[DIYMarco133]

I am trying to install new Emerson 1F85U-22PR Thermostats to replace my still functioning but seriously old White Rodgers 1F35-210 Thermostats. According to the product literature the 1F85U-22PR is compatible with 3 wire zone valves (also White-Rodgers Type F19-0097). The heating system is an oil fired hydronic heating system. The existing thermostats are wired directly to the zone valves. Here is a picture of the existing wiring behind the thermostat. I need to know where to connect the wires that are currently connected to the 4, R5 and Y6 locations. Also, please let me know if you think there are other specific settings that need to be made on the new thermostat so it will function properly (jumpers, heat pump settings, etc.). There is no cooling system that will be attached to the thermostat. Any help would be greatly appreciated. Instructions for the 1F85U-22PR are found at this link, but I did not find them very helpful. h ttps://climate.emerson.com/documents/1f85u-22pr-instructions-en-1594366.pdf

 

[surferdude2]

You only need 2 wires to control a 3 wire zone valve. You will be connecting to the Rh and We terminals on the new thermostat.

The old stat had 3 wires connected but probably wasn't using the green wire.

Connect the red wire to the Rh terminal and the white wire to the to the We terminal.

Do not connect the green wire but dress it out of the way for possible use later if you tell me that this thermostat also controlled an air conditioner. You didn't mention that yet.

ps. That's a lot more stat than you need... don't forget to install the batteries.

 

[DIYMarco133]

Thanks surferdude2 I will try removing the green wire on the existing thermostat to test if it works. There is no A/C attached to the existing thermostat. Do you have another suggestion for a thermostat to use? I was researching and kept finding that most 2 wire therms won't work with a zone valve since it has to be told to close when temp is reached. Something about most 2 wire therms are basically off/on switches, but when interfaced with a zone valve, off has to also send signal to close the valve. This is the thread where I got most of the info

Thermostat upgrade on 3 wire hydronic system

 

[surferdude2]

You can check at the valve to see if the green is connected. The ones I am familiar with only need the thermostat to supply voltage to the valve motor terminals. The third wire on the valve is connected to a microswitch that closes a circuit to energize the boiler. When the thermostat opens, the valve closes by a spring it contains. You can check the valve and see if it has that spring on it.

 

[Ebierley]

You can check at the valve to see if the green is connected. The ones I am familiar with only need the thermostat to supply voltage to the valve motor terminals. The third wire on the valve is connected to a microswitch that closes a circuit to energize the boiler. When the thermostat opens, the valve closes by a spring it contains. You can check the valve and see if it has that spring on it.

White Rogers makes a zone valve that is power open and power close. Hence the need for a three wire compatible thermostat


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[surferdude2]

If your valve isn't the spring close type, you will have to connect the green wire to the Y terminal on the new stat in addition to wiring the red and white as before. Then you will need to program the new stat to operate in the auto changeover mode. I think that's 88 in the menu, turn that selection on since it's off by default. I don't think there is any other change you need to make to get it operating in what is commonly referred to as the "SPDT" mode.

 

[surferdude2]

Do you have another suggestion for a thermostat to use?

*
If you don't need all the bells and whistles of the stat you're considering, consider something simple and easier to install. The Honeywell T87K would be worthy of consideration.

It works on just about any heat system:

System Types
• Gas or oil heat (T87K)
• Gas, oil, or electric heat with air
conditioning (T87N)
• Warm air, hot water, high-efficiency
furnaces, heat pumps, steam, gravity
• Heat only
• Heat only with fan (T87N)
• Heat only, 2-wire, and 3-wire hot-water
valve (power open and close valves)
(T87K)

 

[surferdude2]

A good thing about wiring a thermostat for a low voltage zone valve is that you can't harm anything by getting it wrong. It'll either work or not, won't lose any magic smoke. With 3 wires, you have 3! (three factorial) ways to wire the terminals, which is 6 different ways. If you knew one wire's location for certain, it cuts the options down to only two ways, one right and one wrong... flip a coin.

Side note; Some tower mounted antenna rotors are fed with 8 conductor cables. If you don't know how the tower top motor board is wired, don't even think you can try different combinations down at the control head and get lucky. Since 8! is 40,320, you will be climbing that tower to get the correct sequence. Been there and had to do that... several times.

 

[beenthere]

The green wire will connect to the O/B terminal of that new thermostat. Then you need to configure the terminal as a three wire power close. Which is installer set up number 20.

 

[DIYMarco133]

Here's what I ended up doing. Got rid of the White Rodgers Zone valves. Installed new Taco zone valves. Installed new Taco Zone Valve control board. Installed new Honeywell TH9320WF5003 Wi-Fi 9000 Color Touch Screen Programmable Thermostats. Since I already had 3 wires to the old thermostats I didn't need to pull new wires to the thermostats but did pull new wire from the zone valves to the zone valve control board. System is working great now. I bailed on the White Rodgers zone valves because their 3 wire zone valve needed 5 wires in order to attach to the zone valve control board (one extra wire to zone valve control and one extra wire to the thermostat).

 

[AHanfi]

Here's what I ended up doing. Got rid of the White Rodgers Zone valves. Installed new Taco zone valves. Installed new Taco Zone Valve control board. Installed new Honeywell TH9320WF5003 Wi-Fi 9000 Color Touch Screen Programmable Thermostats. Since I already had 3 wires to the old thermostats I didn't need to pull new wires to the thermostats but did pull new wire from the zone valves to the zone valve control board. System is working great now. I bailed on the White Rodgers zone valves because their 3 wire zone valve needed 5 wires in order to attach to the zone valve control board (one extra wire to zone valve control and one extra wire to the thermostat).

Hello DIYMarco, can you please share picture of new wiring? I am in same situation and need to replace my old Whiite Rogers 1F35-210 to a new digital one