thermostat for a steam boiler

Jamie Hall

My VisionPro, at least, has no way of recognizing when the Vaporstat shuts things down -- all it knows is that it hasn't reached the set point yet. On the other hand, if the 'off' cycle on the system is short -- and it should be, if everything is sized right -- the end of cycle cycling doesn't cost much in efficiency, as the boiler is still good and hot when she fires back up. The end of cycle cycling is almost inevitable if the system is sized properly and the setback is too deep; as someone said, try to keep that setback to about 5 degrees -- or use the multi step feature to bring the temperature back up more slowly when you want to recover.

tbousky

thermostat for a steam boiler

I have a steam boiler that is heating a 3 flat apartment building. A traditional thermostat with a single temp setting causes the boiler to cycle on and off frequently and never lets the radiators heat up fully to radiate heat after the boiler shuts down. Seems like there must be a thermostat with a range setting that is 3-4 degrees different. When I am home I do this manually and it is much more comfortable and probably more efficient.

Appreciate any recommendations.

adambuild

!

Sounds like the anticipator might be out of whack. We use the Honeywell VISIONPro 8000 on all steam jobs with great results. We program for steam and set the CPH for 1. Good luck.

tbousky

thanks!

I will check it out.

mel rowe

Adam, when I look at the Vision Pro stats, I see three models. Which one do you use? Thanks.

Bill W@Honeywell

The TH8110U1003...

is the single stage heat/cool model. Remember that you need to "tell" it that it is working a steam system; set it to 1 cycle/hour. Also, if you don't plan to use it for central AC, follow the installer setup and "tell" it that, too. For wiring, use R&W, for heat only. Also, don't use a deep setback. Try 5 degrees as a max, the "flywheel" effect of a steam system is considerable. These are available from any Honeywell distributor or your heating professional. There is no retail equivalent.

mel rowe

Thanks Bill, for the info. I have been interested in trying to find a better stat, but wasn't sure if the Vision Pro would work on my steam system. I don't quite understand how the stat will be able to provide one cycle per hour, since currently my boiler cycles on for about 35 min. and then is off for well over an hour. What do you think the cycle would be like with the Vision Pro controlling it?

David Nadle

1 CPH is a maximum.

The 8000 will call for heat whenever the room tempereature is 1/2 degree below the set point, but never more frequently than once per hour (if you've set it correctly for steam). I have the 8000 on my steam system and it works great.

If your old thermostat had a wide temperature swing then you may see the boiler cycling more often with the VisionPro, but again, not more often than once per hour.

Tom Hopkins

vision pro cycling

I have a Vision Pro on my 2 pipe steam system. It is true that it officially cycles only once per hour (or twice, if I set it that way), but at least as mine is wired, it does not count boiler stops when the boiler pressure is satisfied by the the Vaporstat.

Thus, if the boiler does not make temperature setpoint before cutting out on pressure, it will cycle off and on until setpoint is met and count that as one cycle.

I think my boiler would be more efficient if the Vision Pro would recognize when the boiler cycles off on pressure and end the cycle. Recovery times might be a little longer, but at least the losses from short cycling would be eliminated. Any tricks out there?

Thanks,

Gary

mel rowe

David, thanks for the reply. My system currently has a Honeywell T87F stat. It seems that I have to set the heat anticipator to the far left (1.0) in order for it to stay on long enough to fully heat all rads. The end result is the cycle I mentioned of about 35 min. on and over an hour off. Logically it seems that this is not the optimum way to operate, but when I reduce the heat anticipator setting by very much, it shuts off too soon. Obviously I'm confused by all this and my questions are whether if shorter on/off cycles might imrove the results, and how do I get there? But if the Vision Pro cph setting only limits the number of cycles, I don't see any improvement, unless I'm missing something. (Which wouldn't be the first time.) Any clarification will be appreciated.

Tom Hopkins

Your system is opposite of mine ....

In your case, your boiler is not running long enough to get things hot, while mine gets all the radiators hot in a little over 20 minutes, then cycles off on pressure.

I look forward to the reply from Honeywell, but I believe the Vision Pro will let the boiler run for up to an hour straight. I think it will then repeat the cycle again, but I am not sure. For example, will it do 55 minutes burn, 5 minutes off then 55 minutes burn? I think it will based upon how mine runs.

Is your system properly vented? There may be other reasons why it is taking so long to get steam to all the radiators.

Gary

David Nadle

How's the comfort?

Personally I wouldn't worry about heating the rads all the way across if the house is comfortable. Also, I think a long off period is a good thing, unless it's the result of overshooting the set point and making all or part of the house too warm.

Anticipating what the experts would ask here: Are the mains vented and insulated? If not, doing those things could decrease your on period by a lot.

I don't know what will happen to your cycle if you connect a VisionPro. It might stay the same. As I said, 1 CPH is a limit. It's not going to force the system on once an hour if heat is not needed.

A while back I saw a whitepaper from Honeywell describing the rationale behind setting cycles per hour vs. setting a temperature swing. The end results are very similar. I can't do the paper justice here but I thought it made a lot of sense. And it works well at my house.

David Nadle

I think it can run longer than an hour

My understanding is that the thermostat won't energize its relay more than once per hour, but even if after burning for 60 minutes the room temp was still below set point the tstat would not shut off.

Tom Hopkins

Thanks, Jamie ...

From what I can see, my boiler can produce a 2 - 3 degree rise for one full cycle. We have been setting back 5 beacuse I wake up when the boiler fires in the middle of the night and because 58 is more than warm enough to sleep.

I have the adaptive recovery enabled. I guess I'm spoiled because my equipment at work is controlled by PLC's (Programmable logic controllers). Given a little programming flexibility at home, making the boiler do what I want and be most economical would be a cinch given inputs for the Vaprostat and the thermostat and then controlling those using appropriate logic.

I believe similar results can be achieved with an on delay timer (Keep the boiler off for a set period after cycling off on pressure). I believe the adaptive recovery on the tstat would then adjust to the new heat up rate.

Gary

SusanC

VisionPro 8000 set at 1cph

I have a VisionPro 8000. The 1 cycle per hr. is not a problem. The boiler will run for example 90 mins. (or more or less) if that is required to satisfy the thermostat that the set temperature has been reached. If it's so cold outside that the room temperature cools the roughly 1/2 degree within e.g. 20 mins. after a 90 min. run, the boiler will run again. Apparently and luckily it appears that the 1 cph means that the thermostat allows response to only one new call for heat per hour; the boiler response to the new call for heat can take any length of time

JohnG_3

My >10 year-old Honeywell CT34XX programmable thermostat has finally failed and I am looking at the Honeywell VisionPRO 8000. I'm looking at the owner's manuals on the Honeywell web site and I can't find anything having to do with configuring the thermostat for a steam system and 1 cycle/hour. I think I am looking at the manuals for model #TH8110U1003 but perhaps I have the wrong one. What is the correct manual and how do you configure the unit for steam & 1 cycle/hour?

Eric L._2

set it to 1 cycle/hour

I would like ti know how to set it to 1 cycle/hour as well. Thanks.

Eric

Phil_17

I answered my own question. The setup for the number of cycles per hour is documented in the Installation Guide, but not the Owner's Manual. The VisionPRO 8000 is intended to be installed by a pro and so certain information only appears in the Installation Guide.

Owner's Manual is here.
Installation Guide is here.

archibald tuttle

so cowrong me if i'm wrecked

I just ran the vision pro 8000 series manual including advanced functions and i can't find the setting for cycles per hour. The only function that even seems to relate to cycle length is the recovery function. I'm not sure where it gets that, maybe from an average over time, but if it doesn't have an outdoor input, I don't know how it would know when to start the cycle in anticipation of the recovery time.

But I don't see any direct setting for either system type, e.g. steam, etc, differential, or cycles per hour.

Again, the cycles per hour or the effective differential that the thermostat uses to achieve the cycles per hour should vary with outdoor temperature. Maybe the vision pro keeps a moving average so it slightly adjusts from shoulder season to winter and back to shoulder -- the old bell curve of the heating season.

Anyway, if this is suitable it is on sale here for less than a c note.

There is also I think an 8320 that is supposed to handle more heating loads, does this use remote indoor sensors? I currently use invensys 9700i and 9701i (battery vs. 24v ) because they have an adjustable differential and accept a remote indoor sensor.

(They also accept an exterior sensor but for display purposes only)

I'm paying in the hood of 85 or 90 bucks plus another 25 for the sensor.

these have proven to be more or less the ideal thermostat for some steam systems I have where a three decker is running off of one thermostat. generally, it is the shoulder seasons that produced the problems. In really cold weather it took long enough for the 1 degree unadjustable differential thermostats to make temperature if we chose the location well such that the whole house got more or less heated. I've tried, probably never to the level of lost art science, using adjustable air vents to slow down the faster radiators and that is the theoretically favored solution, but an adjustable differential is still handy for getting a handle on cycles beyond the even heating issue. Also, the remote indoor sensor means that when I have nighttime service calls I can deall with the vast majority of macro issues from the basement rather than having to enter apartments -- not to mention that the temptation for tenants to fiddle with the thermostat is reduced (and the coded based lockout on the invensys (aka robertshaw) tends to limit them fiddling with it even in the basement. Although the good and bad of that is that you can defeat the security by taking out the batteries or turning off the power to the 24v model. Makes it easy to recover control if you lost track of the security code, and for the most part I haven't had intentional tenant disruption, but I try to keep actively engage heating complaints, even ones that appear invalid, so they don't feel they have to resort to taking matters into their own hands.

I'll be interested to hear if the honeywell can duplicate or exceed these features and whether the multiple heat controller can average or take the lowest common denomninator of several remote readings to control a single heating call as well as control several calls to circulators or he like for separate zones from a single controller. Also interested in how the security lock out functions. The manual tells you how to set the lockout, but not what code or approach is required to undo it. Does it ask for a numerical code.

Lastly, since it is a touch screen, how about a frigging digital keyboard appearing on the screen instead of up and down areas for numerical entries. I understand you're always going to end up with arrows to scroll through functions or menus for the most part but I -for one -would much prefer direct numerical input. Maybe you can't justify the size or hardware needed to accomplish this on a pushbutton model (although i'm not sure why given that the numerical keypad has to be one of the most widely manufactured bits for off the shelf adaptation that exists beyond an on and off switch) but with a relatively large touch screen i would think it would be a natural.


Brian



If there is some

Phil_17

The cycles/hour setting is documented in the Installation Manual, not the Owner's Manual. I posted the link upthread.

Leah Frances

JohnG, thanks for supplying those links. Extremely helpful.
bruhl

archibald tuttle

vision pro

Bill,

still trying to figure out whether the 8320 for instance that handles up to 3 heating loads has remote sensors for the additional zones or???

I looked at the wiring diagram on the install and I see the W and Y for several heating zones but not a connection for a remote indoor sensor, unless the remote outdoor sensors double or maybe I looked to quickly.

Brian

PS- John G, thanks for pointing out the difference between the install and users manual.