Help wiring Honeywell RTH7400D
#1
01-14-06, 12:21 PM
Help wiring Honeywell RTH7400D
I'm attempting to replace the old thermostat for my heat pump with a new programmable Honeywell RTH7400D.
The old setup was:
O (white wire)
G (green)
Rc (red)
Y jump W (yellow)
The new tstat manual suggests:
O -> O/B
G -> G
Rc -> R jump Rc
Y -> Y
W -> AUX
So I'm not sure what to do about that jumpered Y/W pair. Everything else seems straightforward. Do I need to jumper the Y/AUX on the new tstat to mimic the wiring on the old? Any help would be greatly appreciated.
Thanks!
The old setup was:
O (white wire)
G (green)
Rc (red)
Y jump W (yellow)
The new tstat manual suggests:
O -> O/B
G -> G
Rc -> R jump Rc
Y -> Y
W -> AUX
So I'm not sure what to do about that jumpered Y/W pair. Everything else seems straightforward. Do I need to jumper the Y/AUX on the new tstat to mimic the wiring on the old? Any help would be greatly appreciated.
Thanks!
#3
01-14-06, 08:20 PM
As far as I know, it's just the heat pump. We just moved into the place, but if there was some kind of back-up heat, it would be news to me. Never came up in any discussions with the realtor, previous home owner, or the inspector that checked the place over before we moved in. We're out in Phoenix, AZ, so I don't think there's much need for it.
Definitely no gas -- no gas line into our house. Nothing that runs on heating oil either. And unless there could be strip heaters or anything else hidden out of sight, I think it's safe to say there is no backup heat.
Definitely no gas -- no gas line into our house. Nothing that runs on heating oil either. And unless there could be strip heaters or anything else hidden out of sight, I think it's safe to say there is no backup heat.
#4
01-17-06, 03:36 PM
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Go to the air handler, and take a look if you see any larger breakers there.
Where are you out of?
You almost will need back up heat for extream cold days, and for defrost cycle.
Other wise, when it goes into defrost, you will be getting cold air out of the vents.
Where are you out of?
You almost will need back up heat for extream cold days, and for defrost cycle.
Other wise, when it goes into defrost, you will be getting cold air out of the vents.
#5
01-17-06, 05:14 PM
Really only took a cursory look, but didn't see any larger breakers.
We're in Phoenix -- extreme cold isn't an issue, but maybe for defrost?
How about this: would it hurt to jumper Y and AUX even if there isn't backup heat? Is that not possible/not a good idea on the RTH7400D?
We're in Phoenix -- extreme cold isn't an issue, but maybe for defrost?
How about this: would it hurt to jumper Y and AUX even if there isn't backup heat? Is that not possible/not a good idea on the RTH7400D?
#6
01-17-06, 07:01 PM
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I wouldn't jumper it till you trace back the W wire back to the air handler. if the W wire is tied to W on the air handler, then for kicks, t-stat off, and jumper R and W at the air handler., and see what happens with the air handler.
if you feel some warmth, and/or burning smell, then you have electric heat.
if you feel some warmth, and/or burning smell, then you have electric heat.
#7
01-17-06, 07:34 PM
Ok, I guess I'll have to climb up and take a closer look (air handler is in the attic.)
What about the opposite? Is there any harm in not jumpering Y and AUX and seeing what happens?
Thanks for the help, by the way!
What about the opposite? Is there any harm in not jumpering Y and AUX and seeing what happens?
Thanks for the help, by the way!
#8
01-18-06, 07:58 PM
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IF you have electric back up heater, and if you jumper Y and AUX at the t-stat you will be turning on the heat in the summer when you run your A/C, and with the heater running, it going to rack up your electric bill!
#10
01-18-06, 09:49 PM
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Nothing..
Here is what Letter suppose to do..
O/B- Opens the valve for heating from the outdoor unit.
G - Powers up fan when t-stat fan switch is "ON", and cooling
Rc -> R- Power from the transfromer
Y -turns on compressor at the outdoor unit.
W -Heating side.
AUX- Heating when t-stat is switched over to EMRG Heat.
Here is what Letter suppose to do..
O/B- Opens the valve for heating from the outdoor unit.
G - Powers up fan when t-stat fan switch is "ON", and cooling
Rc -> R- Power from the transfromer
Y -turns on compressor at the outdoor unit.
W -Heating side.
AUX- Heating when t-stat is switched over to EMRG Heat.
