HAI RC-80B only works with backlight?

[theedudenator]

I just installed a HAI RC-80B.
Everything seems to work ok, heat kicks on, cool kicks on, fan only kicks on.

I woke up this morning to a cold house.

It seems that it work ONLY if the back light is ON!
So I can override the temp and the furnace will kick on.
But I have to keep pressing the overide button (or any other button) to keep the furnace running.

As soon as I let the backlight time out and shut off, it turns the furnace off.

From what I have read this is normally the opposite problem.
When I get home I am going to try to jumper the backlight to always be off, but figure I would post here first.

 

[cornutt]

I just installed a HAI RC-80B.
Everything seems to work ok, heat kicks on, cool kicks on, fan only kicks on.

I woke up this morning to a cold house.

It seems that it work ONLY if the back light is ON!
So I can override the temp and the furnace will kick on.
But I have to keep pressing the overide button (or any other button) to keep the furnace running.

As soon as I let the backlight time out and shut off, it turns the furnace off.

From what I have read this is normally the opposite problem.

That is strange. Does your system have a common wire? If so, maybe it's become disconnected. If not, then perhaps your fan relay is going bad. I'm grasping at straws here.

 

[theedudenator]

I am not sure if I have a common

Red
White
Yellow
Green

I also have a blue wire that was connected to my old thermostat, I did not connect it to the new one.

My furnace worked fine with the old thermostat...

I wonder if my furnace is sensing a change in the load when the backlight kicks off, thus starting the shut down sequence?



That is strange. Does your system have a common wire? If so, maybe it's become disconnected. If not, then perhaps your fan relay is going bad. I'm grasping at straws here.
[/quote]

 

[electron]

I have heard before that the backlight can cause issues on these thermostats. Usually a separate power supply is recommended, or turning it off might fix it as well. Keep us posted!

 

[nightwalker]

It sounds like it doesn't have a common if the unit only works with the backlight on. You'll have to check the heater to see which is the common on your unit.

 

[theedudenator]

It sounds like it doesn't have a common if the unit only works with the backlight on. You'll have to check the heater to see which is the common on your unit.

I changed the jumper on the unit to have the backlight on all the time.
Now it works fine.

I looked at my furnace and the manual. I am not seeing a "common"

W1 W2 Y G RH

W1 and W2 are jumpered together at the furnace.

So I don't have a common on my furnace then?

 

[theedudenator]

Looking at the wiring for my furnace I do not have a common connection.

So now I need to run a separate power source?


I changed the jumper on the unit to have the backlight on all the time.
Now it works fine.

I looked at my furnace and the manual. I am not seeing a "common"

W1 W2 Y G RH

W1 and W2 are jumpered together at the furnace.

So I don't have a common on my furnace then?
[/quote]

 

[pete_c]

Initially the same thermostat would cause problems with HVAC motherboard and the thermostat itself would act up.

I had to add an additional power source for mine. Its been a couple of years now and all is well.

 

[AnthonyZ]

RC80's are current hogs.