Nest thermostat with munchkins boiler

tquarticelli

I have a munchkin boiler installed in 2005 (gas hit water furnice- heat only). I have Ann old Honeywell thermostat with no wire designation. I traced the 2 wires,,red and white, back to the furnace. They attach to a small box that indicates R and C. Nest thinks it’s likely to be R and W. Any thoughts on how to proceed?

tquarticelli

See photo of wire connection

Jamie Hall

Are those the only two wires? The thermostat -- even a Nest -- functions by being a switch in the circuit between one terminal of the transformer -- which is in your picture and the boiler control (which may or may not be on the boiler) and then coming back to the other terminal of the transformer. It is highly unlikely that the two wires you found at the thermostat are the same two on that transformer.

tquarticelli

Thanks for your response. The thermostat only has 2 wires connected to it, a red and a white. I traced the wires back to the image I showed. That small box is connected to a larger junction box. There are wires that connect to a water heater from that junction box. I will attach more pictures if you think that will he helpful. Thanks very much for any advice or assistance. I will post more photos shortly.

JUGHNE

The red and white wires you see at the thermostat are not the same ones you see in your picture.
If they were you would have a dead short destroying the stat.
Somewhere between the two is another red/white cable spliced in.

Actually you should be able to install any 2 wire thermostat upstairs where the existing one is now.
The Nest may not function like your old.

Ironman

If the Munchkin has outdoor reset on it, the Nest is NOT the type of thermostat to use with it. It will make the boiler less efficient because it's a modulating appliance. The Nest is not for modulating equipment; its Logic will work against the boiler's.

tquarticelli

Thanks. Should I connected the 2 wires at the old thermostat (white and red color) to the nest thermostat where it says W and R?

JUGHNE

See what Ironman said before your post.

Jamie Hall

And I second @JUGHNE 's comment. See @Ironman 's post. The Nest thermostat is designed for, and works pretty well, with hot air heat. It is not designed or intended for either hot water or steam, regardless of what the starry eyed folks in Silicon Valley say, and will give disappointing results at best.

Harvey Ramer

If you want a thermostat that you can access via smartphone, look at the Ecobee or the Honeywell lyric. They are both compatible with your system.

I never personally tried the nest because I didn't trust the tech. The company has no HVAC experience. From everything I hear from respected fellow contractors who have tried them, they are garbage.

tquarticelli

You are correct. I looked closely and the white and red wires first get split to several wire nuts with wires that lead to 2 locations on the boiler and one to the water heater. See photos and let me know your thoughts as to which leads the white and red wires at the thermostat should be attached to. Thanks very much.

ratio

I wouldn't call them garbage. They seem very well made. I just see them as a user interface that was looking for a job to do. It's simple enough to turn the temperature up & down (once you get to the right place!), & flexible enough to adapt to (tediously) entering a Wi-Fi SSID/password. If I was less charitable I'd say that with the way the internet runs today anything that provides concrete user profiles like occupancy, linked to a person (& make no mistake, they know your first name) is worth it's weight in diamond studded platinum covered gold; but I honestly believe that the driving force was "Hey, I've got a neat idea for a user interface. What could we do with it?" coupled with too much disposable income.

& steam is an edge case that went "meh, close enough". Terrible!

Jamie Hall

I hate to rain on your parade, @tquarticelli , but you -- or someone qualified -- needs to trace all those wires and determine, with some care, which ones go where, and then wire the thermostat properly. I certainly wouldn't comment on that based on the photographs.

I would note that there are three possibilities which might arise from mis-wiring. First, and least obnoxious, is that nothing would work. Second, and slightly more obnoxious, is that any one of the gadgets would work, but not properly. Third is that you will burn out the transformer, the thermostat, one of the other controls, or the whole lot of them.

JUGHNE

I think he could hook any tstat to the existing wiring coming out of the wall and touch nothing downstairs. We are just talking about a switch across the wires upstairs. Now if the tstat "robs" power from the system to keep power for memory, that has happened for a long time. But, did I read somewhere that Nest will shut down heating to rob power for memory???
That is a reason to get a minimum of 3 conductors to tstats to provide full 24 VAC from red, common and then have a "W" switch leg.
I have never done anything with a Nest. Just read about it here.
I have learned that many tech supports if talking to the homeowner will insure them that their product will work properly.....and if not then you need a pro because there is something wrong with your system?

tquarticelli

Thanks everyone. I will get someone in to look at this. I appreciate all your responses and time.