New Wood Boiler with storage propane tankless backup question

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marcomjl

Member
Aug 2, 2011
19
CT. Last Green Valley
Hi guys, here is the details of the system setup.

Radiant floor setup
Attack 45dpx wood gasification boiler
DIY heat storage tank
Navien NCB-E Combi propane tankless boiler.

Right now going through installing all the radiant.

My plan for everything is the Attack wood boiler heating up the thermal storage tank water. When the radiant system zones call for heat it will be from a coil in the thermal storage tank. In that same heat coil circuit will be the tankless propane boiler working in a pass through state. If the set temp in the coil/tank reaches say 110 degrees the tankless will be relayed to start up and heat the supply call from the zone.

Anyone have any experience/tips on this setup?
I must add that the tankless boiler and the radiant system will be completed first and later this year I plan on adding the storage tank and moving/installing the wood boiler in place.
 
Last edited:

peakbagger

Minister of Fire
Jul 11, 2008
6,486
Northern NH
If you are planning a system you may want to review this biomass heating course https://www.heatspring.com/courses/...iciency-biomass-boilers-sponsored-by-nyserda/ The instructor is generally regarded as the #1 biomass heating expert in US. He has a lot of good concepts. He has similar paid courses but New York State paid to offer this course to any firm designing and installing biomass heating systems that qualify for a subsidy.
 

marcomjl

Member
Aug 2, 2011
19
CT. Last Green Valley
If you are planning a system you may want to review this biomass heating course https://www.heatspring.com/courses/...iciency-biomass-boilers-sponsored-by-nyserda/ The instructor is generally regarded as the #1 biomass heating expert in US. He has a lot of good concepts. He has similar paid courses but New York State paid to offer this course to any firm designing and installing biomass heating systems that qualify for a subsidy.

Thanks for the tip. I actually own and have read John’s book Modern Hydronic Heating. It is very informative and a great reference.

Right now I am going to lean towards an aquastat to control the tankless for backup. Just curious to see what others might suggest pros/cons.
 

Fred61

Minister of Fire
Nov 26, 2008
2,444
Southeastern Vt.
That's basically the way my system worked and it worked well. I used a flat plate heat exchanger to heat the storage water and the copper coil for the radiant.
One thing that wasn't clear in your description was which water (storage or system) was going to be heated with fossil fuel.

When my storage reached my low setting (which I set at 100::F I had a diverter that bypassed the storage so I didn't heat the storage with my oil boiler.
 
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marcomjl

Member
Aug 2, 2011
19
CT. Last Green Valley
That's basically the way my system worked and it worked well. I used a flat plate heat exchanger to heat the storage water and the copper coil for the radiant.
One thing that wasn't clear in your description was which water (storage or system) was going to be heated with fossil fuel.

When my storage reached my low setting (which I set at 100::F I had a diverter that bypassed the storage so I didn't heat the storage with my oil boiler.

The system water will be heated by the tankless propane unit.

What kind of diverter valve. 3 way solenoid? One on the return and supply of the coil coming out of the storage tank?
 

salecker

Minister of Fire
Aug 22, 2010
1,478
Northern Canada
My backup oil boiler is tied into my house side of the heat exchanger with close spaced tee's.
Once i stop burning wood for the season and want to heat with oil i shut off a valve on my exchanger so there is no unnessary heating of my storage.