Smart Thermostats and Single Pipe Steam Systems

PMJ

The big logic problem with this is obviously the dramatic variation in time from fire to when heat is actually being put into the space. This time varies easily by a factor of 4-6 times depending on time from last firing, which varies dramatically with demand conditions. It is theoretically possible for this to be "learned" by a smart thermostat. Maybe they do, maybe they don't. They aren't going to show us their algorithm. So as I read here and elsewhere people "fiddle" using trial and error to find the "best" combination of things they allow you to adjust.

In my own experience I found it critical to know the exact point from fire when radiators actually begin radiating. A simple thermal switch is all that is required on the feed pipe of a remote radiator to supply this information to the control. That made for a clean solution to the problem. It also, unfortunately, puts one in the "not off the shelf" control space. But I think getting the best and most even result out of intermittent fire in systems plumbed for continuous steam requires it.

OuterCapeOilguy

The only thermostat I am aware of which will work with a two-wire system is the Lux “Geo.” I have installed four of them in two houses I own which have old two-wire systems controlling hot water baseboard heat (and in one zone, fan-forced convectors). They work well, but with one drawback; used with two-wire systems, they depend upon lithium battery power, and the batteries end up needing replacement every few months. For that reason, I would never sell one to a customer. 

exqheat

Yes. The delay allows the temperature to reach from the radiator to the thermostat.

exqheat

The delay gives the heat from the radiator to travel to the thermostat across the room.

Jamie Hall

trivetman said:

@pgf

does programming the 10 minute delay increase efficiency much as opposed to just letting the system cycle on pressure until the final set point is reached?

No. If anything, it decreases, since when cycling on pressure the boiler is already up to, or very close to, temperature, as is all the piping -- while even with a ten minute shutdown you have to bring it all up again.

PMJ

Jamie Hall said:

trivetman said:

@pgf

does programming the 10 minute delay increase efficiency much as opposed to just letting the system cycle on pressure until the final set point is reached?

No. If anything, it decreases, since when cycling on pressure the boiler is already up to, or very close to, temperature, as is all the piping -- while even with a ten minute shutdown you have to bring it all up again.

My position is that pressure is ever and always a negative to both comfort and efficiency.

ChrisJ

Jamie Hall said:

trivetman said:

@pgf

does programming the 10 minute delay increase efficiency much as opposed to just letting the system cycle on pressure until the final set point is reached?

No. If anything, it decreases, since when cycling on pressure the boiler is already up to, or very close to, temperature, as is all the piping -- while even with a ten minute shutdown you have to bring it all up again.

The piping (in theory) and the boiler all should be insulated, somewhat at least.
Piping with 1" insulation on it isn't going to cool much in 10 minutes, and under most conditions the heat "lost" is lost into the heating space anyway.

I would say it depends on how the system is installed and where it's located.
In my situation, that heat isn't lost and I'd prefer a delay over feeding fuel to make pressure I don't need.

Jamie Hall

If you are making more pressure than you don't need, either set your vapourstat lower -- or use the timer trick. You're quite right -- once the system is up to whatever pressure is needed to operate -- which is often only a few ounces -- you don't need any more.

And @PMJ -- pressure, per se, isn't what we are interested in --and shouldn't be talking about. It's pressure differential which is what I'm concerned with, and I really don't care what the gauge pressure is; it's the absolute pressure differential between point A and point B which is of interest (and necessary). A distinction which you understand, I'm sure --but not everyone does.

PMJ

Jamie Hall said:

If you are making more pressure than you don't need, either set your vapourstat lower -- or use the timer trick. You're quite right -- once the system is up to whatever pressure is needed to operate -- which is often only a few ounces -- you don't need any more.

And @PMJ -- pressure, per se, isn't what we are interested in --and shouldn't be talking about. It's pressure differential which is what I'm concerned with, and I really don't care what the gauge pressure is; it's the absolute pressure differential between point A and point B which is of interest (and necessary). A distinction which you understand, I'm sure --but not everyone does.

I'm thinking the understanding is that any header pressure number is the differential over atmospheric - if the system is open vented - with the open vented radiator being at atmospheric. These systems will run easily with header pressures in single digit inches of water - I don't think @ChrisJ 's one pipe ever exceeds that and I know I don't. So while I agree with your point, to me any pressure in the boiler header that is enough to use a vaporstat(let alone a pressuretrol) as stopping point is way higher than necessary and wasteful.

ChrisJ

PMJ said:

Jamie Hall said:

If you are making more pressure than you don't need, either set your vapourstat lower -- or use the timer trick. You're quite right -- once the system is up to whatever pressure is needed to operate -- which is often only a few ounces -- you don't need any more.

And @PMJ -- pressure, per se, isn't what we are interested in --and shouldn't be talking about. It's pressure differential which is what I'm concerned with, and I really don't care what the gauge pressure is; it's the absolute pressure differential between point A and point B which is of interest (and necessary). A distinction which you understand, I'm sure --but not everyone does.

I'm thinking the understanding is that any header pressure number is the differential over atmospheric - if the system is open vented - with the open vented radiator being at atmospheric. These systems will run easily with header pressures in single digit inches of water - I don't think @ChrisJ 's one pipe ever exceeds that and I know I don't. So while I agree with your point, to me any pressure in the boiler header that is enough to use a vaporstat(let alone a pressuretrol) as stopping point is way higher than necessary and wasteful.

I can heat with 0.25" WC.
It will climb, I guess because the radiators need or want a little more to push extra air out, I don't know. But I'm betting if I slowed the boiler down a little more it would heat completely with 0.25".

The highest I've seen under normal conditions is 0.75 to 1" and that's with full radiators. This is gauge pressure obviously, but since my system is vented to atmosphere I'm pretty sure it's also the pressure difference between point A and B,C,D,E,F,G,H,I,J,K.

Even with half of the TRV's shut it won't go much above 2".

There's two reasons for this.

1: I undersized my boiler against all recommendations on this forum.
2: I vent my radiators as fast as I can, also against most recommendations on this forum.

I'm sure there's no reason systems shouldn't run in a vacuum, radiators are, after all condensers. The only reason I haven't bothered trying is I can't see a way to control mine the way I do with TRVs and a few of mine are grossly oversized.

pgf

I confess that when I implemented my scheme to control the pressure cycling, I was thinking of the losses from starting/stopping the burner, and the losses from the open flue damper. It also just felt wrong to hear it cycling so often while working at my cellar desk, next to the boiler.

ChrisJ

pgf said:

I confess that when I implemented my scheme to control the pressure cycling, I was thinking of the losses from starting/stopping the burner, and the losses from the open flue damper. It also just felt wrong to hear it cycling so often while working at my cellar desk, next to the boiler.

It makes much more sense in my opinion, to shut a system down and let the radiators dissipate some of the stored energy than to keep bouncing the boiler off the "rev limiter" so to speak.

Then fire it back up in 10-15 minutes, and let it fill the radiators again, if need be. Chances are that won't happen.

Jamie Hall

Folks, let's all remember that every steam system is different... and what works marvelously on one may work remarkably poorly on another one.

ChrisJ

Jamie Hall said:

Folks, let's all remember that every steam system is different... and what works marvelously on one may work remarkably poorly on another one.

That's probably true.
But the issue is only one side is pushed here rather than experimenting and trying to get more out of systems.  

I am happy to see many are recommending smaller pickup factors...  20-33 rather than 33-50.

Dave_61

Just a homeowner here, but I have been very happy with the way my Ecobee works with my steam system. We have sensors in the master bedroom and bath. The thermostat is in a large room. We also have a sensor in our family room. We had our boiler replaced by a very knowledgeable contractor who did a great job of matching the new boiler with our radiators' EDR. Depending on the time of day, I have different sensors active. We only drop our nighttime temp by about 3 degrees. But even on a cold day, the house is pretty uniformly warm, and we have no issues wth cycling on pressure. We also do not get overshooting temps as I believe that the Ecobee takes the outdoor temp into account and "learns" how long it takes to heat on a given day. If I understand correctly, it will shut off the oil burner a little early to allow the residual heat in the radiators to finish warming the house.

exqheat

Lets's step back a bit. The anticipator for the T87 was designed to shut off the boiler before the temperature from the radiator hit the thermostat, offering a delay in the boiler fire, in order to avoid the overheating of the room. Thermostats that do not have anticipation capability, need to be set to a setting that will estimate the middle of the droop. Droop being the difference between the high and low temps in the room. This will minimize comfort disparities. Time delay is the time the boiler is shut down to avoid overheat and the time the thermostat is satisfied. This time can be coordinated with the calculated time needed o heat the space. These times should be calculated and adjusted each hour, due to heat loss change over time.

ChrisJ

exqheat said:

Lets's step back a bit. The anticipator for the T87 was designed to shut off the boiler before the temperature from the radiator hit the thermostat, offering a delay in the boiler fire, in order to avoid the overheating of the room. Thermostats that do not have anticipation capability, need to be set to a setting that will estimate the middle of the droop. Droop being the difference between the high and low temps in the room. This will minimize comfort disparities. Time delay is the time the boiler is shut down to avoid overheat and the time the thermostat is satisfied. This time can be coordinated with the calculated time needed o heat the space. These times should be calculated and adjusted each hour, due to heat loss change over time.

Yeah.
And they do, do this.

exqheat

Precise pressures are different for different heat loads. A pressuretrol is fixed, as aqua stats are fixed. That is where the comfort and energy waste originates. Developing a method for precise adjustment of temperatures and fire times is the key.

Jamie Hall

There's and interesting set of tradeoffs... the simplest triad is these three: high reliability, reasonable cost, high sophistication and precision. You can have two, but at most only two, of those three at a time.

exqheat

Depending on the application you can have the control for $400+thermostat+installation. reliability is given. Precision is original.

Logik

The T-87 in my big cold Foyer would way overshoot even if the anticipator was pegged. The house has 26 radiators.

A very big advantage, for me, of the Honeywell Redlink non-programmable thermostat that replaced it is that, since the thermostat itself requires no wires, it is possible to experiment with thermostat placement relative to radiators. At the moment I have the main Redlink thermostat a foot from the cold end of a radiator in a third floor office. This has worked very well, along with Alexa "routines" I mentioned earlier in the thread, to gradually ramp up the set temp over several hours early in the morning. (The auxiliary wireless "Comfort Control" is bedside in the master bedroom.)
Another possible advantage of using Alexa is that from 4th generation on, full-sized Amazon Echo devices have a temp sensor that can also be used in "routines" to control the Redlink system, or any wifi thermostat that can be linked to Alexa, so you can let the temp from any location with an Echo control the boiler. I haven't done that; I just use it to check a bedroom temp, using voice.

Jamie Hall

You do point out one advantage of the wireless thermostats: you can move them until you have them in the right place. No thermostat -- whether an old reliable T87 or the whizziest California dream -- can work properly if it isn't in a good location.

exqheat

It is simpler to get the wireless, as you can move as often to get the sweet spot. T87 will require running the wires each time you move it.

Logik

On T-87: I replaced mine around 1986. I think this happened: I added a Flare (R.I.P.) stack damper to the 9 inch diameter vent on the American Standard 300k btuh steam boiler. Good for efficiency, but this greatly increased the current flow through the thermostat. The anticipator in the T87 is a wee coil in series with whatever it controls. Adding the load made it misbehave no matter how the anticipator was set. Perhaps others had a similar experience - or perhaps I misremember.

exqheat

need to ck and correct wiring. You put thermostat in series with another circuit. Thermostat should be direct to TT.

New England SteamWorks

A 3-conductor thermostat wire is required for smart thermostats (smart = any thermostat which is WiFi capable). If that is present, we use a Taco 501 to make the connections. It's overkill, but the 501 is a stock item for us, and they do the job simply and perfectly.

pfeiffeh

I recently replaced by 30 yr old Boiler with a new UTICA 1604 (single Pipe Gas Heat Steam - 2 wire thermostat and my Nest didnt work well. Went with the non Smart Honeywell 6000 and it works fine but really want a Smart thermostat for a number of reasons

exqheat

Thermostats are not smart. Theyturn the system on and off. Precise control takes thermostat activity and converts it into BTU replacement precision for minimum fuel use.

KarlW

Continuing this resurrected thread…

Before I went with my designed for radiant heat smart Netatmo (works great but not sold in the US), I had great luck with an Emerson Sensi. It’s quite simple as far as thermostats go, but connects smartly to Apple HomeKit and others, and you can put in remote temperature sensors.