Honeywell RTH111B To Replace Duotherm T-Stat

[homeschoolin]

I have been reading about this thermostat upgrade and have the RTH111B unit on hand to replace a Duotherm that was the original equipment in a 2008 Cedar Creek fifth wheel. I have searched and read various posts, opened the Duotherm to examine the wires and opened the Honeywell to examine its connections. The wiring seems clear from older posts as follows (wire color on left, Honeywell terminal on right):

Red---tape off
Yellow---Y terminal
White---W terminal
Brown and Blue---combine into G terminal (allowing hi fan speed only)
Green---R terminal

This wiring will leave three unused terminals on the Honeywell --- B, O, and RC. In some of the older posts that I read, the Honeywell units have had a factory installed jumper wire running from R to RC. My unit does not have the jumper wire. Do I need to install a jumper to make this work properly?

I see many install an additional switch to permit low and high fan speed switching while others skip this step. We have always just run our unit on high speed without paying much attention to the low speed option. Is the low speed much quieter or different than the high speed? If yes, I might wire in the switch. Can anybody direct me to a online source for a correct switch for this task? I would prefer to install the switch on the Honeywell mounting plate vs. a separate switch cut into the wood paneling. Amazon is my preferred online retailer. Thanks.

[homeschoolin]

I looked at the Radio Shack switch. Looks like I would need to solder on the wire connections. Since I have no solder tool or experience with soldering, and since the low speed is of debatable value, I will wire for high speed operation only.

One response mentioned that I needed the jumper from RH to RC. My Honeywell has R and RC terminals, but no RH. So I assume that I just need to jumper from R to RC. Thanks.

[Iraqvet05]

Not sure if the RTH111B and the RTH111B1016 are the same size but I can tell you from personal experience it was nearly impossible to fit the Radio Shack mini STSP switch in the housing of the RTH111B1016. I had to hack away at the inside casing to squeeze that switch in.

[Old-Biscuit]

Yes you need a jumper wire between RC & RH.........Green wire

You can install the mini switch BUT HIGH Speed Fan will work best.
Low Speed Fan can cause 'icing' issues in high humidity
Low Speed Fan doesn't move much air....... and noise level is about same as High Speed Fan

Whether you want low speed is your choice.
As wired you will get High Speed Fan

[donn0128]

Yes, there are times when you will want low AC fan.
Radio Shack, mini STSP switch is what you want. About four dollars.