Air Conditioning Question

[Brian Tymchak]

Morning all,

Over the weekend the temperatures got up in the upper 70s and we decided to fire up the AC. Unfortunately, the house did not cool down. I noticed that the air compressor (Trane XL15i) was cycling on/off constantly, about every 15 seconds. I've got an appointment to have it looked at, (it's under warranty) but does anyone know if that behavior might stem from low refrigerant? This unit was installed new last May, along with a new evap coil in the furnace unit. It lost refrigerant after about 2 months, which was ultimately diagnosed as leaky service valves on the compressor. Those were replaced last Fall. I'm wonidering if maybe I still have the same problem but the continual cycling of the compressor seems odd to me. Hoping maybe an AC expert can explain that.

Thanks for your help, Brian

[Matt Meiser]

We have the heat pump version of that unit. Ours just ran and ran and ran when it was low due to a bad braze in the coil.

[Myk Rian]

You got it right. Low refrigerant. Apparently it didn't get fixed the first time.

[Rich Engelhardt]

I noticed that the air compressor (Trane

Trane - bah - 'nuff said.

Trane, Kohler and Chrysler products are three things I'm on the warpath against.
Moen is --><-- this close to getting on that list too...

[Ted Calver]

You may have blown a capacitor. Happened to ours twice now...same symptoms.

[Mike Lassiter]

Morning all,

Over the weekend the temperatures got up in the upper 70s and we decided to fire up the AC. Unfortunately, the house did not cool down. I noticed that the air compressor (Trane XL15i) was cycling on/off constantly, about every 15 seconds. I've got an appointment to have it looked at, (it's under warranty) but does anyone know if that behavior might stem from low refrigerant? This unit was installed new last May, along with a new evap coil in the furnace unit. It lost refrigerant after about 2 months, which was ultimately diagnosed as leaky service valves on the compressor. Those were replaced last Fall. I'm wonidering if maybe I still have the same problem but the continual cycling of the compressor seems odd to me. Hoping maybe an AC expert can explain that.

Thanks for your help, Brian

I have saw poor cooling caused by low refrigerant and the unit ran constantly - just cooled poorly. I am not aware that home central type units will cycle the compressor on and off like a auto does if the refrigerant gets low; but some might. On a central unit, I don't see a benefit to cycling the compressor when you can turn off the unit when it reaches set tem. On an auto the engine is running as you drive, and the belt also has to continue turning the pulley on the compressor. The only way to stop the compressor is by a clutch that is electrically energized to engage or disengage it. Auto's have both low pressure and high pressure sensors to control the operation. I would think a low pressure sensor on a home unit would be a good safe guard in case there was a leak it might save the compressor from damage. I do know they have a temp sensor that is suppose to cut the power if the compressor overheats - so not sure the low pressure switch be needed. Please advise what is found - I am curious about this.

[Joe Tilson]

The capacitor sounds correct, the Compressor is trying to start then cuts off due to overload. 90% of AC problem are electrical, or they were in my day.
Good luck,
Joe

[Matt Meiser]

BTW, my guy said a fall install can result in a low charge because the ambient temp is lower. That's what they thought was up with mine the first time. Then it happened again 2 weeks later and since it was close to 100 the first time they knew there had to be a leak.

[George Bokros]

Perhaps they did not fill it properly because of the cool temperature or it lost the refrigerant over the winter because of a small leek. We had our HVAC replaced in Nov 2012 and they did not even try to fill it. They said they need ambient air temp to be least 70. They came out in the spring to do the start up of the AC side.

George

[Mike Lassiter]

The capacitor sounds correct, the Compressor is trying to start then cuts off due to overload. 90% of AC problem are electrical, or they were in my day.
Good luck,
Joe
That reminded me of mine, yes! Capacitor went out and the compressor would make a loud humming sound for several seconds then stop. Then condenser cooling fan was running but not the compressor. Found the capacitor swelled up. This happened on Sunday morning - Mother's Day several years back. Got the number off it and called "Jim" who does a/c work and he told me he would leave it at his shop for me. He was just leaving to take his mother to lunch for Mother's Day.
It took about 5 minutes to replace it. $35 part. Glad I knew where to get part on Sunday. I would have sure hated that service call bill....

[Brian Tymchak]

Thanks for the replies guys!


We have the heat pump version of that unit. Ours just ran and ran and ran when it was low due to a bad braze in the coil.

That's what I would expect to happen too. The fact that you have the same model leads me to think I have another problem.


You may have blown a capacitor. Happened to ours twice now...same symptoms.


Capacitor went out and the compressor would make a loud humming sound for several seconds then stop. Then condenser cooling fan was running but not the compressor. ..

That's interesting. That could be the same that I'm seeing. I don't notice the loud hum, but I didn't distinguish between the compressor kicking in/out vs just the fan running. I'll look at that tonight. They'll be here on Wednesday, (my choice due to work schedule), but they were willing to have someone out this afternoon, so I certainly can't gripe about that.

This is strike 2 on this unit. I bought it on brand name and warranty (12 years) but I'm slowly getting a bad feeling that I've got a lemon....

[Brian Tymchak]

OK. AC guy has come and gone. His diagnosis is a bad thermal expansion valve (TXV) in the condenser coil unit (in the furnace housing). He checked refrigerant levels and it was within acceptable range. He put some in anyway to over pressure the system a bit and it did make the compressor run a little longer before kicking out. He said he was able to see a pressure imbalance indicating the TXV was not regulating the refrigerant pressure properly. The compressor was kicking out because it saw low pressure on the incoming side. He said there are high and low pressure sensors on the compressor that kick it out when it sees an imbalance like that. So, seems plausible enough. Unfortunately, they don't stock the valve and needed to order it, so I guess this cold snap is a bit of a blessing. Mother Nature just need to keep it under 70 or so for the next week (or so).

I guess in some small way, I'm glad it's not another slow leak and it's fixable with a new part. But I did have to get my digs in and told him that Tranes are supposed to be bullet proof and if that unit had one more problem anytime soon, I would be asking for a new system. He agreed, although until I hear that from the owner, I won't put too much stock in that guarantee..

...Now to figure out why the sump pump all of sudden sticks on ... Never a dull moment around here... Would be nice to spend some time cutting up a piece of wood one of these days.

[Larry Browning]

Wow! You turn on the AC when the temp gets to 70s? We play a game at my house every spring to see how long we can go without turning on the AC. One year we made it to the middle of June, when the outside temp got to about 87. I was good, but SWMBO caved!

[Brian Tymchak]

Wow! You turn on the AC when the temp gets to 70s? We play a game at my house every spring to see how long we can go without turning on the AC. One year we made it to the middle of June, when the outside temp got to about 87. I was good, but SWMBO caved!

Yea, we like it a bit cooler. Also the house is stucco/brick/lots of windows and doesn't have much shading so if it gets sunny outside even with temp in low-mid 70s, the upstairs heats up pretty quick and stays that way. It does make for a pretty cool woodshop in the basement though with the cold air settling down there...

[George Bokros]

OK.
...Now to figure out why the sump pump all of sudden sticks on .

If it has an internal pressure switch that controls the pump the switch is probably bad. I had that happen to mine. Installed my back up pump and ordered a switch from the mfg. Installed it and then put the original pump back in. Kept the spare for the future. Would rather have a new pump as a back up than a used one with years of use on it.

I actually have two pumps in the sump, had to replace the original one after 14 yrs. One is an AC the other is a battery powered one for when and if the power goes out a night or when we are not home. Both pumps have separate floats to control each one.

George

[Brian Tymchak]

If it has an internal pressure switch that controls the pump the switch is probably bad. I had that happen to mine. Installed my back up pump and ordered a switch from the mfg. Installed it and then put the original pump back in. Kept the spare for the future. Would rather have a new pump as a back up than a used one with years of use on it.

George

Yep, I figure a new switch is in order. And wrt backup pump, I figure I'm going to do much the same. I don't have a backup on the shelf, so I think with this "opportunity" I will fix that situation.

[Matt Meiser]

My last couple pumps had float switches that failed on, and in 1 case burnt up the pump. Seems like they fixed the burnt contacts problem by making them weld the contacts. Luckily I have 2 interconnected sumps so I put a pump in each, plus a battery backup in the other (SE Michigan is drained swamp--depending on the time of the year I may have minutes before a flood.)