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View Full Version : Hooking up an older 2 wire T87F to Rheem air handler


JSolCanby
Jan 27, 2007, 07:14 PM
Hi,

Some Background: I have a Rheem heat pump air handler that used to be in my house and now I'm trying to install it in my shop. I removed the A/C coils and disconnected one of the heat strips. All that is left is a blower and 9.6kw heating strip. I was going to use the Rheem thermostat but I found my older 2 wire - Honeywell T87F that had been used temporarily on this furnace when my house was under construction 20 years ago and we needed heat because of the drywall guys. At the time, the outside units weren't set and we needed just heat and the blower and the T87F did the trick. Now this is exactly what I need to do for my shop.

Now to my question: I want to use the T87F but I can't remember exactly how the thermostat was wired. With only two wires I believe the Red wire on the thermostat connected to the Yellow 24v transformer but I'm not sure about the White. I believe it should connect to the Heater Control wire which is Black(W). However, something tells me that during construction the White was connected to BOTH the Heater Control and the Blower Relay which is Black(G). Does that make sense?

It's going to be in the 30's here all next week. I don't really want to screw something up by trial and error and would appreciate any advice on connecting this T87F.

Thanks

Joe

labman
Jan 27, 2007, 07:49 PM
Pretty much, the white wire from the thermostat will need to connect to the coils for both relays. The other coil terminals will then need to connect to the other transformer wire.

NorthernHeat
Jan 28, 2007, 09:31 AM
24 volts from air handler to R on T-87 then W from stat has to connect to the heating and fan relay in the air handler.

JSolCanby
Jan 28, 2007, 02:05 PM
Hi,

Some Background: I have a Rheem heat pump air handler that used to be in my house and now I'm trying to install it in my shop. I removed the A/C coils and disconnected one of the heat strips. All that is left is a blower and 9.6kw heating strip. I was going to use the Rheem thermostat but I found my older 2 wire - Honeywell T87F that had been used temporarily on this furnace when my house was under construction 20 years ago and we needed heat because of the drywall guys. At the time, the outside units weren't set and we needed just heat and the blower and the T87F did the trick. Now this is exactly what I need to do for my shop.

Now to my question: I want to use the T87F but I can't remember exactly how the thermostat was wired. With only two wires I believe the Red wire on the thermostat connected to the Yellow 24v transformer but I'm not sure about the White. I believe it should connect to the Heater Control wire which is Black(W). However, something tells me that during construction the White was connected to BOTH the Heater Control and the Blower Relay which is Black(G). Does that make sense?

It's going to be in the 30's here all next week. I don't really want to screw something up by trial and error and would appreciate any advice on connecting this T87F.

Thanks

Joe
Hey thanks to you both. The thermostat and the furnace work like a champ. Thanks again