Will the Nest (not E or Learning models) work with this old configuration?

[JonJon2]

Hi all,

I'm submitting pictures of my old White/Rodgers Thermostat. I'm going to replace it with the Nest. Nest only model. Not the E or Learning model.

The configuration test gives it a go. I'm not sure. Want confirmation from a knowledgeable person, not a computer question, and answer test.

Thanks in advance. If you suggest any readings, please let me know what to check. There are only the two wires connected to the thermostat. One is White and the other is Red. As you see, there is electrical tape connecting the wires. Not wire nuts. Also, the wires are solid. There are two wires snipped and not used. I'm not too sure of the colors, as this is a very old thermostat. Seems that the cut, unused ones are Blue, and/or Green or Black. My heating system is Gas heated water to radiators. No Air Conditioning.

Thanks.

[Houptee]

You will need to connect one of the spare wires preferably Blue to the C on the Nest and then at the boiler to the C common of the transformer.

Where on the boiler do the 2 wires connect now can you take a picture and post it.

Some older boilers do not have a C terminal easily identified such as if it goes to a Honeywell switching relay.

[JonJon2]

 Houptee, thanks for the reply. See my pictures of present (heat only) thermostat I have. In First Post.  My system is Gas, water heater. To radiators. Boiler is Crown Jamaica Series. Gas fired water boiler.   These are pics of wiring near the boiler in the basement.  Have no idea what is going to what.

[Houptee]

Ok looks like you have spare blue wire wrapped around the brown thermostat cable.

You can use the Blue for the C wire.

Now you have to follow the Red wire back to the transformer (looks like they spliced Red to one of the Black wires that goes to the transformer screw).

The other screw (not the one Red goes to) on the transformer is your Common aka C wire connection.

So connect the Blue spare wire to the transformer C screw and then at the Nest connect Blue to C.

Then Red to R and White to W on the Nest.

You should mark the black wire that goes to Red wire and also the transformer screw with some red nail polish if you have some when you figure out which screw and wire is red.

[JonJon2]

Thank you. I'm going to have to clean all the wires. I couldn't take great pictures due to the heat of the pipes, and positioning of the wiring.
Why do I have to go through all that trouble of using a blue wire for "C" common if the Nest doesn't require a "C" connection? Shouldn't I just use the two leads at the thermostat I have now? (Red & White)? Then, not to bother, all the other splicing and tracing. The thermostat is just an on/off switch at a set temperature. I only have heat, and I'm not going to be using a scheduler. The video and written info on the NEST reads I don't need the "C".

My NEST is not the NEST E or the NEST LEARNING variation.

Below is what is posted on the PSE&G Market Place page. >>>

What's a C-Wire?

The Nest Thermostat is designed to work without a C-wire. However, in some cases, a C-wire may be needed.

A C-wire (common wire) is a low voltage power wire that many modern thermostats require for their features to work. Many older homes don’t have a C-wire because mercury and battery-powered thermostats didn’t require one.

The Nest Thermostat works with most 24V heating and cooling systems, including furnaces, air conditioners, boilers and heat pumps with either forced air or radiant delivery.

It works with conventional systems that have one stage of heating and cooling and a second stage of either heating or cooling. It works with heat pumps that have one stage of heating and cooling and either aux or emergency heat. And it works with HVAC fans.

The Nest Thermostat is designed to work if your home doesn’t have a common (“C”) wire. In some cases, particularly if you have a heating- or cooling-only system or use a zone controller, a C-wire or other power-supply accessory may be necessary.

[Houptee]

You will have problems without a C wire down the road most likely because C is like the negative on a battery and keeps power to the Nest all the time so it doesn't run off the battery.

Read the last paragraph of what you posted above about Heating Only systems it says you will need a C in most cases.

All you have to do is look at the brown cable in your pic it has Red and White coming from the Nest correct?  So you then look at the red wire, it splices to a black wire, it then goes to the transformer. Yay you just figured out your R + side of the transformer! Mark it with a dab of your wifes red nail polish.  Now the other screw is the C Common terminal of the transformer.  Go back the thermostat cable unwrap the wires they coiled around it and hook blue to the C screw.

Then hook blue to C on Nest.

Now you will always have a C wire if you change to a different brand down the road etc.

[JonJon2]

Thanks again, and Happy New Year.

Well, I was just trying to avoid all the tracing through the floors. I have an old home. Just like me. I'm sure this will be the last system I'll have. I'm 70 this year.  I can just meter the wires out for continuity, but I'll have to buy wire for the portion that was cut, so they can reach from the boiler to the upstairs. I didn't want to dig into the walls.  The last paragraph says the "C" MAY be necessary. To me, that means I might need it but don't.  Thanks for writing, I can use my wife's nail polish. That gave me a chuckle. I've been happily divorced since 1989, and a single parent of a mentally handicapped Boy. He's most likely older than you. He's my Air Force Brat. An Air Force Doctor gave him brain damage at birth by using forceps instead of giving my "x" a cesarean.  Well, that's that. He's still my baby. I'll have to give a good cleaning to the wires to actually see if any color still exists. I was expecting my NEST by FedEx today, but it didn't show.

I'll power down the entire house and do some continuity checks to see what the hell the boiler installer did.  I don't want to screw up the heat, as being living in North Jersey does get cold. Hope to get it going. Thank you so much for your kindness, and help. If they don't shut down this thread, I'll let you know how it went. Oh, and I think you're confusing the installed thermostat I have now with the Red and White wires coming from them. That's the old (White/Rogers) one I'm going to replace. Not the NEST. (That has all scheduling programming for heat and A/C which I don't have, and won't need.) That's using ONLY Red and White.  RH that's connected. I guess for heat, as it has a slot for RC (Cold) and the White connection with the white wire. As I said. I only have a heat system. Crown boiler to old radiators. Keeps the house very warm. Just wondering what I'll have to sell of value to pay for the heat this year.  State of N.J. utilities commission gave PSE&G a 20% raise on rates in a flick of an eye.

God Bless, be safe.

[Houptee]

Oh you are in NJ im in Monmouth County NJ!

Happy New Year to you too!

I marked up your pics to see if you can answer my questions of which brown wire goes directly from boiler room to the old Tstat.  One of the wires with the wire nuts must go up thru the house to the Tstat. Does it have extra wires coiled around the wire coming out of the wall behind the old Tstat or is there only 2 wires in the cable behind the old Tstat?

[JonJon2]

I did some tracing last night. Found that I wouldn't have to screw with putting wires up through the walls. You have a bird's eye. That brown wire sheath cover is for all the colored wires from the thermostat to the boiler. Just need a bit of time to get back to you. My boy is ill. I was expecting him to go back to day program. That's the only time I have free.

There is some odd splicing. There is a pump and water heat flow up to baseboard radiators on the second floor, but they are never used. I don't use upstairs any longer. Put up a dormer decades ago, but it's only for storage now. The baseboard radiators were VERY NOISY. There was a thermostat put in up there too. The pump from the main boiler to the upstairs hasn't worked for over 20 years. So, it's basically dead. An air bubble developed in that part of the system too. I didn't care to bleed it, as it's not used. At this point, I would need a new mortgage to use it for the gas bill. When I can turn off all the power to the house, I can clean up the wires. Make some continuity tests too.  There's one wire spliced going to that Honeywell unit that doesn't make sense. I'll get you some better pics, and try to mark them up. You've been a great help. Still haven't received the NEST. The delivery date from FedEx keeps changing to a later time. That cold blast messed up a lot. I'm in Essex County, Nutley. Great town if the Crazy $$$ hungry commissioners stop selling beautiful brownstone homes to build dual use store, and apartments on for the tax money. The idiots even let Annie Oakley's beautiful three-story Victorian be torn down to put up tow crappy square houses. If they used Legos, it would have been the same look.

[Houptee]

OK so both the brown cables go to the thermostats (one you no longer use for 2nd floor).

Just figure out which brown cable is for the downstairs thermostat and follow the red that wire nuts to a black wire, then the black goes directly to the screw on the transformer correct?

That is your R on the transformer, the other screw will be the Common of the transformer.

Its like a battery Red is + (positive) and Common is - (or ground).

Just connect the blue (extra wrapped wire on the brown cable) to the Common of the transformer.

Then go to the Nest and connect blue to C on the Nest.

The Switch with the Red plate is all you need to turn off that shuts off power to the boiler you do not need to turn off the power to the house jut turn off that red switch before you do the thermostat wiring,

No need to snake any wires up the walls at all just connect the one wire by the boiler (The Blue  coiled wire to Common on the transformer).

[Nestsuckstoohot]

Mine did not match the colors or the number of wires. So I guessed. Made a jumper and after two tries had it working. Can’t break it with low or no voltage. 

[Houptee]

You are not supposed to put jumpers on the Nest what terminals did you jumper?

[EdwardT]

Hi folks,

@Houptee, thanks for the help!

@JonJon2, how's it going with your Nest Thermostat? Still need our help?

Thanks,

Edward

[Jhonleanmel]

Hi there,

Chiming in to see if you still need assistance with this. Let us know if you have additional questions ― we'd love to help.

Best,
Mel

[Jhonleanmel]

Hi everyone,

Just one quick final check in here since activity has slowed down. We haven't heard from you in a while so we'll be locking this thread if there is no update after 24 hours. If you have any new questions, updates or just a discussion topic, feel free to start a new thread in the Community.

Thanks,
Mel