Nest Learning Thermostat

drtom

I recently purchased a Nest Learning Thermostat (<a href="http://www.nest.com/">www.nest.com</a>)

I followed the installation instructions and the thermostat did not get any power. It turns out that I have a 16volt transformer (I read this on the side of the transformer) and the Nest thermostat requires 24volts to get enough power. Is it okay for me to simply replace my 16volt transformer with a 24volt transformer? Or is it possible that this will ruin my heating system? My heating system is a simple boiler that uses natural gas and heats water to make steam for my radiators.

nicholas bonham-carter

16 volts

see if you can get the numbers off the gas valve, and any other information such as the electrical requirements of the valve, and the baso switch which the thermocouple connects to. a professional installer maybe required here.

remember that most thermostats have to be set for steam heat with one cycle per hour, or else comfort and fuel economy will suffer.

please keep us informed about your experience with this nifty-looking thermostat. many of us here believe that a nighttime setback will actually save no fuel because the system has to heat everything up again after the setback. so the best efficiency is obtained by keeping a constant temperature, or at most a few degrees change. perhaps you will not want it moving the set-point around on its own, except when you are going away for a few days.--nbc

drtom

Oops!

Boy was I wrong! I have no idea what the voltage on my system is. I retraced the wires from my boiler back to my thermostat and there is no transformer at all! (The one that says 16 volts appears to go to my doorbell). And the wiring diagram printed on the side of my boiler specifically says that a transformer is not required. My NEW question is...

If I add a transformer into the line between the boiler and the thermostat, will I screw up my boiler? Thanks in advance!

drtom

Cycles per hour...

I asked the people at Nest if their thermostat would control cycles per hour and they told me that it is set at the factory for one cycle per hour and that it cannot be changed. They also told me that the thermostat will Learn what the most efficient heating strategy is, and then I won't have to guess if I should set the temperature down or if I should leave it relatively constant at night.

Mark Eatherton

You could have a milli volt system...

Or not. In any case, we'd need to know a lot more about the boiler and existing controls to be able to make a recommendation. If you do put a transformer onto a millivolt system, you WILL be replacing the gas valve.



It may require you to set a transformer, a relay and possibly a 3 wire thermostat wire depending upon how thier thermostat works (power robbing, verus no power robbing.



Need boiler manufacture name, model number etc.



ME

drtom

Pictures!

Okay, I am attaching pictures to this post.































So, the question is... If I add a 24 volt transformer to this system (enough voltage to power the Nest Thermostat) will I ruin my system. The wiring diagram says to avoid adding a transformer, is that the final word?

Gordan

You can't use it

Powerpile is a millivolt system. Read this:



http://support.nest.com/customer/portal/articles/206324

Mark Eatherton

You could, but....

It is going to require a qualified technician to set a transformer/relay in order to make it work. You will need to replace the current 2 wire thermostat wire with a minimum of a 3 wires in order to make it work.



Whether or not it is worth it is up to you...



Personally, I think its a lot of glitz and glitter.



Consider placing an outdoor reset control at the heating appliance, and skip turning the thermostat up and down. Its much simpler to install. If you want to reduce you energy bill for heating by 30%, consider replacing the dinosaur with a new modcon boiler. More money, yes, but cutting your fuel bull by 1/3 is pretty substantial.



ME

drtom

Glitz and Glitter

The reason that I want to use this thermostat is because I really like the aesthetic. It is attractive, and that is important to me. However, it is not so important that I want to damage my current system which seems to work fine. So, is it really possible to add the transformer? Or is that just asking for trouble?

And who is a "qualified technician"? Is my licensed electrician not qualified? What about my plumber?

Gordan

Well, the Nest folks say it's not compatible...

They're not providing alternate wiring schemes for "switched" vs. "AC in." Besides, wouldn't you need four wires? As in, two switched, 24VAC, and ground?

Mark Eatherton

Not a simple matter for homeowners to do...

Hence, not recommended in their instruction book. They are wanting to make switch out quick and simple. Their electrical engineers know how to do it, but it takes it out of the hands of a weekend warrior with tools scenario.



It is just a glorified switch with some AI on board.



ME

Mark Eatherton

Doc...

In my estimation, you would want to use someone who understands the operation of a millivolt gas train, a hydronic heating system with substantial experience handling and working on electricity.



I know of one electrician that I could trust doing what I want, and he's retired.



I know very few plumbers who understand everything there is to know about hydronics, and electronics/electricity. They are out there, but rarer than hens teeth.



Where are you located?



I need to take a class on reading and retention. You can't place a modcon boiler because you are on steam. There is an outdoor reset controller available for steam, and savings can be as high as 15%.



I also noticed on your moniker that you are in Rhode Island. Lucky for you that one of the countries BEST heating technicians is located in your state. Tim McElawin (semi retired) can possibly do the work for you, or hook you up with someone who can if he is too busy.



Tim's contact information is Tim McElwain





ME

Mark Eatherton

And another thing....

I'm not sure how often or how long you get power outages, but your present boiler WILL work without electricity. Modifying the logic as I have proposed will negate that ability during a power outage.



ME

drtom

Tim McElwain

I just called Tim and asked for his opinion/advice...

He made his stance very clear... "You will be all set if you just leave your old thermostat in".



Looks like the Nest Thermostat is Not for me.

Mark Eatherton

He's the man...

And if he says skip it, then I'd skip it.



ME

neophytehomeowner

imho

as i understand it, complex setback algorithms like the one use by the Nest thermostat are useless for saving energy because recovery of temp eats up the gains of setback. Agree that most thermostats are ugly and Nest looks a lot better, but the idea of playing around with temps unless it is a vacation home is overblown as a way of saving energy or money.

GW

yes

I did the training video and was rather amazed at how, when you crank up the heat, it 'tells' you how long it will take to reach that set point. I guess that's not rocket science (the nest knows where you're located), but it must take the little critter some time to learn.



Yes, a relay would be needed. or a taco SR501

AaronH

Simple Circuit will make it work!

Just two components and some quick wiring and the Nest will work with millivolt.



120v>24v AC Transformer: http://www.homedepot.com/h_d1/N-5yc1v/R-203193109/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053



24V Relay: http://www.delcity.net/cartviewitem?item=73982&search=24v+transformer



1) Disconnect the thermostat wires from the gas valve, and connect them to the terminals on the relay.



2) Connect the transformer 120v circuit to mains power



3) Connect one thermostat wire to the transformer, the other to one of the coil terminals on the relay.



4) Connect a wire between the 2nd terminal on the transformer and 2nd terminal on the relay for the coil.

Gordan

Yes, yes... the emperor's naked

Show-off. :-) Yep, the key is to never even send the millivolt stuff up to the thermostat, but to keep it all in the basement.

Mark Eatherton

Easy for you to say... Aaron

But how comfortable is the good doctor (or anyone else reading your response) at handling line voltage, which CAN cause death? Hence the reason for my recommending a qualified contractor.



Not everyone has the same skill sets or competence levels. I didn't look at the wiring schematics for the stat, but I assume there has to be a hot, neutral and switch leg (3 wires total) going to the stat. Milivolt systems are strictly two wire, and it is a special wire (low resistance) at that to avoid power transmission losses.



I've seen people wire their own systems, and it worked great, as long as the basement light was left on. As soon as they turned off the basement light, they had no heat :-)



Remember, not everyone reading this stuff is qualified to simply re-wire their heating system.





ME

AaronH

Agreed Mark

Yea, I've seen some pretty scary "home-brew" electrical wiring in my line of work as a marine electrician.



That said, the transformer I picked off HD's website is plug-in which avoids 120v wiring. The rest is really no more complicated than swapping out the thermostat. If the good doctor would like a wiring diagram, I'm happy to provide one.



Remember: although a little bit of knowledge can be a dangerous thing, not sharing one's knowledge with others should be a crime.

John Mills_5

Easy for a pro

If you want this stat, call your favorite heating dealer. This is not a hard project for a PRO. Hardest part would be getting a new wire from the boiler to the stat location if the Nest needs a common. I agree with the rest, not a DIY job but if you want it, go for it with a good tech. 

drtom

Qualified?!

I think I'll pass.



It isn't worth it to me to create a system that doesn't work when the power goes out (like in an ice storm). Also, my licensed electrician, who came highly recommended by a successful local contractor suggested that he could just add a 24volt transformer to the system without changing anything else, so if he is any example, I think that a Qualified Technician around here is a little hard to find.

Al Corelli_2

Sixteen Volts.....

Sounds like a doorbell transformer.

GW

nope

Keep shopping for another electrician

Mark Eatherton

In fairness to the Sparky...

If he was asked only to set a transformer on the boiler so that the NEST could get 24 volts, then he would have been OK. Trouble starts IF he tries to interface the old and new controls.



ME

Ex Maine Doug

Easy problem to solve

I would just install the Nest on the wall in a spot where everyone will see it and let the old existing stat run the steamer.  You could show the Nest off to all your friends and tell them that your heat even works when the power goes off. They will rush home and Nest sales in RH will go up.  Everyone gets happy.

Tim Potter

DC vs AC Relay

I think the relay you referenced from Del City is 24v DC, the modern heating controls are 24v AC, The transformer looks like it would work fine, but you would have to substitute something like the RIB (Relay in a Box) or similar.