I have an old thermostat from MapleChase. It has 7 wires and is currently wired as follows:

C (black)
L (none)
R (Red)

Y2 (none)
Y1 (yellow)
E (black)
G (green)
W2 (white)
O (red)
B (none)

Note that the first three connectors are in one horizontal row (from left to right), while the remaining 7 connectors are in one vertical row (from top to bottom).

I just bought a new thermostat from Honeywell (Model TH8320). The layout of the wires are quite different. I found 5 corresponding letters, but could not find E and O on this new model. (actually, I see an E, but it's marked outside, so for heat pump only).

Questions: Are those letter meaning the same for different models? If so, why are there differences? How do I map the missing one (O and E)?

Please help.

Thank you very much!

What are the labels on the new honeywell? You will need to read the owners manual on this thermostat, I'm pretty sure that you have to go into the installers menu and manually set it up for a heat pump.

Thank you very much for your answer. Here is the layout of the new thermostat:

Left row from top to bottom:

Y2 o Y2
L o
E o
AUX o W2
S1 o S1
S2 o S2

Right row from top to bottom:

RC o RC
R o R
W o D/B
Y o Y
G o G
C o C

Where the o in the middle stands for connector. The outside label (left of the left row and right of the right row) is for heat pump, and inside label for conventional.

Questions again: Are those letter meaning the same for different models? If so, why are there differences? How do I map the missing one (O and E)?

If I could post photos, it would be much easier.

BTW, I have another thermostat downstairs from Lennox, which is quite similar to the one I just bought from Honeywell. However, the layout is quite different. The wires are not well color-coded.

I'm not sure if I can just try different combinations - will it break something if wired wrong?

Hi folks, I found the user manual for MapleChase 09620 which is now Robert shaw 9620.

http://www.icca.invensys.com/manuals/robertshaw/110-732e.pdf

With this manual, it is easy to figure out how to switch the thermostat now.

From your detailed description I found this:

Robertshaw 9620 Digital Programmable Thermostat (http://www.icca.invensys.com/robertshaw/9620.htm)