Two Boiler layout w/drawing

AmericanNYer

Mid 1800s house, has an oil boiler as well as a wood fired boiler. Previous owner had disconnected wood boiler, the rest of the piping was in bad shape. Looking for thoughts on this layout. Plan is utilize wood boiler when I can, oil boiler the rest of the time. If this is acceptable, looking for thoughts on how to add in dhw.

Appreciate any input.  

hot_rod

What type of wood fired boiler? They ofter run much better with a bit of a buffer tank. What type of heat emitters? Radiant slab, fin tube, etc.

Take a read through this for some piping and control options.
https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10_0.pdf

AmericanNYer

Thanks, I'll go through that now. I watched some videos by Caleffi on hydronic piping systems to get to what I thought was the best design. Very helpful.

Cast iron radiators 

Oil boiler: EFM PK 440
Wood boiler: Harman SF160

EdTheHeaterMan

There is a better way. It seams the manufacturers of hand fired equipment are slow on the uptake of Pumping Away from the expansion tank and other good design ideas.

I have had some customers with wood stoves connected to the existing oil or gas boiler. I wish I was there to plumb them in before the project was completed by the wood stove company or DIY. There would have been a more efficient way to create heat and DHW if it were designed a little different. There would also be a better auto changeover from wood stove to automatic heating without wasting lots of heat up the chimney when the off boiler was reheated by the on boiler.

Do more research. Primary secondary piping comes to mind.

Mr. Ed

mattmia2

Primary secondary with the emitters being the main loop and the 2 boilers connecting in to that loop with closely spaced tees seems like the simplest. There are numerous places you could put a buffer tank in that setup depending on what you want it to do.

AmericanNYer

Thanks for the help. I went off my last sketch. Is this what you suggested?

EdTheHeaterMan

That is definitely a better design.
You are pumping away from the expansion tank


This will also work, maybe a little better at keeping the heat from the operating boiler from overheating the off boiler, wasting energy

random12345

@AmericanNYer Can I ask why you want to use the wood boiler at all?

EdTheHeaterMan

random12345 said:

@AmericanNYer Can I ask why you want to use the wood boiler at all?

Obviously because he is young and energetic and has no idea how much work it is to chop and split wood for a whole winter.

AmericanNYer

Thanks everyone for the input. I live on a pretty decent size piece of property with endless supply of wood. Semi-young, have a bit of an idea how much work it is to split and stack. My son is starting to figure it out though. But the house came with the boiler, I want to have the option to heat with it. 

psb75

Primary/secondary plumbing is a good "start." Should also have heat storage tank for efficient use of the solid fuel burner. System also needs thermostatic mixing valve for boiler protection (anti-condensation) for wood burner e.g. Thermovar. Danfoss etc. Also should have a heat dump zone for grid-down scenario for solid fuel burner. Have people forgotten how to burn wood anymore?

hot_rod

a buffer tank will make a huge difference in the amount of fire tending that will be required. Without it you may get over heating and require hourly fire tending to adjust the burn to the load 

You need a return protection valve also to keep it running hot and avoid creasote formation

Their piping drawing leaves a bit to be desired, but does show a tempering valve

I went from a 120 to 300,  finally a 500 gallon buffer to tame down the wood burner I had

The Idronics shows wiring options also. But the piping and wiring logic need to match

https://downloads.hearthnhome.com/installManuals/SF160_SF260_SF360.pdf