Techuseh compressor

[mfry]

A year and a half ago I replaced a compressor that had low compression. And today the new compressor has lost compression also. For a walk in cooler.
Tecumseh model AHA-4518AXD with hot shot as the refrigerant.

My question is, what would cause lost compression in a compressor? Compressor starts great, but the lost compression is baffling me...

I really hate to put in another R12 compressor at this time, but the customer purchased a 5 year warranty. So, swapping to a new compressor with a newer refrigerant, is not an option.

Whats the root of this evil?

Thanks in advance...

[k-fridge]

What is superheat?
What is discharge temp?
What are your pressure control cut ins/outs?
Pressures?
Pump down system?


We need some info to help

[jpsmith1cm]

Well, you probably lost valves. This would account for the 'lost compression'.

What is the running superheat? Does the condenser get regular maintenance? Did the coil ice up? Evap fans get turned off?

Lots of options, and these don't include low ambient options like a bad crankcase heater.

[pageyjim]

A year and a half ago I replaced a compressor that had low compression. And today the new compressor has lost compression also. For a walk in cooler.
Tecumseh model AHA-4518AXD with hot shot as the refrigerant.

My question is, what would cause lost compression in a compressor? Compressor starts great, but the lost compression is baffling me...

I really hate to put in another R12 compressor at this time, but the customer purchased a 5 year warranty. So, swapping to a new compressor with a newer refrigerant, is not an option.

Whats the root of this evil?

Thanks in advance...

Could be slugging the compressor, check s/h after change, check cch, acid, loss of oil etc...

[mfry]

This compressor had no signs of flood back when I installed it. The temperature is solely controlled by the P/controller...15# cut out 38# cut in. Installed in southern California and no low ambient temps here. I don't know the super heat or discharge temps yet.

The one thing I suspect is, this restaurant has zero maintenance, with a very old and very dirty evaporator come to think of it. I will examine the evap tomorrow when I install the warrantied comp. I bet its dirty as hell.

All the bells and whistles I could install to prevent further failures, the customer would refuse. I'll just state the recommendations on the invoice and leave it be.
A lot of restaurants are hurting right now and this restaurant is one of them...

[jim147]

Do they make a bells and whistles kit for lack of maintenance that I don't know about?

Was the evaporator very dirty a year and a half ago?

jim

[PortaChill]

MRFY,

You answered your question in your last post(dirty evap).That would cause your slugging problem...

[k-fridge]

This compressor had no signs of flood back when I installed it. The temperature is solely controlled by the P/controller...15# cut out 38# cut in. Installed in southern California and no low ambient temps here. I don't know the super heat or discharge temps yet.

The one thing I suspect is, this restaurant has zero maintenance, with a very old and very dirty evaporator come to think of it. I will examine the evap tomorrow when I install the warrantied comp. I bet its dirty as hell.

All the bells and whistles I could install to prevent further failures, the customer would refuse. I'll just state the recommendations on the invoice and leave it be.
A lot of restaurants are hurting right now and this restaurant is one of them...

You need to check the actual superheat. Typically on a W/I cooler; 8* at the coil and between 20 and 30* at the compressor. Also come back with some pressures and we might can help you more. Does the unit have a high pressure cut-out on it? If the evap is that dirty, the condenser probably is too. That guy could have been sitting there running head pressure that was out of sight.

[mfry]

Installed the new compressor today. The evaporator was clean and clear and 25 deg superheat at the comp. Everything looked good. Still wondering why the comp lost compression...

At this point, I am going to side on part malfunction in the compressor...

[rayr]

What is superheat?
What is discharge temp?
What are your pressure control cut ins/outs?
Pressures?
Pump down system?


You sure do ask a lot of questions.:yes::yes:

[k-fridge]

You sure do ask a lot of questions.:yes::yes:

My wife tells me the same thing. :LOL:

[captain123]

It's too late now to check temps & pressures, but low compression "usually" is caused by bad valves that have been exposed to liquid refrigerant. Also called compressor slugging, caused by low air flow over the evap coil (dirty coil & fan blade or a bad fan motor) or an over charged system, or an evap coil that ices up and stays that way for too long a time.

[scac1971]

I had a problem like that on a 40 ton split system. System was new ran perfect for 3 years then it started eating valves. Changed them twice within 2 years.

Found that they had updated there fire alarm system. When the church would burn its incense for special services it would trip the alarm. The fire alarm expert had wired the blower to shut off when alarm went off but the condensor would keep running. He said didnt think it would matter. I fixed it with him standing there so he would know next time.

[K_Neil]

Cutting blade in the sidegrinder above the seam. Drain as much oil as possible. Depends how bad u really have to know. Happened here too. Plastic wrap on bowls of food are hard on valves too.

[mikep]

I believe your valve problem is due to the Hot Shot refrigerant. It has been our experience that this refrigerant does not carry the oil back to the compressor very well. You are starving the top end of lubrication. Ever since this refrigerant hit the streets as an R-12 sub, we have seen a lot of lubrication related failures on the conversions.

[jim147]

I believe your valve problem is due to the Hot Shot refrigerant. It has been our experience that this refrigerant does not carry the oil back to the compressor very well. You are starving the top end of lubrication. Ever since this refrigerant hit the streets as an R-12 sub, we have seen a lot of lubrication related failures on the conversions.


Can you describe the units you've seen having problems with Hotshot?

I used a bunch of it before the 134 retrofit compressors started coming out. I can't remember replacing any compressors after using Hotshot. (Many of these repairs were evap replacements.)

jim