boiler sizing

sean_21

i have a question about boiler sizing i know alot of guys size their boilers by the rating plate of the old boiler.i also know that this is the wrong way to size them.i am unsure how to size them up the correct way,please teach me.

Ron Schroeder

Sean

Go to the top of this page and click Heat Loss Calcs, download the free Slantfin software to do a heatloss, doing a heatloss on the building is the only way, unless your upgrading a steam system then you need to figure the EDR of your radiators but the heatlooss needs to be done just to make sure there is enough radiation to start with. Any questions with the calcs and bring them back here and someone will show you the way.

Brad White_64

Size Matters

HW and steam boilers are sized differently.

HW is sized to the calculated heat loss (not the radiation). The radiation output is useful to know, but having "too much" is really a good thing from an efficiency standpoint. But heat loss rules here.

Steam is sized by the connected radiation (EDR). If a boiler is too small, you will not heat the entire connected volume. Subordinate to this is a presumption that your radiation somewhat matches your heat loss at least. (Chances are it far exceeds your heat loss especially if you have insulated, replaced windows, etc.)

Bottom line, size steam boilers based on connected radiation, hot water boilers based on calculated heat loss.