I am attempting to install a programmable thermostat (Honeywell RTH7500d) to replace my old non-programmable Lennox 51M33), but have a question as to which wires go where on the new one.

The old unit uses wires O, R, G, Y1, W1, C, E, T2, and T1, with a jumper between W1 and E, as well.

The quick start guide of the new unit mentions O, G, Y, Y2, W, W2, R, Rc, and AUX, so am a little confused by some of the 'extra' wires that may or may not be needed.

Thanks in advance for any guidance!
Ryan

 

The additional T terminals are for a remote temperature sensor.



Using setback temperatures in heat mode should be avoided with heat pumps.
The electric heat strips will kick in during recovery and raise the electric bill.

 

Your current thermostat uses an outdoor sensor to aid in backup heat operation that your new one doesn't use. It is also not recommended to use a setback thermostat on heatpump system with back up electric heat.

A heatpump is designed to run slow and steady to make heat. If your temperature is more than 2-3 degrees below the set point.... the electric heat will come on.

O---> O
R---> R/Rc
G---> G
Y1---> Y
W1---> Aux/E use a jumper
C---> C

T1 & T2 ---> tape off.... not used

Advanced setup. Step
170 ---> 7
180---> 1
190---> 0
270---> 9

 

I do not know what the following refers to. Is it part of the programming of the new thermostat? Thanks in advance!

Advanced setup. Step
170 ---> 7
180---> 1
190---> 0
270---> 9

 

You must also configure the new thermostat to match your system.

PJ has posted important settings to enable this thermostat to correctly control your system.

 

Based on my current stat using an outdoor sensor (and new one doesn't), and that it is not recommended to use a setback stat on a heatpump system, would I be better served staying with my current one?

Or can the new one be configured (such as what PJmax suggests in his Advanced Setup) to overcome these shortcomings?

Thanks a bunch for the help,
Ryan

 

You can use programming to save money in the cool mode.

 

So my new Honeywell programmable stat looks to be beneficial during the cooling season (summer), but the opposite during the heating season. In my case, does anyone think I should potentially switch back and forth (current stat in winter / new programmable stat in summer) in order to save on energy usage? I was thinking a programmable was the way to go, but from what I've learned about how heat pumps work, I'm having doubts.

Ryan

 

I would install the programmable stat and use the Hold button in heat mode.

 

Hello again. I have finally found time to install my new Honeywell thermostat. Today, I had a question, so I called the Honeywell hotline phone number, and I was told that I need to have a HVAC contractor install a 'fossil fuel kit', otherwise the compressor may get damaged.

Is this correct? I'm really getting bummed, as I thought I was nearing the end of getting the new installed myself.

We were talking about the T2 and T1 wires (Outdoor Temperature Sensor connections, per the old thermostat's manual). I was thinking that the T1 and T2 were simply not used with this new thermostat and could be taped off.

Please advise,
Ryan

 

Do you have a gas furnace in use with this heat pump?

If you have a dual fuel application you want a VisionPro TH8320 stat or higher series.
Fossil fuel kits are from the dinosaur age (80's).