New system boiler size questions

Constantin

... then size the indirect to cover your peak water needs. That is, unless you're in need of hot DHW all the time.

There are free programs available on the internet like the HE from slant/fin that allow you to calculate a heat loss on a more modern computer. Whether to go through all the effort again depends on the confidence you have in you earlier results, I imagine.

Your large radiators will allow you to run the supply temps at a low level, which ought to boost efficiency. Ideally, you'd make them at least large enough to comfortably heat your home on a design day with 140°F supply water temperatures.

Marty_8

New system boiler size questions

I have a home built in 1987 2500 SqFt the insulation is OK R11 in the walls R13 in the
attic space that is accessible. That will be increased to R 30+ . It is a retro fit job so no
contractor is willing to give me the time of day. I plan to install Single Plate Flat Panel
Radiators in the house. The type can be seen here http://www.blueridgecompany.com
The total BTU output for the radiators would be 51,862 in a perfect world. But I do plan
to add on to the house an other 900+ SqFt so I’m trying to figure out how large of a
boiler to use. I don’t want to over size the boiler. I’m looking at a Munchkin T80 or M80
boiler and a superstore SSU45 gallon indirect water heater they can be seen here.
http://www.hotwaterproducts.com/HTP/Munchkin/Munchkin.htm OR here
Http://www.2hsc.com I live in Sacramento California So we don’t get the freezing
weather for days on end. I have the original heat calculations for the house but they were
designed around a forced air system using a program that ran on an old 286 computer. So
should I design a system around the heat loss of the house OR the total output that the
system can put out? Like I stated before the radiators can put out 51,862 BTU but the
super store call for a boiler size of 141,000 BTU That seems to be a bit over kill to me.
Any suggestions? Or does anybody have a similar system.