Tweak Basement Air

[nsdienes]

As I understand it, the air on our 2009 Meridian uses the second compressor only if the actual temp is over the set by some amount (have heard 3 degrees). If that option is controlled by the thermostat (only component where that difference can be determined) then a signal or an "on contact" should be made in the thermostat via wire to the air conditioner. If it is a contact then one or two wires out of the thermostat should control the second compressor. Does anyone know what wire (s) it is? Bottom line is that I would like to control activation of second compressor manually. Can I do it? Is it harmful?

Thanks

Nick

[mikf]

Nick, not sure how to do what you want to do, but what are you trying to acomplish? if it is not cooling properly maybe something is wrong.

[Harry B]

The yellow wire controls compressor #1 and the orange wire controls the #2 compressor. These are located in the thermostat.

You can measure them with a volt meter. Active line measures 12VDC.

[AFChap]

Even when the temp differential is set for MORE than 3 degrees, causing the 2nd compressor to power up, the OEM setup delays the 2nd compressor kick-on to even out the power usage. That is what allows you to run both compressors on a 30a connection w/o tripping breakers and/or damaging you electric appliances. If you simply want to control whether or not #2 comes on (not use it sometimes) you can do that by manually flipping the breaker for #2. Mine is under the side of the bed, and I have used the breaker sometimes on 30a power so we could have some cooling from 1 compressor and still run a coffee maker etc w/o risk of exceeding available power.

[DancinCampers]

Several items to consider:

The t-stat has a one minute delay built in when second stage cooling is called for.

The PC board momentarily turns off the outdoor blower motor when second compressor is started.

I would think that tieing together the first & second compressor, y1 & Y2, should work on 50A, but would cause problems on 30A.

My choice would be to disable the reversing valves with a double pole single throw switch (115vac), then switch the y1 to w, with a single pole double throw switch (12v). This would force the PC board to thinking it was in heat pump mode, but without the reversing valves operating.

In heat pump mode, all actions are accomplished by the pc board, and both compressors always operate.

Also, you would need to reverse the indoor and outdoor coil thermisters.

I am not sure if you could add the switch to the reversing valves without opening up the unit.