Nest Thermostat Discussion...

[SolomonMan]

All,

I was over my sons place helping him with projects today. (Broken Dryer Belt, a Couple leaking pipes (One cracked - that got me over there),and Thermostat swap.

The Energy company offered a Rebate on the Nest Thermostat System (Not the Learning One) last year and we picked it up and its sat in the shipped box for about a year now.

Anyways I was thinking it would be a quick job as I currently have a Nest Learning Thermostat at my place and it was not a problem to install. (Old Rheem 90 Furnace)

At my boy's place he has a York Stellar Furnace (120K) (Natural Gas Forced Air) put in by my late father and I back in 2001 replacing a Old Gravity Fed Coal converted to LP Gas Furnace. That job was a decent task as most of the duct work on this two story home was replace/deprecated/adapted. House was built in 1882. There is no Central Air Conditioning or other Heating and Cooling Devices in the Home. The Thermostat Wiring is Solid Core Thermostat Wire I am not sure of AWG but it was sold as Thermostat Wiring at that Time. It is quite literally a straight drop to the furnace say maybe 12 ft of wire between floors including organized neat connections.

The Furance Connections (at Furnace) consist of 4 Terminals (Red, Green, Yellow, White). Yellow is not Connected (Think Y Extra wire not used Scenario)

The Old Themostat, a Programmable From Honeywell,.I believe I put in the place back in 2005. Replacing another Honeywell that we put in 2001. The 2005 one had more programmable options so I added it. The late Honeywell Thermostat Utilized 3 of the 4 wires (RC, Green, White).

This previous Thermostat to the Nest also used a Jumper from RC to RH (came in place with thermostat originally).

So Basically the way I understand things, Please correct me if I am wrong, is the Red Wire is 24 Volts DC. The White is for Heat. The Green is for Fan Blower. If the Yellow was involved it would be for the Central Air.

If there was a C wire its a Common 24 Volts Continual. (For Items such as the Nest Thermostat charging etc).

So In the Nest (Phone app) setup it pushes (Forces) the user to Buy their Nest Thermostat C Wire Adapter.

This Actual Nest C Wire Adapter appears to be nothing more than a box with connectors while many other competitors are using a 24 DC Transformer which just replaces the C Wire. The Competitors boxes can be for more than just Thermostats.

If during the Setup you say that you have this Adapter it will let you progress thru the steps and the Thermostat/the furnace seems to function fine. If you do not say you have the adapter it tells you its incompatible. I temporary said I did have the Adapter as I had already mounted the optional back thermostat mount plate and the base plate to the wall and proceeded to completion.

The thermostat does display N260 Error on occastion which means no Common Wire Detected.

My question I guess is the Common Wire is also a 24 Volt source, the way I understand things. Why not just split (Jumper) the Red Wire to the Common Connection on the Thermostat? This would create a parallel connection of 24 Volts.

It appears that the Nest C Wire Adapter is doing something similar as there is no additional transformer.

The only thing I can think of is the Amperage may not be there but many of the 24 Volt Non Google /Nest Adapters are only .2 amps to a max I have seen of .5 amp at 24 Volts. The .5 amp one handles more than The Nest Thermostat (EcoBee and Honeywell) as well as other Household 24 volt needs.

Unfortunately this is not something you can get a confirmation on from Google/Nest. Not to mention I would also assume it would be different from furance to furnace (24 Transformer capability/setup).

The Adapater probably has a few diodes etc for protection I bet.

Thoughts, Anyone try something similar?

Chris
SolomonMan

[redwire]

Re: Nest Thermostat Discussion...

Wiring the Nest is a torture exercise. google has dumbed down little blurbs and videos, trying to make it easier for the masses. Nope.

Not an expert but it appears the Nest must have full time power, compared to older versions that were quite fine power stealing to do charging and then running off the battery for the short time heat/cool was activated.
It doesn't seem to be a reliable strategy now, oddball malfunctions and error messages. The Nest needs dedicated power.

Power comes from the C wire which is a problem for many homes as C is not run to a thermostat typically.
I can't find technical details or a teardown of the Nest Power Connector C wire substitute module. It appears to just siphon enough power for the Nest from the other control lines

If you don't have air conditioning (cooling) then I would just use the extra Y wire to supply the C. Label it though. So you're connecting the yellow wire at both ends to the C, breaking the law of colour codes but saving the need to run a new cable to the thermostat with more conductors.

R - red 24VAC hot
W - white 24VAC common

[SolomonMan]

Re: Nest Thermostat Discussion...

RedWire,
Thanks for the Response!

Everyone is saying I should have a C connector at the Furnace. The other Connectors at furnace are labeled Clearly.

Its another one of those, I wished I took a pic of the Model Number/layout before I left my son's type of thing.

I do have all the Manuals on these York Furnaces (I have three homes, all have Yorks within Five years of each other and all put in by my dad and I.

I threw this same question out to a DIY Group I follow and then someone suggested the reuse of that wire (Y) as well. (Easy enough)

They Also said,
"

Standard HVAC systems use 24V AC and "C" is the "other wire" that completes an electric circuit.

Basically on the transformer that makes this 24V, it will have 120V hot and neutral feeding the incoming side, and R and C on the outgoing side.

A basic thermostat doesn't need C because it is just a switch and doesn't actually need power to work, or if it does it gets it's power from disposable batteries.

Thermostats that do need power to work either need R and C wires, or they "steel power" from between R and one of the other "open switch" wires that are not being used at the time (which isn't a very reliable way to do it).

So yes, inside of the furnace there will be a C wire, but perhaps it's not labeled. If you can follow the wires inside back to the low voltage side of the transformer, R usually goes directly to one side of it, while C would be the other wire (and is also usually connected to ground).

Hope this helps.
"

So there must be a C connector and I might have to use my DMM to find it but sound like I need to locate it. The funny thing about this is I swear I remember my late dad cussing something about the C wire when he hooked things up originally.

So another thing I am wondering, not related to this Post... but some work I will be doing in the late spring once our battery backup sump is installed in the basement. I have not done AC HVAC before but will be installing my first AC System. There will be a new furnace in the mix as well. The question, then does the AC Condenser unit more than likely run off the Y and C Wires? The C wire being the Common for it as well. Am I correct on this assumption?

Thanks again for the help,
Chris

[redwire]

Re: Nest Thermostat Discussion...

What model is the furnace? There's a York Stellar, Stellar Plus. For a pic of the control board.
The control board will have a C terminal, I would use the Y wire (wrongly) for running C to the Nest. Or get the C wire adapter module.

But if you want to run the Nest with A/C then I would pull a new thermostat cable with more than 4 conductors. This isn't too bad if you use fish tape, small video inspection cam (Lowes) etc. as the cable usually just goes straight down to the furnace room. If you want control over the fan, A/C you need say 6 conductor cable or add another 4 etc.

York furnaces are rare up here, I've repaired one a few times GY9S080B12UP11J, it doesn't do so great in Canadian winters. A few times it was rusty dirty flame rod, and the last was the silicon nitride hot wire igniter. York part is $140 but I put in a generic $20 part (hint keep a spare). The heat exchanger had a recall over water build up and corrosion and rust. It just has so much water in it running at say -30°C and the flame rod gets a rust build up and the leakage current trips the flameout detection. Realistically most furnaces and A/C are chinese parts - the blower, fan, pressure switch etc. so I don't have a lot of brand loyalty. Lennox are junk so far.

I see your post https://www.diychatroom.com/threads/...ussion.744494/

[SolomonMan]

Re: Nest Thermostat Discussion...

RedWire ,
I will be up at my son's on Tuesday.

I believe it is Stellar Plus. All of them are High Efficiency 97% if I remember correctly.

From the different things I have read the common (C) wire if one is not present we can just bolt it to the side of the furnace. I will use the yellow wire as the Common Wire.

The plan is to take a good look again when I get there for the C Connection on the furnace. If its not in plain sight with my (ultra-bright) flashlight I will look the model up online and pull the manual.

I also am up there on Tuesday putting replacing a Dryer belt system (belt, pulley, and rollers).

Thanks,
Chris

[redwire]

Re: Nest Thermostat Discussion...

From York control board pics, "C" it's on the terminal strip at the end. If instead you have all spade terminals, it's labelled there too.
Common problem is cold solder joints on furnace control boards, so try to be gentle with it, and don't forget to shut off power when going in.
I'd also give the flame rod a cleaning, this winter sucks so far.

[SolomonMan]

Re: Nest Thermostat Discussion...

All,
We got it today when I was at my boys.

Basically we found that there was a C wire. Its kind not as apparent then the other wires. I have included a picture.

After installing it with the Wire and hooking it to the thermostat the N260 error and the no charging notification went away.

I should add its the lower right one (blue).

Thanks everyone for the help,
Chris