Compressor Doesn't Start Reliably (tech claims theormstat is problem???)

[secstate]

Hi folks I need some input from the forum. This is my first posting though I have lurked here a while.

Late last week I noticed that my downstairs AC (technical details provided a the end of this post) was putting out air at the ambient inside air temapture. I went outside and instantly noticed that while the blower motor in the condesor was running the compressor was not (it is a reciprocating compressor that makes an obvious though not loud noise when running). A also felt the suction line and it was the ambient outside tempature. So the inside and outside blower motors were on but the compresser was not. I sat there and "watched" it for a while and all of a sudden the compressor starts to groan and starts up but sounds like it is struggling for about 10-15 seconds. Further experimentation shows that the compressor will always start if the time between the last time it was run and the next time it is started is 10 or more minutes. Any less time than that and the compressor will start around 65-75% of the time (often making some odd protest noises). When the compressor doesn't start the outside and inside blower motors run and the compressor does eventually start with some protest about 5-10 mins. later. Once on the compressor stays on until the thermostat shuts everything off. My Chronotherm III thermostat has a 5-6 minute delay built in but that does not appear to be sufficient.

So I call the contractor I have used before to replace the upstairs HVAC equipement (and been happy with) and the earliest they could come out was today (Tuesday). Which is fine since I know they are busy. I turn off the downstairs AC since leaving a sometimes stalled compressor presumably powered seems like a bad idea to me.

So the tech comes out today and unfortunately I am out of town so my wife speaks with him. He says the compressor has a cracked valve and will "eventually" need to replaced (this was indicated by the refrigerent pressures being off as the low side was high and the high side was low) but that the intermittent compressor operation is due to our Thermostat and that is what needs to be replaced. He told my wife that it was okay to operate the unit and that there was no need to replace the compressor until it died completely. It does cool the house fine, though I did notice that as a heat pump it was less effective this winter than before (it seemed to run much more often and for great lengths of time between cycles).

So my questions are:

One I don't believe that the theormostat controls the compressor directly so I do not see how that can be the main problem. It is a high quality Chronotherm Honeywell installed about two years ago. If the thermostat was the problem, wouldn't it impact the inside and outside blower motors as well?

Two worrying about my theormstat when I have a "sick" compressor seems to me like a mechanic trying to sell me new tires for a car that has a dying engine :-).

Three I don't believe it is safe for my wife to run the AC with a compressor that is may burn itself out if it doesn't start.

Four the tech did mention that there is generally a 10 year warranty on compressor from Trane and this unit is currently 8 years old. How do I go about checking on this as the unit was installed prior to my purchase of the home and I don't have the paperwork.


A bit about my equipment, the condesor unit is Trane SEER 10 heat pump (I think XL1000 but I am out of town so cannot check). It was manufactured in the 1st half of 1997 and appears to have been installed on 7/17/1997 due to this date being scrawled on the back of it. The inside unit is a Trane gas furance circa 1986, original to the house. I assume the evaporator is original to that time but I am not sure. Based on the upstairs unit, the orginal heat pump was pobably an old GE from 1986. The thermostat is a contractor grade Chornotherm III (NOT the cheapened Home Depot version) that was installed about two years ago.

Sorry for the length of my post and I appreciate your advice.

Miles

[dave_slo]

You could have a number of problems, and the compressor could be going bad. But as far as the thermostat causeing the compressor not to start properly, as long as the delay is working, I don't think so.

Sounds like you need to find a different tech.

[hvacfella]

It appears that your systems pressures are not equalizing fast enough before the next cooling cycle is initiated ; this makes the compressor start under an elevated pressure instead of an equalized pressure. A properly sized Compressor Hard Start Kit would be the remedy for this scenario. Trane will offer one as an Option for your particular model unit -- i would obtain another Service Tech to give you a second analysis as changing out the thermostat is not the answer for the compressor laboring trying to start. All the thermostat does is send a signal to the A/C's contactor and after that, the unit and its internals take over.

[tinknocker service tech]

first if the compressor isnt starting up it may need a hard start kit. since the valves are going bad as stated rather then waiting for it to just burn out and cause more problems and it is under warrenti have them replace it now.
worn valves will cause you to spend more to cool your house and as it gets hotter out the more chance it will give out and not pump at all. if it burns out there is a strong chance accid will get into the system and more problems. get another opinum and replace it

[secstate]

Thanks guys! I was coming to that conclusion but I wanted to make sure I wasn't losing my mind. I'll call another tech. I am assuming I should leave the AC off till we get it looked at? At least if I don't want to damage my compressor any further?

Miles

[secstate]

Originally posted by tinknocker service tech

worn valves will cause you to spend more to cool your house and as it gets hotter out the more chance it will give out and not pump at all. if it burns out there is a strong chance accid will get into the system and more problems. get another opinum and replace it

That was my opinion when I heard it was likely bad but the tech appearhently didn't think it was worth doing ???. I am a strong believer in fixing problems earlier rather than later. Pay some now or more later :-). Even if I have to pay for it myself I am not going to leave that compressor there if a second tech tells me it is dying.

[hvacfella]

Miles, Yes...if at all possible., leave the A/C unit off whenever you believe it to be malfunctioning. If you absolutely need to run it, then, make very certain the Compressor inside starts up on its first attempt ... which may require you using it at far greater intervals ; and, if it isnt cooling after its been on for 5 minutes, then, its time to keep it off till a qualified Service Tech looks at it. Secure a qualified 'Trane' Service Tech because they undergo specific training on Trane equipment and will typically diagnose it right the first time.

[mark beiser]

The XE1000 heat pumps built in 1997 had a 5 year compressor warranty.

The difficulty starting could be due to a number of problems, none of wich have anything to do with the thermostat in your case.
It could be something as simple as a weak run capacitor. If the capacitor is weak enough, in addition to the compressor having difficulty starting, it could even cause the system to run with higher than normal suction pressure and lower than normal head pressure.
There needs to be more diagnostic work done before condemning a compressor than just looking at the pressures.

You need to get a qualified service tech out to look at it. It doesn't sound like the one you got really knew what he was doing...

If your compressor does have bad valves, they didn't just fail on thier own, something caused it. The cause needs to be found and corrected.

[ultratec]

Just going to through my 2 cents in. Yes, you need another service tech. You may have like was stated a few times, a few problems. The bad valve diagnosis on the compressor by a un qualified tech, could be a bad (leaking) reversing valve It may be bypassing giving you the high back and low head, causing the compressor to run hot. No sense in telling you how to check this, he should know! If the compressor is to be changed, replace the reversing valve, unless a qualified person like most on this forum, can say its the compressor, I would replace the valve also, period.

[Diceman]

Is that post available in a Cliff's Note?

[secstate]

Hee hee, sorry about that :-). Cliff Notes version:

1. Compressor doesn't always start with rest of system.
2. Called tech.
3. Tech comes, spends much time on cell with unknown party presumably asking for assistance in diagnosis or perhaps setting up date with girlfriend.
4. Diagnosis is "weak compressor but starting problem caused by thermostat."
5. Suggested action from tech ignore compressor replace thermostat???

:-)

P.S. Thanks to all for all the advice. I am going to call somebody tomorrow who sells/repairs Tranes.

[tinknocker service tech]

Originally posted by secstate
Hee hee, sorry about that :-). Cliff Notes version:

1. Compressor doesn't always start with rest of system.
2. Called tech.
3. Tech comes, spends much time on cell with unknown party presumably asking for assistance in diagnosis or perhaps setting up date with girlfriend.
4. Diagnosis is "weak compressor but starting problem caused by thermostat."
5. Suggested action from tech ignore compressor replace thermostat???

:-)

P.S. Thanks to all for all the advice. I am going to call somebody tomorrow who sells/repairs Tranes.
this says it all call a real tech and find out what is truely wrong

[Black Adder]

My two cents worth (unfortunatly Canadian Cents so probably only 1.5 cents worth). No way a thermostat will cause the indoor blower, condensor fan but not the compressor to start. Sounds like your tech doesn't know his ass from a hole in the ground. Check the capacitor, check the reversing valve is opening fully, check for start up amps, although if it is not blowing the breaker it is obviously not pulling more amps on start up than allowed. I have a strong suspicion that the start cap is not working correctly. Before changing out the compressor try changing the capacitor. It is a much cheaper fix than changing out the unit.

[secstate]

I appreciate the help I have gotten so far. I had a Trane specailist come out today. He checked reserving valve and capacitor and came to the conclusion that the compressor is bad. Which is good (well except of the news of course). However when my wife asked him why it had gone bad in 7 years he said "who knows they sometimes just go bad for no reason." Maybe I have been hanging around here too much but I recall a quote from here that compressors "don't die they are killed." The tech said to replace the compressor but I am a little concerned to throw good money after bad if the next one will have such a short life.

I am in the mid-atlantic region, Richmond, VA, and I think a compressor should last more than 7 years here unless I am unlucky.

Should I just replace it or get another opinion?

[docholiday]

could be a number of things, when they replace the compressor have them give the unit a once over. You might consider a new outdoor unit if the current models will match your indoor unit, (all new warranty) other wise you have the remaining 2.5 years left. (the new compressor doesnt get a 10 year warranty).

[smokin68]

First off, it shouldn't take a non-txv 10 minutes to equalize pressure throughout the system. Then you have a 1997 condenser added to a 1986 evaporator. Hope you get your warranty.It shouldn't have anything to do with the t-stat,unless the t-stat is dropping out it's contacts in the middle of a call for cooling, which I doubt. I wish you could post all the pertinent information....subcooling,superheat,delta t,ampdraw,etc. but i realize the tech has that info. With that 1986 furnace, I'd look for a new complete system before band-aiding this one. Have an acid test done if you choose to replace the compressor...inexpensive. JMO

[hvacfella]

'I appreciate the help I have gotten so far. I had a Trane specailist come out today. He checked reserving valve and capacitor and came to the conclusion that the compressor is bad. Which is good (well except of the news of course). However when my wife asked him why it had gone bad in 7 years he said "who knows they sometimes just go bad for no reason." Maybe I have been hanging around here too much but I recall a quote from here that compressors "don't die they are killed." The tech said to replace the compressor but I am a little concerned to throw good money after bad if the next one will have such a short life.
I am in the mid-atlantic region, Richmond, VA, and I think a compressor should last more than 7 years here unless I am unlucky.
Should I just replace it or get another opinion?
'

ME: If you have a Heat Pump System, the compressor works year round so you cant expect it to last as long as a regular A/C unit compressor would. Here in Illinois, a typical Heat Pump compressor is good for roughly 8-10 years ; less if it hasnt gotton regular maintenance. If i were you, id consider a replacement Outdoor Section with an extended warranty this time around. Keep y our Indoor Section and line set BUT have them serviced and flushed out well before placing the new Outdoor Section into operation. Lastly, have it serviced EVERY year by a competent Tech in both modes of operation (heat and cool).

[secstate]

Originally posted by smokin68
First off, it shouldn't take a non-txv 10 minutes to equalize pressure throughout the system. Then you have a 1997 condenser added to a 1986 evaporator. Hope you get your warranty. <part of quote snipped> I'd look for a new complete system before band-aiding this one. Have an acid test done if you choose to replace the compressor...inexpensive. JMO

Yeah I think the one part old one part newer is my problem (or part at least). NIETHER Tech came into the house to look at the evaporator which amazes me (I believe that also means they could not have done the superheat subcooling correct?). I don't want to band aid the system but there is also a high liklihood that I may move in the next year so I don't want to spend 4k on an all new system only to move in a 9 months. I don't for one second believe I will get a penny more for my house because of am all new HVAC system.

The second tech did write on the reciept 75 (PSI?) suction 185 head. Outdoor tempeture was about 85 degrees and inside according to my wife was 75 degrees. No mention of amperage draw or superheat or subcooling.

[secstate]

Originally posted by hvacfella

ME: If you have a Heat Pump System, the compressor works year round so you cant expect it to last as long as a regular A/C unit compressor would. Here in Illinois, a typical Heat Pump compressor is good for roughly 8-10 years ; less if it hasnt gotton regular maintenance. If i were you, id consider a replacement Outdoor Section with an extended warranty this time around. Keep y our Indoor Section and line set BUT have them serviced and flushed out well before placing the new Outdoor Section into operation. Lastly, have it serviced EVERY year by a competent Tech in both modes of operation (heat and cool).

I agree the heatpump compressor does work year round but the secondary heat is gas and below 40 degrees or so it cuts over to the gas furnace so it doesn't see quite the use of a heatpump only system. I don't know about the maintenance before my ownership which was 2 years ago. I have had the system inspected to the tune of 90-150 dollars a year since I took over.

[pecmsg]

Your H P is still cheeper to operate then gas above 30 Deg. Replace the condencing unit and stay H P. It's a selling point for the house.

[secstate]

I agree for those sophisticated enough to know the heatpump gas combination is great. However those who understand are few and far between. I have tried to explain the advantages to a number of technically savy people I work with and they have no understanding of why it is good. If I were going to spend the next ten years in this house for sure I would replace the whole system tomorrow with a new high efficiency gas furnace AND heat pump. But there is a 50/50 chance I will change jobs next summer and move. The people like me and you who understand these things and are willing to pay for them are few and far between.

[tinknocker service tech]

75/185 at 85 degrees outside and cooling fine
i must be missing something what did he say was wrong with the compressor and did he install a hard start kit

[Shophound]

I'm thinking if this is the typical Trane heat pump with spine fin coils, they haven't been cleaned since 1997, are now filthy dirty, and this unit's been running a high head pressure for some time. So, either this has stressed the compressor valves, or stressed the run capacitor, or weakened the internal relief so it's bypassing at a lower pressure, or...

IOW, I'm with Beiser. If the compressor is going out there's a reason why, and that reason needs to be found and eliminated.

[indian]

Originally posted by secstate
I agree for those sophisticated enough to know the heatpump gas combination is great. However those who understand are few and far between. I have tried to explain the advantages to a number of technically savy people I work with and they have no understanding of why it is good. If I were going to spend the next ten years in this house for sure I would replace the whole system tomorrow with a new high efficiency gas furnace AND heat pump. But there is a 50/50 chance I will change jobs next summer and move. The people like me and you who understand these things and are willing to pay for them are few and far between. Remember where you are, can you say dual fuel or ground source?

[secstate]

Originally posted by shophound
I'm thinking if this is the typical Trane heat pump with spine fin coils, they haven't been cleaned since 1997, are now filthy dirty, and this unit's been running a high head pressure for some time. So, either this has stressed the compressor valves, or stressed the run capacitor, or weakened the internal relief so it's bypassing at a lower pressure, or...

IOW, I'm with Beiser. If the compressor is going out there's a reason why, and that reason needs to be found and eliminated.

It is a typical Trane with the spine fin coils and I agree I need somebody to tell why it the compressor is failing. The problem is the two techs have not bothered to investigate or least to tell my wife when she has asked (number one said he didn't know wait for it do die and two said it just happens. If anybody knows a decent tech/company in Richmond VA I would LOVE to hear from you. I have tried company I was happy with in the past and a Trane "Comfort Specailist" neither gave us an intelligent (or any) explanation.

[secstate]

Originally posted by tinknocker service tech
75/185 at 85 degrees outside and cooling fine
i must be missing something what did he say was wrong with the compressor and did he install a hard start kit

No hard start kit installed (at least since I have owned the house which is about two years). First tech said the problem was a "cracked valve" the second tech said "worn valves".

[Shophound]

Originally posted by secstate

Originally posted by tinknocker service tech
75/185 at 85 degrees outside and cooling fine
i must be missing something what did he say was wrong with the compressor and did he install a hard start kit

No hard start kit installed (at least since I have owned the house which is about two years). First tech said the problem was a "cracked valve" the second tech said "worn valves".

Have either of the technicians that's been out bothered to clean the condenser coils? Whether or not this is a direct contributor to your troubles, if you plan to keep this condenser and swap out the compressor, the outdoor and indoor coils should be cleaned.

If I were the technician at your home here's what I would check before condemning the compressor:

a) Allow compressor to start and run normally. Observe startup and running amperage draw.

b) Record pressures, superheat, and subcooling readings after system has been online awhile and has balanced out. Check temperature of lines across reversing valve to indicate any bypassing of refrigerant.

c) Note temperature rise over outdoor coil.

d) Note temperature drop over indoor coil.

e) Note condition of outdoor and indoor coils, and condition of indoor blower wheel. Note any restrictions to indoor air flow (return duct collapse, supply register dampers closed, etc)

f) De-engergize system and observe time involved for system to equalize. Note whether system uses TXV or piston in either or both coil sections (being a heat pump).

g) Check strength of capacitor.

h) Check integrity of compressor motor windings.

i) Check condition of compressor contactor.

j) Check condition of compressor terminals for any corrosion or burning of wires.

k) Backwash condenser coils.

l) Restart unit and observe all conditions after balance-out.

m) Stop unit and allow five minutes to equalize. Restart.

0) Give customer options according to my findings.


That might seem like a lot for a tech to do on a service call where he feels rushed for time due to a high stack of tickets sitting in the passenger seat of his van. If he's experienced and skilled he can knock out these checks with ease and arrive at an informed diagnosis rather than tossing out "Uh...sometimes they just do that."

[secstate]

Shophound thanks. I guess I am on to tech number three. They haven't done anything near that. Neither tech bothered to even look at the evaporator inside. No mention of coils or cleaning of coils for sure. Any advice on finding a competent tech wiling to do this or getting a tech to do this? Asking neighbors and looking at certifcations (i.e, Trane comfort specialist havent' helped).

[tinknocker service tech]

every thing shop hound said is or should be standart check befoere you condem a compressor. it realy does not take a long time and if done properly you will know the reason the compressor is going bad. cleaning the outside coil is not a hard or time comsuming thing. my consern is since i am going by presure alone 75/185 at 85 degrees is not showing bad valves. with out superheat and subcooling dont realy know what is going on in the system but the valves are not showing blow by to me. as far as starting is the cap weak did they even test it. is the contactor pitted and burnt. about ten years ago a tech condemed a compressor because it wouldnt start. he installed a new one and guess what wouldnt start. i was sent out before a third one was put in and contactor was so pitted couldnt get enough voltage to start the compressor but the fan ran
changed the contactor and it still works. if compressor is having trouble starting a hard start kit will not hurt it and a time delay will also help to
you have two differant readings from two differant techs and something just isnt making sense to me. not trying to be a smart ass but in my opioun something esle is goig on and the compressor isnt it

[secstate]

Originally posted by tinknocker service tech
is the contactor pitted and burnt. about ten years ago a tech condemed a compressor because it wouldnt start. he installed a new one and guess what wouldnt start. i was sent out before a third one was put in and contactor was so pitted couldnt get enough voltage to start the compressor but the fan ran

You are an absolute genius! I went out to clean the coils today (they weren't bad at all). While there I decided to look at the contactor. I may not know much about AC units or thermodynamics but I do know a lot about electrical/electronics and the contactor's contacts were so pitted and there was so much carbon that I am shocked that the thing comes on at all.

[chillbilly]

That compressor doth protest a bit too loudly.

[tinknocker service tech]

no lucky guess if this is the problem
i would recomend haveing a hard start kit installed with a time delay on break. this will relieve any problems if the unit is trying to start under heavy losd conditions.