My sister lives in Florida. She says it been very hot this year.
She has a two year old Trane a/c system.
The compressor will occasionally make a strange noise. She called the company that did the install and they told her occasionally the compressor is running backwards due to the power going off and back on very quickly.
They told her they can install a timer for $400 that might fix it.

Are they talking about a DOB timer like an ICM203?

Is there something else that might work better?

Thanks for your time!
Jim

 

I'm guessing this an old scroll compressor.

Yes..... the ICM203 is one delay you could use.
Most thermostats have a 5 minute delay built in but if the thermostat is battery operated.....
it won't detect a power outage.

 

first, the A/C must be running when there is a power intermittent. The motor will not start due to a power intermittent. Does the strange noise coincide with any other evidence like lights dimming? It is inconceivable to think the motor's rotor can coast to a stop(lost all magnetism) on an intermittent and start rotating in the opposite direction with power restored because it requires a change of motor connections (with motor stopped) to change rotor rotation.

 

The system is two years old.

I did a google search and there is info that this does happen.

 

Would you provide website(s) that discuss this motor reversal phenomenon? Would appreciate.

 

Here's one.
https://hvac-talk.com/vbb/showthread...ning-backwards

 

With the older scroll compressors..... depending on where it was in the cycle..... high head pressure could force a reversal on a power interruption and restoral.

 

Sounds like the timer is the solution. but $400 is a little too high.

 

I also believe $400 is a little too high.
It looks like the ICM203 timer gets wired in series between the yellow wire and the contactor.
What would be a good settingh for the delay?
Thanks.

 

OP, thanks for the website. I learned something new today. I still claim an AC motor rotating in the opposite direction based on the current through the stator coils, has to be affected because this opposite rotor current, due to voltage created by its conductors cutting the magnetic fields from the stator coils, negatively effects torque. Once the AC motor power is cycled off to on (with the rotor coming to rest) the rotation will be correct. It is impossible to know what damage this does to the AC motor since it appears the manufacturers didn't design for this condition.

 

That module can go anywhere in the Y thermostat line to the contactor. It interrupts one wire.
Five minutes is a good setting.

 

Thanks to everyone for the help!

 

I don't buy it. She said occasionally, but didn't clarify how often that was, but still how often does anyone's power go off and back on very quickly. Once or twice per cooling season maybe? This is a 2 year old Trane system and I would expect Trane to have some real answers.

 

I think the compressor is short cycling- the same as if you pull disconnect in and out while working on it ---the compressor gets hot- and makes a grunting noise. I would need to know more about when this happens- and if it only happens after "brown out" situation---there is a product- let me go look on my truck that you can install---in the meantime if you can provide more information. Trane is a super expensive- system- and I seriously doubt- I have never heard of a compressor running backwards. That is ludicrous.

 

intermatic compressor defender- cd1-024R--to protect against surge/brownout/short cycle. This is what I have used for situations where they have brownouts and then the compressor makes that grunt noise. Its 83$ at amazon- and is NOT complicated---any handyman could install it in 10 minutes.