Thermostat Compatibility - 3-wire (RWG) White Rodgers 1311-102

slg04012

Recently purchased a home with a boiler and wanted to replace old mercury thermostats. System has 2 White Rodgers zone valves type 1311-102 and 3 wires, red, white and green. Tried to replace with Honeywell programmable thermostats, but could not get valve to close. Was told these thermostats are not compatible. Is there an affordable programmable thermostat that would be compatible or an alternate approach?

Jamie Hall

A thermostat is a switch. It may require common power as well -- many newer ones do. The old mercury ones -- which are a good deal more reliable -- were strictly switches, so the first question would be how many wires do you have coming to your new thermostats? And what are they connected to on each end?

slg04012

We have 3 wires, red, green and white. Originally put them in R G and W terminals. I was told the G is the issue, and that I’d need a different thermostat compatible with 3 wires, but that the green wire may need to go in the Y terminal. We tried this on the thermostats we have now, but it did not work. Honeywell apparently calls this a series 20 wiring setup.

Jamie Hall

Colour isn't that much help. Who knows if the colour code was followed correctly? Depending on the particular model Honeywell, it may need two wires, three wires -- or as many as six. However, in any case, two of those wires act as a simple switch. If a third wire is called for, it's usually a common return for power, which is supplied on one of the other two wires. When heat is called for, the switch is closed and power is sent to the controlled device (in this case, a zone valve). Similarly, the zone valves need two wires: a switched supply (which come from the thermostat) and a common return. What you need to do is to identify which of your coloured wires is which at the zone valve, and then hook them up to the proper terminals on the thermostat. Don't even count on the colour of the wire being the same at both ends! Who knows what splices lurk in the dark corners. Trace them out, hook them up properly, and you should be fine.

This is not a thermostat problem. It's a wiring problem.

Steamhead

@slg04012 , in a Series 20 circuit, the switch makes one contact to turn the device "on", then makes another contact to turn it "off". The third wire in the circuit is common to both.

What model thermostat are you trying to use?

ratio

It's a power open, power closed setup. Some Honeywell stats (& others I'd imagine) are capable of doing this directly, check the manual. It should be possible to make any stat you like work with the addition of a relay.
A Honeywell TrueZONE zoning panel will work, it has the right contacts for what you need on the damper output relays. It has the advantage of easily opening up for use any RedLINK wireless stats.

slg04012

@Jamie Hall I can find the wires on the zone valves, but then how do I know where they go on the terminal? I’m pretty sure my red and white wires are correct, it’s the green wire to close the zone valve that seems to be wrong.

@Steamhead Honeywell RTH2510B1018/U1 and RTH221B1039/U1

slg04012

@Jamie Hall
Here is a photo, looks like 2 whites in 2, 1 white in 5, 1 red in 4, 2 green in 3, 2 red in 1, and 1 green in 6.

Jamie Hall

If @ratio is correct -- and he usually is -- there has to be a relay in there somewhere, or the mercury thermostats wouldn't have worked either. As I noted above, all the mercury thermostats do is close a switch to provide a connection between the two wires which connect to them. You have more wire tracing to do...

Alan Welch

An alternate approach would be to replace the zone valves.

Jamie Hall

Or put the mercury thermostats back...

slg04012

@Jamie Hall we already disposed of the mercury ones.

@Alan Welch the zone valves are functional, so that's not a cost we are interested in. Would rather just purchase compatible thermostats.

Solid_Fuel_Man

What was going to your old thermostats? Just the R and W, or were there 3 wires to the mercury stats?

slg04012

@Solid_Fuel_Man three wires, Red, White, and Green

Jamie Hall

Shame about the mercury thermostats, but what's done is done.

Now. What terminals, exactly, on the mercury thermostats were connected to which wires in the wall? If you don't have that information, you are going to have to trace each wire, regardless of colour, as I've said before. You simply don't have a choice. The thermostats you have are compatible with the zone valves you have -- if they are properly wired. No thermostat will be compatible if the wiring isn't right.

So you know where to start anyway.

slg04012

@Jamie Hall we can't 100% reliably say we knew the exact terminal setup for the mercury ones unfortunately. That being said, once we trace the wires, how do we match up the terminal numbers on the valve to the terminal letters on the thermostat? Like how do I know what letter terminal 6 corresponds to for example, assuming the colors may not be correct?

Again I am confident in where we have placed the red and white wires, its the green one that is the problem. We tried it in both the G and Y terminals with no success.

John Mills_5

Since those are White Rodgers zone valves, a lot of Emerson stats support them. For programmable, the 1F85U-42PR is a nice stat.

Steamhead

Here are the ZV instructions:

https://climate.emerson.com/documents/type-1311-hydronic-zone-valves-instructions-en-us-1568984.pdf

From these, it looks like your thermostats won't work directly with these ZVs. You have two options:

1- wire the thermostats so they operate single-pole double-throw relays which then operate the zone valves, or

2- get different thermostats that will work with Series 20 controls directly. IIRC most of the Honeywell VisionPro 8000 units have this capability.

Jamie Hall

Here's your wiring diagram for the zone valve.
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/White Rodgers - 1311-102 - Wiring Guide.pdf

Note that it is a power open power close unit. I'm not sure what your old mercury thermostats were; if they were the typical Honeywell T87, not sure how they were hooked up (the T87 doesn't have a power close contact). You will either need a thermostat which does have a power to close contact -- or a relay.

HVACNUT

The Honeywell T6 Pro has power open/power closed for Series 20 wiring using the "B" terminal.

slg04012

@John Mills_5 Can't find that model in stores.

Jamie Hall

slg04012 said:

@John Mills_5 Can't find that model in stores.

Not surprised. It's a professional model, and the big boxes aren't likely to even know what you're talking about.

JUGHNE

Look at your other posting.

Solid_Fuel_Man

One of the wires white, red, or green is the common. Another one is the open command, and the last is the close command. What everyone is saying is correct. I'd use a 24vac relay and make the 3 wires to the t-stat a red white and common, or RW and C.

slg04012

@Solid_Fuel_Man Thanks. The green wire is close command, I know that for sure. Based on how the relay is wired, I'd venture to guess that the white is actually the common and the red is the open. But trying to avoid guessing. If that is the case, should I have reversed the white and red wires, and put the red wire into W and white wire into R?

The system did open with Red into R and White into W, not sure if it would still open in the reverse. If I did reverse them, and put the wires in as follows:

Red --> W, White --> R, Green --> G, is there a chance this would solve my problem or not because it is not an SPDT t-stat? Note the t-stats I am attempting to use are Honeywell RTH2510 and RTH221.

slg04012

HVACNUT said:

The Honeywell T6 Pro has power open/power closed for Series 20 wiring using the "B" terminal.

@HVACNUT is there somewhere that explains that in a manual?

HVACNUT

> @slg04012 said:
> (Quote)
> @HVACNUT is there somewhere that explains that in a manual?

Page 4. Left side. Third example.

Jamie Hall

slg04012 said:

@Solid_Fuel_Man ...

Red --> W, White --> R, Green --> G, is there a chance this would solve my problem or not because it is not an SPDT t-stat? Note the t-stats I am attempting to use are Honeywell RTH2510 and RTH221.

In a word, no. There is simply no way to wire an SPST switch to behave like an SPDT.

slg04012

Thank you so much everyone. This conversation really helped me to figure things out. Was able to go to Lowe’s and find an affordable LUX TX500Uc 5/2 Day universal thermostat, compatible with a hot water heating 3 wire zone valve. Installed two (one for each zone) and they function perfectly! Each unit was reasonably priced. It turns out my white wire was common (terminal Rh), red wire was open (terminal W1) and green wire was close (terminal A).

In case this helps anyone else in the future, 5 terminal on my zone valve connected to terminal Rh on this t-stat, terminal 6 on my zone valve connected to the A terminal on this t-stat, and terminal 4 on my zone valve connected to terminal W1 on this t-stat.

PA_COWBOY

I’d like to expand on this dated forum-I have somewhat of a similar situation but with added complexity. My original home heating system is 3 zones of fuel oil-fired hot water baseboard with dated, 3-wire, 1F35-910 White-Rodgers stats and 1311 zone valves. We added a ducted heat-pump system with back-up electric heat to two of the zones, controlled by a Nest stat.

Pref 1: replace the 2 stages of e-heat with the hydronic system so the hydronic system automatically kicks-in as needed. I don’t think this is functionally possible – a 3-wire connection from the Nest? Any thoughts?

Pref 2: replace the 2- W-R stats with 2- zone valve compatible, Wifi stats-preferably single stage, heat only – no need for programable, smart versions. The only zone valve compatible, Wifi stat I’ve found is Emerson Sensi but it’s over qualified for what I need. Does anyone know of any other options?

Steamhead

Use a SPDT relay with a 24V coil to translate between the Nest's SPST contacts and the 1311.

SuperTech

The Honeywell T6 pro wi-fi is compatible with the three wire zone valves. I'd rather have that then the Nest

PA_COWBOY

Thanks for that Steamhead. To 'further enhance' the complexity - I will not need the blower running when calling for the 'boiler' alternate heat - can I disable the blower on alt heat cycle?

I'm curious, why is there a resister in the 1F35-910 W-R stat between the (red) hot and the (green) valve close terminals?

PA_COWBOY

Thanks SuperTech - I like what I read about the T6.

Can you advise how it would replace the White?
"R" on Z-Valve to "R" on T6 (hot)
"G" on Z-V to ___??__ on T6 (closes Z-V upon satisfying stat)
"W" on Z-V to W (heat stage 1) on T6 (opens Z-V upon stat call for heat)

SuperTech

It looks like it will utilise the B terminal.