Another boiler sizing question

So I am getting ready to order a boiler. Trying to decide between a 40 or 60 series. Can you double check my thinking?

When I put a large addition on our house I had a heat loss done. Of course I can't find it now. But I remember it was right around 130 - 140k btu. At the time I installed a new Peerless boiler with beckett oil burner. I was right on the line between a 3 or 4 section boiler. I went with the four section (rated output of 155k).

At the the time based on the heat loss I used a .85 gph nozzle at 140 psi which equals a 1.05 at 100 psi, so...

1.05 gph X 138700 at 83 % efficiency is about 122,000 btu/hr

Seems like a 40 series would be a good match? Or I could be way off---

I will be burning a mix of pine and hard wood. And yes it is seasoned (have about four cords of each ready to go) Don't plan on storage for the first year.

Thanks in advance

henfruit said:

What brand of boiler are you looking at?

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I'm thinking about the biomass 40. I like that it can burn pellets and coal. I have a tree guy that has told me he can give me all the pine I want. So I figured I might try burning a mix pine and hardwood. Maybe try some coal on cold nights.

jebatty said:

But I remember [heat loss] it was right around 130 - 140k btu.... At the the time based on the heat loss I used a .85 gph nozzle at 140 psi which equals a 1.05 at 100 psi, so…. 1.05 gph X 138700 at 83 % efficiency is about 122,000 btu/hr

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Based on these calculations, your heat loss must be less than 122,000 btuH unless there are extreme times that your oil burner is running constantly, non-stop, and the house is cooling down, as the oil burner is only supplying 122,000 btuH.

I assume you will retain the oil burner as a back-up. If so, you will want to balance how much you will use back-up vs wood. I would tend to agree that based on your numbers, and with the back-up, a 40 series would be an OK choice.

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You are right -- must be less than 122 (I am sure that it has a .85 nozzle at 140 psi) At the time I had FW Webb do the calculations/sizing based on the measurements I provided. They spec'd a 4 section boiler. My friend who owns a oil burner service company thought the heatloss numbers were a little high - - thought I would be fine with the lower firing rate.

I guess he was right because the house maintains heat just fine and the boiler never runs full time.

I will keep the the oil as a backup -- hoping to reduce oil consumption by 50% first year. Currently use 1000 to 1200 gallons.