Ah, but here's the catch..what are you doing for hot water Mark?
Mark, it is impossible to....
give you an exact heat loss on your home without knowing anything about it's age, construction, r-values, u-factors etc..
Ashrae winter design temp for Philly is 14. Personally, I would design for a 70 indoor temp at 0 outside with a 15 mph wind.
I can tell you that 60k sounds a little low unless home was built with newer style construction, r19 ext insul and decent windows (better windows if they are large)or upgrade a great deal if an older home. Heat loss programs are JIJO, so don't make too many over assumptions when inputting info. A good rule of thumb that I have use successfully is this:
well insulated, modern home- 18-25 btu's/sq ft
avg to poorly insulated- 25-35 btu's/sq ft
poorly to not insulated- 35-45 btu's/sq ft
barn- 45-60 btu's/sq ft
your home at 60k rings out to 25/ft based on your info. remember the net output of the boiler needs to meet or slightly exceed the heat loss, not the input
curious about the answer to another post- does this boiler need to make domestic hot water such as with tankless coil?
I have a stand alone gas-fired hot water heater. My gas bills in the summer almost go to zero. I have no plans to use an indirect fired hot water heater.
I thought 60K was low, too, but that wasn't the first pass. I had to scale-back on some of my facts. I believe that I made very few assumptions. For example:
house was built in 1955.
I know there's R-11 in the walls and attic. Nothing in the crawl space.
The 2 new rooms that I just added: R-15 in the walls; R-30 in floors and ceilings.
Recently replaced all windows with double-pane, argon filled vinyl.
Re-sided the entire house with R-4 foam under vinyl.
I used 13 degrees outdoor temp, 68 degrees indoor.
The only assumption I made was "infiltration". I had no idea what to use, so I used "average".
!!!CORRECTION!!! The second program I used makes infiltration very easy. So, again, I believe that I made very few assumptions.
[Edited by mark115 on 03-10-2005 at 08:52 PM]
ok, sounds like you've made some improvements to the house. not telling you 60k is not enough- I assumed your house was built in the 50's or earlier by the boiler age and have never seen exterior wall insul in a house that was built then ,unless it was gutted later and added. good luck
I've decided on a boiler: 103 MBTUH input. And, I like the idea of an outdoor reset. Let's just leave that alone for a little while. Of course, if there are any major objections, please reply.
Now, onto circulators. Several people have recommended 1 circ per zone. Sounds like a good idea. What exactly is "head-feet"?
Dof3 suggested, "If you are planning on replacing the boiler, why don't you use a P/S piping system. Then put a mixing valve in the zones that are too hot."
I'm not exactly sure what is meant by a Preliminary/Secondary system. Is that the same as what someone described to me as a "two-pipe system", where there is 1 loop for each zone, and the radiators are Teed-off of it?