Common question regarding thermostat

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

http://www.hometech.com/learn/hvac.html
--
SVL




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sweet, thanks!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
--
SVL




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
To answer the question you need to post the make and model of the old thermostat

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hey Paddlepop,
It's a White-Rodgers 1D56W-380

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks Paddlepop... but I'm still not to sure where to connect the black and red wires on the new thermostat.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The 24V Active (single transformer) RH + RC goes to R ) C goes to the common on the transformer. There should be no connection to R - RH - RC ( There is no terminal for C on your old thermostat so locate the wire at the transformer

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just as an after thought, there is no COMMON wire connected to any terminal on your old thermostat. So if you are absolutely sure that the RED wire was RH and the BLACK wire RC and that you have a single transformer and these two wires were bridged Then one of these two wires can be disconnected from the transformer ACTIVE and connected to common SAY THE BLACK WIRE this wire can then be connected to C on the new thermostat. The wiring would then be RED wire R transformer to R new thermostat and BLACK wire common transformer to C on the new thermostat

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I was just thinking if that'd be possible... thanks man, you've been a great help.
Really appreciate it.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
--

Christopher A. Young
Do good work.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks Stormin,
There actually isn't a jumper... am I able to get one from anywhere?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jason wrote:

If I were you I'd get a second opinion.
hvacrmedic
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Chris,
You idiot......if you can't give accurate advice then SHUT THE FUCK 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...
--
SVL




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.