Hot Compressor

[jstch00tme]

quick question, new compressor, delfield reach-in, r-22, good pressures, box temp 38-42, compressor extreeeeeemly hot to touch, drawing 7.2 amps eventualy trips external overload. any ideas?

[nike123]

quick question, new compressor, delfield reach-in, r-22, good pressures, box temp 38-42, compressor extreeeeeemly hot to touch, drawing 7.2 amps eventualy trips external overload. any ideas?

Quick answer, new compressor old problem, more data nedded!;)

[paul_h]

please elaborate on what these "good pressures" were.
Also suct and dicharge temps, also what is the labelled FLA as I'm used to 220v compressor current draws.
What type of compressor or model ie scroll, recip? Is it psc, or are there relays for a start winding to drop out? Is the overload rated to cut out a 7A, or is it cutting out for some other reason?
Any info on whether the system is TX or capillary, the condenser condition for cleanliness and airflow, and the subcooling.
Any percieved problems such as location, ambient etc?

edit: how long does it run before cutting out?
My best guesses are something wrong with heat rejection (condenser) or it's a recip that is supposed to drop the start winding out but the relay/cap isn't working

[The Viking]

So,
As Nike pointed out, we do need more info.
As a minimum:
-Suction pressure
-Superheat
-Discharge pressure
-Subcooling
-Discharge temperature

Good hunting.

[Electrocoolman]

Capilliary system?

Changed drier with compressor? ....Partial obstruction in capilliary?

Non condensables in system?

Overcharge of refrigerant causing loss of condenser effective area?

[Kh1971]

is it new installation or your are changing only the compressor?

[jstch00tme]

hmmm, lets c what i can remember, 60 over 125, txv, 30 oz charge, new compressor and dryer, clean evap, good fan, runs great out of cubby hole, slide it back in and she goes off in about 5 min.

[jstch00tme]

correction, compressor still extreemly hot out of box, but stays running, and mabey more like 150-75 on high side.

[powell]

hmmm, lets c what i can remember, 60 over 125, txv, 30 oz charge, new compressor and dryer, clean evap, good fan, runs great out of cubby hole, slide it back in and she goes off in about 5 min.
125 HP is low, was this a typing error?

Those Delfield units have tight little condensing unit compartments. I'd examine the coiled up suction/liquid line set. It could be kinking when you slide the unit in.

[jstch00tme]

powell, yes first thing i checked ( had similar problem before) here is a little more backround, arrived onsite with compressor not running, found wire from overload disk to common completely fried, replaced starting equipment with 3-in one, unit ran for about 15 min. then tripped overload, pulling about 8.3 amps at time, FLA for that compressor was 7.1 unit is 11 years old, asumed bad windings/breaings in old compressor, replaced compressor and dryer, and now new compressor exibits same symtoms (almost) although i do not have the spec sheet for the new compressor it is running close to the old FLA of 7.1, but unbelievably HOT to touch!

[nike123]

What is TD of condenser, or what is air in and off temp of condenser. Could you be more precise with HP reading? What is superheat and subcooling?

[Electrocoolman]

Has this unit always been on R22. Given age it might have originally been on R12?

Sounds as though there is a lot of air recirculation when unit fitted into compartment.

Condenser might look clean on the surface but have you tried shining a torch through it and blowing it through with Nitrogen/Compressed Air

[jstch00tme]

ok, complete specs.... box temp 39, suc= 48psi Dis= 175psi suc temp 6" from compressor= 37-56 (changing as tvx's open/close) Keep in mind there are 2 expansion valves! dis temp 4" from comp.=135 temp 4" out of cond.=114 amp draw.= 7.4 charge= 30oz r-22 (no conversion, r-22 from factory)

[Gary]

Check the voltage at the compressor terminals with the compressor running.

[The Viking]

despite what almost everyone of these self proclaimed experts will tell you, NO ONE knows everything there is to know, no matter how many years they have been at this, for example, read my post "hot compressor" despite all the info I have givin, no one seems to know what wrong!!! Some things just defy logic!!!

Just00you,

Nobody here, to the best of my knowledge, has called himself an expert.
We are all friendly engineers that are using this forum as a means of exchanging experience, thus learning from each other.

I'm sorry but YOU got a customer with a problem that YOU are unable to fix, YOU are the guy on site with YOUR tools on the machine and when YOU get stuck we will all (well most of us anyway) try to give you friendly advice but that's all we can do, advice.
Ultimately it is your hands that have to repair that machine, we can not see it, we can not hear it running, we can not take a different measurement or try to adjust things.

Say that you, the guy on site have an 80% chance of finding the fault, then not even the most experienced guys giving you advice over an internet forum will have more than ~60% chance of nailing it.
All we are able to do is giving YOU food for thought.

The best you can do is to take as much data as possible of the running conditions of your plant, post it here (BTW, we are used to different guys posting in different units of measure and most of us will convert it to whatever units we are most familiar with. The only thing I would say is to indicate what units you used for example 1C for one degree Celsius or 100psi for one hundred pounds per square inch).
After you posted all data, sit back and watch the replies, take it all onboard and when you go back to site YOU are, hopefully, better armed to deal with the problems.
(And please remember to tell us what happened after you been back to site)
This is a great place for gaining more experience by tapping in to fellow engineers experiences BUT there is no way a forum will ever be able to replace "hands on" testing.

Oh, but the way.
To me, with my limited experience, an expansion valve hunting of 19 F (I assume it's F) sounds excessive, even if there are multiple valves. (is the suction pressure also unstable?)
And a discharge temp of 135F (again, I do assume we are talking F), isn't really enough to give a hot compressor...
As others has suggested, have you checked all wiring? (including that the start and run windings are feed the right way around, I've seen it in the past when compressors that are using the start winding to run has over heated.)

[jstch00tme]

yeah, sorry about that post on the other page, what i ment to say was although he might have seen 1 or 2 people nail a problem quickly the fact is that even the best will get stumped at some point. and not to listen to anyone who tells him otherwise. as for the suc press. no it does not change with the suc temp change. and the voltage is 120v

[philfridge]

Sounds like you wired it up wrong ie its running on start windings maybe

[nike123]

ok, complete specs.... box temp 39, suc= 48psi Dis= 175psi suc temp 6" from compressor= 37-56 (changing as tvx's open/close) Keep in mind there are 2 expansion valves! dis temp 4" from comp.=135 temp 4" out of cond.=114 amp draw.= 7.4 charge= 30oz r-22 (no conversion, r-22 from factory)

You didn't answered what is condenser TD or what is temperature of air entering in condenser.

[jstch00tme]

ambient air is apx. 70 as for wireing it wrong, notta chance, only two wires guys, one marked nutural one marked line, put the black on the line terminal and the white on the nutural terminal.

[The Viking]

Silly question,

But what make/model compressor is it we are talking about?

[nike123]

ambient air is apx. 70 as for wireing it wrong, notta chance, only two wires guys, one marked nutural one marked line, put the black on the line terminal and the white on the nutural terminal.

Let see your data if I correctly converted that units. You have 15°F (7K) TD at evaporator and if that evaporator is forced air that is good and if it is static evaporator, that is small TD.

You have 25°F (14K) TD at condenser which is good. Then you said that you have 114°F at condenser outlet which mean that you don't have any subcooling.

Then you also have big hunting one or both of TEV valves. This is 11K of change.
Taking in consideration errors in measurements we could say that sometimes you don't have superheat at all, and sometimes you have 10K of superheat.

The system is short of gas or you have some restriction at TEV valves or the TEV valves are not adjusted or malfunctioning.
What is position of bulbs and are they isolated and out of influence of hot air and surrounding hot pipes.
Do you have any receiver and sight glass?
If system is short of gas, then that is reason why compressor overheat because it is cooled with gas and if it is superheated that much.

What is total superheat?

[Gary]

...and the voltage is 120v

...measured at the compressor terminals with the compressor running?

[Gary]

With a discharge temperature of 135F/58C, it's highly doubtful that the compressor is overheating. The temperature in compressor paradise is 140-160F/60-71C. This may feel hot to us humans, but to a compressor it feels just right. And rotary compressors run even hotter, because the crankcase is on the high side.

This looks very much like an electrical problem. To be more specific: When the old compressor fried, it drew heavy current flow. This heavy current went through a switching device (contactor, relay, thermostat, pressure control, etc.) to get to the compressor... and it fried the contacts in that switching device.

[nike123]

When the old compressor fried, it drew heavy current flow. This heavy current went through a switching device (contactor, relay, thermostat, pressure control, etc.) to get to the compressor... and it fried the contacts in that switching device.

Gary, read this carefuly:

powell, yes first thing i checked ( had similar problem before) here is a little more backround, arrived onsite with compressor not running, found wire from overload disk to common completely fried, replaced starting equipment with 3-in one, unit ran for about 15 min. then tripped overload, pulling about 8.3 amps at time, FLA for that compressor was 7.1 unit is 11 years old, asumed bad windings/breaings in old compressor, replaced compressor and dryer, and now new compressor exibits same symtoms (almost) although i do not have the spec sheet for the new compressor it is running close to the old FLA of 7.1, but unbelievably HOT to touc
There is nothing wrong with old compressor, now new "starting equipement" or new compressor. They both behave same.

Then:



Dis= 175psi dis temp 4" from comp.=135 temp 4" out of cond.=114

suc temp 6" from compressor= 37-56 (changing as tvx's open/close) Keep in mind there are 2 expansion valves!

[Gary]

Gary, read this carefuly:

There is nothing wrong with old compressor, now new "starting equipement" or new compressor. They both behave same.

Then:

We can't see it from here, we can only go by the description. I see nothing on the refrigerant side that would justify the high amperage... and "unbelievably hot" doesn't tell me anything (that's what thermometers are for).

The only solid clue we have is the fried wire on the overload. If the current is heavy enough to fry that wire, then it can fry the thermostat contacts (or whatever else is in that circuit)... and burnt contacts can drop the voltage/raise the amperage.

[The MG Pony]

I'm with gary this is sounding like an electrical issue.

Have you taken a full set of measurements of the unit while running? Voltage on run winding? on start winding?

What are the contact resistances when closed? Only takes 4 or so ohms to wreak havoc.

[paul_h]

We can't see it from here, we can only go by the description. I see nothing on the refrigerant side that would justify the high amperage... and "unbelievably hot" doesn't tell me anything (that's what thermometers are for).

The only solid clue we have is the fried wire on the overload. If the current is heavy enough to fry that wire, then it can fry the thermostat contacts (or whatever else is in that circuit)... and burnt contacts can drop the voltage/raise the amperage.
My opinion too, a blockage or compressor being hot due to TX or shortage of refrigerant, would give low amps even if the compressor was hot.
My only reservation is because they have a lower voltage in the U.S. , is 7A normal or not?
A melted overload wire means electrical fault to me, especially since the compressor was changed, which to me means a new refrigerant charge and all the refrig temps and pressures verified correct (and they do seem OK, at least not out enough to fry an overload) High head pressure cause overloads to trip, which is not a symptom shown here. (or long periods of running, but that's not the impression I get?)

But we still have not got the compressor make/model or even how long it runs for before the trip. And apparently this is a compressor than runs straight off the mains, just two wires, active and neutral, no control circuit or start winding/relay.

[nike123]

We can't see it from here, we can only go by the description. I see nothing on the refrigerant side that would justify the high amperage... and "unbelievably hot" doesn't tell me anything (that's what thermometers are for).

Agree!


The only solid clue we have is the fried wire on the overload. If the current is heavy enough to fry that wire, then it can fry the thermostat contacts (or whatever else is in that circuit)... and burnt contacts can drop the voltage/raise the amperage.
From my experience as electrician (23 years), fried wire is when long enough short circuit currents is been the case.
On the other hand, melted or carbonized wire insulation is almost always the case when high (or normal) current flow thru loosed connections.

As you said we could go only by description. We don't know what he meant by "completely fried wire". Just insulation, or wire and insulation.

He said that he changed compressor and start group.
That should eliminate faulty compressor or elements in start group if they are correctly chosen, fitted and wired. On the other hand, he did not said what is voltage at compressor terminals and you are right when asking him to examine that to confirm right power supply to compressor terminals.

Also, he said that current is 7,2 A or 7,4 A now, what is close to FLA. If we take in consideration that measuring instruments have error than that could be good current or bad current depending on error.
I think that with this currents it will take some time to overheat if everything else is OK.

I just wanted to point that also subcooling is non existent, and that (lack of refrigerant) also could be cause for compressors overheating (if that is case at all) because there is not enough refrigerant to cool down engine.

[powell]

Silly question,

But what make/model compressor is it we are talking about?
Excellant question. I have a sneaky suspicion....................:rolleyes:

[Larry2]

runs great out of cubby hole, slide it back in and she goes off in about 5 min.


Has someone been there before you and replaced the condensor fan motor and installed the fan blade upside down (backwards)? It would move air, just not enough.

[philfridge]

This is a old problem which fitting a new compressor did not solve . Ok so you mis diagnosed the original fault , you are not alone in this but i think you need to check the compressor electrics you have wired up something incorrect . Did you fit new electrics to this new compressor ?? As i stated before your compressor may be just running on start windings and overheating .

[jstch00tme]

thanks for all your help on this guys, turns out we had a faulty expansion valve killing our superheat 90% of the time, a new valve fixed our problem!

[The MG Pony]

Ah good for ya mate! and verry good on ya for updating us! Thanks.

I hate it when they just never return!