A/C unit operation question

[Sam 7]

I just purchased a 76 international it has an Armstrong TRH25-14. I am not sure what normal operation should be. I turn the fan to low speed on the unit, set the switch on the stat to cool then when the compresor kicks in the fan reduces speed to about half. Seems to me it should stay the same. Im thinking it has a relay or something bad.

Also is there a way to have the fan be controled by the thermostat or is it on all the time?


Any help would be great!

Sam

[Gasgano1979]

I hope you dont mind if I hijack this thread but I figured since I have the same model unit as you i would fit right in...

Ive got a bad contactor on my unit. The compressor will not engage or cycle as a result.

I was wondering if anyone out there could point me to a proper replacement part/part number.

Ive spoken with a local HVAC supplier and they can find many contactor that's will work, however, since they cannot accurately cross-reference the current part nor does the part have any voltage specifications on it, they cannot find me a proper part for this specific application.
At the very least I hope someone can tell me the voltage ratings required for this part.

Below is all the info I have to go by...

Armstrong Furnace Company
Model: TRH25-14-11

Contactor
Make: RBM
Numbers listed on Contactor
128306-1955S
275B-018
7717


Sources of info I have found:

Original Owners Manual for AC Unit
http://www.airstream.com/wp-content/...f18e4e4aa2.pdf

Images of the current defective part and other parts of the AC
http://i16.photobucket.com/albums/b3...ps7fcfhabc.jpg

http://i16.photobucket.com/albums/b3...psrzccect0.jpg

http://i16.photobucket.com/albums/b3...psoqfxz5wo.jpg

http://i16.photobucket.com/albums/b3...psdemyzaha.jpg

http://i16.photobucket.com/albums/b3...pszvtvp63d.jpg

[TG Twinkie]

The contactor is rated for 120 volts.


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[TG Twinkie]

Sam 7
What is the power source? 20 Amp?
What size cord are you using?
The symptoms sound like voltage drop due to an inadequate power source.


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[Gasgano1979]

Originally Posted by TG Twinkie

The contactor is rated for 120 volts.


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I appreciate the quick reply.

is that 120v on all 4 plug-ins?

[TG Twinkie]

Everything except the thermostat circuit is rated for 120 volts. The thermostat circuit is 24 volts AC.


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[xrvr]

Plugged into at least 20 amp source?. Twinkie has the right idea. Peace,Jim

[Sam 7]

Originally Posted by TG Twinkie

Sam 7
What is the power source? 20 Amp?
What size cord are you using?
The symptoms sound like voltage drop due to an inadequate power source.


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You are correct.

Mine works as it should. Just needed to remove my head from my backside.

[Gasgano1979]

Originally Posted by TG Twinkie

Everything except the thermostat circuit is rated for 120 volts. The thermostat circuit is 24 volts AC.


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Would you happen to know what would be a suitable replacement?

I didn't have a chance to go back by the hvac shop today due to work and probably won't be able to tomorrow either.

[4RXLA]

Mine only works when plugged into a 30 amp source. 20 amp will pop the breaker

[Gasgano1979]

Also, would you happen to know what the voltage drop and the time delay that is required to work?

[TG Twinkie]

10% is too much.
Why would you replace the A/C if only needs a new contactor. The old Armstrong unit can be repaired. It is a much better unit than the new ones.


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[Gasgano1979]

Originally Posted by TG Twinkie

10% is too much.
Why would you replace the A/C if only needs a new contactor. The old Armstrong unit can be repaired. It is a much better unit than the new ones.


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I do not want to replace the Armstrong unit.
I want to replace the contactor but the local supplier nor the internet can show a suitable replacement for that part.
I spoke the the man from the HVAC store a little while ago, while knowing that the unit is 120v helps his search, he still needs to know what the voltage drops and time delays are.
He has boxes upon boxes of contactors, but he wants to know what the exact specifications are on the old unit so that he can give me the right part.
Neither up is has been able to find that specific info.
We both have found the original manual for it, which i posted above, but it does not list the specific requirements of the contactor functions.

[TG Twinkie]

I am confused with your statement on voltage drop. There should not be a voltage drop when it comes to the contactor. It has a 120 volt coil and the contacts are rated for at least that.
When it comes to any time delay. Once turned on, the start relay is the first to pick up. It gets the compressor motor turning. Once it is turning the run relay (contactor) picks up and the motor continues to run.
The compressor loads and unloads based on the thermostat setting.
To my knowledge the unit runs continuously unless you shut it off.


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[tbashin]

I know this is an older thread but I have the TRH25-14 that has been working great until last week the compressor start capacitor went bad (swollen up at the top too). I have the original Armstrong maintenance guide for that series and it says to refer to the parts guide for part numbers but the at parts guide section is missing. Does anyone have a part number or replacement part number for this capacitor? Mine the numbers are too bad to read.