Common question regarding thermostat

Aug 27, 2005 18 Replies
J

Hi guys,



I'm in need of some help.



I just bought a Robertshaw 9851i programmable thermostats (any comments?) and I'm not quite sure how to connect everything. My current thermostat uses the following wires:



Rh - Heat Transformer Rc - Cool transformer Y - Cooling Control W - Heating Control G - Fan control relay O - Cool active reversing valve B - Heat active reversing valve



The new one I just bought has these:



C - 24 VAC Common R - 24 VAC transformer G - Fan relay Y1 - Cooling Relay B - Heat active reversing valve W1 - Heating Relay O - Cool active reversing valve H - Humidity relay D - Dehumidity relay



The only thing I'm confused about is the "C" and the "R". Where do I connect my former Heat Transformer ("Rh") to? The C or the R? Would the Rc go to the C? I'm just not sure because their names don't correspond and I don't want to risk anything.



A black wire is connected to RC on the thermostat and the a red wire is connected to RH on the thermostat.



I went and checked the furnace and both the RED and BLACK wires are connected to "R". Does that I connect the black and red wires to "R" on the new thermostat?



Am I way off?? Any help would be much appreciated. I've done lots of research on the internet, but I'm getting a little confused.



Thanks in advance,



Jason


Vote
Twitter Facebook LinkedIn
J

Hey Paddlepop,

It's a White-Rodgers 1D56W-380

Vote
Twitter Facebook LinkedIn
P

A) Take the black wire loose from 'R' at the air handler, because only the red wire needs to be connected to 'R' there.

B) Now use this black wire to pass 'C' to the thermostat instead......if there's no C terminal at the air handler then you need to connect it to the transformer lead that is opposite R

( though C is probably not absolutely needed at the thermostat, without it you will likely get poor battery life and /or none of the led indicator lights will work )

HTH

Vote
Twitter Facebook LinkedIn
J

Thanks Paddlepop... but I'm still not to sure where to connect the black and red wires on the new thermostat.

Vote
Twitter Facebook LinkedIn
J

I was just thinking if that'd be possible... thanks man, you've been a great help.

Really appreciate it.

Vote
Twitter Facebook LinkedIn
J

Actually, I just realized...

There's only an R on the new thermostat ... so I wouldn't need a jumper anyways.

So do you still think that I should just fold back the black wire and be done with it? I'd still connect the R from the furnace (red wire) to the R on the new thermostat.

Vote
Twitter Facebook LinkedIn
P

Chris,

You idiot......if you can't give accurate advice then SHUT THE F*CK UP !!!

There is no 'jumper' and there's also no 'RH' terminal on his new thermostat........

Also, he really should run "C" from the AHU out to the new thermostat--while many stats don't actually NEED that connection, there are some that absolutely do....otherwise, at the very least he will get poor battery life, and any led indicator lights on the new thermostat will fail to work...

Vote
Twitter Facebook LinkedIn
S

Abandon the black wire. Fold it back, and wrap it around the wire bundle.

Connect the red wire from R to RH on the thermostat. Leave the small jumper wire from RH to RC.

Vote
Twitter Facebook LinkedIn
R

If I were you I'd get a second opinion.

hvacrmedic

Vote
Twitter Facebook LinkedIn
T

I can't imagine why a link on a 15 year old post no longer works. Do you by chance have the phone number for Packard Motors?

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required