Load sharing Btu's

mikemac52

Two adjacent rooms open to each other for 8' on their common wall with only 3' or so on either side of the opening. The two rooms, one with an open stairwell, contribute heat from their radiators to the second floor hallway. The stairwell lands at the opening between both rooms.

Should the heat be considered shared equally enough between the two radiators and so sized similarly, or the radiator in the room with the stairwell be given more of the task and sized larger?

Originally the radiator across from the stairwell was sized larger even though the rooms are similar, but we knocked down most of the wall between. Parts of the stairs do "see" the other room's radiator.

Jamie Hall

Probably the room with better connection to the stairwell could be a little bigger -- but with that much opening...

That type of space is almost impossible to heat evenly with radiators -- and quite impossible to predict exactly.

STEVEusaPA

How much of the stairway and 2nd floor hall are adjacent to exterior walls/ceilings?

mikemac52

Stairs against outside wall, with large single pane window w/fixed storm windows and another DH at the top of stairs just for fun running about 16 feet.

About 2200 Btu heat loss. No heat source in 2nd floor hall.

More fun but 1/2 the size on the 3rd floor. 1300 Btu's.

This worries me most. Those two rooms the downstairs at night feeding the upper area when 2nd floor doors are shut.

mikemac52

Do I need to add all or most of the upper hall's heat loss to the 1st floor rooms?

Jamie Hall

Nothing like an open floor plan to make life more interesting. In answer to your last question about the upper floor heat loss, yes, I think I would add it in, and not count the contribution (which will be small) from the rooms opening off the hall -- those rooms should be radiated for their own heat loss.

However.

That just gives you the total heat loss which needs to be compensated by the total radiation in the space, and doesn't help a bit with deciding where to put how much radiation. I still think I'd put more of the radiation in the space with the stairwell -- but I'd be prepared to spend some time fiddling with vents, if it's one pipe steam, or with inlet valve settings if it's two pipe steam or hydronic.

mikemac52

Two pipe hydronic. Hmm... valves. Do they make anything with a day and night setting or are TRV's robust enough to dial down every night? Even though I'd probably forget.

mikemac52

Here are my numbers, combined two rooms and both stairs/ halls have 6400 Btu's heat loss.

@140 F water temp approx 72 square feet of radiation needed. Is 40 sq foot radiator for the stair room and 32 sq foot with TRV for the other a good compromise?

Alone the non stair room only wants 20 square feet of radiation.

Original radiators had 65 and 47 square feet of radiation respectively.