change TStat wiring from conv to heat pump to use AUX heat

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change TStat wiring from conv to heat pump to use AUX heat

Post by jonatay325 » Thu Dec 27, 2012 11:38 am

My setup includes a Lennox Heat Pump with with auxillary heat. I have a single unit in a 2 story house, so I have 2 seperate Honeywell TH6220D thermostats with a Honeywell HZ322 TrueZONE.

Last night I noticed that my system was taking more than 2 hours to increase 2 degrees when the outside temp was about 20 degrees. The thermostat was set on 68 while we are at work and then to 73 at 5PM for when we get home and it just wasnt getting to 73 in the house. I ended up calling the installer and he explained that the thermostat should automatically kick on the aux heat (or stage 2 as he called it) if it was wired to do so. After checking, we realized the thermostat was wired conventional as shown -

Red wire to R (and a jumper to Rc)
Yellow wire to Y
Brown wire to C
White wire to W
Green wire to G
Orange wire not used
Blue wire not used
Black wire not used (I think there is a black wire, but I couldnt get it out of the wall yet)

We then checked the TrueZONE and it was programmed for the auxillary heat to be activated by the thermostats. Of course the auxillary heat never came on because the thermostats were not wired to do so. So, just to get the aux heat to come on, we programmed the TrueZONE to come using the stage 2 timer set to 20 minutes. This worked and got my house warmed up nicely in no time.

I say all that just to ask how I need to wire the thermostat for the heat pump so that I can utilize full capabilities of my thermostat so that the thermostat will automatically kick on the aux heat when needed and it will give me the option to use the Em heat at the thermostat down stairs instead of running up stairs to the unit in the closet to turn it on. Another function I would like to use is the "Auto" System setting that changes between Heat and Cool automatically. The conventional wiring setup does not allow me to do this.

I believe this can be changed from conventional wiring to heat pump with the wiring that is already in the house (spare orange, blue, and possibly black). Is this true.? How would I connect it.? Also this may sound like a stupid question, but do I need a different terminal block on the thermostat to switch between conventional and heat pump or ar they one in the same.? I just noticed that the conventional is at the top which is where the wires come into, but the heat pump labels are at the bottom and there are no openings at the bottom of the terminal block.

Here is my thoughts on the wiring, please correct me if I'm wrong.

TrueZone____Wire Color_____TSTAT
R___________RED__________R (jumper to Rc)

Also, for the thermostat installer setup, do I change it as -

System - 5 2heat_1cool heat pump
Changeover - 0 OB terminal energized in cooling
Fan - 1 Electric Furnace
Heat Cycle - 9 For electric furnaces
Second stage Heat cycle - 9 for electric furnaces
Emergency Heat cycle - 9 For electric emergency heat
Compressor cycle - 3 Recommended
Second stage compressor cycle - 3 Recommended for most compressors
System setting - 1 Auto changover (Heat_Cool_Auto_Off)

Thanks in advance for your help!


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- change TStat wiring from conv to heat pump to use AUX he

Post by Freon » Thu Dec 27, 2012 2:42 pm

Forgive me but I am not familiar with Truzone. But first let's get the basic heat pump working.

A heat pump has a changeover valve that switches the condenser from cooling to heating. That changeover valve is usually connected to the O terminal of the thermostat using the orange wire. Check at the indoor air handler for an O connection most likely using the orange wire. In the Thermostat setup you tell the thermostat to energize the valve for heating or -
Quoting -

Also, for the thermostat installer setup, do I change it as -

System - 5 2heat_1cool heat pump
Changeover - 0 OB terminal energized in cooling

The installation manual will tell you what the Lennox heat pump needs. As it is now set at the thermostat, the thermostat will energize the Lennox condenser changeover valve for cooling. Verify that fact. Since you have not connected the changeover valve O wire, you're getting the heat because the valve can't be energized by the thermostat.

At the air handler, where I assume the electric heat strips are, you should see a connection for Aux or maybe W2. The thermostat Aux should connect to that terminal usually using the White wire.

If this is a new system and under installer warranty, give them a call. They can help more effectively and it should not cost you anything.

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