Bad Valves?

[newgage]

rayr


"Why would you want to change a TXV just because ""it had been there for some time""?? That is ludicrous.


Point taken.

Before I replace the compressor I want to eliminate the possible causes.

Liquid floodback caused by defective txv.

Liquid floodback caused by incorrect txv setup

System was overloaded because rooftop remote condensor was very dirty AND had three out of four sides blocked with plywood AND only had two out of three fans running. Most likely cause my guess.

Oil return problems? Compressor application? I still have to look into the compressor compatibility. K-fridge pointed out the compressor being a medium temp compressor. I checked in the supplier catologue and found a medium temp compressor that was very similar in model number , however it differed slightly.
The condensing unit (Hill model:RJOWC5 S/N:C-9450-1 ) had a coplemetic Model : LAL 1 0310 TAC.
The supplier catologe had LAL0310TAC.

I merely thought of the valves as an after thought. While the system is open extra cost is not that much and may or may not give me some comfort that I won't have to go back later to find a dead compressor caused by the TXV. I realize though that it may not be a popular choice.

Found out the gas was R408a.

[Edited by newgage on 05-25-2006 at 12:14 AM]

[rayr]

Your line of reasoning is to be commended, in the fact that you are looking as to "Why". the compressor failed.

I would Change the compressor then check system operation.
Check the superheat at the compressor when the system is running and also when set point is reached. 99% of expansion valve failures have the X valves in the closed or partally closed position. It may indeed have to low a superheat setting but that can in all probability be adjusted.

If it were my job, I would definetly check compatability of compressor, go with 404-a, (POE of course) and do a couple of oil changes. And monitor the system. Of course clean cond coil, and evap. coil, proper air flow all should go with out having to say it

[newgage]

Makes sense in regards to how a TXV will fail.

Just curious why you would go 404a. That is my peference since
it is something I carry and makes for easier service.

However, receiver is full of R408a. I am leaning towards letting it run on present charge and checking all the vitals after its running. Any thoughts?

[newgage]

Also, I find it odd that this compressor has supposedly been in place for years and apparently it has been has been cooling a freezer on a medium temp compressor.

[k-fridge]

Originally posted by newgage
Also, I find it odd that this compressor has supposedly been in place for years and apparently it has been has been cooling a freezer on a medium temp compressor.

I've seen it many times, compressors have some "wiggle room" built into them that will often allow them to survive under less than ideal conditions. That compressor is not only a med temp it's R-12 rated.

I think the problem is clear, it's both a mis-application and it's running on R-408 which those compressors had a lube problem with before they added the oil pumps. Replace the compressor with the right one containg an oil pump, be sure everything is in parameters, and you should be fine. I would use POE in it, it's good for the R-408 or the R-404 if you decide to change. If you go with 404 though I'd let it run a day and do another oil change.

As for changing the TXV, I don't think it's a bad idea. Though it may not be neccesary, I often do this when I've had multiple failures or lost a compressor to trama just as a preventative measure. On freezers I like to use MOP valves, the low temp Copelamatics are a bit sensitive to high back pressure at start up. Sometimes the cost of replacing the valve can be less than the time it takes to dial in an old one.

[icemeister]

I don't believe that the LAL-0310 is a misapplication at all. Copeland lists that compressor for both R12 and R502 in their performance calculator.

Also, in browsing through a dusty old Hussmann applications manual I found that back when R12 and R502 were the flavors of choice, they used the LAL-0310 in their conventional condensing unit lineup for R502 LT such as the HICA-0325RL right in between the slightly smaller capacity HICA-0315RL with an LAH-0310 and the larger LAC-0310 in the HICA-0335 unit.

I agree that replacing the TXV is probably a good idea if only for added insurance. The condenser situation catches my eye though. This compressor is on a three fan condenser? Is it a remote multi-circuited condenser? What kind of head pressure control do we have?

With three sides blocked off it hints to me that there may have been cold weather head pressure control problems involved and operating at extemely low head could in fact have caused such a breakup due to loss of TEV control and subsequent severe floodback and/or slugging.

[rayr]

He states that he is not sure what refrigerant is in it. And apparently the system has been Hacked to some degree, (one fan motor missing). Why take a chance, gonna be married to the job anyway. 404-a is a much better choice of refrigerants. Very forgiving in the event of leaks. Most all of us have had very good sucess with it for med temp and low temp.

[k-fridge]

I don't believe that the LAL-0310 is a misapplication at all. Copeland lists that compressor for both R12 and R502 in their performance calculator.

I was going by the chart on the A-1 compressor web site, it lists a LAL afor med temp 12 only. Some years ago I bought one from them, I ordered a LAC and they gave me a LAL by accident and since it was Christmas eve with a freezer down I installed it. The apllication guy at A-1 (Orr Refrigeration at the time) called me a couple of days later when they caught the error and had me change it because he said he was afraid it wouldn't hold up.

http://www.orrbilt.com/cope1.htm

[smilies]

Like Ice said, comps were rated for different refrigerants and btu's. It's all about how much that cylinder fills with each stroke

[k-fridge]

Originally posted by smilies
Like Ice said, comps were rated for different refrigerants and btu's. It's all about how much that cylinder fills with each stroke

And how much current the motor draws while it's doing it, and whether or not that amp draw is within the parameters listed on the data plate.

[newgage]

Got a price on new compressor today.

No rebuilds around here that I know of and the A-1 site kept freezing up on me.

Local supplier says Compressor is low temp with R408a. Am trying to find specs on it. I did not ask about a comparable compressor with a oil pump as was mentioned earlier.

This job I was offered to do on my own outside of work and have been advised by higher powers than me that I could be taking a big risk due to the fact that I dont have all the history and what if compressor died again. Is there acid in the oil? Is oil lodged in evaporator? Is it piped right? Are there defrost problems? Customer was too cheap to fix condesor fans on roof. Will customer pay for big job that it has become and can I expect a n unhappy marriage to the equipment .

I personally think it was due to the obviuos. Very little heat rejection = high head = high compression ratio

There are two other semihermetics tied into the same condensing unit. Multi circuit? Three seperate Condensors in one? Fan cycling is on pressure switch.

If I went to 404a would POE oil cause problems from scrubbing the lines and plugging TXV screen? Should high pressure nitrogen be ran through all lines in order to remove oil residue?

[4x4freak]

This job I was offered to do on my own outside of work and have been advised by higher powers than me that I could be taking a big risk due to the fact that I dont have all the history and what if compressor died again.

Not to mention the fact that if you get caught doing side jobs you could get fired.

[newgage]

Not a concern. My tools. My materials. Different market since we are an hvac company and do very little refrigeration. Other guys in company have things going on once in a while too. I dont do this often but I see it as gaining valuable experience. A well rounded tech make a good employee. I will do and try anything that improves my knowledge and skills. As long as I feel confident I can do a quality job. Boss wants me to make money for him and I do. As for training we are for the most part left to do that on our own.