Install Honeywell RTH111
I am replacing a Colman Mach Tstat with a Honeywell RTH111. Before I do this, I have checked the voltage on all wires. I am surprised to see the unit Green wire that I would think is ground has 12.6 v...
Forum Discussion
The thermostat will use DC power to run the items.
Standard operation of a home thermostat is for the wires to be used as listed.
R terminal, a red wire, and probably connected to the ungrounded 24 VAC (in a home, and in the case of MY RV ( a fleetwood Bounder) it is +12 volt DC))
G terminal green wire that normally when energized will turn on the indoor fan.
W terminal, normally the white wire and will normally turn on the heater
Y terminal, normally a yellow wire that will normally turn on the cooling system
C terminal is normally used in programmable thermostats and would be the grounded 24 VAC system in a home, but not normally needed in the standard RV application. They might have used any color wire for the C terminal. I normally would use black or brown wire for this connection when installing a system in someone's home or business, but there is not a 'standard' color, so normally I would be looking at the thermostat, or the heating unit to determine what color was used for the 24 volt return wire.
You might also find another terminal on a home system. It might be O terminal or B terminal, and might use the Orange or Blue wire, it is most common on a heat pump, and will activate the reversing valve. This is sometimes energized in heating, but more commonly is energized in cooling. This is because should the reversing valve break, default to heating is desired. Yet I was working on a newly installed heat pump last week, and the resident complained that it was blowing out cold air, I found a poorly connected orange wire at the O terminal, and quickly solved the problem! By making this connection, the reversing valve was energized, and it went from cooling the room to heating it.
What I would put into my RV if I installed a programmable thermostat would be the Honneywell 6000 series, where it is powered by a pair of AA batteries, and has the ability to shut off, auto change over from heat to cool, and does not require it be run on AC power or DC power. Do not use the Common wire with a DC power system, as it is designed for 24 VAC only between R and C terminals, or can be run from the DC battery included with the thermostat.
Good luck with your project!
Fred.
Standard operation of a home thermostat is for the wires to be used as listed.
R terminal, a red wire, and probably connected to the ungrounded 24 VAC (in a home, and in the case of MY RV ( a fleetwood Bounder) it is +12 volt DC))
G terminal green wire that normally when energized will turn on the indoor fan.
W terminal, normally the white wire and will normally turn on the heater
Y terminal, normally a yellow wire that will normally turn on the cooling system
C terminal is normally used in programmable thermostats and would be the grounded 24 VAC system in a home, but not normally needed in the standard RV application. They might have used any color wire for the C terminal. I normally would use black or brown wire for this connection when installing a system in someone's home or business, but there is not a 'standard' color, so normally I would be looking at the thermostat, or the heating unit to determine what color was used for the 24 volt return wire.
You might also find another terminal on a home system. It might be O terminal or B terminal, and might use the Orange or Blue wire, it is most common on a heat pump, and will activate the reversing valve. This is sometimes energized in heating, but more commonly is energized in cooling. This is because should the reversing valve break, default to heating is desired. Yet I was working on a newly installed heat pump last week, and the resident complained that it was blowing out cold air, I found a poorly connected orange wire at the O terminal, and quickly solved the problem! By making this connection, the reversing valve was energized, and it went from cooling the room to heating it.
What I would put into my RV if I installed a programmable thermostat would be the Honneywell 6000 series, where it is powered by a pair of AA batteries, and has the ability to shut off, auto change over from heat to cool, and does not require it be run on AC power or DC power. Do not use the Common wire with a DC power system, as it is designed for 24 VAC only between R and C terminals, or can be run from the DC battery included with the thermostat.
Good luck with your project!
Fred.
