Thinking of getting a wood boiler...

[stevepick]

Here in Newfoundland we are facing the potential of electricity rates rising by over 50% by 2020 due to the build of the Muskrat Falls hydro station in Labrador. I currently have hydronic heating with an electric boiler, infloor on the main and baseboards in the finished basement. I already balk at the bills I have to pay during the winter months. And here in Newfoundland, winter is a long season.

So to cut my usage I am looking at installing an outdoor wood boiler, something like the P&M 28-40 or the Optimizer 250. My house is a log a frame ~ 2400 square feet. I also have a separate 700 square foot garage that I will add to the system. I will also heat DHW with the boiler.

The in-floor heating is installed poorly I've discovered when investigation a leak from the kitchen drain. It's hung on the joists, only using reflective material below. I have some heat transfer plates on the way and will slowly get them installed correctly, room by room from the basement using adequate insulation once the plates are up. Even the rim joists are not insulated. Sheesh.

I have done a fair bit of reading over the weekend on various setups and systems. From what I gather I should run the boiler loop 24/7, then when the house calls for heat, it will fire up my current system, without running the electric boiler, using a plate exchanger to transfer heat from the boiler, then continue the line to another plate exchanger on my electric DHW boiler.

In the garage I operate a water to air exchanger with a fan.

All make sense so far?

My questions are mainly about plate exchanger sizes? A 20 plate (5x12?) sounds like plenty for my DHW needs. What about for the hydronic? Will the same do, or is something a littler larger needed?

My other question is about wiring the electric boiler so it runs normally without the heating element firing? Where can I find some details on that?

Below is my current electric boiler setup. I'll have the wood boiler loop come in from the right, attach to a HX in the lower return line of the boiler, then run over to my DHW into a HX, then back out again.

Thanks for any and all help/opinions.

(Aside - I tried signing up at outdoorwoodfurnaceinfo.com but never did receive my confirmation emails for two accounts I tried to setup.)

 

[Karl_northwind]

I think you have the right idea. a 20 plate would do your DHW adequately, and I'd suggest a 40-50 plate for your space heating. If you have a local dealer, I'd look into the Heatmaster G series boiler along side the P&M. Both Canadian made.
it looks like you have a mixing valve between the electric boiler and the floor loops, so that's good. Put the flat plate HX in line with the main pipe to or from the boiler and pipe it counter flow (opposite directions) Put an aqua stat on the boiler pipe to open the circuit on the wires that call for the electric boiler to turn on (TT contacts) as long as the wood boiler loop is hot. should be in good shape.

now start lining up dry wood.
good luck
Karl

 

[stevepick]

Ok, after reading your reply 10 times I think I understand. Can I use the aqua stat in the wood boiler to control the TT contacts of the electric boiler? The P&M boilers have aqua stats to control temps/fan already. So do I run an wire from that one into the house along side the boiler pipe?

I'll look into the Heatmaster boiler as well.

I was thinking of sourcing wood now and installing next year. But part of me wonders if I will regret waiting.

Thanks Karl.

 

[peakbagger]

Don't consider a wood boiler unless you also install thermal storage.

 

[maple1]

Don't consider a wood boiler unless you also install thermal storage.

I'm a big fan of storage, but I don't think I would say that with certainty. I'm not sure storage is so much a necessity or large gainer when talking an OWB. Which I think is what the OP is talking.

 

[maple1]

Here in Newfoundland we are facing the potential of electricity rates rising by over 50% by 2020 due to the build of the Muskrat Falls hydro station in Labrador. I currently have hydronic heating with an electric boiler, infloor on the main and baseboards in the finished basement. I already balk at the bills I have to pay during the winter months. And here in Newfoundland, winter is a long season.

So to cut my usage I am looking at installing a wood boiler, something like the P&M 28-40 or the Optimizer 250. My house is a log a frame ~ 2400 square feet. I also have a separate 700 square foot garage that I will add to the system. I will also heat DHW with the boiler.

The in-floor heating is installed poorly I've discovered when investigation a leak from the kitchen drain. It's hung on the joists, only using reflective material below. I have some heat transfer plates on the way and will slowly get them installed correctly, room by room from the basement using adequate insulation once the plates are up. Even the rim joists are not insulated. Sheesh.

I have done a fair bit of reading over the weekend on various setups and systems. From what I gather I should run the boiler loop 24/7, then when the house calls for heat, it will fire up my current system, without running the electric boiler, using a plate exchanger to transfer heat from the boiler, then continue the line to another plate exchanger on my electric DHW boiler.

In the garage I operate a water to air exchanger with a fan.

All make sense so far?

My questions are mainly about plate exchanger sizes? A 20 plate (5x12?) sounds like plenty for my DHW needs. What about for the hydronic? Will the same do, or is something a littler larger needed?

My other question is about wiring the electric boiler so it runs normally without the heating element firing? Where can I find some details on that?

Below is my current electric boiler setup. I'll have the wood boiler loop come in from the right, attach to a HX in the lower return line of the boiler, then run over to my DHW into a HX, then back out again.

Thanks for any and all help/opinions.

(Aside - I tried signing up at outdoorwoodfurnaceinfo.com but never did receive my confirmation emails for two accounts I tried to setup.)

View attachment 164618

I've got an electric boiler for backup heat. It doesn't do anything unless it is called for heat, and as long as you keep it hot, the elements shouldn't come on with that call. I think I can lower the temp it maintains via a temp setting dial on the boiler - so you could lower that to help reduce instances of the elements briefly kicking in or short cycling.

 

[stevepick]

Hi Maple1,

Yes, I'm looking at an outdoor wood boiler, and as I understand it, it's best to run the OWB loop 24/7. So storage doesn't make sense in this case does it? The Heatmaster G200 has a 190 gallon tank. The P&M Optimizer has 240.

Or do I add indoor storage and would that reduce the number of burning cycles to maintain heat? Something like a 100 gallon insulated tank?

 

[stevepick]

Ah, I see. I can get a simple inline aqua stat plumbed in the OWB line, inside the house and tied to my electric boiler. Then if the OWB line is cold, the circuit closes and allows the electric boiler to run.

Can someone point me to an example online? Still not sure if I'm looking for the right thing.

 

[Karl_northwind]

Ok, after reading your reply 10 times I think I understand. Can I use the aqua stat in the wood boiler to control the TT contacts of the electric boiler? The P&M boilers have aqua stats to control temps/fan already. So do I run an wire from that one into the house along side the boiler pipe?

I'll look into the Heatmaster boiler as well.

I was thinking of sourcing wood now and installing next year. But part of me wonders if I will regret waiting.

Thanks Karl.

in a typical install, you would let the OWB do it's thing, and use that second aqua stat (not the one on the OWB) to keep the backup electric from turning on as long as the OWB pipe is hot. once it cools down, the backup will kick in.
no wires run between the OWB and the basement boiler.

 

[stevepick]

So something like a Honeywell L6006C1018 strap on aqua stat? I would simply strap it so the probe is on the OWB pex pipe coming in. Before it hits the first HX?

 

[maple1]

in a typical install, you would let the OWB do it's thing, and use that second aqua stat (not the one on the OWB) to keep the backup electric from turning on as long as the OWB pipe is hot. once it cools down, the backup will kick in.
no wires run between the OWB and the basement boiler.

Might that complicate things if all other system controls are tied to the electric boiler? E.g., if the electric boiler can't get power - it might not be able to turn on a system circ? I know with mine, on a call for heat, the electric boiler gets activated & it starts its system circulator. A separate control inside it then turns the elements on & off as needed to maintain the boiler temp. So maybe if the OWB is going to circulate 24/7 thru one side of a HX, you would only need to tie a second circulator to the other B side of the HX that starts when the load circ does. Or, even simpler, just plumb the B side of the HX in line with the system return just before it enters the electric boiler so whenever the system circ is running, it is pulling hot water off the HX and into the electric boiler as long as the OWB is operating. Which should prevent the elements from coming on. If the OWB isn't operating, then the elements will activate as needed.

 

[stevepick]

I think Karl covered that in his initial post:

Put an aqua stat on the boiler pipe to open the circuit on the wires that call for the electric boiler to turn on (TT contacts) as long as the wood boiler loop is hot.

I basically need it all to work as it should, with the exception of the heating elements firing. My system has three zones, 2 upstairs, one in the basement, each controlled by a separate thermostat. The circulation starts before the heating element fires when heat is called for by the thermostats. I just need to prevent the firing of the heating element when the OWB pipe is hot enough.

I think I have enough information to go on. Now I need to source a OWB. No dealers on the island will make that a little difficult.

Thanks for the input Maple.

 

[stevepick]

Here's a more detailed view of the electric boiler. The pump on the left is for my basement baseboards. The pump on the right is for the 2 zones of inflow heating on the main floor. When I get the OWB installed I will add a couple more baseboard heaters to my loft bedroom and ensuite. Though it's a bit tight there now...

.

 

[maple1]

I think Karl covered that in his initial post:

Put an aqua stat on the boiler pipe to open the circuit on the wires that call for the electric boiler to turn on (TT contacts) as long as the wood boiler loop is hot.

I basically need it all to work as it should, with the exception of the heating elements firing. My system has three zones, 2 upstairs, one in the basement, each controlled by a separate thermostat. The circulation starts before the heating element fires when heat is called for by the thermostats. I just need to prevent the firing of the heating element when the OWB pipe is hot enough.

I think I have enough information to go on. Now I need to source a OWB. No dealers on the island will make that a little difficult.

Thanks for the input Maple.

My thought on that, based on what I'm remembering about mine (which could be fuzzy by now), is that my electric boiler needs to be turned on before it will in turn start a load pump. So if I set it up like that, the circulators wouldn't start. Mine is a bit different setup, with my two boilers - each has a system circulator that each one starts depending on which one is heating. But I think that's how the electric boiler side works.

Usual disclaimer - I could be wrong.

 

[stevepick]

I don't know myself, I just figured it would be bad to operate the heating element without circulation running first, to avoid over heating. But that's me just guessing. I'll have to watch it in operation to refresh my memory, see how it is wired, and look at some documentation. Thanks again.

 

[Karl_northwind]

I assumed (maybe incorrectly) that there were multiple zone pumps (the 2 GF 1558's on the right) and therefore there is a zone control somewhere, not in the boiler. that zone control would have the TT wires to the boiler and the zone pumps would still turn on. if the boiler is set right, you could just eliminate the aqua stat and let the boilers internals stay turned off via the internal thermostat. since there's no flue to lose heat up and little thermal mass, it should be fine that way too.

 

[stevepick]

Thanks again Karl. I'll do some investigation on the weekend. It would be ideal if I don't have to use an aqua stat. It makes sense that the boiler wouldn't fire the heating element if the water is hot enough on it's own.

There is a low and high temperature settings in the side of the boiler, but I was led to believe that was 2 temp settings, low for the in-floor, and the high for baseboards in the basement, as opposed to on/off temp settings.

I have a Slant Fin Monitron EH 20kw boiler - ~68K btuh.

 

[stevepick]

Here's another question, per my image in post #13, would installing the HX to the right of the return lines draw enough water through to heat the system? I don't have room to install the HX to the left of the returns, between the returns and the boiler.

When the pumps are pulling water through a zone, does the short return line out of and back into the boiler circulate enough water for a HX?

 

[maple1]

If I understand you right - I don't think that will work. It would be putting the HX into the line just before your mixing valve? So it will be sending hot water to both inlet sides of your mixing valve.

I think I would try to get the HX plumbed in right under the boiler, as close to the return inlet as I could, even if you had to rearrange some plumbing right there to do it. Then there would maybe be enough convective flow up into the boiler when the zones weren't circulating to help prevent it even more from cycling the elements.

 

[stevepick]

Thanks Maple. I'm referring to the right of the returns, on the bottom of the loop back to the boiler. But I'm thinking your right, the HX should be plumbed in between the returns and the boiler. Which will be a pain. as there's not a lot of room to work with as is.

Another issue I have is that I have two separate temp zones, one hot for baseboards in the basement, and one at a lower temp for my inflow heating. Not sure what to do about that given the HX will pump out one temp. which will be a lot hotter than what I need for the in floor.

 

[maple1]

Looking at your pic - it looks like the circ on the right is the infloor one? Since it looks like there is a mixing valve at the bottom of it? And the pipe at the right of the returns you mention is sending return water to the right, to the 'cold' side of the mixing valve. So keeping the electric boiler hot with wood shouldn't change anything with the way it works now. The mixing valve is determing the temp of the infloor water.

It looks fairly easy from the pic to get more room under the boiler. Just cut on the left & right side of the 3T return group, take a piece out of the pipe that goes right from there, and move the whole 3T return group to the right. There looks to be lots of room to move it with the couple feet or so of bare pipe to the right. You might have to cut & splice in pieces to extend your 3 return pipes enough to give room for the Ts to move over, not sure how much slack is in them. (Will have to for sure with the copper one.) Should definitely be doable though without a lot of trouble, looks like a decent place to get at. Then maybe plumb the HX in between the ball valve I think I see there, and the return T on the left.