep in mind that the high delta-T adds to the energy usage and shortens the life of the system as well.

Thanks Gary, I did mention that to the client too. They did get the cabinet very cheap, second hand. It's in a superb condition (cosmetically). So even after the repair bill, it was still a very cheap buy for my client, so they are happy if they only get a year or two out of it.

Sorry, I just saw your other post. I did consider putting a small fan behind the grille. Actually I was thinking of two computer case fans, as they would be about the right size, but I don´t know if they would move enough air, I would have to look into that. For now, I´m going to leave this job alone, as it is working and the customer is happy.