Outdoor Wood Furnace radiant heat setup questions

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traparatus

New Member
Nov 21, 2021
5
British Columbia
Howdy, folks. Firstly, thanks to all of you for sharing your knowledge. This place is a treasure trove of information.

I purchased a house a little while back that came with Central Boiler CE 550 Titanium HD(gasification boiler). The house is located in northern British Columbia, featuring severe winters. It's a log house, sitting on a concrete slab. There is a full basement, main floor and a loft. Total area is about 3000 sqft. Current heating setup is a water-to-air heat exchanger mounted in a forced air furnace with electrical backup. There is also a tube water-to-water heat exchanger for domestic hot water.

I would like to migrate to radiant heat throughout the whole house.

Can someone help me get started on designing a radiant heating system to be powered by this wood furnace? Do I need an indoor water storage tank and if so how big should it be? Would panel radiators be the way to go or is there a way retrofit a radiant heating line into the basement ceiling? Is there somebody on here who can design a system such as this and create technical drawings (for a fee, of course)? Nobody in my village of ~4000 people has the slightest idea of what the hell I'm talking about. I realize this is a loaded question and I'm hoping someone can point me in the right direction to get started.

Thanks. Also, on a side note. If you have a chance to NEVER deal with Central Boiler, go ahead and take it. By the by, the worst company I've ever had the displeasure of communicating with.
 

E Yoder

Minister of Fire
Jan 27, 2017
595
Floyd, VA
I would think panel rads would be considerably easier to add than running radiant floor piping in an existing house. Unless the basement is unfinished.
I dont do a lot of radiant tho.
 

Bad LP

Minister of Fire
Nov 28, 2014
1,784
Northern Maine
Panel radiation is my vote.
 

traparatus

New Member
Nov 21, 2021
5
British Columbia
Thanks for the suggestions. Radiator panels are definitely the easiest to retrofit, though cost is pretty spicy.

Can someone help me clear up this temperature differential situation.

My Central Edge OWB keeps water around 185F. It needs to burn regularly as it is located outside and is not designed for batch burning, like a Garn or some such. It's an unpressurized system, open to atmosphere. I assume it needs to be interfaced to a radiant heat system through a heat exchanger. Panel radiators seem to like around 120F.

So, for example, I get a buffer tank, heat it up to 185F, let it cool down to... say... 100F. What's my wood boiler doing during this time? Is it just smoldering? Typically that boiler runs on ~2 hour burn cycles. Burn for ~10-15 minutes, smolder for 1.5-2 hours. Working like this it already creates more creosote in the fire chamber than I know what to do with. I can't imaging stretching this burn cycle for any longer.
 

E Yoder

Minister of Fire
Jan 27, 2017
595
Floyd, VA
I'd run the panel rads at 180 and let the OWB cycle as it was designed to do.
I have run panels rads direct off the wood boiler (OWB) without a heat exchanger but the units I install are stainless and the water stays pretty clean.
 

salecker

Minister of Fire
Aug 22, 2010
1,526
Northern Canada
I have cast iron rads in my house,love them.
I run my storage to 185 ish and refire around 120.The rads will produce heat from lower temps
i don't have an outdoor reset,not sure if that would make a difference in my heating abilities.
I got 6 free cast iron rads this summer.
 

maple1

Minister of Fire
Sep 15, 2011
10,809
Nova Scotia
Thanks for the suggestions. Radiator panels are definitely the easiest to retrofit, though cost is pretty spicy.

Can someone help me clear up this temperature differential situation.

My Central Edge OWB keeps water around 185F. It needs to burn regularly as it is located outside and is not designed for batch burning, like a Garn or some such. It's an unpressurized system, open to atmosphere. I assume it needs to be interfaced to a radiant heat system through a heat exchanger. Panel radiators seem to like around 120F.

So, for example, I get a buffer tank, heat it up to 185F, let it cool down to... say... 100F. What's my wood boiler doing during this time? Is it just smoldering? Typically that boiler runs on ~2 hour burn cycles. Burn for ~10-15 minutes, smolder for 1.5-2 hours. Working like this it already creates more creosote in the fire chamber than I know what to do with. I can't imaging stretching this burn cycle for any longer.
With a boiler/storage system, you burn the boiler and heat storage until the fire is all gone. Then when storage cools to where it's not heating anymore, you make another fire. Repeat all winter. Storage + OWB is not an optimal combo.
 

traparatus

New Member
Nov 21, 2021
5
British Columbia
With a boiler/storage system, you burn the boiler and heat storage until the fire is all gone. Then when storage cools to where it's not heating anymore, you make another fire. Repeat all winter. Storage + OWB is not an optimal combo.

Right. The thing is, as I understand it, I MUST have some kind of buffer storage to interface the OWB to radiant heating in this house.

The boiler is located just above basement level, located outdoors and open to atmosphere. All water connections currently run below the level of the boiler. There is no way I can pump water in an unpressurized system all the way to the second floor. Plus, this would require using stainless steel radiators or some serious corrosion protection, as E Yoder has alluded to.

So, there has be some way to transfer heat from OWB heated water to separate radiator water. Does anybody know if a simple tube heat exchanger, like the one I currently have for heating domestic water, is good enough to interface from OWB to radiators?
 

E Yoder

Minister of Fire
Jan 27, 2017
595
Floyd, VA
Buffer storage is not a necessity in my opinion. An outdoor furnace is designed to cycle with the load.
I've pumped 30+' higher than the top of the OWB using an open (no pressure) system. Keep the pumps low and purge thoroughly with full house pressure before attempting to circulate.
I hooked up an air handler in an attic with a coil yesterday, probably 15-20' higher than the OWB. No issues. It's all in how thoroughly you purge the air. Pipe sizing needs to be on the small side to keep water velocity high enough to push air bubbles through to vent out at the OWB.

I understand that some would disagree and never design a system like that. There are so many different ways to get heat in a house that the discussion will continue forever. :)

I should mention that the OWB is stainless in the systems I do but I use regular cast iron pumps, etc. I found the key is keeping the water treated properly and testing yearly. The really cruddy systems I've seen are usually not treated or tested properly at all.
 

traparatus

New Member
Nov 21, 2021
5
British Columbia
Buffer storage is not a necessity in my opinion. An outdoor furnace is designed to cycle with the load.
I've pumped 30+' higher than the top of the OWB using an open (no pressure) system. Keep the pumps low and purge thoroughly with full house pressure before attempting to circulate.
I hooked up an air handler in an attic with a coil yesterday, probably 15-20' higher than the OWB. No issues. It's all in how thoroughly you purge the air. Pipe sizing needs to be on the small side to keep water velocity high enough to push air bubbles through to vent out at the OWB.

I understand that some would disagree and never design a system like that. There are so many different ways to get heat in a house that the discussion will continue forever. :)

I should mention that the OWB is stainless in the systems I do but I use regular cast iron pumps, etc. I found the key is keeping the water treated properly and testing yearly. The really cruddy systems I've seen are usually not treated or tested properly at all.

Very interesting. I've definitely read many precautions regarding setting up an unpressurized system in this manner.

I'm crunching some numbers and I see that indeed running a buffer storage is not at all necessary and a simple plate heat exchanger will do the trick.

Do you run a backup system for your radiant heat? My aim is to have an electric boiler as a backup to the outdoor wood furnace. I think that pretty much eliminates the option of running directly from the OWB to radiators. I gotta have some sort of reliable back up here as we plunge down to -40F with unfortunate regularity.