Heat Loss Calculation and Practcal System Design

[Como]

I have worked out our Heat Loss at c450,000 btu using Slant Fin. We are at nearly 10,000 ft, the calculations asked for altitude so I am assuming that is factored in.

This is with a delta of 85F, -20 to 65.

Now a system with this capability is unaffordable, we do have a wide extreme of temperatures at all times of the year. My gut feel is to look at a zonal system, something that will allow us to keep the core areas of the building at a reasonable temperature in extreme conditions. I have looked through past posts, something on the line of a Garn or EKO 80 with lots of storage, both with a Propane Boiler back up would seem the way to go. The big Garn is getting on for $40k, so it would need to be the 2000. The current forced air system can not heat the building and is too expensive to run anyway.

I just wondered if anybody else has had to make similar choices and how it worked out.

 

[MrEd]

How big is your house? That is a huge heat demand...are you sure all you calcs are right?

What are you heating with now? and how much fuel does it consume?

 

[Como]

5,500 sq ft
110 years old
48 large Single Pane windows, tall ceilings, on the Natonal Historic Register.

I did allow for some improvements on current levels of insulation!.

Current 'heating' with wood stove and 3 Propane Forced Air Furnaces, currently mainly just the wood stove, supplemented by Electric Radiators in the bedrooms. I do not have acurate numbers for past consumption/ performance. The current system could not keep the building at 65F.

 

[MrEd]

Wow...if it was me I'd spent 1/2 the money on the biggest system I could afford, and the other 1/2 of figuring out how to be as energy efficient as possible. I'd imagine that even if you could afford a 450K BTU wood boiler, you are going to have to process a heck of a lot of wood.

Besides the heating bill, sounds like a great place! Wish I could offer more advice. How about a picture of the place?

 

[Como]

Trouble with this building and insulation is you only go so far, solid brick and big windows, which we will be refurbishing, storm windows, insulate the foundations, floor is tricky due to access.

But we will have lots of beetle kill locally.

 

[stee6043]

Do you really figure the -20 to 65 is your average temp. differential? Or is that worst case? Some may suggest that you size your boiler for worst case but man, with those kinds of numbers, I'd suggest you go with a more average change of say 20 to 65 and see what you get. Yeah, maybe you'll have a few days a year where the temp in the house isn't prime but you surely should be okay "most" of the time?? It sounds like you might be one of the few people out there that could run a gassifier at full burn all day long with no storage! You've got quite a heat load....

 

[Como]

I have run through the numbers a few times, if I take a positive view I can get the numbers below 400,000. But we also can have a big wind chill factor, and that is not taken into account.

-20 is the worst, I am told last winter was the worst in years, nearly 2 months of extreme weather.

If I take the low down to 0F then we get to around 300,000. Forecast is for 14F tonight, 45f high today. Our December to February Average is about 5f, but there is a big difference between night and day.

Switzer would seem to have the capacity, but I am out of area I think.

The Garn WHS 2000 could get me through the night assuming a full charge with a Propane top up if we need the temperature or have severe cold. I am guessing that we would burn 30 or 40 cords a year. Which is better than an estimate I had of $20,000 per year for propane, at current pricing.

I looked at the Garn Video, WI is pretty cold, I am assuming a better insulated building even though the same size but it still did not seem real.

 

[Nofossil]

I don't know if this is the problem, but if you're calculating how much baseboard you need, you'd have to have more at higher altitudes because thinner air doesn't transfer as much heat.

The total heat loss from the structure at higher altitudes should be slightly LESS, for the same reason.

What do you get for BTU loss if you tell the program that you're at sea level, all other values being the same? If it says your heat load will be less, then I think you could use the lower number for boiler sizing and the higher (at-altitude) number for figuring out how much baseboard you need.

That's my analysis. Any thoughts?

 

[Como]

Excellent point.

When we sized our instantaneous hot water system we lost about 25%, from memory, output compared to sea level. Boiling water takes much longer.

I just ran the calcs again, it makes no difference to that part of the calculation. My guess is that it is factored in when choosing the Boiler. Which begs the question what the modifiers are for wood boilers. Never seen this mentioned. Wonder if it cancels out.

I was told I would need a 750k Propane Boiler.

 

[Nofossil]

Interesting. I'd expect boiling water to take LESS time, since it boils at a lower temperature. Must be that transfer from the flame/flue gas to the exchanger is also less effective.

That implies that heating appliances might need to be oversized, at least in terms of HX surface area. For gasifiers, the fans might need to run faster or at least the shutters might need to be open farther since a cubic foot of air has less mass.

Your heat loss numbers seem really high, though. I made my own handmade version of the Slantfin 20 years ago. backed up by 17 years of oil consumption and three years of wood consumption. My peak heat load (3500 square feet, 70 inside and -20 outside) is about 30,000 BTU/hr.

 

[DaveBP]

How about running two boilers in parallel. Two stage systems are used with other fuels and controllers are available. Run the first boiler when conditions are not so extreme and run both when the temp and wind are really bad. Might be more efficient than having a giant boiler that is way overkill for much of the year. Probably cost more up front, though.

 

[atlarge54]

Would you be willing to share a bit on the history of this home? What was the original source of money to build and maintain this home (mining, timber etc.)? Was it a year round home originally or a summer resort? If a year round home, how many servants were typically kept to staff it? How long have you been involved in this project and are you begining to have second thoughts? I can't even begin to wrap my mind around the thought of burning 30 to 40 cords of wood per season. I wish you the best of luck in your project.

 

[Como]

In order!

Is there another product other than Slantfin I could use to check my numbers?

Sounds like I need to check with the manufacturers allowances for altitude.

I was thinking of running in parallel, using the Porpane to top up. But the Propane option here is very expensive.

Builiding was built in 1897 by the Railroad as a Hotel/Restaurant. Heated by coal stoves. Year round operation, I know in the 1920's it was run by a large family so say 4.But they operated it 24/7. We moved in in February, and YES!