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grc00127

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Discussion starter · #1 ·
Just bought this house last winter so this season is the first that I'm running the A/C. A/C condenser unit is a Carrier 2.5 ton Tech 2000 - model 38TR030300 (circa 1990). 3.0 ton evaporator coils matched with new Trane XV95 furnace. I've noticed an intermittent issue lately - that the lights in our house very slightly dim up to 5 or 6 times, followed by the A/C compressor starting up. Seems like it needs multiple start attempts before it gets going. A few times, while the system was already off, I would turn off the disconnect outside, turn the thermostat down, go back outside and kick the unit on while I there to hear\see it for myself. I could not replicate the issue, it started just fine. The A/C seems to run very well, keeps the house very cool. The only weird noise the condenser sometimes makes sounds like a stick being shoved in a fan - this seems to come from the compressor (not the fan) and only on initial start up, lasts for maybe a second. While it's running and when it shuts down, the unit sounds just fine. The other thing I should add is that from what I can tell by standing next to the outside wall nearest the condenser, the condenser fan is running while lights repeatedly dim, followed by the sound of the compressor starting. So it's just the compressor having the issue, not the entire unit.

From what I can tell it's either the capacitor, the condenser logic board (HN67PA025A), or the worst scenario, the compressor going bad. The logic board just seems to be a protection from short cycling... so if the compressor really was going bad, what logic is determining that it isn't starting, disconnecting power, then reattempting?

Thanks in advance for any advice.
 
#2 ·
You might be right.
However, this is not a DIY site. It says so on the page where you sign up.
 
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#4 ·
The tech on site will be better qualified to make that diagnosis than those of us on the internet. He'll have more complete information.
 
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#5 ·
Stupid question...have you washed the outside AC unit out? Shut off the 220volt, wash unit out with a hose, let it sit for at least an hour and then turn back on and see if repeats. If it does, call a professional. Oh yeah, make sure your filter is clean and NOT A PLEATED 1" FILTER!
 
Discussion starter · #6 ·
Yes the outdoor unit is very clean. Coils have been cleaned and no overgrowth around it. It doesn't shut down after running for a while, so it would seem like heat is not an issue here. It only happens randomly when starting up. I will be calling someone, but my fear is that they will just want to replace it and will make any excuse to do that, even if it's a simple fix.
 
Discussion starter · #7 · (Edited by Moderator)
So this past Monday I decided to test the 35/5 capacitor myself, the herm side was 33.1 and the fan side was 5.01. Since it was within it's 6% range, I left it alone and called for a tech visit.

Now to today - tech arrived this morning and decided the capacitor was out of range, with his reading of 33.1, and also recommended that the main relay in the condenser get replaced, since the contacts were getting pitted. He said the capacitor was "more than 1.5 less than 35" but 6% of 35 is 2.1...so... He's the pro, and I'm not, so I told him to go ahead and replace them. Afterwards I (nicely) asked him about the 6% range for the cap, and he then said that well 33 may be within range, but due to the symptoms it should be changed anyways.

The whole time he was out by the unit, he could not replicate the issue of the failed starts. As he was in the house, right before he left, the system did it again, and he observed the multiple power dips before the unit kicked on. He followed up the $ bill by saying that it's most likely the compressor and it's hard to tell how much longer it will last. He did confirm pressures were good, and it had a good amp draw, 8 amps. If the comp was in it's beginning stages of seizing, I would think the amp draw would be pretty high. He also didn't know much about the logic board in the unit. He attempted short cycling it and said the logic board protects it by providing a 3 second start delay, but that was it. Didn't know if it provided any additional functionality. So now I'm $ down, and have the same symptoms as before, albeit with a new relay and capacitor.

He was professional and courteous the whole time, but I'm wondering how much of the parts replacement was him performing actual troubleshooting, and determining they actually needed replacement, or if he was trying to wing it, and grab some commission at the same time. I understand with the relay, since I did see the black spots and pitting on the contacts. But I'm almost certain that was a good capacitor he replaced. I'm also unhappy that the logic board was looked over. On Angies List, this dealer beats all others in the area, hands down. I don't think I'd get a better tech going anywhere else.

Is it common for a compressor in it's beginning stages of failure, to intermittently fail to start, but once it does get started, runs fine with minimal amp draw?
 
#8 ·
Yep sounds like a good cap to me. Call his service manager and tell him what you posted here.

Did he discuss adding a high quality hard start kit?
 
Discussion starter · #9 ·
I was debating calling the company but I didn't want to toss him under a bus if he had a legitimate reason for recommending replacement.

Yes he did recommend a hard start kit, but from what I'm reading online from you pros (and the tech agreed too), that's just a temporary band-aid and complete failure is not far down the road. If the symptoms get worse and breakers start to pop, I may consider it to buy myself some time.
 
#10 ·
grc00127 said:
I was debating calling the company but I didn't want to toss him under a bus if he had a legitimate reason for recommending replacement.

Yes he did recommend a hard start kit, but from what I'm reading online from you pros (and the tech agreed too), that's just a temporary band-aid and complete failure is not far down the road. If the symptoms get worse and breakers start to pop, I may consider it to buy myself some time.
Click to expand...
There are certain circumstances where the addition of a hard start is not a sign the compressor itself is going out. Although this is a very common misconception.

Left alone and not starting it will fail soon. I recommend a true 3 wire hard start install ASAP.
 
Discussion starter · #11 ·
SBKold said:
There are certain circumstances where the addition of a hard start is not a sign the compressor itself is going out. Although this is a very common misconception.

Left alone and not starting it will fail soon. I recommend a true 3 wire hard start install ASAP.
Click to expand...
Can you go into detail on what those circumstances are? I will call the service manager asap if a hard start can save this unit.

Appreciate your insight.
 
#12 ·
Is it a recip or scroll? And indoor unit metering device can cause a hard start kit to be reqd.

And incoming power (low voltage) could cause unit to need a hard start.

Since I'm only guessing I cant say for sure it would save it. Although left alone its doing more harm.

I still recommend a hard start now. And not a 2 wire one.

It will help the compressor last as long as possible.
 
Discussion starter · #13 ·
SBKold said:
Is it a recip or scroll? And indoor unit metering device can cause a hard start kit to be reqd.

And incoming power (low voltage) could cause unit to need a hard start.

Since I'm only guessing I cant say for sure it would save it. Although left alone its doing more harm.

I still recommend a hard start now. And not a 2 wire one.

It will help the compressor last as long as possible.
Click to expand...
It's a Copeland scroll compressor. The tech didn't mention anything about seeing low voltage, but I'll measure house voltage the next time the unit acts up. I'll give the service manager a call. Maybe he can put the cost of that cap towards the hard start kit. Thanks again for your help.
 
#14 ·
After reviewing your previous post I see that unit in question is 20+yrs old.

Also scroll compressors do usually not suffer from starting problems like recips.

If the incoming voltage (not just to house but to unit itself) is adequate the compressor may indeed be struggling.

Still feel like a hard start would help prolong its service.
 
#15 · (Edited by Moderator)
hard start kit

This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here.

You can find the rules for posting and qualifications here.

Further infractions may result in loss of posting privileges.
 
Discussion starter · #16 ·
Can someone tell me what these solenoid valves do when installed on the high pressure side, by the evaporator? I have one of these installed.

http://www.ebay.com/itm/ALCO-CONTROLS-COIL-TYPE-AMG-EF-11JE-121-CARRIER-VALVE-SOLENOID-/300725255567

I realized that this thing stops the high and low side from equalizing. I read through a forum on this site about how this has several benefits including instant cooling when the system kicks on...but wouldn't the compressor be starting against extremely high pressures?? Same thing as short cycling?? When the system shuts down, the lines are dead silent, no equalization.

This would explain why every time I, and the tech, started the condenser from the outside with the main disconnect, it started every time and we could not recreate the problem. The air handler, and solenoid valve were already operating, hence line pressure was equalized.
 
#17 ·
grc00127 said:
Can someone tell me what these solenoid valves do when installed on the high pressure side, by the evaporator? I have one of these installed.

http://www.ebay.com/itm/ALCO-CONTROLS-COIL-TYPE-AMG-EF-11JE-121-CARRIER-VALVE-SOLENOID-/300725255567

I realized that this thing stops the high and low side from equalizing. I read through a forum on this site about how this has several benefits including instant cooling when the system kicks on...but wouldn't the compressor be starting against extremely high pressures?? Same thing as short cycling?? When the system shuts down, the lines are dead silent, no equalization.

This would explain why every time I, and the tech, started the condenser from the outside with the main disconnect, it started every time and we could not recreate the problem. The air handler, and solenoid valve were already operating, hence line pressure was equalized.
Click to expand...
Wow rarely do I see that added but I believe it is in the manual that carrier wants it.

It does do exactly what you stated and I installed one on my own personal unit. I too have a scroll.

Scrolls are different and they start (internally) equalized based on their construction. But I believe a hard start is still a recommended upgrade.

If on a rare occurrence it is causing the compressor some strain you could have them either remove it or add a delay to outside unit to let it equalize before compressor starts. No real harm would be done at this point.

What is the length and elevation difference roughly between the outdoor unit and indoor.
 
Discussion starter · #18 ·
I'd estimate the line length at 10 feet (15 max), and maybe 2 feet elevation difference between the line entry\exits to the evaporator and condenser. Air handler is in a typical basement and condenser is at ground level.

Service manager didn't call me back yet, so I'll add this to the list of our conversation items. Another thought is that the chatter the unit sometimes makes on startup could be a weak valve in the compressor (per the tech), so if that's the case, maybe it's not starting equalized?

Again, SBKold thank you very much for your help and extremely prompt responses.
 
#19 ·
Scrolls don't have valves. But if its chattering - the orbital plates could be contacting each other I suppose.

You could try it starting equalized by the methods I mentioned and see if that makes a difference ....but according to all technical documents it shouldn't - but there is always a chance it could help yours.

And with the short lines it should be of no harm to remove it. Except loosing that cyclic efficiency.
 
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