Navien NCB-240/130H and Nest Thermostat Issue

dlotito · October 26

I have a three zone system. Zone 1 with 4th Gen Nest Learning thermostat works fine. Other two zones have Nest Thermostat cconnected. As soon as I add thermostat to base, heat turns on and stays on. I have three wires connecting thermostat to Navien. C to C, R to R and W to W. Can someone explain what is going on and how to fix this?

Thank you

Jamie Hall · October 26

Probably what looks like R, C, and W wires at the thermostat aren't R, C, and W wires in the basement….

dlotito · October 26

I pulled the cover off the Navien and see the zone controller outputs. They are marked R, W and C. I confirmed the wiring matches the thermostat.

dlotito · October 26

This is the zone controller. I had the installer come back and add a third wire to the C output of each zone. I just didn't snap an "after" picture.

SuperTech · October 26

Check the installation instructions, perhaps it's a setting? Do you have a multimeter? That would really help with figuring this out. Is there any splices in the wiring?

Navien with a Nest thermostat....two of my least favorite things combined together. Seems like a recipe for a lot of problems.

EdTheHeaterMan · October 26

https://forum.heatinghelp.com/discussion/comment/1816331#Comment_1816331

You and @pecmsg secretly love that thermostat. Just afraid to admit it

pecmsg · October 26

There still Garbage……………only good as Hockey Pucks and skeet shoot!

EdTheHeaterMan · October 26

What about this idea

Old system wiring to old zone valves looked like this:

New wiring to the Navien boiler is actually this

When it should look line this

Double check the wiring from the thermostat to the boiler control as @Jamie Hall suggested. There may be one of the thermostat wires crossed. that will make things go wrong fast.

If you are absoutel sure that there are no crossed wires, and you get the same problem, then just for 💩 & giggles connect all three thermostats in the basement where you can see all three thermostat wires from end to end. If it works that way, then there is a compromised wire in the walls somewhere.

Jamie Hall · October 26

And while you are checking wiring, really check. Don't assume anything. Remember that there may be crossed splices in the wiring. Remember that there may be broken wires. Remember that electricity is colour blind.

If you twist R and W together at the thermostat. the circ. pump and boiler should fire. If they don't, problem. If you put a multimeter between R and C, you should have 24 VAC. If you don't, problem.

dlotito · October 26

So, from the picture above that says. "The one that works", it looks like you want me to swap the C and W wires between the Navien and the thermostat. Correct?

EdTheHeaterMan · October 26

https://forum.heatinghelp.com/discussion/comment/1816391#Comment_1816391

Not Exactly… that can get you in trouble.

We want the R on the thermostat to really be connected to the R on the Navien
We want the W on the thermostat to really be connected to the W on the Navien
We want the C on the thermostat to really be connected to the C on the Navien

It might be that simple, but don't just start swapping any wires. Know that you have a wire that is the same on both ends. Don't assume that there are no splices in the wall somewhere. If you suspect that there is a problem do the test I mentioned above. Remove the base plate of all three thermostats from the wall and connect all three thermostats in the basement where you can see both ends of the thermostat wire right in front of you.

Swapping a W and a C may cause the R to get connected to C in the Navien control to short out the transformer on the control system. If you do that then the Factory Installed Smoke may be released from the control transformer. …and that can be expensive.

dlotito · October 26

I can physically see the entire wire from the finished basement thermostat running to the Navien. I am sure that there are no splices. If one of the wires are broken, I don't think I would see this behavior. I'm not sure what to do next.

SuperTech · October 26

Next thing to do is get a multimeter or hire a service tech who has one and can figure it out for you.

EdTheHeaterMan · October 27

https://forum.heatinghelp.com/discussion/comment/1816411#Comment_1816411

So, you are sure about the wire in the basement…

What about the other two thermostats?

If you are not sure what to do next, I have an idea. What if you removed the other two thermostats from the wall. sub base and all. Connect short pieces of thermostat wire (about 6 feet long) to the Navien zone control locations. Now connect the other end of the thermostat wire to the sub base of the two thermostats you took off the wall two sentences ago. Now put the thermostats on the sub bases and see what happens.

This test will require you to actually do something other than stare at the problem. It will require some 6 foot pieces of 3 conductor thermostat wire and a screw driver. You may need to use a wire cutter and a wire stripper.

After you actually try this, let me know what you find.

Hope this information is helpful

Navien NCB-240/130H and Nest Thermostat Issue

Comments

Categories