Correct Heatloss?

clammy

Actually the supply house i use does the heat lose correctly and are almost always come up with what i fiqured but there are a few supply house in my area (bigger with multi location)who have performed heat loses for my working mates who loses where nearly double of what i came up with after just using a slant fin program and i left alot of room for lee way.These other supply houses i really don't deal with i have 2 or 3 places i deal with the drives a little longer but i get everything i need they know me for i guess 20 years and hardly ever give me the run around the others i have given chances to show me how good they are but there off my hook i waited 1 1/2 months for a v500 vent kit and they billed me for it on the boiler pick up and did not notifie me when it came in i guess if i don't do 200 thousand i'm dirt but i don't let them do my heatlose i just don't want to buy wall to wall baseboard where i only need 1/2 the board .I have yet to encounter the other way only on jobs where they went light with insulation after the fact and did not properly seal overhangs cieling joist and the likes peace and good luck clammy .

adambuild

Correct Heatloss?

Just did a heatloss on a 2400 s/f home in Northern NJ with Slant/Fin software and came up with 78,000btu. Does that sound even close to real?! Did I miss something? The existing beast in the basement is rated at 270,000btu input!?

Thanks, Adam

Dave_4

That

sounds about right. Do it again if your not sure.The size of the existing boiler is not germane to the selection of a new one, as you have found out.

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clammy

heat loses

Adam heat lose programs don't live i have only been doing my own for about 2 1/2 to 3 years and each one i do the more i realize how much heating equiptment is over sized even when some supply house do it for you .At first i was a bit hesitant but it's been a while and each one i have followed i have yet to have 1 call concerning not enough heat even when we have had cold snaps and i work and live in north jersey .Computer aided heat lose programs are one of the best tools avaviable to properly size room conventors and boiler ever job i do i use a heat lose prograqm to ensure that there no promblem in the future and thatevery thing will work right from start .Recently did a home heatlose about 65,000 house is about2800 sq ft supply house heat lose i believe was about 120,000 big difference espically when it come to amount of baseboard installed . peace and good luck clammy

Steve_35

That beats our record.

The largest furnace/boiler we've replaced was just slightly over 3 times more input than needed. Double is pretty common.

Unknown

clammy

I`ve had that happen alot too. But did you ever have it go the "other-way"? I checked new home with my S/F program and came-up with more than the supply-house got!

Joe_30

Sounds right. Here in Minneapolis our 2400 sq ft two story, 1940 vintage [think sawdust within 1" tarpaper envelope insulation, but with added thick attic R38 insulation], calculated to 96K btu,so used a 108 k net boiler. At -20* the boiler still runs only 60% of the time. For your comparison.

EBEBRATT-Ed

Check it again but it probably ok.


ED

Unknown

If this is decent modern construction, you're averaging 30 BTUs/sq ft there.. that's high for most homes that I see these days.

Charlie from wmass

I had one where it is a 1797 house, no insulation and only storm windows over single pain glass. House is 9600 ft2 and about half is heated the rest is closed off in the winter. Four large fireplaces are in place and in working order in the original section of the home. The boiler that was in place was 102 input on gas. The home never got above 60 if it was below 30 outside. I have now install HB smith gb 200s with staged fireing and outdoor reset controls. The people wanted a redundent system to protect the home for possible freezing temps and to protect the antiques from extreme temp changes. They are also going to be extending the heat to the rest of the home. They do not plan to add insulation or change the windows as they are more interested in the historical integrity of the home then the heat loss. But how could 102 K for boiler input rating ever have been figured?

Unknown

I hear ya Charlie,,,,,,,,,,,

That`s what makes me "wonder", in the situation I`m in! Wholesaler originally did-it for the guy, but I wanted to check-it myself, my #s are higher. Now the guy want`s to argue! I may turn the job down! I checked, and re-checked, mine is always higher!

pennron

heat/loss comparison

Hi:

we have 2400 sq.ft ranch circa late 2003 with pella windows, therma-tru doors and velux skylights. live in easton, PA so decent comparison for you.

first heat/loss calc was 68,000 but they did not include the insulation we have in the 1st floor joists (basement ceiling). when that was calculated into the program heat/loss went down to 48,000. fyi....

Brad White_141

My opinion, FWIW

Just did a heatloss on a 2400 s/f home in Northern NJ with Slant/Fin software and came up with 78,000btu. Does that sound even close to real?! Did I miss something? The existing beast in the basement is rated at 270,000btu input!?

As a check figure of 32.5 BTUH per SF on a design day, that sounds about right for:

1) An insulated frame house built between 1900 and 1950 but blown-in (retrofit) insulation and storm windows, re-siding with Tyvek underlayment, caulking and sealing or vinyl/aluminum siding over old siding. Or-

2) More modern frame construction (1970's and later) but insulated from the get-go. Wide variations in quality in each case of course, but you have to start somewhere.

Design outdoor temperatures in the single-digits are also assumed.

The in-between years of 1950-1970's may have been insulated during construction but often with thin insulation (2" in walls even if a 3.5 inch cavity) and if you were lucky, 3.5 inches in the attic. New windows of course help in this case.

The question becomes, how confident are you about the age of your home and the level of installed insulation? How tight is it against infiltration (the greatest heat burglar)?

But overall, a heat loss of 32.5 does not scare me as excessive nor impress me as do the best available. It is comfortably in the middle.

Clearly as Robert O'Brien and others allude, the 270 MBH input beast you have has nothing to do with the heat loss. Even if older and not insulated, I would have trouble seeing a heat loss double yours (in the 65 BTUH per SF check figure range or 150-160 MBH total) and it would still be oversized.

Your revised heat loss, if accurate, would be well-served by a ModCon boiler with an input in the low to mid-90's MBH and could also fire an indirect for domestic HW. If a conventional boiler is used, an input approaching 100 MBH seems right.

Either way, you will enjoy the difference.

My $0.02

Brad