MP66 & Compressor Overheating

[Intermez]

Will make a complete diagram today.

Pull down test: went from 50psi down to 21 in Hg within 1 min. Sat at 21inHg for next 5 min. Turned compressor off and after another 5 min reading still at 21inHg.

Thanks again guys for hanging in there with me. Off to put in more access ports.

Kevin

[US Iceman]

Kevin,

When you have the compressor running in a vacuum, you should only keep the compressor running for about 1 minute. If the compressor is going to pull a vacuum, it will do so rather quickly. Allowing the compressor to operate in a vacuum for 5 minutes serves no purpose.

I was trying to remember something you need to understand about hermetic motors running in a vaccum. Don't do this for very long.

The insulation resistance of the motor decreases quickly in a vacuum. prolonged operation in a vacuum can cause other probelms that may force you to change the compressor.

[The MG Pony]

some of the guys I know who use them as vac pumps have run them upwards of two days at max vacuum so they can tolerate the abuse apperantly, befor I never knew that. I use a low temp unit to vacuum out my play systems at home, till I can buy a rotory vane vac pump.

Any case 21"mg that seems rather high for a low temp unit.

[Intermez]

Thanks for the heads up on pull-down run time. Will not run longer than a minute in the future. Will get to the diagram tonite. Have some temperature measurements, will get more readings and give full report later.

Did find something interesting. Pressure drop from TEV outlet, through three plate runs, and measured at plate outlet is running about 5 psi. Seems a bit high dosen't it?

Will fill that in with more data on pressures and temps.

Kevin

[Intermez]

Latest:

Ran system trying to get it to stabalize. Discharge temperature kept rising. Stopped at 295F, no sign of slowing down.

Found that first plate of three appeared to have lost about 50% of its brine. Made me suspicious bacause of pressure drops through 3 plates I had found earlier (5psi). Easier to bypass this plate entirely than to do anything else.

Ran system with only second and third plates. Was able to get system to stabalize somewhat with discharge temperature about 260F. Ran this way for about 30 min. My camera died so can't attach diagram I drew (figures!). Below is a list of the components, starting at the compressor, through the HP side, TEV, LP side.... Numbers before and after each component are the temperature measurements going into and coming out of that component where I was able to measure. System was still pulling down somewhat so readings were not 100% stable.

80F-COMP-260F
250F-CONDENSOR-115F
115F-RECEIVER-110F (@165psi)
VALVE
109F-FIL/DRYER-107F
107F-30FT. 3/8 LINE-95F
95F-HEAT EXCHANGER-80F
VALVE (pressure here 163 psi)
------------INSIDE COLD BOX
70F-TXV- -5F (@3.5psi)
-5F-PLATE 1- -9F
-9F-PALTE 2- -10F (@1.5psi)
--------------OUTSIDE COLD BOX
20F-HEAT EXCHANGER-40F
40F-30 FT 7/8 LINE-65F
65F-FIL/DRYER-67F
68F-ACCUMULATOR-75F
80F-COMPRESSOR-260F (0 psi @ suction port)

Thoughts?

Thanks, Kevin

[US Iceman]

Kevin,

See notes below. My comments are in red, next to your original data. Everything looks OK until you get to the red areas.


80F-COMP-260F
250F-CONDENSOR-115F
115F-RECEIVER-110F (@165psi)
VALVE
109F-FIL/DRYER-107F
107F-30FT. 3/8 LINE-95F
95F-HEAT EXCHANGER-80F
VALVE (pressure here 163 psi)
------------INSIDE COLD BOX
70F-TXV- -5F (@3.5psi)
-5F-PLATE 1- -9F
-9F-PLATE 2- -10F (@1.5psi) (about 6 degrees of superheat)
--------------OUTSIDE COLD BOX
20F-HEAT EXCHANGER-40F (at this point you about 50 degrees of superheat!, 40F minus -10F)
40F-30 FT 7/8 LINE-65F (now you have an extra 25 degrees of seperheat!, 65F minus 40F)
65F-FIL/DRYER-67F ( 2 more degrees of superheat)
68F-ACCUMULATOR-75F ( 10 more degrees of superheat)
80F-COMPRESSOR-260F (0 psi @ suction port) (+ 5 more degrees of superheat)

Adding up the numbers we have 6+50+25+2+10+5=98 degrees total. If we adjust this for pressure losses we 100 degrees of total suction superheat being added!! (80F at the compressor minus the saturation temperature at 0 psig = -20F = 80F minus -20 = 100 degrees.

That's why the compressor is hot!

The suction pressure loss does not look too bad, but the superheat is not at all helpful.

The superheat looks OK until you get outside of the box. Then somehow, when you are leaving the second plate and getting outside of the cold room you are adding about 30 degrees of superheat. (20F - -10F = 30 degrees). That's way too much! Six degrees of this came from the plates. Then to top it off, the suction heat exchanger is adding another 20 degrees. The two of these equal half of the total!

Does any of the suction line have insulation on it?

Is the suction line outdoors in the sun... Exposed?

Does the accumulator have the liquid line connected to it with seperate connections? Or, does the suciton line come into and leave the accumulator only? Does the accumulator have four connections or two?

Somewhere between the outlet of the second plate and leaving the cold room, you have a major problem...

Pictures of the installation would be nice to have as well as a piping diagram.

[Peter_1]

Just joining again this thread, wasn't able to post sooner.
We finished today a job that normally had to be finshed yesterday. Problem: 3 hermetic units where 3 lines were swapped, even a suction with a liquid line.
Most of the lines were installed underground.

This is a general note for many 'IP-posters': if you're not used to work with psi and °F, then these posts takes much more time to read and to 'understand and translate' them, especially when most of the answering has to be done in the evening after a very busy day. So, most of the times, I stop reading these posts and try to concentrate on other postings.
But this problem is to interesting to let it go now.

See that there were some posts and USIceman answered them all.
A schematic should be very usefull and some pictures is of course the best solution.

USIceman already made the necesarry calculations and conclusions: like already said in my post of 19/08, I think you need to replace the line between last plate and compressor inlet.
But you can do this much moire easily and faster in soft 5/8 copper, 7/8 is in my opinion far too large. And remove the accumulator and the HE at once, you don't need these fancy tricks. The more unnecessary items you install, the more they're prone to failure. (Is thsi a correct expression ?)
It's also only 30 ft of 5/8 copper, installs fast and without a lot of soldering.

I also suggest that you desolder it direct from the last plate and look once with a light in the hole if the tube inside the hole hasn't collapsed like the picture I posted in one of the first posts.

What's seems important for me - but USIceman pointed already to this - is the sudden temperature rise after the last cold plate and before the entrance of the HE.
Then in the HE, there's also something wrong.
What about a defective HE where there's an internal bypass between low and high side?

USIceman, with the 4 connections suction accumulator, you're thinking about the type with a HE build into it?

[US Iceman]

Hi Peter,

Sorry to hear about the underground piping problem. I worked on a job similar to this. Some split units separate by a roof. The installer had the liquid lines crossed between the two condensing units. It was fun to watch the refrigerant move from one system to the next, before I found the problem. It was even more fun to explain it to the owner of the firm that installed it. I have never seen someone get so mad!

USIceman, with the 4 connections suction accumulator, you're thinking about the type with a HE build into it?

That's it exactly Peter. If he has two heat exchangers adding heat to the suction line, that is almost two, too many, if you know what I mean.

The more unnecessary items you install, the more they're prone to failure. (Is this a correct expression ?)

Correct on both counts Peter.

The interesting thing is, with the 7/8" suction line he has almost 3.5 to 5 psi pressure loss. This seems very high, but for the time being, I think it is a minor problem.

I cannot see how he would have this much pressure loss in only 30 feet of tubing??? Especially for this low of a capacity system?

Sorry about all of the IP units Peter. I'm facing the same problem you have. I'm trying to help the guy out, and I still have work to do also. A sorry excuse I know.

[Intermez]

Thanks!!!

Question, could all the temperature readings along the suction side be explained by very low refrigerant flow? Wouldn't this account for all the temperature rise? Pressure readings just don't point me to a particular point of blockage. If the TEV is somehow limiting flow to a low value is it possible to still get a superheat reading of 6F? Just a thought.

Suction line is insulated completely except for the heat exchanger. Suction line is indoors. Accumulator is 2 port, suction side only, no liquid line heat exchanger in the accumulator. Remember also that these readings are not an instantaneous snap shot. It took 5 or 10 minutes to get them.

The heat exchanger is coming out. Question about heat exchangers: I agree that thermodynamically it dosen't gain anything, but 1) dosen't the higher suction line temperature after the heat exchanger reduce heat gain along a long suction line because it is so much below ambient? and 2) in a cold plate system doesn't the lower liquid temperature create more rapid plate pulldown? In a cold plate system people are interested in pull down times more than total energy usage it seems.

Will take some pics as soon as I get camera working. I agree with replacing the 7/8 line with 5/8 line, pain in the butt, due to routing of line, but it is the right thing to do. It's impossible to get a view into the plates without totally unmounting them. They're right up against a panel on the top side of the plates with rt. angle flare connections. Not even sure how to disconnect the lines without removing the plates......which I'll have to do anyway to put in 5/8 line now that I think of it.

Supper time, must go NOW according to wife.

Kevin

[US Iceman]

1) dosen't the higher suction line temperature after the heat exchanger reduce heat gain along a long suction line because it is so much below ambient? and,
2) in a cold plate system doesn't the lower liquid temperature create more rapid plate pulldown?

1) heat transfer wise, the lower TD would add less heat to the gas. So, in theory you are correct. I still don't think the ambient is adding this much heat, unless the suciton line goes through a VERY warm space.
2) Cold liquid does add capacity, which would reduce the pull down time.

I agree with replacing the 7/8 line with 5/8 line,...

Unless the suction line has a kink or blockage in it somewhere, I would stay with the large size. One thing that might be proven quickly by changing the line is to see if the system works any better. Normally I hate to recommend this, but then, since I can't see the system I'm down to trying things.

Earlier in another post you mentioned one of the plates had leaked the glycol out of it. Where did the glycol go?

At this point, pictures are badly needed .

[Peter_1]

On the picture I post now, you can see also a leak I had, the TIG welded seem was teared. The picture needs to be turned 90°
So mostly they leak due to the continuous expansion and shrinking of the ice.
A standing plate tears mostly somewhere against the floor, mostly through a very small leak.

This becomes a really s**y job.

in a cold plate system doesn't the lower liquid temperature create more rapid plate pulldown? In a cold plate system people are interested in pull down times more than total energy usage

Yes and no, lower liquid temperatures means indeed faster pull downs in case this subcooling was created by other means of the system itselves (additional cooler, the ground, lower outside temperatures,..)
But with a HE you expanded also the suction gass with the warm liquid - energy was transfered from one to teh otehr side - so, indeed less liquid must be circulated due to the higher enthalpy of it but on the other hand the compressor must pump a larger amount of expanded gas, so a smaller mass flow at suction side.

So, in my opinion, the first compensates the second and thermodynamically seen, you can't 'create energy' in a HE.

I once read a paper - and I have stored it somewhere on my computer - about the benefit of a HE where they calculated the savings.

Can someone provide me a link to the used TEV of Sporlan? Searched for it in teh weekend but didn't find it.

[Intermez]

But with a HE you expanded also the suction gass with the warm liquid - energy was transfered from one to teh otehr side - so, indeed less liquid must be circulated due to the higher enthalpy of it but on the other hand the compressor must pump a larger amount of expanded gas, so a smaller mass flow at suction side.

Trying to get the "quote" to work as you guys use it. Quote is the above in case it doesn't work.

Understand what you said, but will the compressor in the above situation work harder, pull more amps, and add energy to the system....allowing faster pulldowns? Not interested in creating energy for a free ride with a heat exchanger, but interested in getting more out of the compressor allowing faster pulldowns. Have you ever seen an analysis of pulldown times with/without a HE regardless of energy consumed by the system?

Parker/Sporlan page very out of date. Will look for specs/info on the TEV in system.

[Intermez]

Here are two links that you've probably already seen. The TEV is a GF-1Z that isin't specifically referenced. Unit is one ton, R-12 low temperature bulb charge.

http://www.sporlan.com/10-10.pdf
http://www.sporlan.com/210-60.pdf

Question: If there is a blockage somewhere in the suction side after the TEV why don't I see high pressure readings when I measure the pressure immediately after the TEV?

[US Iceman]

Here is a link to a very good source that one of our other members posted:

http://www.refrigeration-engineer.co...ead.php?t=5590

[frank]

Not interested in creating energy for a free ride with a heat exchanger

The first Law of Thermodynamics states that the amount of energy in any given thermodynamic system is constant. Energy cannot be created nor destroyed.

Energy is described as the ability to do work.

A heat exchanger just exchanges heat energy.

No free ride I'm afraid

[US Iceman]

Kevin,

To use the quotes, try this:

First type in... Left bracket then quote=Screen Name then right bracket

Type or copy the quote you wish to add here.

Then type in... Left bracket then /quote then right bracket

This is the syntax required. What you should end up with is between the brackets, including the brackets. Does that help?

[The MG Pony]

[ quote=Snarfawidget ] blah blah blah [ /quote ]

like that but with out any spaces inside the brackets. Or simply use the word buble thing up top that says "wrap in quotes" after high lighting the text to be quoted.

[Dan]

I once read a paper - and I have stored it somewhere on my computer - about the benefit of a HE where they calculated the savings.

Here's one that says a liquid suction heat exchanger does not improve COP.

http://www.irc.wisc.edu/file.php?id=49

To quote the conclusion of a tedious paper:

Even though the liquid-suction heat exchanger has a negative impact on system performance, the system does benefit from the heat exchanger by preventing vapor in the liquid line before the expansion valve. The system designer must thus be very careful in choosing when to install a liquid-suction heat exchanger in a refrigeration system.

What makes sense to me is that any heat gained in the suction line after the evaporator is wasted work. Thus, transferring as much as possible from the suction line to the liquid line is going to reduce ambient heat gain and improve COP.

[Intermez]

Thanks for the directions on using the "Quote" function.

Did some digging on heat exchangers. It seems the answer isin't so simple. See http://www.irc.wisc.edu/file.php?id=49
It seems that it all depends on the refrigerant used, mostly. Food for thought.

Kevin

[Peter_1]

Seems that this link isn't working.

[Intermez]

Peter,

Tried clicking on the lick a few times. It worked for me. It's a PDF file. Here's the link for their HTML version:

http://72.14.209.104/search?q=cache:...&ct=clnk&cd=12

Hope this works, VERY long link.

[US Iceman]

Peter,

I think this is the report I sent to you earlier this year. It is probably the one you were thinking of.

PS. Kevin, what has been happening with the project? We went from a problem job to the pro's & con's of liquid/suction heat exchangers...

[Intermez]

Got sidetracked on another job. Working on putting in a temporary 5/8 line to bypass the 3/4 to see if that makes a difference. If that works.......then I'll have a least another day to make it permanent. You wouldn't beleive where the 3/4 is routed, but that's another story. Also laid my hands on another TEV, perhaps better (1/2 ton rather than 1 ton and externally equalized), that I'll try. I'm at the point of trying things to see if they make a difference. Another thing I thought of is that since the system was originally R12 with mineral oil, might have some kind of oil/wax mixture sitting in the plates that's causing a partial blockage. Just don't think it is this bacause the pressure drop isin't terrible. If the 5/8 line and other TEV don't do anything I'll try flushing the plates.

Question: If there is a blockage after the TEV somewhere, why don't I see bigger pressure drops on the suction side? Wouldn't I build up liquid before the blockage and see a temperature drop after it?

Thanks, Kevin

[The MG Pony]

why are some owners so frugaly inclined? By now I'd have had the system teared out and a new one put in, then sell the old one as parts.

[Peter_1]

why are some owners so frugaly inclined? By now I'd have had the system teared out and a new one put in, then sell the old one as parts.

Selling parts with probably a fault in it? And selling cold plates already used? It's already a small market for these systems.

And I also disagree with your way of solving this problem, there' most likely nothing wrong with all the plates nor the compressor. So why replace those?

There's somewhere a fault in the system that must be localised and repaired afterwards. That's all.

Replacing all the parts, well, everybody can repair this way everything.
I then even can repair this way a Rolls Royce Trent 500 jet engine.
This isn't the right way because your don't learn anything doing it this way.

These kind of problems, well you can learn so many of it.
Wonder why so few join this thread.

What does "frugaly inclined" means?

[US Iceman]

HI Peter,

What does "frugaly inclined" means?

A fancy way of saying someone is cheap, or will not spend money.

By now I'd have had the system teared out and a new one put in...

This is the difference between a good service tech and a parts changer. Anyone can change parts. Not very many can find the problem and then fix it correctly.

I then even can repair this way a Rolls Royce Trent 500 jet engine.

That's true Peter. I want to be a brain surgeon, but I cant find any spare parts to change.

The system Kevin is working on is one of those he will remember I'm sure. These are the type of problems that make a good service tech better.

[Peter_1]

The system Kevin is working on is one of those he will remember I'm sure. These are the type of problems that make a good service tech better.

"Voila" said the French tech.

[US Iceman]

Peter,

You are such a master of the languages!

[Intermez]

I hate to repair things by swap out. Peter....your suggestion I believe......change the 7/8 to 5/8 suction line bypassing all the "stuff". Unfortunately, I happen to agree with you in this case although the readings don't directly support it. The TEV, that's all my idea, will take full responsibility for that one. Compressor and plates, can't be there.....I hope.

[The MG Pony]

So do I but if time is important on a production system and as you said it was old to boot then seems like the logical choice. Over time I have learnt that after a point there is no reason to continue fixing it up. I've been interested to see the problem solved as well, but an old system that had issues be for hand well like I said thats me.

FYI I didn't say swap out I said flat out replace the whole lot, I'd re-assemble the old one just to figure it out, sell of what was worth any thing.

[Peter_1]

Over time I have learnt that after a point there is no reason to continue fixing it up. FYI I didn't say swap out I said flat out replace the whole lot, I'd re-assemble the old one just to figure it out, sell of what was worth any thing.

And what may be that point for you? Seems that searching too long or dmaking some efforts is the main reason.

For me, the decission to replace an item is when it can't be repaired or a repair will cost more then a new one.

"By now I'd have had the system teared out and a new one put in" is exactly what you said, teare it out.

So many replaces parts without knowing why they replace it. "We will change this part and we will see if it's beter, if not, then we will change another part and left the previous part of course and see if this helps"
I have to admit, that's the reason why I hate to service nowadays airconditioning, you have to replace a whole PCB, without knowing what defective part you're changing. On these PCB's, the part that's broken cost mostly not more then a few cents.
But it's the only way to solve the problem.

[Peter_1]

You said that the valve has a number 1 behind the type.
According to the Sporlan literature, this '1' means that you have a capacity of 1TR, or +/- 3500 Watt.

A 1.5 HP LBP gives +/- 1200 Watt at -20°C, so your present valve is far too large.

Isn't it possible that this valve was placed by the previous tech and that he had turned on the needle so many turns, trying to achieve an acceptable SH that he closed it almost completely?

But if this valve is turned almost completely in closed position, then there's no possibility that it can inject sufficient refrigerant.

You need at least a valve of 1/2 TR or +/- 1700 Watt.

But still the sudden Sh botters me and you have somewhere a point saying that the readings don't support the replacement of the suction line. There should be also an accompanying pressure drop which there isn't.
But a HE can add heat without changing the pressure.

[Intermez]

But if this valve is turned almost completely in closed position, then there's no possibility that it can inject sufficient refrigerant. You need at least a valve of 1/2 TR or +/- 1700 Watt.

The valve I have available is 1/2 ton, will work with 401B, and low temp bulb charge. It's externally equalized, just have to put in equalization connection. Should be trying it today.

But still the sudden Sh botters me and you have somewhere a point saying that the readings don't support the replacement of the suction line. There should be also an accompanying pressure drop which there isn't.
But a HE can add heat without changing the pressure

The heat exchanger is only adding around 20F to the total superheat of 100F. So I don't think this is the problem, surely not helping things thought. Customer said he will allow me to "do some playing" with the system after I get it working. Want to see the difference with/without HE. By the way, took Peter's suggestion and printed out a slightly edited version of this thread and gave it to the customer. He was VERY IMPRESSED. Good idea Peter!! Guess you're OK no matter what everyone else says.

[US Iceman]

The heat exchanger is only adding around 20F to the total superheat of 100F.

Yes but... The heat exchanger and whatever is happening between the last plate and the heat exchanger is contributing about half of the superheat that you have.

Guess you're OK no matter what everyone else says.

Peter is a great guy and I defy anyone to say otherwise.

But still the sudden Sh botters me and you have somewhere a point saying that the readings don't support the replacement of the suction line. There should be also an accompanying pressure drop which there isn't.

This is the part of the problem I don't like. Pictures would really help for us to see what is going on. The data provided supports Peter's comment above quite well.

[The MG Pony]

And what may be that point for you? Seems that searching too long or dmaking some efforts is the main reason.

For me, the decission to replace an item is when it can't be repaired or a repair will cost more then a new one.

"By now I'd have had the system teared out and a new one put in" is exactly what you said, teare it out.

So many replaces parts without knowing why they replace it. "We will change this part and we will see if it's beter, if not, then we will change another part and left the previous part of course and see if this helps"
I have to admit, that's the reason why I hate to service nowadays airconditioning, you have to replace a whole PCB, without knowing what defective part you're changing. On these PCB's, the part that's broken cost mostly not more then a few cents.
But it's the only way to solve the problem.

No I do not do that, I replace total system and log it very well, so next time it needs work there is no guessing you read the log you know the exact age of the parts last opperation don, I am very neurotic about having things tightly organised and loged

[Peter_1]

No I do not do that, I replace total system and log it very well, so next time it needs work there is no guessing you read the log you know the exact age of the parts last opperation don, I am very neurotic about having things tightly organised and loged

Replacing the whole system just for a faulty TEV? Even better!

Keepings logs, running parameters and a sheet of the used material is of course very good, it's even mandatory in Belgium to do this.
Each intervention on the system must be clearly described in the same booklet and when you had a refrigerant loss, then you must describe where, reason and what you have done to prevent it happens again.

But that's not my point.

Nevertheless, you have your way to solve a problem, I have mine.
And there must be a difference, otherwise there should be no competition.

But, we still have a system functioning not properly that needs to be repaired.

[US Iceman]

Replacing the whole system just for a faulty TEV? Even better!

This is just too funny.

And to think... I wasted all of those years sitting in school and listening to the old guys trying to tell me something.

I have not laughed that hard in a while!

[The MG Pony]

This is just too funny.

And to think... I wasted all of those years sitting in school and listening to the old guys trying to tell me something.

I have not laughed that hard in a while!

Lol now come on now, if it where this simple on the system in question I'd imagine he'd be don by now, but long term issues?

I am indeed keen on seeing what the problem is my self.

(As for the old guys I spend nearly ever minute of the day chatting with them when I can; how do you think I've learnt this much? I'm on a 2 year waiting list for my entry course to start)

[US Iceman]

...but long term issues?

Then Kevin will have a life long customer. He tried to fix the system without just changing parts, which by the way, owners begin to notice after the second or third attempt. It does not take them too long before they begin to see what kind of tech is working on their system.

Once you loose your credibility with them, you could solve the problem the next day, and they will think you are guessing again.

Ripping out systems to "fix" problems is an easy way out. I hope the school you go to, does not condone this type of ethic?

[The MG Pony]

you all seem to be jumping to conclusions about my methodology, I would not resort to that right off and oft take times to work away the problem and oft do (Only on computers currently) but if the system has a history of issues and has an odd one then one must consider upgrading. I have a system on my bench in such a state I have worked on it multiple times and have it repaired and this is the 5thed time it needs work (More to it then just that but I'll leave the life story out of it) so I will recommend it is time for them to get a new one. that's what I was stating about this since he said it was having issues be for and if it is a time critical job.

Ripping out and replacing IS NOT THE DEFAULT! you all seemed to assume this is what I was saying when I wasn't.

We all have our own methodologies of doing things (and judging by the loyal customer base for Computer work I have I must be doing some thing right)

either I said it wrong or you miss understood either way we are all way off base as to the thread topic.

[Peter_1]

In the computer repairs, it's of course something different:
1. it's impossible to pinpoint the faulty piece on a PCB, and even if it should be possible, these pieces can't be found.
2. PCB's and all replacement parts are rather cheap, very cheap compared to pieces in refrigeration.
3. These replacements parts are made to replace, not to repair
4. Swapping pieces in a computer takes sometimes less then a minute. Removing a HE is a work of hours.

If it's not the default, well, I only can agree with you.

Perhaps I misunderstood you, but you must be aware that things can be understood different from what you mean, especially by those where English isn't there mother-tongue.

[chilly]

Not to familiar with this system at all guys.
But from a layman s point of view I would at this stage replace the tev and orrifice together (remove faulty tev from equation) also check cappacity of tev and orrifice is correct for system.
Ive pulled my hair out for daus before now because an engineer before me changed the tev for the size he happened to have in the van. (different to the one required)

Also I dont know the system but is their any way to reduce the load in order to test the system?

Has the load changed in recent times and is now too great for the system to opperate.

One last thing R49i is the replacement i use, Maybe the replacement gas your using is the problem, Perhaps try another replacement gas that is a better drop in.

Hope some of that is of use.

[US Iceman]

MG Pony,

Well, English is my native language and I understood you to say,

By now I'd have had the system teared out and a new one put in...

If we assumed too much, then why did you suggest tearing out the system as your second post to this thread?

If I'm coming across too harsh, I aplogize in advance for that, but I do not like the suggestion of tearing out systems, just because the problems are too diffficult to solve.

The important part of this (besides fixing the system) is to keep the owner fully aware of what you are doing to the system.

It is better to explain to the customer you are having some difficulty in finding the problem and then proceed to solve the issues. Most of them will appreciate the honesty and the willingness to carefully review the system before spending money on various parts.

One of the hardest things to learn when you are getting started in this business is... patience. Do not be in a big hurry to solve things.

[Peter_1]

The important part of this (besides fixing the system) is to keep the owner fully aware of what you are doing to the system.

It is better to explain to the customer you are having some difficulty in finding the problem and then proceed to solve the issues. Most of them will appreciate the honesty and the willingness to carefully review the system before spending money on various parts.

I would like to add USIceman: I allways explain my customers what I'm doin and why I'm doing something.
When I'm not sure it's reapaired for 100%, then I also tell client that he can expect troubles and try to predict what troubles we could expect.
Example: there was moisture in the system and the TEV was blocked. I replace the dryer but I tell the client that he has to monitor the sight glassand that the problem can come back.

I learned through the years that if you lie or don't tell everything, that everything will be thrown sooner or later in you face if truth comes above water or another tech comes on site and tells the customer his vision of the problem.

If a customer doesn't or won't understand that a problem can't allways immediately be fixed and that it can take some time before it's fixed, well, then I have happily the opportunity to walk away and he never had to come back to me.

That's the advantage of having too many work

I once had a client who called me at 05 AM on a Sunday morning (in fact night for me )
I hadn't hear the phone and the answering machine took up the line in the office.

He made a second call around 06 AM and we heard someone giving an explanation.
So, I thought, I will see when I wake up at 08:00 AM.

At 07 Am, a 3th call and shouting realy loud through the telephone. I stood up and listened to the recorded tape: that this wasn't the proper way of servicing, that his coldroom already had problems since Thursday(!!!) and that it now on a Sunday morning completely had stopped and it was full of meat.

So I decided to go, I was anyway ready to start my Sunday with a croissant.

I told my wife that I should go first to help him before giving him my view and return with the croissanst so that we could eat together.

I entered at 07:20 his shop and he told me something like: "Well, you came walking I suppose, it's more then 2 hours I called you. You can see that' my fridge will be arranged within minutes " I stood their with my toolcase in my hand and in the other the doorknob and replied "Repeat that once again and I will even not place my toolbox on the ground for you. You can shout to your wife like a dog but not to me. If you don't appologise, then I will leave immediately"

His wife appologised for him and I repaired his coldroom. He's still a client but his attitude is changed since then.

[US Iceman]

I allways explain my customers what I'm doing and why I'm doing something.
When I'm not sure it's repaired for 100%, then I also tell client that he can expect troubles and try to predict what troubles we could expect.

Well said.

This is the reason why I also believe this...

I learned through the years that if you lie or don't tell everything, that everything will be thrown sooner or later in you face if truth comes above water or another tech comes on site and tells the customer his vision of the problem.

This is not the type of advertising you want for your reputation...to have people talking about you badly.

I once had a person similar to Peter's story (I'm sure everyone has a story like this ). He called at midnight with problems on an ice cream case. He knew about the problem at 6PM, but waited until midnight (after he quit trying to fix it himself??). I told him I could be there early in the morning (sunday morning again).

When I arrived, there was another service tech working on the system. He called every company until someone came right out.

He screamed and cursed at me and said it was my fault! I said OK, sorry you feel that way, and good luck with the new tech and went back home to enjoy the day.

Yes, we are off the topic, but these lessons can be just as valuable as learning refrigeration.

[The MG Pony]

Most of them will appreciate the honesty and the willingness to carefully review the system before spending money on various parts.

That would be my first operation would be to solve it, how ever the mentality of this area I live in they'd be at this point wanting it to work, hence by several weeks of looking and geting no where then I'd replace the whole system given that they said it was having issues befor hand.

Then I'd rebuild it at Home and find the problem, becuase I would like to know, but it is what the person wants. It is great the guy wants the old system repaired that is very rare now days (Or at least so it seems in thees parts again)

for some reason I thought this was a time criticle job. and when dealing with old systems with a history of having issues (This is what I got the jist of) it is best to properly build a very well documented one that will give years of truble free service. As the old dock saying goes: you can only patch the haul so many times befor your in a paper boat.

[The MG Pony]

I would not ever lie, that defeats the whole reason to talk, if the info you give is not right then best not waste the air to say it is my saying, no idea how we got on that line of thought, this is what I do, I all ways explain why and what in any field it is the only right thing to do.

Good business is repeat business, and honesty, quality and precision should all ways be the only acceptable out come, and so far I have maintained that stance and methodology and all ways will

[Peter_1]

Any news on this one?

[US Iceman]

Peter, it seems we have lost our little project???

[Sledge]

Hi

It is 12:30 am and I cant read to the end of the thread, not certain if anyone else has posted this...

I have in front of me a publication from Honeywell on retrofitting from R12 to MP66. They state that excessive discharge temperatures and capacity reduction may occur in situations where you have high compression ratios. It can be seen at honeywell website

I am also looking at an article entitled
Compressor overheating Todays's Most Serious Field Problem from Aug 1981 RSC. Without reprinting it here, the author explains the impact of a LL to suction heat exchanger. Adding such a HE to a system with insulated suction line contributes to compressor failures by elevating suction return temperatures.
There is a direct correlation between the discharge temperature and the return gas temperature. The author recommends installation of a desuperheating valve within 6 feet of the compressor.

I am looking at this as a problem of refrigerants gone bad to worse.

If this is a copeland semi-hermetic, I would add cooling water coil around compressor body, or change to different refrigerant. My research is showing that the latest and greatest drop in refrigerant to replace R12, compatible with all oils is RS24. The only issue with it is low temp applications require PE oil, but you dont have to be anal about it. The PT chart for it is almost identical to R12 and minimal glide.

I am going to use this refrigerant on all my changeovers. I would suggest trying it here.