Best Thermostat for Steam?

AdmiralYoda

I've got an older Honeywell programmable thermostat that's on its way out because some of its buttons aren't working anymore.

Years back I set it up for steam, I don't remember exactly how...but I did.  It has worked reasonably well but does tend to overshoot at times.

I'd like to get a new one that has a good track record with steam and has settings for cycles per hour and is good at heat anticipation.  I don't tend to use a setback as the boiler ends up short cycling then overshooting.  I more or less set it and forget it.

What do you pros recommend?

STEVEusaPA

Simplest, dumbest one you can find. An old T87 would be perfect.

AdmiralYoda

Looks like they make a digital T87, I might check that out.

I will admit...I do kind of want to stick with programmable just because I might try small setbacks again at some point after I've tweaked things as much as I can.

Any programmable ones out there worth it for steam?

Jamie Hall

Any of the Honeywells seem to work -- they come in flavours from pretty simple to all kinds of fancy. My own preference would be the T87, which isn't programmable -- but is very reliable. If you could find a mercury T87, they have an excellent anticipator. Takes a bit of fiddling to get right, but they are bulletproof. Hard to find.

The steam settings will be in the advanced menus -- you'd have to look at the manual, but they're not hard to find. Sometimes there is only one -- cycles per hour (set it to 1). Sometimes they add another setting for system type.

The Steam Whisperer

IIRC you generally need the mid to upper grade Honeywell to get the settings you need for steam

Precaud

I changed to Honeywell TH5110D1022 this year and like it a lot.

ChrisJ

The best thermostat in my opinion is the Honeywell Prestige.  I have one setup with the internet gateway, outdoor sensor and three indoor sensors.

I do not believe it's considered a smart thermostat because it's all manual but in my opinion it's the best you can buy period.

It'll do fine with steam set to 1 or 2 cph.  Mine runs my steam and my 2 stage central air.

Jack M

Is there such a thing as “max run time” on a thermostat? If the radiators are “full” I’d prefer the boiler cycle off no matter what the room temperature. 

Jamie Hall

Jack M said:

Is there such a thing as “max run time” on a thermostat? If the radiators are “full” I’d prefer the boiler cycle off no matter what the room temperature. 

Fundamentally, no. A thermostat, basically, is a device which reacts to temperature and sends a signal -- on or off. Now that is not to say that one can't build such a function in, but that makes it a system controller, not a thermostat as such.

There are a number of ways that such a function can be added -- a straight timer, for instance. Or, a little more sophisticated, adding a thermostat to a radiator (or as has been done quite successfully in a number of controllers) one which senses when steam reaches the end of a steam main. Or...

There is one point, though: you say you'd like the boiler to turn off when the radiators are full. However, they will empty exceedingly quickly -- within a minute or two at most -- after their steam supply is cut off. This may provide nowhere near enough heat to meet the space demand, so I'm not exactly sure why you would want to do that. If the heat demand is high, steam radiators can and will run full for a long time.

wam525

I just had to replace mine and installed a Honeywell RTH8560D. Easy to use, program, and is working very well for the past 6 months.

dabrakeman

Below Ecobee support transcript. We will see where it goes but at least they were receptive to the idea.
(order of communication newest to oldest)


ecobee Support (ecobee Support)

Dec 6, 2020, 10:38 AM EST

Hello ....,

I agree with your point "a simple max runtime cutoff for single stage boiler systems with perhaps a selectable min restart time would be a huge advantage in the steam market" and I will be happy to forward your request/suggestion to our Product Development Team for review. Although we cannot guarantee all feature requests/suggestions will be implemented, please know that all are reviewed before any decisions are made.

I’d like to thank you for taking the time to share your thoughts with us. If you have any other ideas or features that you would like to see implemented, please do not hesitate to reach out to us.


Regards,
ecobee support
.

Dec 5, 2020, 7:05 PM EST

Ecobee support,
Thank you so much for your reply. I was pretty sure that indeed not having a 2-stage setup was the reason but was also hoping in a sense it could be faked into thinking there was a 2nd stage which when directed to would simply turn off the boiler. I understand your point/concern that the shutoff may conflict with set point programming but if a boiler is left to run too long it gets shutoff anyway by the pressuretrol as pressure will start to rise once all the radiators are full of steam. This again is mainly an issue with systems that have oversized boilers for the amount of radiators but it is amazing how common this is. Given the amount of discussion on this topic on forums such as heatinghelp.com ("strictly steam") allowing a simple max runtime cutoff for single stage boiler systems with perhaps a selectable min restart time would be a huge advantage in the steam market. I know it doesn't seem like a growing market but there are a huge number of users out there looking for new smart solutions and historic homes are not going away.

Best Regards,
Myself
ecobee Support (ecobee Support)

Dec 5, 2020, 5:38 PM EST

Hello ...,

Thank you for contacting ecobee support.

I checked the installation settings of your ecobee and it only has one stage heating which is why you don't have the 'Stage 1 Max runtime'. That is only for multiple stage heating systems so that you can decide a cutoff when the ecobee should hop on to the second stage after a specific runtime.

Having a 'Stage 1 max runtime' for only one stage heating might sometimes end up conflicting with the set point. As the runtime may reach but the setpoint hasn't and this might create conflict with the programming and system which is why we don't have that option for the one-stage heating system.

If you refer to this article below, it mentions that this setting is for the two-stage furnace.
Threshold settings for ecobee thermostats

​

I hope this helps but feel free to reply back if there's any further query.


Regards,
ecobee support

Dec 5, 2020, 9:37 AM EST

Hello. I have a question, however, about a feature I believe should be on my Ecobee 4 according to the literature but I cannot find on my unit. That is the threshold setting for "maximum stage 1 runtime". Going to the menu that particular setting does not appear to be there. I do have a "minimum runtime" applied which is necessary with steam to prevent the system coming on shortly in advance of a setback and thus not running long enough to get steam to the radiators. Usually want a steam system to run at least 15 minutes. Many steam system boilers are oversized relative to their standing radiation (EDR) so recovering from setbacks can often result in a boiler running long enough that too much pressure is generated and the system has to get shut off by the pressuretrol. It may do some short cycles after that shutting off on pressure each cycle if the thermostat and actual temperature differential remains. Even pressuretrol cutout pressures as low as 1.5 psi is not really good for the system causing issues with the radiator vents in particular. Very very helpful would be the addition of the MAX RUNTIME threshold for these type systems which once you learn your system and know how long it takes for the pressure to start building beyond desired you could set the maximum runtime accordingly. In my case I would like to set it at 60 minutes. So, sorry for the long winded message here but could you tell me whether my Ecobee4 purchased 1 year ago indeed has this capability and if so how I find it if it is not in the same options list as the minimum run time?

Best Regards,

PMJ

Jack M said:

Is there such a thing as “max run time” on a thermostat? If the radiators are “full” I’d prefer the boiler cycle off no matter what the room temperature. 

I'm with you @Jack M . Since most of us own old systems with installed radiation that was never intended to be full, I use a remote temp switch and then a fixed timer from there to get to the same partial fill on every burn no matter what the conditions. There is never a need to be full so I don't ever go there.

Unfortunately, you are not going to accomplish this with just a thermostat.

SteamHeat

I am not a pro, but I have had good service from Robertshaw and Aprilaire thermostats because they have adjustable differential.

I try to have at least a 2 degree difference (3 is better) and that keeps the boiler runs to a fewer number for a greater length of time. Otherwise, with a standard stat with a 1 degree swing, you just spend fuel getting the water to achieve steam and are then shutting down right away. You end up burning fuel and getting little heat from it.

I prefer manual stats rather than programmable. I have them on when home and off when out. The emergency bottom setting prevents freezing if you get stuck someplace while out, but unless you keep your place really cold while home, a freeze is unlikely unless you get locked up somewhere. LOL !

Hope this helps.

MountainSteam

I have a two pipe steam system in a large 80 year old mostly uninsulated house at 9000 ft in the rockies. When I fixed many of the piping issues introduced by the reckless 1990’s boiler installation, I also added a ecobee4. Although many of its features are not useful to me, I’m very happy with it for these reasons:

• Heat minimum on time & Heat differential temperature - By playing with these thresholds, I am able optimize the boiler cycle times.
  
• Multiple remote sensors - By experimenting with remote sensors, and even moving them around as needed on some days, I can somewhat balance the heat throughout the house and take into account the wood stove’s contribution. With the old single point thermostat, I’d end up with some very hot and very cold rooms.
  
• Web portal - The historical cycle data combined with outdoor temperature data has helped me optimize the system. It’s also handy to check the house while I am away for long trips.
  
• Setbacks - I know this is not recommended, but I use 1 to 2 degree setbacks at key times and deliver a cycle as needed for ultimate comfort in my schedule.
  

As discussed in this thread, I’d like to add a “max run time” setting, or better yet a “you got full radiators and the boiler can't make them any hotter just now so give it a rest” setting so that the boiler would not keep running when the radiators are all full of steam. However, like others, I don’t think the thermostat can do that because the time to “radiators full” is not constant and the thermostat has no way of knowing when that’s happened. Also, I want this mostly during unusual times when I have to turn off the heat for a contractor or for some other reason allow a part of the house to cool down. When that happens I can manage the boiler cycles to bring it back to the right temperature gradually so that the thermostat doesn’t call for heat when the radiators are full.

I hope this amateur view helps.

Jack M

I have a mercury T87 on this "one pipe" system. I'm in the house all the time now that school and work is remote. I know that after 20 minutes, the radiators are full and the pressure on the boiler is still at .3
I don't need the boiler to fire any longer so I get up from my chair and move the thermostat to shut down and then move the thermostat back to the original set point. I probably do this half a dozen times during the day. This "manual" shut down keeps the house a nice even temperature, and drastically reduces the run time on the boiler. Fuel consumption is down, less wear on the burner, and I am happy.
Maybe I just need to tweak the anticipator. I did pick up an ECOBEE (and transformer) in hopes of getting "cycle time" that dabrakeman alluded to.

Jamie Hall

If the system is overshooting the set temperature, you do need to tweak the anticipator. Properly set, that thermostat is capable of maintaining temperature within half a degree, regardless of what the weather is doing outside (wind, sun, temperature, whatever...).

That said, it does take some patience to get the anticipator right -- and most folks would much rather plug and play...

Hap_Hazzard

I replaced my LUX TX1500b with a Honeywell T87F. I still have the LUX if you want it, but I'm much happier with the T87.

gfrbrookline

I love my honeywell visionpro 8000. I have 4 wireless sensors that averages the building and I can control it through my phone with their app and gateway as @ChrisJ does. It also lets me see what each sensor is reading with some work so I can confirm that each of the units in my building is reaching the same temperature and the heat is balanced.

Robert_T

My experience (over 50 years) is you need an adjustable anticipator to effectively fine tune heating systems especially one pipe steam. The anticipator is a hidden element in all of these new digital thermostats and is adjusted with the dip switches that come with a one size fits all mentality & adjustment.  A number of old style analogue White Rodgers thermostats still are available with infinitely adjustable anticipators. It is important to note that this fine tuning is most critical with one pipe steam and not so much so with other systems but still can come into play in fine tuning any system for length of cycles.  With one pipe steam it is critical to have some boiler (in between calls for heat) off time to allow condensate to return back to the boiler in order to not have a flooded system. (especially if you have an automatic water adder on the boiler) So how does the anticipator help prevent flooding? The anticipator is simply a little heater built into the thermostat that fools it into thinking it is warmer than it really is allowing it to stop calling for heat for a period of time.  It turns out that in the early days of developing automatic systems (electric thermostats) it was discovered that when the wall temperature reached 70 degrees the middle of the room might overshoot and might be as much as 75 degrees consequently some smart person reasoned that if a small heater was built  into  the thermostat it would serve to equalize the temp on wall (at the thermostat) with the rest of the room. 

Jamie Hall

Good description there! Thank you! The old mercury Honeywel T87s have that, too,, and the work just fine -- once you get them set.

dabrakeman

Having the ability to use remote sensors also helps address that wall temperature issue among other issues.

Jack M

Correction- this is T86 not "T87" as previously stated. The setting on the anticipator is moved to the .4
The thermostat is set level.
Seems pretty extreme.

Newburgh70

MountainSteam said:

I have a two pipe steam system in a large 80 year old mostly uninsulated house at 9000 ft in the rockies. When I fixed many of the piping issues introduced by the reckless 1990’s boiler installation, I also added a ecobee4. Although many of its features are not useful to me, I’m very happy with it for these reasons:

• Heat minimum on time & Heat differential temperature - By playing with these thresholds, I am able optimize the boiler cycle times.
  
• Multiple remote sensors - By experimenting with remote sensors, and even moving them around as needed on some days, I can somewhat balance the heat throughout the house and take into account the wood stove’s contribution. With the old single point thermostat, I’d end up with some very hot and very cold rooms.
  
• Web portal - The historical cycle data combined with outdoor temperature data has helped me optimize the system. It’s also handy to check the house while I am away for long trips.
  
• Setbacks - I know this is not recommended, but I use 1 to 2 degree setbacks at key times and deliver a cycle as needed for ultimate comfort in my schedule.
  

As discussed in this thread, I’d like to add a “max run time” setting, or better yet a “you got full radiators and the boiler can't make them any hotter just now so give it a rest” setting so that the boiler would not keep running when the radiators are all full of steam. However, like others, I don’t think the thermostat can do that because the time to “radiators full” is not constant and the thermostat has no way of knowing when that’s happened. Also, I want this mostly during unusual times when I have to turn off the heat for a contractor or for some other reason allow a part of the house to cool down. When that happens I can manage the boiler cycles to bring it back to the right temperature gradually so that the thermostat doesn’t call for heat when the radiators are full.

I hope this amateur view helps.

I am doing something similar. May I ask what your setbacks look like and what differential you have set? I have a minimum 20 minute run time and a 1.5 Differential. The only setback I have is turning the temp down to 67 at night when sleeping. Wouldn't the vaporstat solve this problem and override the thermostat to turn off the boiler? @Jamie Hall