So frustrated! Is Manual J needed to size boiler, or not?
We're replacing an ancient oil-fired boiler (forced hot water baseboard.)
We have had 4 HVAC contractors come to give estimates, including two of the biggest local oil companies. The boiler sizes have varied in each estimate. ALL of them have used house square footage and baseboard lengths to do the sizing, NONE have done a Manual J (although I provided all of them with floor plans and descriptions of the insulation, etc..).
From my reading it seems like an Manual J is the only correct method to determine correct sizing... is that not correct?
When I asked one of them he said, no, a Manual J is only used when they are designing a whole new system... never with existing baseboard, because in that case you must spec a boiler big enough to run all of them, and no other variables matter.
What to believe?!?!?
If it matters.... the baseboards in our house were added rather haphazardly as various additions were tacked on over the years. I am certain no one ever calculated how many were optimum. Last winter, the ones in the living room (their own zone) rarely came on... because we'd opened up the walls and the adjacent zone -as well as a wood stove- was taking care of that area pretty well.
What should we do?