ok my boiler is too large, now what?

[steelman]

here is the info,
just built a 30 x 40 pole barn. well insulated. 3 inch foundation board under 5 inch concrete with an R value of 15. on the sides of the concrete 6 inch ridged foam r-30. walls are r-19. ceiling reflective board and blown in r-30+.
the ceiling is 14ft ft off the floor. live in Ohio, normal winter around 20 deg.
infloor pex with 4 loops of 1/2 dia. single zone.

i have not started the pellet boiler yet but have asked the same question on another board. wanted to see if you all have the same advice.
i scored an "A-Maiz-ing heat" corn boiler (that i will only use wood pellets in) for a good price. seems to be used little.
it has a variable output of 80,000 BTU to 160,000 BTU. i knew it was on the larger side but thought i would need around 80 to 90,000 BTU out put to keep the barn around 60 deg.
so i have been told that "its too large" " twice to much boiler" "yea maybe even 3 times to big" etc.....
so what are my options?
1. run it at the lowest BTU out put (80,000 BTU INPUT)

2. run it at its lowest, and use a 1,500 gal poly storage tank that i would need to spend more money on to insulate and bury.

3. run it and see how it works.

4. sell it and spend 4 to 5 grand on a smaller boiler.

my thinking is run it see where im at, other than being less efficient at idle for long periods of time what is the next "big problem" yea i know about short cycling, hence the storage question above.

thank you to all, for any advice.
im in this "infloor heat" thing for about $3,000 about just using a turbo heater in the corner. i still want to make it work, just not looking fwd to spending another $1500 on insulating the tank, burying it, piping , pump valves etc.

thank you.

jim

 

[webbie]

I think storage would be a good solution, but work out all the various BTU schemes.....

Some calcs at:
https://www.hearth.com/talk/calculators/water-storage

So, let's take some numbers. You run it at 80K BTU in and get 60K BTU out into the water (if you are lucky, probably more like 50K)......let's say this is during a period when the heat load being used is 25K - so that means another 30K being put into storage. At that rate, it would take 12-15 hours to fully charge up an 800 gallon tank from 120 to 190 degrees - and then you'd have as much as a full day of heat stored assuming you had a system which could reclaim heat from lower temp water.

I wouldn't consider any of this short cycling.

Do some actual heat load studies on the building.....before you make your determination.

 

[Solo Plus 40]

here is the info,
just built a 30 x 40 pole barn. well insulated. 3 inch foundation board under 5 inch concrete with an R value of 15. on the sides of the concrete 6 inch ridged foam r-30. walls are r-19. ceiling reflective board and blown in r-30+.
the ceiling is 14ft ft off the floor. live in Ohio, normal winter around 20 deg.
infloor pex with 4 loops of 1/2 dia. single zone.

i have not started the pellet boiler yet but have asked the same question on another board. wanted to see if you all have the same advice.
i scored an "A-Maiz-ing heat" corn boiler (that i will only use wood pellets in) for a good price. seems to be used little.
it has a variable output of 80,000 BTU to 160,000 BTU. i knew it was on the larger side but thought i would need around 80 to 90,000 BTU out put to keep the barn around 60 deg.
so i have been told that "its too large" " twice to much boiler" "yea maybe even 3 times to big" etc.....
so what are my options?
1. run it at the lowest BTU out put (80,000 BTU INPUT)

2. run it at its lowest, and use a 1,500 gal poly storage tank that i would need to spend more money on to insulate and bury.

3. run it and see how it works.

4. sell it and spend 4 to 5 grand on a smaller boiler.

my thinking is run it see where im at, other than being less efficient at idle for long periods of time what is the next "big problem" yea i know about short cycling, hence the storage question above.

thank you to all, for any advice.
im in this "infloor heat" thing for about $3,000 about just using a turbo heater in the corner. i still want to make it work, just not looking fwd to spending another $1500 on insulating the tank, burying it, piping , pump valves etc.

thank you.

jim

Throw a match in it and watch closely till all heat load demands are met. You need to test fire it sometime. Set it to low fire and see how she purrs. You get scared, just pull the plug out of the wall and summon help. If your not confident with the system, first get someone competent to review your system prior to getting courageous on your own. No need to get yourself or someone else hurt.

 

[Karl_northwind]

I assume this boiler will turn on and off during it's burn cycle? but you just want to keep it from short cycling?

you can deliver 80,000 btu thru that tubing if you deliver the heat to the floor at about 120. if you use an air sensing T stat, you'll have large temp swings in the building (IE t stat turns off at 60 F, building continues to heat up to 65 or 68 F because heat is still coming from the floor. plumb the boiler in, pipe it primary/secondary with 2 circulators and a thermostatic mixing valve to temper water to the floor. Adjust the thermostatic valve till you are able to keep the boiler running steady state, not short cycling. also, use an aquastat to shut off the floor circulator if the return to the boiler drops below 130F. the boiler will turn on and off once per day if you can make that setup work.

you could also add a few pieces of fin- tube radiator on the boiler return to shed heat as the return heats up. 545 BTU per ft for 3/4" fin tube. add 20' and you'll shed a lot of heat and heat your shop faster, and reduce short cycling.

put some extra Tees and shut offs to allow you to later plumb in a tank (maybe a 250 gallon refurbished LP tank?) if you like.

I'm sure there will be others along, but at the risk of sticking my neck out too far, that's what I'd do if I were in your situation. the buffer tank will be the next step if you can't move enough heat out of the boiler. Use hardwood pellets only, as you'll have lower heat output.

hope that helps

karl

 

[Karl_northwind]

I think storage would be a good solution, but work out all the various BTU schemes.....

Some calcs at:
https://www.hearth.com/econtent/index.php/articles/using_storage_tanks_with_biomass

So, let's take some numbers. You run it at 80K BTU in and get 60K BTU out into the water (if you are lucky, probably more like 50K)......let's say this is during a period when the heat load being used is 25K - so that means another 30K being put into storage. At that rate, it would take 12-15 hours to fully charge up an 800 gallon tank from 120 to 190 degrees - and then you'd have as much as a full day of heat stored assuming you had a system which could reclaim heat from lower temp water.

I wouldn't consider any of this short cycling.

Do some actual heat load studies on the building.....before you make your determination.

You beat me to the post.....

I hadn't thought about the output of the boiler. all I work with is european equipment, which is rated on output. the whole project just got even easier.

 

[jebatty]

Poly tank for btu storage - I wouldn't touch it.