I have an old carrier thermostat model q674j119 or t874g1790 for my oil furnace and heat pump. I tried to change this with Noma programmable thermostat model 52-2558-8 but everythings not working.
This was the wiring for the original thermostat:
O -> Orange
R -> Red
W2 -> White
G -> Green
C -> Black
L -> Blue
Y -> Yellow

Following the directions, this is the way I have the new thermostat connected:

H2 ->
H1 ->
B -> Blue
O -> Orange
RC -> Jumper with RH
RH -> Red
G -> Green
Y -> Yellow
W -> White

Black -> nowhere

What will I do to fix this?

I would remove the blue wire from the B terminal. Leave the blue and black unused and taped so they can't short out.
The blue wire was on L before and that is used to flash error codes using the thermostat. This stat does not use that.

Quote:

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Originally Posted by rotsen

I have an old carrier thermostat model q674j119 or t874g1790 for my oil furnace and heat pump. I tried to change this with Noma programmable thermostat model 52-2558-8 but everythings not working.
This was the wiring for the original thermostat:
O -> Orange
R -> Red
W2 -> White
G -> Green
C -> Black
L -> Blue
Y -> Yellow

Following the directions, this is the way i have the new thermostat connected:

H2 ->
H1 ->
B -> Blue
O -> Orange
RC -> Jumper with RH
RH -> Red
G -> Green
Y -> Yellow
W -> White

Black -> nowhere

What will I do to fix this?

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I think this thermostat does not support heat pump + furnace.

Quote:

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Originally Posted by METT

I think this thermostat does not support heat pump + furnace.

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Your probably right. It doesn't look like it has second stage heat for your emergancy heat.