will this system work?

[steelman]

this look like it will work?

some info.

infoor hydronic heat in a barn. floor and building well insulated. pellet boiler A-Maize-Ing heat 80,000 to 160,000 BTU, 80 % eff.
single zone with circuit manifold. would like to use one pump but i think i may need a pump for the load loop.

i want some boiler protection, min of 140 return water temp. so that's why the bypass before the tempering valve. but i want to keep the floor tubing protected as well. thinking a mixing/ temper valve set around 100 to 120 deg. the pex says its good for 180 but that seems hot to me.

i know the boiler is kind of large for the building 1,200 sqft. but its what i got. maybe some day ill pipe in some storage.

i have been looking at many plumping systems on the net and this seems the one with the least parts. like i said i could use another pump and if i do ill space a couple "T"s close together to allow for the Primary/secondary circuits between the supply and return manifolds and the tempering valve.

so if you have time please let me know what you think. would like to only sweet this thing together once.

any and all reply's are grateful.

jim

 

[Clarkbug]

Jim,

I would suggest something like this unit from Caleffi

http://www.caleffi.us/caleffi/en_US...s~news_detail_0000144/type/newshome/index.sdo

It will provide hydronic separation for your system, allowing you to have a boiler loop and a load loop. I would also consider making something similar out of a 100 gallon propane tank to have a buffer. Might help with cycling of the boiler, and gives your load a chance to choose where to pull from.

My other thoughts are that I would move the strainer to before the boiler, but after the pump, so that you dont have crud in the boiler itself. Get another pump for the load side, just to make your life simpler. Otherwise with bypassing going on you will have a rough time getting water to go where you want it to go.

 

[__dan]

Without storage, the biggest problem will be matching boiler output to the load. I'm guessing the boiler is way bigger than the load and I did not see any turndown capacity or modulating of the firing rate of the boiler on their website.

Before doing anything, you would want to know how many btu's the 1200 sf slab can absorb and dissipate at steadystate, not cold start, but steadystate. Radiant is a constant flow system at a lower water temp and at steadystate, after the slab is brought up to operating temp, the delta T around the loop and the maintenance btu's may be very small. It would be a problem in your drawing trying to absorb a 100,000 btu output into a 12,000 btu load. You need to know the btu's of the load and of the radiant distribution system. Can the boiler turn down and modulate firing to that number or will it short cycle? Can the boiler tolerate short cycling?

The boiler return bypass needs another look also. Typical would be a pumped bypass or a three way thermostatic valve, or both.

 

[heaterman]

With a boiler that size on a small load you probably better add a good sized buffer tank or it will short cycle to death.
When designing a pellet boiler driven system you want to shoot for no more than 1 on/off cycle per hour. No more.
If you can get up to 1 cycle /2 hours you're doing it right.

The one I am running in my own house has 756 starts in 3383 hours or about 1 on/off cycle every 4-1/2 hours over the course of the last year.

 

[steelman]

Without storage, the biggest problem will be matching boiler output to the load. I'm guessing the boiler is way bigger than the load and I did not see any turndown capacity or modulating of the firing rate of the boiler on their website.

yes the boiler has an adjustable BTU output. the pellets are controlled by cycle rate and volume. draft fan is dampered as well. the boiler is 80% so im looking at a min output BTU's of 48 to 50,000.



The boiler return bypass needs another look also. Typical would be a pumped bypass or a three way thermostatic valve, or both.

i have looked at the 3 way thermostatic valves, as well as a 4 way. i was thinking that throttling the bypass valve to give a % or restriction and force some of the water to tempering valve. the more i think about the load side im sure i will need a pump on the supply to the load. after the tempering valve.
describe some of your thoughts on the pump in the bypass.

thank you for the reply.
jim

 

[__dan]

The best plumbing diagrams I have seen for wood boilers are on the Tarm USA site if you have not seen them.

www.woodboilers.com

Given your diagram of what you intend, the typical boiler return protection is the Acaso LK 810 loading unit, pump with the three way valve in one unit.

For simple, a loading unit is indicated.

 

[maple1]

That won't work - the flow going into the bottom of the 3 way thermo valve is against the direction of flow that the pump would be pulling it.

Aside from that, do you have more heat loads you can pipe your boiler to? Like your house? If not I definitely think a buffer/separator/storage tank will be needed - that is very little load for that boiler. I think - I don't know anything about it aside from the BTU numbers you posted.

 

[Bob Rohr]

this look like it will work?

some info.

infoor hydronic heat in a barn. floor and building well insulated. pellet boiler A-Maize-Ing heat 80,000 to 160,000 BTU, 80 % eff.
single zone with circuit manifold. would like to use one pump but i think i may need a pump for the load loop.

i want some boiler protection, min of 140 return water temp. so that's why the bypass before the tempering valve. but i want to keep the floor tubing protected as well. thinking a mixing/ temper valve set around 100 to 120 deg. the pex says its good for 180 but that seems hot to me.

i know the boiler is kind of large for the building 1,200 sqft. but its what i got. maybe some day ill pipe in some storage.

i have been looking at many plumping systems on the net and this seems the one with the least parts. like i said i could use another pump and if i do ill space a couple "T"s close together to allow for the Primary/secondary circuits between the supply and return manifolds and the tempering valve.

so if you have time please let me know what you think. would like to only sweet this thing together once.

any and all reply's are grateful.

jimView attachment 127578

Here are 3 options. Two thermostatic valves, sized for the flow rate, or motorized valves with a control that monitors boiler return temperature. I agree a buffer tank will make a much more controlable system.