New Thermostat Hookup Verification - Heat Pump/Heat Coil Auxiliary


Old 11-30-11, 06:39 PM
Thread Starter
Join Date: Nov 2011
Location: USA
Posts: 3
Received 0 Votes on 0 Posts
Smile New Thermostat Hookup Verification - Heat Pump/Heat Coil Auxiliary


After reading through the forums, I think I was able to install a new Honeywell RTHL3550 Non-programmable Thermostat. Nonetheless, I had a few simple inquiries and wanted to get a second set of eyes on my work.

I replaced an older, (double) mercury switch Honeywell which had the following hookups:

O - orange
W2 - (jumper to E)
E - White & (jumper to W2)
G - Green
R - Red
X - Light Blue
Y - Yellow

The Heat Pump is outside, with the blower in the attic. It uses resistance heating for emergency/auxiliary heat.

The new thermostat owners manual had a screw diagram with its default nomenclature and provided alternative nomenclature just in case it was labeled differently from the existing wires. I will provide the alternative nomenclature in parenthesis. Here is how I hooked it up to the new (So, Old - Color - New):

C (X) - Do Not Connect (taped up the light blue X)

L - Empty
E - White - E (jumper to Aux)
W2 - jumper - Aux (jumper to E)
G - Green - G
O - Orange - O/B
Not used - Not used
Y - Yellow - Y
R - Red - R (jumper to Rc)
Rc - jumper - Rc (jumper to R)

So, I think I did that right. I didn't have to deal with any of the cautions, which end in, " ...stop now and contact a qualified contractor ... "


1. Is Auxiliary heat essentially the same as emergency heat?
2. If I see the auxiliary heat text pop up on the digital display, should I be concerned (above 35 degrees outside)?
3. Is it possible that this new thermostat would run my heat pump differently than the old thermostat, with respect to auxiliary coils?
4. Can I expect a huge cost savings running 68 degrees rather than 70 degrees?
5. Could I remove the batteries and power the new thermostat by using the light blue (X) wire from the previous setup - and if so, would to which new thermostat post.

Anyway, that is about it. Any input is greatly appreciated. I am really just concerned about my wiring, so feel free to comment on that and not my questions if it makes it easier to respond to this post.

Sponsored Links
Old 12-06-11, 06:05 PM
Thread Starter
Join Date: Nov 2011
Location: USA
Posts: 3
Received 0 Votes on 0 Posts
Well, it has been a week since I posted and while the post has been viewed a hundred times, there has not been an answer. I take that to mean that my supplemental questions were pretty stupid or they exist elsewhere on this forum. I was a bit lazy, I admit.

As far as my wiring hookup, it appears to be functioning correctly, so I believe I hooked it up correctly.

Anyway, thanks for looking at the post. Peace.
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: