Problems with Google Nest Thermostat

Ithaca_Mike

Hello, and thank you in advance for any help!
We recently installed a new Google Nest smart thermostat (3rd generation), and are having a problem with the heat turning on when it's not called for. I've read about this common problem on the Google forums, and tried some of the simple "settings" solutions to no avail. The radiators are getting hot at times (not constantly) without it being called for - not only when the heat setting is well below the room temp, but when the thermostat is actually turned off.
We have gas heat with baseboard radiators; no AC, so only 2 wire connections within the thermostat. There are only 2 zones: the full house heat, and the indirect water heater next to the boiler. Each zone is controlled with an Erie "pop top" actuator, and I wonder if the problem lies within the wiring to these (and/or between them), because the times when the heat turns on inappropriately seems to be when we've just run hot water (and thus activated the water heater to turn the boiler on).
I'm having a really hard time understanding the wiring diagrams for these devices. Each one is new within the last few years, replacements when the previous ones failed, and I connected the wiring just as I found it. I'd be happy to post photos of the actuators or anything that might be helpful, but I thought I'd start here for some guidance. Thank you!! - Mike

EBEBRATT-Ed

Nest will not work reliably without a "C" common wire. They have a battery in them that needs charging and uses a lot of power. Investigate if you have a third wire in you thermostat cable.

Then you will have to decide weather to through the Nest away or do some rewiring and add a transformer and relay

HVACNUT

This is definitely a new issue since the Nest's? 
The Erie zone valves have levers outside. Do they move freely?
Locked open?
If there's an extra wire you can connect to Common at the transformer for the zone valves to make the thermostats 24v powered like they should be. 
I hate it when my new toy doesn't work.

Ithaca_Mike

To answer the questions posted above: This is definitely a new issue with the Nest, and there is not a 3rd wire in the thermostat wire. I really want to start by making sure the wire connections are correct. I really don't know all the functions here, so I'm just going to write it out like I'm a 4 year old and hope someone knows how it's supposed to be:

There are 2 zone valves. Each has terminals marked Th, TR, Th/TR, and 2 terminals marked ES.

Valve #1 (house heat) has the wire from the house thermostat connected to Th/TR (red) and Th (white).

It has 2 wires coming from the transformer on the boiler: wire 1 connects to Th/TR (red) and TR (white). Wire 2 connects to the 2 ES terminals.

A wire connects the ES terminals on valve #1 to the same on valve #2 (indirect water heater).

A wire connects the Th/TR (red) and TR (white) on valve #1 to Th/TR (red) and Th (white) on valve #2.

The only other wire to valve #2 is the thermostat wire from the water heater, connected to Th/TR (red) and TR (white).

And again, what's very clearly happening is that the house heat is coming on strong when the water heater calls for heat (i.e. when we start using hot water), even though the house temp is well above the set temp on the thermostat.

The other thing I don't understand is the thermostat wire. When I replaced the thermostat, I found that there were 2 separate thermostat wires coming from the wall (like colors twisted together and connected as one wire to the thermostat), but just one emerging in the basement and connected to the zone valve. I connected them as-is to the new thermostat. When Google support said that there should not be 2 wires into each terminal, I didn't believe this to be the source of the problem but investigated it - I separated the two, determined which one leads to the boiler by continuity testing, and tried it with only this one connected. Then, the thermostat said that it was receiving no power - yet another thing I didn't understand - so I re-connected both. Like I said, the second wire here is also a thermostat wire, but I have no idea where it leads.

Thank you for your help, and your patience with a novice!

Mike

Jamie Hall

First, the Nest requires three wires to operate properly, regardless of what the wizards in Silicon Valley say.

They are a power supply -- usually, but not always, a red wire. A common return for the power back to the transformer -- often yellow. A switched wire, usually white, which is connected internally to the red wire when the thermostat is calling for heat and is otherwise not connected internally, but must, of course, be connected to the appropriate screw on the Nest base.

I admit to being rather puzzled by one section in your wiring description. You state that there is a red wire from TH/TR on the Zone 1 valve to TH/TR on the zone 2 valve, and a white wire which connects from TR on the zone 1 valve to TH on the zone valve. Then also a red wire from Zone 2 TH to one terminal of the water heater aquastat a white wire from Zone 2 Th/TR to the aquastat.

I think you may have two problems, not just one -- and that they may have been hidden until you installed the Nest. First, the wiring of your zone valves just doesn't sound right. I'm not an expert on Honeywell valves -- which these sound like -- but somethings odd there. Second, the Nest needs constant power, or its actions become at best unpredictable.

EBEBRATT-Ed

@Ithaca_Mike

Even though Nest tells you you can run with 2 wires they are wrong. You need 3 wire to operate with a Nest. The Nest has a large battery that needs recharging which means you need a third (common) wire.

If you run a Nest on 2 wire it attempts to charge the battery by "power stealing" when the heat is off. This doesn't work

My nephew installed one in his house worked for a year ok then failed. It was hooked up 2 wire.

he kept getting error code and erratic operation.

I ran the third wire and installed a relay and installed a dedicated transformer problem solved.

Nest will never admit they are wrong

We get several "nest" service calls here a week, they are always trouble

Solid_Fuel_Man

I've I stalled many many many Nest, and other smart WiFi thermostats. 

3 wires or it won't work! End of story. 

I can post a wire diagram for you, but you ABSOLUTLY MUST have 3 wires at the thermostat or it will randomly call for heat as it's stealing power to try and charge the battery. 

I repeat 3 wires must be brought to the thermostat. It is usually a pretty easy job to pull a new 3 or 4 wire cable up to the thermostat location. 

AdamInEvergreen

@Ithaca_Mike full disclosure I didn't read every word in the thread and I have limited experience, but am in the process of researching how to get c-power to my thermostat. There are a variety of ways to get C-power to a nest thermostat;
-No extra wire coming from heating appliance to thermostat; use a wall wort power plug (this is super easy so perhaps worthwhile for diagnostic purposes) or a doorbell transformer (hard wires in to electrical system, probably involves some drywall damage to install)
-If you have an extra wire there are a few c-wire adapters out there, including a google nest branded one...they hook up in your boiler (or whatever) room and provide juice on that extra wire running from your boiler to your thermostat
-If you have the extra wire it may work to install a Taco (or whatever) Zone valve controller
-There are some other c-wire adapter products that are applicable if you have more wires related to a heating plus cooling system...("Venstar Add a Wire") but I haven't looked into this because it isn't applicable to me

Lastly...I haven't found a product that does this that is actually available. (Edit it appears the google nest c-wire adapter does this)..but this site details adding a device in your boiler room that allows more power draw over 2 wires without tripping your heating system in to the on mode. They may have discontinued it for good reason...
https://thesimple.zendesk.com/hc/en-us/articles/115002871751-C-Wire-Adapter-Module-Installation-Guide


Wall worts, honeywell and Google nest c wire adapters:

Ithaca_Mike

All the feedback is appreciated. So, to take the Nest back, or install 3 wires? I've never run wire behind finished walls, but I'm generally a do-it-yourselfer and could probably do it. It looks like the only portion of the run that I can't see and reach from the basement is the 6 ft drop from the thermostat straight through the floor. I'll do my homework on technique but I welcome any pointers! And, Solid Fuel Man, if you could tell me which wire connects to which terminal in the Nest, that would be appreciated, since these connections will be different. Thanks again!

Can anyone advise on the wiring to and between the 2 Erie Pop Top zone valves? I would think it would always be the same for such a simple system, but I can't seem to find an easy diagram.

Solid_Fuel_Man

You will connect the R, W, and C conmections on your Nest to the new 3 conductor cable. 18/3 gauge is fine. 

You should be able to fish the new cable up that 6 hidden feet, if you are lucky the old 2 conductor cable isn't stapled and you can simply tape the new cable to the old one and pull it down. Also you can use a string with a washer on it and drop it down the drywall hole. This would require making the hole in the basement bigger most likely. 

Take a picture of your zone valves and post them here and we can better advise you on how to connect the 3 wires down in the basement. 

You are only controlling one zone valve with the Nest correct?

AdamInEvergreen

@Ithaca_Mike actually the Google Nest c wire adapter looks like it may do what you want...need to figure out how to wire it in your boiler room but it does appear that it will let your Nest draw extra power over your existing two wires without tripping the system on.




Edit: Also, sounds like replacing your existing 2 wire thermostat cable with a 3 wire might be pretty easy. You'd probably attach (not terminate) a brand new cable to the old one with something like electrical tape then use the old wire to pull the new wire through. Obviously you have to be pretty gentle with the pulling, but if it is actually straight down through the floor and you can get beneath it should be cake.

robertfromnj

Google Nest requires a third wire--the common wire--to keep the battery charged. The battery runs down 'cause the thing is always talking on the wifi. Other thermostats, like the Honeywell, live for years on a set of batteries because they just keep time. That doesn't take much juice.

The fact is, wifi doesn't really need that much power. You could sneak that much power out of the thermostat circuit without starting the burner...if you could get some cooperation from the engineers at Beckett. Then you could keep using that two-wire pair that's been buried in your walls for eighty years. Indeed, some folks have figured out how to jumper a couple of terminals with a 1000 ohm resistor and get the Nest to work on two wires. Your mileage may vary.

Beckett has a fifty-dollar solution, but it will still require a new thermostat wire. You replace the transformer and the plate under the Genisys controller. Now you have five terminals on the furnace, including a common. It comes with a warranty. Beckett 51950U. Cheaper at my plumbing supply house than Amazon.

Solutions that ADD a transformer to power the Nest strike me as trouble. You never, ever want two supplies powering a single circuit. That's asking for trouble. An "isolation" transformer? The engineer in me isn't convinced.

FWIW, Holohan was interviewed by the New York Times. He said the Nest doesn't do much for steam systems. It has no adjustable hysteresis. When the temperature goes down one degree, the furnace goes on. When the room air gets to temperature, it turns off. That's not the way radiators or radiant heat work.

Jamie Hall

Interesting commentary, @robertfromnj and, of course, that is what the wizards of Silicon Valley suggest. According to them, the problem isn't the Nest, it's everyone else.

The problem with the ingenious solution is that while it actually does work, for some devices, some of the time, it is hardly universal. Current stealing -- which is what any two wire solution is going to need, ultimately, depends on the insensitivity of the controlled device to the stolen current. For some devices, 20 milliamps or so just isn't going to make any difference. Some devices, more sensitive to small currents, it will cause erratic operation. Some devices will look at it as a closed circuit and never turn off.

Then there's the minor problem that when the thermostat is acting as a close circuit, the charging circuit in the cute widget isn't charging. That's OK, if the thermostat only calls for a few minutes at a time. But if it calls for an hour? Maybe the battery in the widget can hold out... and maybe not. Then what? Widget shuts down -- and shuts down the call for heat.

No. The notion of charging over a two wire circuit which is also a control circuit is fundamentally flawed, except for devices which are built to multiplex. Which these aren't. California's call for everyone else to march to their drum is not a solution.

Ithaca_Mike

OK, thanks again for the input. I'm going with a new 3-wire - it looks like I'm gonna have some difficulty running it through the wall/floor, I can't get the available slack in the existing wire to slide (maybe it's stapled in there). So I'm hooking it up first to see if everything will indeed work. Right now, I don't know where to put the "C" wire on the zone valve, so if someone can tell me from this picture...my finger is on the existing (old) 2 wire in the photo. The obscured connection on the lower left is "Th/TR".

pecmsg

If your pulling wires make it 8 strand. 

Ithaca_Mike

I really do appreciate everyone's time, and it's great that some really experienced and knowledgeable people have weighed in. The problem is, I, although a reasonable intelligent person, really know very little about all this. And with all my reading in the last 2 days, I'm finding the vocabulary confusing, because different people use different terms for the same thing.
So, I'd really love it if someone could make this very simple for me. I picked up a 4-wire thermostat wire, and will not be using blue. So I have, in my Google Nest Learning thermostat (generation 3), my red in Rh, white in W1, and green in C. On the zone valve, I have these terminals: on the left, 3 terminals - top to bottom, Th, Tr, and Th/Tr; on the right, 2 terminals - each labeled ES. I'd like to know where to attach my 3 wires.
I believe that if I hook up my new wire correctly, I can try it out, and it will work; I say this based on the empirical proof that, although I don't understand the connections between the two zone valves, everything had been working just fine before.
Thanks again!

AdamInEvergreen

robertfromnj said:

Solutions that ADD a transformer to power the Nest strike me as trouble. You never, ever want two supplies powering a single circuit. That's asking for trouble. An "isolation" transformer? The engineer in me isn't convinced.

Genuine questions...is this that dissimilar to a relay? Also isn't a battery on the thermostat a power supply in the context of your statement?

Jamie Hall

AdamInEvergreen said:

robertfromnj said:

Solutions that ADD a transformer to power the Nest strike me as trouble. You never, ever want two supplies powering a single circuit. That's asking for trouble. An "isolation" transformer? The engineer in me isn't convinced.

Genuine questions...is this that dissimilar to a relay? Also isn't a battery on the thermostat a power supply in the context of your statement?

It's a little more complex. In general, one doesn't want to power supplies on a single circuit, no. However, there are many exceptions. In the case of the Nest -- and other three wire required thermostats -- an independent transformer powering it is not really on a single circuit, although the transformer (on C and R) does share a terminal -- but not the whole circuit -- with the thermostat switch (actually a Triac, I think -- although it could (and in my view should) be a relay), which is on R and W. The battery in the Nest -- as in many other devices, such as the computer on which I am typing -- is charged from the external power supply (C and R for the Nest), and floats on the external power when that is available.

In the simplest thermostat setup, where the thermostat directly controls the burner control, all the thermostat does is close a switch, and the that completes a circuit with its own power supply in the burner control. In more complex systems, using a zone control board or some such, the power supply for the thermostat circuit is on the zone control board, and again all the thermostat does is close the circuit.

Where things get interesting is when one needs more power for some reason than either the burner control can provide (very limited) or the zone board or whatever. In some settings, one can parallel another transformer with the one on the board (I wouldn't do that with the burner control!) provided both transformers are connected in phase and both are powered off the same line circuit.

The place where the two wire dodge for the Nest causes difficulty is that internally, in the absence of external power on C and R, the Nest will try to use the burner (or zone) power which is present between R and W. This works, but only -- as I implied above -- if the device controlled by R and W is tolerant of what is, in effect, a medium resistance short between R and W, and if the internal switch in the widget is open enough of the time to actually keep the battery charged, and if the external device can, in fact, supply enough power. On most applications for which the Nest and friends were designed -- air conditioners, heat pumps, and forced air furnaces, with all electronic controls -- these conditions are usually met, and the two wire work around will work. But the Nest was not designed with older forced air furnaces in mind, never mind steam or conventional hot water systems, and even more radiant floors and the like (they simply don't exist in the Bay Area of California) so, not surprisingly, it works poorly when it works at all.

The resistor gimmick sometimes suggested works because it effectively increases the resistance of that short circuit on the burner control. It is a delicate balancing act between providing enough current to charge the Nest's battery and yet not enough current to trip the burner or zone control. In electronic terms, it is a kludge. In my view, a megakludge.

Ithaca_Mike

Again, I'm loving the academic discussion, but still looking for where to put my new C wire on the zone valve. I think I found in the chapter above that the Nest would like the C wire to be on the "TR" terminal on the zone valve. Is there anyone out there that can say simply "Yes" to this statement, or "No - the wire from the C terminal in your thermostat needs to go to the ____ terminal"?

EBEBRATT-Ed

@Ithaca_Mike

It's hard to sy because we don't know ho they hooked up the zone valve. And the colors can be confusing. And if someone reversed the wires it would probably still work.


So do this.

Find your transformer. One wire from the transformer should go directly to the zone valve. That would be your "C" common wire. If you have multiple zone valves the "C" wire will also feed those valves

Then to make sure that that was the "C" wire find the other wire coming off the transformer. This is your "R" wire and it should go to "R" on the thermostat(s).

Then "w" from the thermostat goes to the valve to power it open

R & W from above should be hooked to your old thermostat wire.

If you need more help come on back

Ithaca_Mike

Just the fact that you say "It's hard to sy because we don't know ho they hooked up the zone valve" makes me think I'm still not communicating the way I need to, because I thought I listed absolutely every wire connection to each of the 2 zone valves above. So I really don't know what the missing info is here. But in the meantime, I hooked it up the way I thought I understood it, and it seems to be working properly. It would be nice to know that the wiring between the 2 zone valves is as it should be but at this point I don't know how else to ask the questions. Thank you to the DIYers who gave help to try to solve the problem.

Jamie Hall

Not really missing. What I -- at least -- would need to know is not the wire colours, but the exact connections from whatever your power source is to each of the control or controlled devices and on through to whatever other devices there may be. Individual wires, not bundles or pairs.

I'm not trying to be difficult -- but unless I can follow, wire by wire, connection by connection, I can't do much.

EBEBRATT-Ed

@Ithaca_Mike

I will post a diagram tonight or tomorrow.

Ithaca_Mike

Yes, I listed, wire by wire, connection by connection, each end of each of the 2 colored strands of each wire. I named the color so that the reader would know what terminal is on each end of said wire; I do realize that the color of the wire does not bear upon its functional properties. Honestly (and I'm not trying to be difficult either), at this point I don't know what else I could provide. Seriously...how else could I lay it out?
The power source is the transformer on the boiler. As I listed, I see (2) two-strand wires coming out of it, and both of them attach to the same zone valve (zone 1, the house heat). This is part of what I don't understand - how the flow of power goes, and why one of these wires has both red and white attached to the ES terminals.

EBEBRATT-Ed

Here you go.

Just so you know

TH/TR on the zone valve is a "dummy terminal" in other words nothing inside the valve is connected to that terminal. It's just a splice point to hook the two R wires together. You could take the wires off that terminal and wire nut them and it would be the same thing.

The end switch on the valve is just a set of contacts. When the zone valve is closed (not powered) the end switch contacts are open. When the thermostat opens the valve the end switch contacts close. Chances are all your zone valve end switches are wired in parallel and usually either start the boiler or start a circulator or something. Its just contacts the power come from whatever the end switch starts so reversing the wires on the end switch does nothing.

And on the valve TH/TR is the dummy terminal TH (usually white) is power from W on the thermostat to open the valve. TR is the common wire from the transformer. So for the valve to open you would have 24 volts between TH & TR

kb3hvp

I think the valves are not wired correctly. Think of the TR as TRansformer and the TH as THermostat. The transformer is wired to both sets of TR terminals. The boiler is connected to both sets of ES terminals. The thermostat and indirect are connected to the appropriate TH terminals.

Ithaca_Mike

I'm still confused - I have 2 wires, each carrying 24V (tested) coming from the transformer (is this normal with a multi valve system?) They connect to Tr on each valve, correct? So what is the "burner control" in figure 4 above? That connects with Es but I don't know from where! I have no other wiring than what I've listed - a thermostat wire for each zone valve, two 24V wires coming out of the transformer, and a couple wires connecting the 2 valves (where I'm trying to determine the proper connections)

Given this info, could someone tell me where these wires should go? Can the transformer wire run, as it is, to just zone 1 valve, and then use a connector to valve 2? If so, can you clarify where it should attach on each end (because I think this may be wrong as it exists)? And if that is the setup, where does the second wire from the transformer go?

And, I now have run a 3-wire from the smart thermostat, and I still don't really know where the "C" wire should attach on the zone valve.

Jamie Hall

Thermostat to zone valve: one wire from R on thermostat to TH/TR on zone valve. One wire from W on thermostat to TH on zone valve. One wire from C on thermostat to TR on zone valve.

Transformer to zone valve: one wire to TH/TR. One wire to TR.

The thermostat power comes from TH/TR and TR. TH is from the switched W terminal on the thermostat and powers the zone valve open.

The TH/TR terminals on the zone valves can all be connected together. The TR terminals can all be connected together. The TH terminals are unique to each zone valve thermostat pair.

Zone valve to boiler: one wire from ES (either one) to T on boiler. One wire from the other ES to the other T. These switches can be wired in parallel. The ES terminals are simple switches. The necessary power for them comes from the burner control.

EBEBRATT-Ed

@Ithaca_Mike

Mike I posted a wiring diagram for you in my previous post. Did you not see it?

Solid_Fuel_Man

White
Green
Red

Those go on thr zone valve in that order, on the left 3 terminals. 

Jells

Just read this whole thread and am confused. My 2 Nest-E units with 2 wire seem to work perfectly on zones of my 5 zone hot water system. Am I not noticing erratic behavior or are there more variables?

EBEBRATT-Ed

@Jells

Time will tell. Nest's have a battery in them that charges through the wiring. The battery takes a fair amount of power.Problem is it can only charge when the equipment is off. It's called "power sstealing" Most of them seem to work ok in the beginning and then get erratic and fail to work. They have to be hooked up with a third (common) wire regardless of what nest tells you.

Maybe your will be different. Time will tell

Jells

EBEBRATT-Ed said:

@Jells

Time will tell. Nest's have a battery in them that charges through the wiring. The battery takes a fair amount of power.Problem is it can only charge when the equipment is off. It's called "power sstealing" Most of them seem to work ok in the beginning and then get erratic and fail to work. They have to be hooked up with a third (common) wire regardless of what nest tells you.

Maybe your will be different. Time will tell

So the duty cycle determines the issue? These are both used with significant daily setbacks since they're for bedrooms and living area, which are empty much of the day.

I had been thinking of using one for a whole house steam system with no setbacks at all, assuming it's learning functions would be able to smooth out the rise and fall of the cycling which is currently 5 degrees. It sounds like that will not work.

Jamie Hall

Yes. I believe -- I haven't tested it -- that the key parameter to getting the things to work with two wires is the duty cycle. The "barttery" (it may be a supercapacitor) hasn't a whole lot of charge capacity even when it is new, and thus it can't keep the thermostat running for a long heating cycle -- but I'm not sure just how long is long. They do seem to be able to recharge quickly. They seem to work pretty well with no more than 5 to 10 minutes calling for heat (or cool), and then about as long to recharge, but things appear to get squirrely if the call time is longer.

HomerJSmith

I'm late to the party, but my Dad always said that I would be late for my own funeral.

Ithaca_Mike, kb3hvp post with wiring diagrams is correct, but only look at fig.4 and ignore the other diagrams.

L1 & L2 on the transformer are at 110Vac. The other two wires coming out of the other side of the transformer are the 24Vac transformer secondaries. We label one wire from the transformer secondary as 24Vac the other wire coming out of the transformer a Common. (C wire)

The 24Vac (R wire) from the transformer goes uninterrupted to the thermostat thru the TH/TR tie screw, the thermostat closes and the 24Vac goes to the zone valve motor connection (TH) and the other wire from the zone motor goes to (TR) the Common (C wire) of the transformer. That's a circuit. That circuit turns on the zone valve motor which closes the switch to the ES connections, which goes to the TT connections on the boiler aquastat, turning on the boiler.

If you look at Fig.4 zone valve wiring connections, You will see that the TH/TR connection is the 24Vac from the transformer to the thermostat. The TH connection from the thermostat goes to the zone motor. The return from the zone motor goes to the TR connection which goes to the common (C wire) of the transformer. When the thermostat closes the zone motor turns on.

Where does the new 4 conductor cable from the Nest connect to? The Red conductor connect from the TH/TR screw on the zone valve to the R terminal on the Nest. The White conductor connects from the TH screw on the zone valve to the W connection on the Nest. The Green wire connects from the TR screw on the zone valve to the C connection on the Nest. The Blue wire is just extra.

I believe this is correct, I hope it doesn't burn down your house.

robertfromnj's, comment is wrong. Putting two transformers in parallel is no problem if they are connected in phase. But that is another story for another time. That's like putting two pumps in parallel, it just increases the flow (current).

You must have some idea where the transformer that's powering the sys is, the aquastat or an external transformer. Transformers have VA (volt/amp) ratings. Zone valves, boiler circuitry, and Nest thermostats gobble up VA. You want to make sure that the transformer rating isn't superseded. If so, you have to add an auxiliary transformer in parallel to the existing power supply or replace it with another higher VA rated transformer.

I tried to make this as lucid as possible, but if not, attribute it to my insobriety, after all it is the Holidays.

Ithaca_Mike

Thank you everyone offering help. I've read it all, including the diagrams. I've had everything as it should be, except...I'm still unclear about the boiler connections. The feedback here all references the connections to the boiler, or the "T" connections, and I don't know how to correlate this with what I'm looking at. I don't know what the T connection is. The only wires I have associated with the boiler come out of the transformer box, and they each carry 24Vac. Are we talking about one of these? Right now one is connected to Th/Tr and Tr as it should be, and the other is connected to both of the ES terminals - all on zone 1, the house heat, with corresponding connections to zone 2 valve. I think this 2nd wire is wrong but it's the way I found it before I replaced the thermostat and wire. Can I test the functions of these two wires? Or does it not matter? I've got the cover off the transformer box, I can see where everything goes within it, but it means nothing to me. Would photos help? The system is basically working, but I think the house heat still runs when the water heater kicks the boiler on.

Jamie Hall

We tend to talk about "T-T" connections. Which do come off the boiler ignition -- and all they want is a closed switch. The do show voltage -- but from the burner control. Do NOT attempt to connect them to anything which is powered directly from a different transformer! You can connect them to the normally open contacts of a relay, or to an independent solid state switch (usually... some caution is advised there) but in any case they do NOT want power.

HomerJSmith

I don't see a pic of your transformer box(?), post one. The ES screws also carry current, but in the zone valves, they are isolated from the thermostat circuit. The TT circuit is the low voltage circuit, 24Vac, that the ES switch when the zone motor closes allows current to flow. That circuit operates the safety switches, the gas valve, circulator relays, etc.

A single transformer can supply all the needed current to operate both sys but there is a limit to how many current gobbling devices, one can run off one transformer.

There is a variation between manufacturers as to boiler control strategies. The TT connection is just the transformer connection. The manufacturer doesn't always label the board with a TT connection. They may label it as something else, but it is the same transformer connection between the 24Vac and common secondaries with a series of closed safety switches in between.

I'm not sure I got that right.

Jells

Wow, I just installed a Nest for my new basement 'kickspace heater' loop. There should be circle in hell for software designers who can't leave well enough alone, and those who redesign a product and use the exact same name but with a non-explicit 'x-gen'.

The new Nests I got from my utility for free seem to be the 3rd gen, not the Nest E that I got from them last time for $60 each. And they don't work with the old Nest app with it's great graphical weekly programming, you need to use the worse design of the Nest Home app.

So far, it seems like it doesn't work as well as the E with the 2 wire system. But it is working without some of the intrusive bells and whistles I didn't need anyway.

EBEBRATT-Ed

No wonder we get so many "Nest" calls on here. The utilities are giving them away

pecmsg

EBEBRATT-Ed said:

No wonder we get so many "Nest" calls on here. The utilities are giving them away

Its more to do with the product!

NEST gives them to the utilities with a good line of BS!