Hi,

I hope somebody can help me since Honeywell customer support was useless.
I'm upgrading old RobertShaw thermostat to a new HoneyWell RTH8500 one.
My old RobertShaw connection looked like this:
Connected:
G
O
Y1
W1
C
R
Not Connected: B

I installed the RTH8500 and connected it the following way:
R into RC (jumpered with R)
O into O/B
Y into Y
G into G
C into C
W into Aux (jumpered with E)

The unit works perfectly for cooling. No problems there.

I experience the problem with heating.
My heat-pump is not designated to heat, it is ONLY for cooling.
When I turn on heating, thermostat turns on both heat-pump (which it should not) and my electric baseboard heating (which should be the only one turned on).

I called Honeywell and they told me its impossible to turn on just electric baseboard heating without heatpump on this thermostat, which I find very hard to believe.

The problem as I understand it is the following:
I have only 1 stage of heating (baseboard). The way I wired is for 2-stage heating system (where my heat pump is assumed to provide heat as well).

How do I wire it to make Thermostat think my baseboard is the only heating source and not turn on heat-pump while in heating mode?

I though just plugging W1 wire into O/B (where O is right now) could help?

Thanks a lot!

Oleg

You would have to look at the program in the instal guide to tell the system it is a one heat one cool tstat not a heat pump. When it is programmed for a heat pump it will turn on the heatpump. If it is programmed on a one heat one cool it should only turn on your baseboard heating. I will try to find instal guide and see if I can help you further.

You are going to want function 170 option one 1 for one heat one cool.this will run your system as an electric heat for baseboards and an air conditioner. There is not an option to run both your heatpump and basbaords individually on this tstat.
On that note you will have to go through all of the functions and make sure they are all set correctly.

Also won't be using heat pump wiring to configure the wires. Use the electric or gas wiring schematic.