Church Zone Control

Chuck_17

A church with a 2 pipe steam system (very common). The sanctuary is located above several “classrooms” on the ground level (also very common).
Right now the steam boiler is controlled by a thermostat in the sanctuary.
They want to install control to be able to heat the classrooms during the week without heating the sanctuary to full temperature.
Idea #1:
Install thermostatic control valves on the sanctuary radiators with 24V actuators and a (one) programmable thermostat. Move the regular boiler thermostat to the lower level (one of the classrooms).

Concern #1 – When the sanctuary needs heat, the boiler may not actually start because the lower level is satisfied.
Solution? – Have the sanctuary thermostat also be able to start the boiler.

Concern #2 – The lower level may over heat if the sanctuary all of a sudden wants to raise the temperature.
Solution? - Start the higher setting early enough in the weekend so it has time to even out. Leave some of the sanctuary radiators without control valves.

Has anyone done work like this? Suggestions?

Chuck_17

Side note- It would be awkward to install control valves on the lower level radiators. See photo. Near the left radiator you can just see a branch up to one of the sanctuary radiators.

Jamie Hall

Well... The idea of putting remotely controlled TRVs on the sanctuary radiators will, indeed, work.

However, there will be two problems -- which maybe you can live with and maybe not. First, when the sanctuary radiators are shut down, the boiler will be wildly oversized for the classroom radiators (it's probably oversized anyway, but it will be a lot more oversized) which will lead to a good deal of cycling. Second, you have two choices for control and recovery in the sanctuary, neither of which are very good: you could either put the thermostat in the sanctuary in parallel with the one in the classrooms. Then, when it called for heat, the boiler would run. Unfortunately, the odds are that the classrooms would overheat something fierce. The alternative would be to have the sanctuary thermostat just control the TRVs, and figure out how far ahead of the need for sanctuary heat to turn it up. This would take some fiddling; it might well be that it would have to start trying to recover a day or two ahead, and might well vary with how cold it was outside.

A better way to do it would be to split the system and have two boilers -- one for the sanctuary and one for the classrooms -- but from what I see in the photo it looks as though the same mains supply both, with the sanctuary feeding up and the classrooms down. So that would also involve new mains. And be expensive.

Maybe I'll think of something else...

nicholas bonham-carter

Is the system well balanced now so that all the radiators get steam at the same time? Making sure of correct operation can often result in great savings for the whole building.
It seems to me that due to their closer proximity to the boiler, that steam will go first to the classrooms, and therefore a sensor for the classrooms, will be satisfied before the sanctuary gets too warm. Perhaps the sanctuary radiators could have TRV's on them, which of course would have to be individually turned up before the services.
The Ecosteam controller may be able to select indoor sensors, and achieve this slightly better solution, without costly repiping.--NBC

Chuck_17

I was thinking that leaving some of the sanctuary radiators (there are 10 total) without TCV's would help with the over sizing and the control coordination between floors.
Any massive re-piping is out of the question (economically). However some sort of better control at the boiler may be an option.

EBEBRATT-Ed

Put TRVs in sanctuary. Put a thermostat in classrooms and leave the one in the sanctuary. Use a selector switch to pick which stat will run boiler. Set trvs to maintain sanctuary heat at a lower temp when classroom is being used. When sanctuary is used flip selector sw and turn up trvs it will run as it now does.

Not the best but minimal $ and will help save fuel. semi-auto-manual system

Charlie from wmass

The lower level would need piped with a drip and separate TRV's to each radiator. Are the radiators trapped of just piped into a wet return?

RobG

If your boiler is capable of a two stage gas valve that would help with the sizing issue as well as the options above.