Nest thermostat working as expected?

NewbieInQueens

Hello everyone, was hoping for some input for anyone that might've installed a Nest thermostat on their steam system. The issue or question I have is the boiler seems to stop calling for heat or maybe it is because it's getting cut off at the pressure.

Scenario:
Thermostat set to 80 degrees, room temp 70 degrees (NEST turns orange here)
Boiler will run for about 20-30 minutes
Thermostat still set to 80 degrees, room temp perhaps 71 degrees, BUT Nest no longer orange or says "Heating", instead it just shows the room temp and the desired temp

Now for the next 2 hours or so, every 8 minutes the boiler stops running for about 3-4 minutes. So 8-10 minutes on, 3-4 off. While the boiler is running, the Nest is ORANGE, during those 3-4 minutes it stops, the Nest is not ORANGE.

To me it sounds that perhaps it is cycling and the Nest only lights up to reflect the boiler is running. But I want to make sure that the problem is that the Nest is just stopping calling for heat instead.

Nest tech support is worthless, the guy said that if it's NOT Orange it's not calling for heat. In my mind perhaps it never stops calling for heat, but only uses Orange to reflect when the boiler is actually running.

Hoping perhaps someone that is more familiar with Boilers could clear this up for me,
thanks all

Abracadabra

Not sure how nests work, but don't they supposedly "learn"? If so, is this a recently installed nest? Maybe it's just trying to learn your system.

nicholas bonham-carter

Disconnect the Nest, and short out the terminals to simulate a call for heat. See how the system behaves, and make sure that all radiators are getting steam at the same time at a couple of ounces.
Where is the nest located?--NBC

BobC

Was the system working normally before you installed the nest? If it was then the thermostat may not have been set up correctly.
I found this online from someone that installed it in a house with steam heat. Read it to make sure you went through the setup correctly.

https://ambroselittle.wordpress.com/2012/11/24/installing-nest-in-a-100-year-old-house-with-radiator-heating-a-guidereview/

If you had never run the system with the nest I would put the old thermostat back on the system and see how that behaves. Then we will know if it's a system issue or a thermostat issue.

Bob

NewbieInQueens

Thanks for all the replies,

So I had already turned off all the Nest learning features, I use it strictly as a normal thermostat, but I only needed it to be able to control via the web since I live far away from the property.

I would also under normal circumstances just replace it with a normal thermostat to test the behavior of the boiler, but I am out of town (idiot me should've tested this before, but once I saw the boiler was running, I never let it run the full day to test since it was summer)

Also, it's my first year with this property so I am not sure if the boiler cycled that way before. I know, lots of mistakes on my part, learning slowly

So figured someone who had a nest would know if the Orange screen means it's calling for heat or only to represent when the boiler is running

Jamie Hall

I believe that if the Nest is orange, it's calling for heat. If not, not. And what you are seeing is a system which is nicely set up for forced hot air heat.

I have heard that it is possible to set up a Nest for steam -- one cycle per hour or thereabouts, but I've never tried it myself. Apparently, according to that link, there is a setting for "radiators". You might try that.

You may also find that using big daily setbacks costs you more in fuel than you might imagine... steam doesn't play well with big daily setbacks.

Jchris

It may be that the pressure control is interrupting all power to the system-including the controls. If when it is in those 3-4 min breaks, there is no loop power to the thermostat, the Nest may not know what is going on.

vaporvac

Someone recently posted about a similar problem with the ecobee smartstat. Do you have a cycleguard auto refill? This shuts the boiler down about every ten minutes to check for foaming or something and can go off on LW which then resets the Tstat. If you have it and are losing any water due to a leak or just a surging waterline due to oil, this may be the culprit. I'll try and link to the post when I have a longer minute. Found it: http://forum.heatinghelp.com/discussion/151939/ecobee-smartsi-repeatedly-shutting-off#latest

ChrisJ

I tried a Nest on steam and took it back the next morning.

I'll be honest and admit it was only hooked up one hour so it really didn't get tested but during the initial hour it locked up for no apparent reason and that was enough for me to be done with it.

David Nadle

I looked into the Nest when it first came out and there seemed to be no way to set a 1 hour cycle.

TheRooster

I have a Nest on my steam system, maybe I can help.

So if the Nest is calling for heat but the display is BLACK not ORANGE, most likely one of the safety devices cut power to the Nest. That may be the pressuretrol or if you have a Cyclegard on your system, the 3-4 min may be for an intermittent water level check although that wouldn't explain why it runs for 8 minutes between cycles.

It was good that you disabled all the learning features, they don't work with steam radiation. The nice thing about the Nest, and why I use it, is for the schedule and the internet connectivity. I like to turn on the boiler when I know I am heading home and I like to monitor the temperature when I go away in the winter.

Nest also has some problems with certain transformers so you may need to run a common wire to the Nest. Sometimes the Nest gets buggy if the power is constantly cut to it.

NewbieInQueens

TheRooster said:

I have a Nest on my steam system, maybe I can help.

So if the Nest is calling for heat but the display is BLACK not ORANGE, most likely one of the safety devices cut power to the Nest. That may be the pressuretrol or if you have a Cyclegard on your system, the 3-4 min may be for an intermittent water level check although that wouldn't explain why it runs for 8 minutes between cycles.

It was good that you disabled all the learning features, they don't work with steam radiation. The nice thing about the Nest, and why I use it, is for the schedule and the internet connectivity. I like to turn on the boiler when I know I am heading home and I like to monitor the temperature when I go away in the winter.

Nest also has some problems with certain transformers so you may need to run a common wire to the Nest. Sometimes the Nest gets buggy if the power is constantly cut to it.

THANKS! that was the confirmation I was looking for. I only have a pressuretrol and suspected that was why it had a long 1st run cycle when the system was cold, then the 8on/3off is the boiler cycling.

I'm guessing that is not optimal, going to have all the vents checked out to make sure they are working as expected. I do know the boiler is oversized by quite a bit and am going to replace it in the spring.

KC_Jones

TheRooster said:

I have a Nest on my steam system, maybe I can help.

It was good that you disabled all the learning features, they don't work with steam radiation.

I have had the learning feature on my steam system for over 10 years and it works just fine for me. Are you saying it doesn't work with the Nest or you don't think it works on any thermostat? If it's the second I would disagree as I have experience to the contrary. It took a few weeks when I first installed it, but after that it had the timing down pretty well. I just replaced the boiler and venting and I noticed it overshot the first couple times because I sped the system up dramatically, but it is getting better with each day. It is essentially relearning the new system. FYI I have a separate thermometer next to the thermostat so I can see the truth.

TheRooster

KC_Jones said:

I have had the learning feature on my steam system for over 10 years and it works just fine for me. Are you saying it doesn't work with the Nest or you don't think it works on any thermostat?

I just meant the Nest, the radiator setting on nest is geared towards hot water and not steam, at least that was what the techs at Nest told me last year.

KC_Jones

Ok lol. I believe this ties in with the CPH setting not being present with the Nest? I wonder if Honeywells new Lyric has this setting to work with steam? I am getting a new thermostat soon so I am just starting to do my research.

Paul_11

Your nest is either wired wrong or broken.
it will be orange whenever the desired temp is higher than the actual room temp
I have seen many programmable tstats wired wrong and all power to them goes off whenever a safety or operational control turns off the boiler
I would double check the wiring

I use the Nest on steam two ways
1) as a remote override of the heat demand signal with a Tekmar 279 control if my customer has the $ and a 3 story or more building
2) When my customer does not have the money or lives in a single level home.

TheRooster

Paul said:

Your nest is either wired wrong or broken.
it will be orange whenever the desired temp is higher than the actual room temp
I have seen many programmable tstats wired wrong and all power to them goes off whenever a safety or operational control turns off the boiler

Paul, the t-stat is neither wired wrong nor is it broken. If a safety device cuts power to Rh while the t-stat is calling for heat, the display goes black. The Nest is operating as it should.

Paul_11

NOT IN MY HOUSE IT DOESN'T
If you use three wires and if the Nest is wired so it is powered up constantly, it stays orange even when a safty limit shuts down the boiler.
I think you said it in your answer.
Don't wire it so the boiler can interrupt the power to the nest.
I just went and double checked my own boiler by lowering the aquastat.
The boiler shut off and the nest stayed orange.

NewbieInQueens

I will say, I realized after posting this that I could also test with another NEST I have in my other home. That is one is wired with 3 cables (r, w,c) and when I cranked up the heat it displayed the same behavior with the Orange turning to black when the pressure cut off.

Also maybe that makes sense, because in order for the Nest to display the runtime (fuel burned), it should only log when it's Orange (running), because when it cuts off it is not burning fuel right?

Paul_11

I just opened up my nest and checked the wiring.
I'm using RC, C, and W1 and mine stays orange even if the boiler if off on high temperature limit.

So I switched the wire from RC to RH and checked it again just now and it made no difference

The nest stays orange even with the boiler off on high limit either way.

Now I have to say that mine are hot water boilers with a Taco six zone relay.

I have the w1 wire going back to the TR connection on the taco relay which turns the heating pump on and turns the boiler on.

In any case I can't see how the Nest could know that a high limit has interrupted the signal and the boiler is off.

BUT just because I'm curious and I'm a certified Nest installer, I called Nest and asked them.

Nest technical support says that the nest does not measure boiler run time but only the amount of hours the Nest is calling for heat.

Nest confirmed that the Nest thermostat has no clue if the boiler is on or off and will remain orange as long as the room temperature is below the desired set temperature.

So if your Nest is not operating that way, call them at 855-469-6378 and figure out why.

David Nadle

If you don't have a dedicated power wire to your thermostat, can't you use batteries as a backup? An alternative is to mount a relay to the boiler jacket and run the thermostat directly off the transformer secondary, letting it switch the relay instead of the controls circuit.

SWEI

The electronics in a typical programmable thermostat consume a trivial amount of power -- easily supplied by a small battery or two. Smart thermostats come with a full IP stack, a webserver, and a WiFi radio, requiring an order of magnitude more juice.

TheRooster

The Nest has battery backup, and everything that I have seen, even in the Nest energy usage, the Nest does not track usage while the Rh is not powered (ergo, while the safety devices have locked out the circuit).

Now IF YOU HAVE SOME SORT OF BACKUP POWER TO THE THERMOSTAT!!!! Like a dedicated relay, transformer or other control device, YES, the Nest will stay ORANGE while calling for heat because it does not KNOW if the burner is running or not.

I think it is actually is to our advantage that the Nest keeps track of when the burner is firing or not. In the energy usage, you can actually see when the burner cuts out because of a safety device.

handbanana

The Nest is great for remote control, and reporting, but for steam it seems funny.
I have one at home, on a one pipe steam system. After reading this, I paid closer attention to the orange/black and cycling.
It's cold here (nassau cnty LI) tonight, and coming home to a warming boiler(remote control) from a 2° setback I noticed short cycling at about target temp. I figured IT"S COLD!!! Trying to maintain....
It was the thermostat, not the ptrol cycling..trying to maintain room temp in my drafty windowed 1925'er.

I have a 2 wire hookup to Nest, and it does switch from orange to black within a minute of the ptrol cutting out.
It knows...
By the way - I HAVE seen Nest display a message to the effect of "HEATING DELAYED" during the pressure relief period between cycles. Not always though.
https://nest.com/support/article/Why-is-cooling-or-heating-sometimes-delayed

Anyone have a preferred remote capable tstat for one pipe steam?

SWEI

With a two wire connection, you are powering the Nest down at the end of the cycle. You need a proper 3-wire connection including the common terminal. No update on whether they ever implemented a 2 CPH option for steam.