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Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 19524
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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My name is ***** *****. I'm trying to wire my nest

Customer Question

Customer: My name is ***** *****. I'm trying to wire my nest thermostat to my existing White-Rodgers Zoned Heating system
JA: Thanks. Can you give me any more details about your issue?
Customer: Sure... I opened the thermostat and found 6 wires (3 for ac), 3 of which go to the heating system. Green was connected to terminal "6-Six", Red to "W" and W to "Rh". At the zone (1311-02), Green wire connects to 6, Red wire to 4 and White wire to 5. I can't figure out how to wire to my nest since nest doesn't mention what to do with 6-Six.
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Submitted: 10 months ago.
Category: HVAC
Customer: replied 10 months ago.
Thermostat is a White Rodgers 1F97W-71. Zone valve is a White Rodgers 1311-02. I have one 3rd generation Nest thermostat that I am trying to control one heating zone with.
Expert:  Rick replied 10 months ago.

Since no one else has responded I'll give you the answer you probably don't want to hear. You can't use a Nest with a 3 wire White Rodgers zone valve. The thermostat options are very limited for these zone valves

Customer: replied 10 months ago.
Hello, Thanks for the response. Is this something specific to White Rodger's valves, or generic to all zone valves? Part of the reason I'm asking the question here on justanswer is that I saw the following discussion, which seems very close to my situation and may have a solution: http://my.justanswer.com/question/guest/198bead6b715450a8da355fd27584680
My thermostat is a different model, but presumably, this solution would work with my setup.
Expert:  Rick replied 10 months ago.

White Rodgers 3 wire zone valves are unique. Virtually every other zone valve (with the possible exception of MiniMag) should work with a Nest. All I get with that URL is the question, no answer because there isn't any.

Customer: replied 10 months ago.
Perhaps you can search your website using keywords from the question and see the original response? If not, I'm including a cut/paste transcript of the discussion as I see it when I go to the page. The original technician appears to be recommending the use of a relay. You'll notice that they are using a white rodgers valve too. They are using model 1311-103, while I'm using model 1311-102 (not -02 as I said earlier, that was a typo). The conversation eventually drifts off and I can't tell if the recommended solution worked out or not. Perhaps we can contact the original HVAC technician who was answering the question? The website makes it seem like Douglass was the technician, but as far as I can tell, that's not a real person. It's the same picture/name used when you sign up at the website and I think that's just a marketing thing. I suppose he could be real though. Anyways, here's the transcript (abridged):I have a white rodgers 1F35-910 3 wire thermostat, (red,White, Greeen wires) Can I use the NEST programable, and how would I wire it. I have been unsuccessful. The furnaces stays on after set point is reached.Douglas: Hi, I'm Douglas and I am here to help you resolve problems with your heating and cooling equipment. I love the nest thermostat but we need to know what we are controlling. Is this a forced air system or a boiler?
Customer: It is a boiler with zone valves. I'm only using it in 1 zone
Douglas: Ok… I need to do a little checking to see how we can get around the issue of not having a common wire. In the mean time, have you noticed if there is a spare, unused wire in the bundle coming out of the wall?
Customer: There is no spare. 3 wires only. They correspond to red connected to #4,white to #5 and Green to #6 on current thermostat. The wiring at zone valve has similar numbering, then the additional zone valves have wiring connecting each one.
Douglas: The red to white drives the valve open with a call for heat, the red to green drives the valve home. The nest doesnt have a way to do this internally but it can be done by adding a relay near the boiler... I'll work on a diagram but basically, the thermostat will now control a relay with multiple contacts and that will control the zone valve....The relay is wired in such a way that Red from the transformer goes to the relay contacts common and up to the thermostat and the green goes on the normally closed set and on to the zone valve. The white to the valve connects to the normally open contacts and the white from the thermostat drives the coil. A common must go to the other side of the coil on the relay. This way on a call for heat, the relay switches and powers the white at the zone valve to open it, when the thermostat satisfies, the relay returns to its unpowered state and feeds power to the green driving the valve closed. Otherwise we would need a zone valve that is powered open and has a spring return close function. Do you know where the transformer is that powers the low voltage system?
Customer: I am fairly good at this stuff. I can find the transformer if you describe it. I've looked at all the connections and taken photos of all. Is the transformer attached to the boiler directly or on a seperate mount.
Douglas: It can be on the boiler... or if you have multiple zones. It should have a wire leading to the zone valves… In the drawing below, I used black to be the white wire since white wont show up.
Customer: Would this affect the other zone valves if I didn't want to change them? The transformer wires attach to the 1st zone valve and I suspect the others are jumped from valve to valve? What would be the description of the relay when I go to but it? Electrical store or HVAC?
Douglas: No, it wouldnt impact them at all, just leave any wires that lead to other zones alone. They are parallel circuits.. You may end up with multiple wires on the transformer terminals.
Customer: What type of relay switch do I buy ?
Douglas: Its going to be a 24v coil with either single pole double throw or double pole double throw.. let me find a part number. you will probably have to go to an HVAC supply house to get it or order it online. here is an example...http://www.grainger.com/Grainger/Magnetic-Relay-6AZU4
Customer: replied 10 months ago.
Customer: I'm Sorry, the transformer wires (2) now attach to the 1st zone valve. The other 3 zone valves connect off the 1st with 3 wires. Do I disconnect these transformer wires (2) and attach the relay to the 1st zone valve,and where do I attach them? Currently the red from transformer attaches to white wire from thermostate,(at 1st zone valve) and white of transformer to #3 of zone valve.
[Snip: discussion about sending a diagram/photos]
Douglas I dont recognize those valve controls. I may not be able to look them up till I get in the office tomorrow. I dont want to mislead you
Customer: They are White-Rodgers "Zone-A-Flow" Type 1311-103, .4 amps.
Douglas Ok...I'll look them up and we may have to revisit some of this and I will get back with you.
Douglas: Im really struggling with this. If it were on my house, where I had time to play with trial and error, it would be one thing. Sometimes we tend to overthink it and after a day or rest, I am sure it can be done. I know a relay would work. Basically we just need to simulate the thermostat actions and control that relay with the nest. I have to make a few mods to the diagram I gave you before but its still going to be a standard 24v single pole, double throw relay... I just have to clarify something before I redraw it... I am working on that now. Again, if 3 wires from a standard thermostat can control it, a relay is nothing more than a substitute for the thermostat. The nest simply will control the relay.
Customer: It looks like I received a reply from you. I'm unable to to retrieve it. Could you repost it here.
Douglas: No matter what we need a relay and common, ill post the image this evening when I get to my computer. I'm working from my iPad now and don't have the file here. You can cut the 3 wires between the valve and the thermostat and connect them like this. THe black wire represents white since I cant draw white easily. You will need to add the additional common, take it from the common terminal on the valve where there is already at least one wire. I used blue but you can use any color. I would just mount the relay on the joist near the valve. The blue box is the 24 volt, single pole, double throw relay. The terminals on the right are the coi. Usually these are marked 1 and 3
Customer: replied 10 months ago.
I found the diagram the technician sent to the customer at the following link: http://www.emprendedor.link/white-rodgers-thermostat-wiring-diagram/34/have-a-white-rodgers-1f35-910-3-wire-thermostat-redwhite/
Expert:  Rick replied 10 months ago.

Yes you can do this with a relay. Do you have a question about the wiring diagram?

Expert:  Rick replied 10 months ago.

One caveat, this may not work with the latest gen Nest. You might get a no voltage at R error. Best to contact Nest abut this possibility.

Customer: replied 10 months ago.
Ah! Great information. I'm trying Nest support right now to get an answer to that "no voltage at R error". In the meantime can you tell me what you were reading (provide a link) that mentioned this potential problem?
Expert:  Rick replied 10 months ago.

It's something I've run into here with a Nest connected to an isolating relay.