Room heat loss calcs

baylis

I would like to put a new steam one pipe boiler in a six family masonry building.

How does one determine exactly how many BTUH each room needs.  I've heard conflicting methods.  Some say measure the cubic footage, others the heat loss of only exterior walls and ceilings.  Any help would be appreciated.

Thanks

Len

nicholas bonham-carter

New boiler

Are you just checking the existing radiators for correct sizing? Use the SlantFin heat loss app for the BTU requirements for each room.

To size the replacement boiler, the combined total radiation EDR of the building radiators must be tallied-not the heat loss. The EDR is expressed in square feet of steam, and then a boiler whose square feet EDR matches most closely is the right choice. When you use this method, the piping factor is already factored in. Simply replacing the boiler with another one of the same size may not give good results.

You may wish to install 2 smaller boilers each of 1/2 the total needed.--NBC

Gordan

Are you replacing just the boiler?

A steam boiler is sized to the EDR of the existing radiation. Have there been any issues with the radiators being able to keep up in certain rooms?



Radiators should be sized to the heat loss. Heat loss of a room is calculated by cataloging all areas that lose heat and, for each area of different construction or facing a different "outside" temperature, calculating Area * (Tin - Tout)/Rval where temperatures are in F and area is in square feet. Then you add it all up and add your infiltration heat loss (this is proportional to the air volume of the room and the air changes/hr value) and that's your total heat loss.

baylis

Calcs

I want to replace the boiler but first I want to have the proper amount of radiatioon in the room so I can size the boiler to the needed radiation.  The existing radiation is overkill.  I an trying to get the most efficient system.

Thanks

nicholas bonham-carter

Overheated rooms

If this is a building more then 50 years old, which has not been changed,, and has the original radiators, then you can be pretty sure that the radiators were properly sized for the rooms.

If you have had balance problems, then that would be the likely cause of some rooms being overheated.

Take some pictures of the boiler, and your main vents, and we can probably see what the next course of action for you should be.--NBC