Radiator control valves.

Brian1

One steam boiler serves two apartments. The usual t-stat issues. Supplier tells me to put in Danfoss Radiator control valves (RA2000) and disconnect the T-stat. Now, everybody overheats because the boiler never stops running. So, Danfoss says I have to have a outdoor reset or a central t-stat. Any ideas on how to make this work? I am in big trouble here, thanks.

Jamie Hall

Is this

one pipe or two pipe steam?  Makes a difference.  If it is one pipe steam, you need the hotter of the two apartments to have thermostatically controlled VENTS on the radiators.  If it is two pipe, then the hotter of the two apartments needs thermostatically controlled VALVES on the radiator inlets.



Either way, the colder of the two apartments needs to have a thermostat to control the boiler.  Otherwise, the boiler has no clue that things are warm enough, so of course it will run forever.  Bigger installations sometimes use various timers set by outdoor temperatures to do this.  In your case, that would be -- in my humble opinion -- major overkill.



If the colder of the two apartments is rented by someone likely to fiddle with the thermostat, you can get locking covers for them which will at least reduce that problem.

Brian1

One pipe, that is.

Yes, It is a one pipe system. The t-stat is on the first floor and the tenant either leaves it on too high or turns it off entirely. So I am thinking I should put a lock-out t-stat set at 68 in his place, and then let both tenants adjust the RA20000 vents accordingly? Maybe I should use a sensor? I really wish this would have worked as stated by the supplier.

Jamie Hall

You really shouldn't...

have the thermostat -- even a remote sensor or a locked one -- in a space which has only thermostatic vents.  Why?  Sure as Murphy lives, the tenant will turn the vents down below whatever the thermostat is set for, and the boiler will run forever.  You may need aan outdoor reset arrangement which senses the outdoor temperature, and is adjusted to allow the boiler to run for long enough to heat the indoor spaces to whatever is legal or desirable, after all.  It does not, obviously, give as tight or efficient control as a properly setup thermostat would.  I don't suppose there is a handy, heated, common space where a thermostat could live?  In a two unit building, I don't suppose there is.

jimmythegreek

had same problem

My old man has a 2 family side by side w the same setup.  Windows open on one side, freezin on the other.  what I did is read and ask here and I eventually replaced ALL the rad vents and added 2 antlers to the ends of my mains with gorton #2s.  I cleaned up my system and piping and got all rads heating and working.  We had some bad pitched rads and a sagging return amongst other issues.  I even found a few rads switched from original locations to other rooms.  I installed a "landlord" Tstat in a common space which is basically a 70 degree lockout and I cut my gas bill from around 600 a month in dead winter to around 350 so far this year.  I have had bad luck with TRVs and dont care for them personally.  I feel like if Im burning fuel to make heat I want all that heat.  With some effort you can make any steam system run great

Brian1

Thanks.

I apperciate all your help, sounds like I am on track to make these people happy. If you think of anything else, let me know. I'll post after we try these solutions. I am thinking of picking one "control" room and switching that rad back to a standard vent. I guess we will have to play with it.

jimmythegreek

question

u didnt say if you (the building owner) were the one paying the fuel bill.  I suppose you are because its one heating unit, but Ive seen some increase the base rent to make up for this year round.  If I was you I would forget whatever TRVs u have put into the house, and go back to original design of the system.  Remember a long time ago (some 100 yrs or more) these steam systems were the best thing next to sliced bread, and they can still be.  I played w the rental my dad has for half a heating season dialing it in. The best part, I didnt pay anyone for anything, I learned and asked and the great folks here helped out greatly, alot of die hard pros on here.  If you vent your mains well, change back to standard rad valves, change and balance the rad vents, and get the boiler running real low pressure, the house will heat evenly and your fuel bill will be cut by 25% to 50%.  I did it and so can anyone else

Steamhead

Since you have TRVs already

you can use an outdoor control to cycle the boiler, such as a Tekmar 279 or one of the Heat-Timer models. These aren't cheap, but will sidestep the issue of where to put the thermostat.