ecobee thermostat with weil mclain boiler

roberts

I'm looking to install an ecobee to replace my old thermostat. The old thermostat has the red wire connected to R, the white wire to W, and there is an unconnected/unused green wire in the cable that I think I can use for a common.

The question I have is how to make the physical connection of the green wire to the common at the boiler end. There are no wiring terminals, things are mostly connected up via crimped on spade connectors.

There is a transformer that has a C terminal with three wires crimped into the spade connector. One of these wires is connected to a grounding screw on the metal box for the transformer. What I think might be easiest is to cut that wire, strip both (newly created) ends, and make a pigtail to connect to the thermostat cable (with the power all turned off of course).

Any better ideas? Any reason not to do this? Photos below.

Thanks!

Common wire:


Transformer:


Schematic:

Waher

Is there a screw at the "C" terminal? The empty spade connector on the bottom right of the photo makes it look like there's a screw at each terminal and that the black wire at "C" should be able to share space with a connected C wire underneath the screw rather than having to strip any existing wiring.

Once you have your Ecobee set up, in the online portal under "system" make sure the Fan tab on the left is set to at least 15 min/hr (or whatever amount of time it takes for your last radiator to heat up) so that when the thermostat calls for heat it gives your boiler enough time to complete a steam cycle.

roberts

Oh wow, my eyes can't see as well as they used to close up, and there are a lot of wires blocking my view, but I took this video and it does look like each terminal does have a screw. The spade connection and solder tab threw me off. Here's a video if you are curious to take a closer look:
https://photos.app.goo.gl/uk8hjgBwYDYGQRLj6

Once you have your Ecobee set up, in the online portal under "system" make sure the Fan tab on the left is set to at least 15 min/hr (or whatever amount of time it takes for your last radiator to heat up) so that when the thermostat calls for heat it gives your boiler enough time to complete a steam cycle.

Wow, thanks for the tip! I was imagining the ecobee would not run a fan as it would know one wasn't connected? I was also a bit nervous about how well the ecobee would play with the timing of things as it does take my system a while to heat up. If the "fan" is on for 15 min/hr what does that even mean when the only control the ecobee has is making the connection on the one pair, either calling for heat or not?

Thanks again,
Rob

Waher

Someone else suggested the fan setting, I'm not actually sure it does what I think it does.
EDIT: there's a different setting for minimum heat run time

Maybe try letting the system run without the setting and see if it works fine first?

roberts

I installed the ecobee this morning. The two thermostat wires from the boiler-side are both black and it turned out that the 24V one was W and the other side was R. So at first the ecobee didn't come on. Swapping the red and white wires so that the 24V actually did make it come on.

However, a couple times when running the ecobee went dark and became unresponsive. I suspect that where I'm getting the 24V from is sometimes switched off by the boiler, for example, maybe there is another control in series with it in between the power source and this "thermostat" wire.

Looking at the above schematic it looks like the low water cutoff does in fact come between the thermostat connection and the 24V connection. Maybe that was triggering?

I'm thinking I should just install an isolation relay and use a separate 24V transformer. Then I'll know I have a good power source.

Waher

Someone else either on Reddit or this forum stated that their Low Water Cut-off cycling a self test every so often would kill the power to their Ecobee.

Waher

https://support.ecobee.com/s/articles/Threshold-settings-for-ecobee-thermostats
It looks like Ecobee's have a heat on minimum run time of 5 minutes that is adjustable. That's probably the correct setting to tweak instead of "fan" run time if the default behavior isn't working well with your system.

I wish there were more in depth discussions on this topic. Seems many people have these thermostats on 1 pipe steam systems but don't talk about the settings other than the curmudgeon's wishing everyone would go back to analog thermostats. =( Discussions seem few and far between without any real conclusions or clear advice.

SteamBoiler

I have a Weil McLain with similar wiring that I am controlling with a Nest. Look at my post history for a schematic for an external 24V 40VA transformer with isolation relay, it is basically your wiring ladder diagram with the extra components and connections. I couldn't get the Nest to run reliably directly off the boiler transformer, kept getting 3 minute power steal heat calls. I figured Nest's R being downstream of the LWCO wasn't helping but didn't want to move more wiring than absolutely essential.  I have my setup running reliably now for the last half of last winter and the first half of this one.

SteamBoiler

As an addendum to my previous post it looks like you are only connecting R and W of Ecobee to G and Y of boiler right now. As you surmised first of all that is downstream of the low water cut off so any intermittency with that unit will affect power to Ecobee. Next you absolutely do want to use that extra wire you seem to have to connect C of Ecobee to C of boiler. But adding an external 24V transformer and isolation relay is trivial if you have a power outlet close to the boiler and makes the thermostat independent of boiler power. Nest and Ecobee draw quite a bit of power.

roberts

Hey thanks for the comments @SteamBoiler .
I went searching for the thread you mentioned, I didn't actually find it, but I did find this very interesting thread:
https://forum.heatinghelp.com/discussion/186137/temp-differential-for-steam

Regarding the isolation relay, I did find this schematic from ecobee:
https://support.ecobee.com/s/articles/ecobee-thermostat-installation-with-an-isolation-relay

And I ordered this from Amazon:
https://www.amazon.com/dp/B09MVXSSP8?psc=1&ref=ppx_yo2ov_dt_b_product_details

and this transformer:
https://www.amazon.com/gp/product/B085TLYBFX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Seems pretty straightforward. One thing I'm not sure about is mounting of the isolation relay. It's probably easiest to just mount it to a joist on the ceiling of the boiler room in my basement. But maybe it would be more protected inside the boiler cabinet? But that seems more difficult. I guess it doesn't matter.

SteamBoiler

Hi @roberts

The wiring is pretty straightforward, for now I left my isolation relay hanging in my boiler cabinet as the wiring spade lugs hold it securely, should probably just duct tape it next to the boiler transformer board.

My transformer is 24V 40VA, outputs 1.67A. I wanted this high of a current capability since Nest by itself draws 200mA and in addition the isolation relay draws another 200mA when ON. Since I was burned by the Nest spurious power stealing calls when wired directly to the boiler I wanted lots of error margin from the external transformer re: current drive.

https://smile.amazon.com/gp/product/B083R621RV

This is my isolation relay, it is an Emerson 90-380. https://smile.amazon.com/gp/product/B000LDCPQS

roberts

Ah, thanks for that. You convinced me that going with a larger transformer is a good idea.

johncharles

@roberts I've lived with an Ecobee on a steam system for 4 years. It's not clear if you have steam or hot water from your posts above. But I'll share my configuration.

I keep my "Heat Differential" at 0.5 this is the most comfortable but on mild days where the boiler hasn't run in a while and is cold it can often shut down before even the closest radiators get heat. There is a second setting called "Heat Minimum on time" I set this to 20 minutes. This gives me a really nice balance between having a pretty tight swing which keeps the house temperature in a tight comfortable band and also preventing Ecobee from short cycling the boiler.

Ecobee seems to have a really good algorithmic anticipator built in so setting a diff of 0.5 using a set point of 70 as an example tells Ecobee to start the boiler 69.5 degrees but it will *NOT* turn off the boiler at 70 it will learn how long to run the boiler and usually turns the boiler off around 69.7 which is actually only a 0.2 degree swing. This is I'm assuming dependent on how your heat emitters react. I have big heavy cast iron radiators in my house, if you are controlling a hot water system with fin tube it will adjust and will run the boiler longer as it won't see as much overshoot.

One other thing which confuses a lot of new Ecobee owners since I think this is different from many other thermostats. The temperature reading on the front of the thermostat is rounded. Meaning that if the temperature in your house is between 69.5 and 70.4 it will read 70.

Using a 1.5 degree differential I find to be very uncomfortable as if your set point is 70 it won't turn the boiler on until you reach 68.5. Assuming a 70 degree set point for simplicity:

0.5 diff = boiler on at 69.5
1.0 diff = boiler on at 69.0
1.5 diff = boiler on at 68.5

Keep in mind boiler off is going to be less than the full swing based on how much over heating happens.
On a related note when you first install it expect some over heating it takes a few weeks for it to start to figure out how much heat is too much heat, but if you leave it it will adjust. Mine is really tight at this point and rarely over heats.

Note: the fan setting mentioned above will not do what you want at all. If Ecobee let's you access the setting (It's pretty good about detecting that you don't have a G or (fan) wire connected) All that would do is energize the G (fan) terminal for 7 and 30 seconds twice an hour. Which for you won't do anything.

roberts

Thanks for all that info @johncharles !

I have a single pipe steam system.

I just set my minimum heat time to 20 minutes, I'll see how that goes.

For anyone following along, this change has to be done at the thermostat, not online, and these instructions helped.

johncharles

Also checkout beestat.io it's really quite nice.I strongly recommend it.

roberts

beestat.io looks quite cool, I generally shy away from giving third parties access to things. But at least it looks like it can only read and not control my thermostat. Maybe I'll give it a try...

SteamBoiler

@johncharles this is phenomenal info and this control over the differential and the minimum run time is really why I recommend Ecobee over Nest, though I have a Nest.

Nest apparently has about 0.5F differential programmed by default and while the heat call duration varies, in general it is about 20 minutes long on average with a range of 15-25 minutes. It takes about 10 minutes for steam to get to the earliest radiators and a little longer if the boiler has been off for a long time.

@roberts once you get comfortable with the thermostat I suggest leaving it at a constant temperature initially as it figures out how long it needs to run for a temperature maintenance call. After some time you can experiment with overnight setbacks. Ours is set to 68F during the day, drop to 64F overnight, and recover in 1F steps from 3.30am to 6.30am. You will see a lot of advice on this forum that setbacks are to be avoided with steam heat, in general the motivation seems to be from people used to the older style thermostats that go from 68F to 64F to 68F in big steps and will cause the boiler to stop on pressure buildup.

Waher

Do you have an Ecobee remote sensor in the room with your further radiator so that the thermostat can see the coldest room at the end of the main?

SteamBoiler

Waher said:

Do you have an Ecobee remote sensor in the room with your further radiator so that the thermostat can see the coldest room at the end of the main?

Not sure if the question was to me. I have a Nest and I don't have the Nest remote sensors. In general there are 2 radiators that are slightly late out of about 15 total, they come on at about 15 minutes into the heat call. They practically never came on with my old mercury thermostat as I believe the heat calls were too short. With our old mercury thermostat the basement and utility room were always hot and the home was always cold (same pressuretrol setting), now that I understand steam heat better I believe that's because the heat calls with the mercury thermostat were too short and the boiler ran frequently but without giving a chance for steam to saturate the radiators. Also borne out by our gas bills, we have used 25% less gas this month compared to the same month last year with the mercury thermostat, and the home's much warmer (and the basement cooler).

The late radiators seem to have the steam traps working (2 pipe system, measured temperature with an IR thermometer) and I may need to replace the main vents. Luckily the late radiators are also in rooms with good radiators, so not a major issue at the moment.

roberts

SteamBoiler said:

@roberts once you get comfortable with the thermostat I suggest leaving it at a constant temperature initially as it figures out how long it needs to run for a temperature maintenance call. After some time you can experiment with overnight setbacks. Ours is set to 68F during the day, drop to 64F overnight, and recover in 1F steps from 3.30am to 6.30am. You will see a lot of advice on this forum that setbacks are to be avoided with steam heat, in general the motivation seems to be from people used to the older style thermostats that go from 68F to 64F to 68F in big steps and will cause the boiler to stop on pressure buildup.

I'm trying to understand why it's such a bad thing for the pressuretrol to kick in? From what I've read, my understanding is that if the boiler has to run for too long, to recover from the setback, that the pressure will get too high and the pressuretrol will cut off the boiler intermittently. I suppose once the pressure drops back down low enough, if the thermostat is still calling for heat, then the boiler will kick in again. I suppose this is not good for the system?

Also, how do I even know if the pressuretrol is kicking in?

We do like the room to be colder at night for sleeping, so I'm hesitant to skip the setback.

Waher said:

Do you have an Ecobee remote sensor in the room with your further radiator so that the thermostat can see the coldest room at the end of the main?

We do have one remote sensor. I currently put it in the bedroom and configured the ecobee to use that sensor when we are sleeping. This is one of the colder rooms of the house.

SteamBoiler

roberts said:

I'm trying to understand why it's such a bad thing for the pressuretrol to kick in? From what I've read, my understanding is that if the boiler has to run for too long, to recover from the setback, that the pressure will get too high and the pressuretrol will cut off the boiler intermittently. I suppose once the pressure drops back down low enough, if the thermostat is still calling for heat, then the boiler will kick in again. I suppose this is not good for the system?

Also, how do I even know if the pressuretrol is kicking in?

We do like the room to be colder at night for sleeping, so I'm hesitant to skip the setback.

My understanding based on browsing this site for about a year, is that in a well designed, implemented and maintained system, steam should be able to saturate the radiators at less than 1psi for a normal heat call. Now on a recovery from setback pressure may build up in sustained fashion and stress the valves, cause noise, clanking, potential leaks etc. We have a 2 pipe system and I can imagine the steam traps at the radiator outputs opening and closing frequently and getting stressed under constant pressure, so I am on board with not letting steam build up excessively. Edit: one thing that's usually mentioned is that steam systems in general are really old and expensive to fix so you don't want to break anything due to stress that may be avoidable.

Myy pressuretrol is set to cut in at approx 0.75psi and differential additive cut out at 1.5psi so it should cut out at approx 2psi in the system (based on advice on this site, they actually want it even lower). On a normal heat call I can't see the needle move on the pressure gauge. Once a year I set the thermostat to an extra long heat call (increment heat setpoint to a few degrees above current) and watch the pressure gauge needle finally move off zero and I can hear the boiler cut out when pressure builds up after maybe 45 minutes of running. This test is very important IMO, you need to make sure the LWCO and pressuretrol are working to control system safety.

Edit: you are absolutely right, in a properly working system if the pressuretrol max pressure is reached the boiler will stop running for the pressure to drop and then start again if the thermostat is still calling for heat.

I like overnight setback as well for the cool home, I am recommending not using a setback initially so that the thermostat learns how long it needs to set the heat call to and then bringing in a setback with gradual recovery once it is stable.

roberts

@SteamBoiler , do you recall how you attached the spade connectors to the thermostat wires? I have some crimp-on spade connectors but I'm getting mixed messages from the Internet as to whether I should crimp those on to solid wire. At least NASA forbids crimping to solid wire. Not sure I have the same standards.

SteamBoiler

roberts said:

@SteamBoiler , do you recall how you attached the spade connectors to the thermostat wires? I have some crimp-on spade connectors but I'm getting mixed messages from the Internet as to whether I should crimp those on to solid wire. At least NASA forbids crimping to solid wire. Not sure I have the same standards.

Crimped. Figured if I lost connection I would know pretty quickly since the heat wouldn't come on

roberts

Makes sense, thanks!

johncharles

I had another thought, while your ecobee is getting used to your setup it might be best to leave the minimum on time off for a while until you see you actually have a problem with your cycles being too short.

Waher

I tried shutting off the minimum run time on mine and so far the Ecobee has been smart enough to not short cycle the boiler. I have one of their remote sensors in a bedroom towards the end of the one pipe system while the thermostat is in a room towards the beginning. It seems to have figured out just the right time to heat to hit the set point stopping a few minutes after filling the last radiator with steam and hitting the set point with the 'momentum' of the heated radiators. I presume Ecobee uses the estimated outdoor temperature from internet weather reports along with an actual measure of the current rate of thermal loss between sensors + the rate of thermal gain to figure it out.

I don't use the away mode or set-backs, but smart heat recovery is turned on. So far so good on Burnham MegaSteam from 2009.

BDR529

If you lose power to the house a good chance the t-stat will get stuck in "configuring" = no heat.
Hope someone is home or close by so they can "power cycle" it.

SteamBoiler

I have a Nest and hence don't have control on the minimum heat call time. What I have observed is that it takes 10-12 minutes for the bulk of the radiators and 15-16 minutes for the 2 laggard radiators to fill with steam. Nest sometimes calls for heat for 13-15 minutes typically on warmish days. If I had the control I would set the heat call time to >=20 minutes to get full value for the heat call energy spent and risk some temperature overshoot.

Jamie Hall

Getting a Nest to play nice with steam seems to be very problematic. First step is to turn off all the smart features. Every single one of them. You'll have to dig in the menus to do that, but they can be strangled. Then somewhere -- buried deep -- there is a way to set the type of system or the cycles per hour, which should be set to steam or one cycle per hour. That may help.

Your time differential between the slowest and fastest radiators is not great enough to worry about, and if the overall time is from a cold start, that's not bad either (if it's from a warm start, more main venting may be in order.

The other solution is to find a mercury T87 and set the anticipator properly and live in peace and warmth...

SteamBoiler

Jamie Hall said:

Getting a Nest to play nice with steam seems to be very problematic. First step is to turn off all the smart features. Every single one of them. You'll have to dig in the menus to do that, but they can be strangled. Then somewhere -- buried deep -- there is a way to set the type of system or the cycles per hour, which should be set to steam or one cycle per hour. That may help.

Your time differential between the slowest and fastest radiators is not great enough to worry about, and if the overall time is from a cold start, that's not bad either (if it's from a warm start, more main venting may be in order.

The other solution is to find a mercury T87 and set the anticipator properly and live in peace and warmth...

Thanks for the comments re: time differential between the earliest and latest radiators. This time differential burnt me with my old mercury thermostat.

I went from a mercury Honeywell Chronotherm to the Nest, and compared to the same month last year, with about the same average outside temperature (as reported by my utility), have used 30% less therms. The main easily available diagnostic for steam system health in my opinion is the heat call duration which Nest logs start, stop times and duration. My mercury thermostat - with anticipator set correctly - was short cycling my boiler and it looks like - in retrospect - heat was getting shut off as soon as it got to the earliest radiators and almost never was the call long enough to get to the latest radiators - so much so that I suspected that the steam traps were bust on these. Now Nest averages 20 minute heat calls which in my home is enough to saturate the late radiators. Calls happen approx once in 2 hours or more frequently depending on outside temperature, which the most frequent being once an hour approx. There is no way to set this, it determines this from the type of system that is input at setup. I have a 4F setback overnight and bring the temperature back up 1F increments in the early am so I don't pressure cycle.

It is incredibly easy to remove the auto schedule on Nest, one doesn't have to "dig in the menus". I agree that Nest auto-schedule is a bust even for people who are on forced air. The type of heat system to set up for comes up immediately when setting up - radiator etc. There are only a few choices for system type when setting up on initial startup. It is not "buried deep". While it is not possible to explicitly set cycles per hour, in practice with its knowing that I am on radiant, it has been at most once per hour for a "temperature maintenance" heat call.

With the mercury thermostat the home was always cold and the basement was always warm. Now the home is comfortable and the basement is too. Same conditions, nothing done to the radiators, same pressuretrol (0.75 cut in, additive 1.5psi cutout, 0-30 pressure gauge almost never moves, I understand this is practically useless). I do need to have someone look at my mains vents as I would like to get steam to the earliest radiators faster than the 10-12 minutes it takes now (it is a relatively warm start typically the boiler ran 2 hours ago).

I would recommend Ecobee (more options) over Nest but as a normal homeowner, either would work and I would never go back to mercury. It is possible one could get the same comfort with a properly set up mercury thermostat but there would be no warning (no heat call log) if it drifted off stable. I love being able to look at the heat call durations and nod to myself that all is well. I love being able to go away on vacation with the boiler set back so I don't have to worry about water level, and bringing the temperature back up slowly on the drive back. No mercury thermostat is going to be able to do that.

pgf

Can someone answer a couple of Ecobee questions? I have a single pipe steam system, and I recently purchased what I think was clearly the wrong smart thermostat for the job -- no control over minimum on time, and the longest cycle time configurable is 30 minutes. So I'm interested that Ecobee seems to have gotten the available settings right.

So:
a) Is there more than one model of Ecobee? Should I be looking at a specific one? I haven't seen any specific recommendations in this thread.
b) Can the Ecobee be used without access to the cloud? My "smart" needs are few:

• configuration of the thermostat from the network
  
• reading the current temperature
  
• setting the setpoint
  

Can the Ecobee do all that?

EdTheHeaterMan

pgf said:

Can someone answer a couple of Ecobee questions? I have a single pipe steam system, and I recently purchased what I think was clearly the wrong smart thermostat for the job -- no control over minimum on time, and the longest cycle time configurable is 30 minutes. So I'm interested that Ecobee seems to have gotten the available settings right.

So:
a) Is there more than one model of Ecobee? Should I be looking at a specific one? I haven't seen any specific recommendations in this thread.
b) Can the Ecobee be used without access to the cloud? My "smart" needs are few:

• configuration of the thermostat from the network
  
• reading the current temperature
  
• setting the setpoint
  

Can the Ecobee do all that?

Does your Ecobee have a model number? If Yes what is it?
If no then do you have the box it came in? Can you take a picture of all 6 sides so I can read them?

pecmsg

Honeywell T87

Available at yard sales.

EdTheHeaterMan

Also. What is the brand name and model number of your steam boiler?

Waher

"the longest cycle time configurable is 30 minutes"
Ecobee will do heating cycles longer than 30 minutes. It doesn't have a maximum runtime setting. It has a minimum runtime setting, defaulting at 5 minutes adjustable up to 30 minutes.

Can the Ecobee be used without access to the cloud?
It will work without internet access as a regular dumb thermostat configurable on the wall, but won't be happy.

My "smart" needs are few:
configuration of the thermostat from the network
Can be done except for the minimum runtime adjustment which has to be set on the physical thermostat under an advanced settings menu. Generally once you figure the minimum time for your system to make steam you could set it to that. I've left mine at the default 5 minutes and not had a problem with short cycling except when interrupted by the low water cut-off cycle guard self test.

reading the current temperature
can be done remotely
setting the setpoint
can be done remotely

pgf

@EdTheHeaterMan -- I don't currently have an Ecobee. I have a Sinope TH1400 that I got because I have one of their baseboard control thermostats and it works really well, and thought that the selectable cycle time (up to 30 minutes) on the TH1400 would suit my needs. But because of their predictive algorithm, the TH1400 often cycles the boiler for just 2 to 5 minutes! Might be okay for some systems, but not steam. (I think it's trying to just nudge the house temp by a little bit, or keep it from overshooting on the way down.) Also, for anyone finding this because they're searching for Sinope: I chose their thermostats because they can use Zigbee, and have a completely open API. I run them with Home Assistant.

My boiler is a Weil-Mclean EG30.

@pecmsg -- I'm not sure why you recommended the T87. Unless I'm missing something, it doesn't satisfy any of my requirements for being remotely accessible. I know the T87 can handle my boiler -- I had one on my wall for 30 years until about 3 weeks ago. In fact, I had two of them: one for daytime and one for nighttime, wired in parallel, along with a computer controlled switch in the cellar that could disconnect the daytime thermostat. I replaced them because although reliable, their thermometers didn't agree with one another, nor with an accurate third thermometer, and their setpoints didn't seem to be accurate either. Setting was always something of a guessing game. It's 2023 -- I want a thermostat that's easy to use.

@Waher -- Thank you for the detailed answer. To your knowledge, do all Ecobee thermostats have the features you describe?

Many thanks, all.

pecmsg

You have Steam heat. Set it and forget it! How many times a day do you Reset the temperature remotely?

pgf

Nighttime setback. And vacation setback. Also used to do daytime setback when we were both working, but now we're retired, so it's up all day.

But really, the answer to your question is that home automation is a hobby for me, and has been, for 40 years -- I'm not going to leave the home heating out of it.

Waher

@pgf, yes to my knowledge all the current Ecobee models have those settings.

You really do not want to do more than a 2 degree setback per hour on a steam system (if you do setbacks, it's best to step them 1 degree per hour). The real benefits of these thermostats is their smart anticipator, remote monitoring, and the ability to put a remote sensor in the furthest/coldest room to make sure a heat cycle runs long enough to heat that room.

pgf

I only just read this morning about stepping the setback. Is that a feature that Ecobee helps with? Or would I need to program that myself?

paul

Waher

You'd have to program a stepping setback yourself with a schedule.