OWB backup...........brainstorming needed

[war-wagon]

so i'm considering adding a furnace as a backup to my OWB. We just finished an addition project and ran a second line from the Woodmaster 4400 to a seperate manifold for the new construction. Now that we are heating close to 5000sq ft, wife is talking about taking a vacation this coming winter; and of course i'm buring a lot more wood. So my question is what are my options for a backup furnace. Ideally i'd want something that I could control to either run concurently with the OWB (say I get held up at work and fire burns out) or to run as main heat source (leaving for a week long vacation).

Curious as to what other have tried, what has worked, not worked.

points to ponder:

Manifolds are roughly 60' apart from the original construction and addition (two furnaces?)

original construction is an open system, addition is a closed system with HX (i believe HX is undersized and prefered the open system, so i may remove HX)

wife now wants central air, (all of our heat is radiant) so if i had to install duct work would it be easier and more economical to supplement OWB with forced air?


just spinning my wheels at this point and dealing with issues that would have been much more convenient to address when building the addition. so in advance i appreciate your feedback

 

[Encore]

If you want central air, definitely go with forced air for your supplementary heating.

I assume you have anti freeze in your system if you plan on going on vacation and not keeping the fire going?

I just have a buddy stop by once or every other day and he keeps the fire going. Turn the temp down to 58 or so and you'll be surprised how much further your wood goes.

 

[war-wagon]

Yes the system has antifreeze. Problem with having someone fill the stove is we are a good ways off the beaten path. Last winter I did have a buddy house sit to keep the stove loaded and take care of the dogs, but he drank all my beer.

 

[Richard@PM]

Hot air

I would agrre that if you want central air then hot air furnace would be the way to go but with new construction what I would also look at is a product for radiant floor heat as well, the product that I like is called ULTRA FIN from Macduf manufacturing, easy to install, heats the air space within the bays instead of direct contact with the floor, this also means no mixing valves, water temp can stay at 185 degrees. Just hot air is very dry and dusty in the house.

 

[war-wagon]

I looked at the ULTRA FIN (never heard of it before), all of the construction is complete and pex is in place for the radiant so ultra fin is not an option. That said the wife mentioned the central air on an unseasonably warm day and that may have been just out of frustration and lack of having air conditioners in yet. So central air is not a must at this point, at least not in my mind. Hers, who knows.


What i'm looking for is ideas on how to set up a furnace to run in conjunction with the OWB so should the fire go out, the furnace could pick up. Now if that means some thermostaticly controlled switches to turn off the pumps on the OWB, and strategicly placed check valves (?, or some sort of configuration with temp regulated valves) so i'm not heating the water jacket on OWB in addition to the house when my water temp hits a certain point. Ideally the process would reverse itself back to OWB should the heatload temporarily be too much for the stove to handle, then once it reached operating temps furnace would shut off.

Maybe I'm totally off the reservation on this one, but I think there has got to be a way to plumb this so the furnace and OWB can run together or I could manually set the system to run off the furnace for extended periods away from the house.

I have no intention of paying the propane man anymore than I have to, but do realize the need for a backup heat source and have to address the wife's desire to leave NY at least once a winter, preferably after deer season.

 

[Richard@PM]

Not hard to do

Getting the wood boiler and indoor boiler to work in tandem is not difficult to do, I do it all the time,just requires using a plate heat exchanger and an off the shelf aquastat to interupt the power to the burner on the indoor boiler. DO IT RIGHT the first time and you both will be happy, hot water or forced hot air. you may PM me if you need help.

 

[NSMaple1]

If A/C is a consideration, maybe think about just putting a mini-split in. They can do both - and no need to mess with your existing setup.

 

[stihly dan]

Yup, what he said.

 

[war-wagon]

Getting the wood boiler and indoor boiler to work in tandem is not difficult to do, I do it all the time,just requires using a plate heat exchanger and an off the shelf aquastat to interupt the power to the burner on the indoor boiler. DO IT RIGHT the first time and you both will be happy, hot water or forced hot air. you may PM me if you need help.

is it possible to interupt the power only to the circulator pumps on the OWB, thus allowing the fan to remain running until the stove got back up to temp (for excessive heat load, for instance EVERY zone kicked on at once) or shut off automatically due to low temp. Also how do I overcome sending hot water created by the furnace back to the water jacket. Though i guess that wouldn't be an issue if the circulator pumps were off. thinking out loud, appreciate the advice and wondering what others have used and what works and what doesn't. i think the multi splits would be a bit of an eye sore, not to mention there would still be the issue of interupting power to the OWB so cold water wasn't circulating in the floor while the multi splits were running.

 

[Richard@PM]

Interupting circulators

Yes you can use an aquastat to shut off circs by simply interupting the power, look at the aquastat as a temp. sensitive light switch, on or off. What I prefer to do however is to interupt the blower on the wood boiler if the temp drops to low and leave the circs running as this does a much better job of protecting wood boiler water temp and stops blower if you didn't feed the boiler and the second aquastat allows the oil or gas unit to return to its setpoint of 185 degrees, heating your home as well as protecting your investment sitting outside. You will burn oil or gas but at that point you will have an Aha moment and realize you should have filled the wood boiler a little sooner. The a-419 controller can be wired as well to set off an alarm or turn on a light when the water temp drops below a setpoint.

 

[mtfallsmikey]

and, a 2-stage 'stat to control everything.

 

[war-wagon]

Yes you can use an aquastat to shut off circs by simply interupting the power, look at the aquastat as a temp. sensitive light switch, on or off. What I prefer to do however is to interupt the blower on the wood boiler if the temp drops to low and leave the circs running as this does a much better job of protecting wood boiler water temp and stops blower if you didn't feed the boiler and the second aquastat allows the oil or gas unit to return to its setpoint of 185 degrees, heating your home as well as protecting your investment sitting outside. You will burn oil or gas but at that point you will have an Aha moment and realize you should have filled the wood boiler a little sooner. The a-419 controller can be wired as well to set off an alarm or turn on a light when the water temp drops below a setpoint.

now bear with me, this is new territory. since i have antifreeze in the OWB and there is already a fan shut off when the temp gets too low, wouldn't it make more sense to have the pumps shut off? also what is the reversal process? if the aqua stat shuts off the fan due to low temp, how do i turn my fan back on when restarting the fire? just wondering.

appreciate all of your help

 

[Richard@PM]

now bear with me, this is new territory. since i have antifreeze in the OWB and there is already a fan shut off when the temp gets too low, wouldn't it make more sense to have the pumps shut off? also what is the reversal process? if the aqua stat shuts off the fan due to low temp, how do i turn my fan back on when restarting the fire? just wondering.

appreciate all of your help

I am not really familiar with your boiler but yes if yours already kills the blower with low water temp and you have non toxic anti freeze in it then you would be fine with turning off the circ with an aquastat

 

[war-wagon]

I am not really familiar with your boiler but yes if yours already kills the blower with low water temp and you have non toxic anti freeze in it then you would be fine with turning off the circ with an aquastat

OWB is a woodmaster 4400, as far as the indoor backup furnace, does that system have to be preassurized or could i keep the whole set up an open system with mixing valves. for some reason i seem to be having better luck with an open system vs HX. just curious

 

[NSMaple1]

is it possible to interupt the power only to the circulator pumps on the OWB, thus allowing the fan to remain running until the stove got back up to temp (for excessive heat load, for instance EVERY zone kicked on at once) or shut off automatically due to low temp. Also how do I overcome sending hot water created by the furnace back to the water jacket. Though i guess that wouldn't be an issue if the circulator pumps were off. thinking out loud, appreciate the advice and wondering what others have used and what works and what doesn't. i think the multi splits would be a bit of an eye sore, not to mention there would still be the issue of interupting power to the OWB so cold water wasn't circulating in the floor while the multi splits were running.

Do you have duct work now or is it all a hot water system?

If you have no ducts now & are thinking A/C, there is no way I would undertake retrofitting the ductwork needed for central A/C with the mini-split technology that is out there now. It could do your A/C & give you back up heat. And could even do all your heat in the shoulder seasons which would then reduce the wood you need to cut every year.

And are you saying that your heating circs run 24/7 - even when the OWB goes cold? That should be an easy one to overcome.

In my case I yanked out a combo wood/oil boiler, and replaced with a new wood boiler with an electric one for backup - A/C wasn't a factor with me. The electric only got used for one day this winter so electricity cost not really a factor either. Lots of things to consider - like how much the backup will actually be used, chimney situation, etc. etc....

 

[Richard@PM]

OWB is a woodmaster 4400, as far as the indoor backup furnace, does that system have to be preassurized or could i keep the whole set up an open system with mixing valves. for some reason i seem to be having better luck with an open system vs HX. just curious

Yes you can go directly into the indoor unit but it is never recomended by me as it leads to problems down the road. I will give you some examples, the water in the wood boiler is quite dirty and because it is open to the atmosphere ( non pressurized ) there will always be air in the system therefore the indoor system will corrode prematurely, it needs 12 -14 pounds of pressure on the inside system to keep the air out. Air in the system will always find the high spot in the heat loop and slow or stop water flow within the loop. Warranty of the inside boiler will be voided if run at atmospheric pressure. If the wood boiler is placed below any heat loop inside the house water will drain back to the wood boiler any time the circulators are shut down. If the heat exchanger is properly sized and installed all of these problems dissapear. I always try to plumb with a primary / secondary loop on the indoor unit as this gives the ability to eliminate heating of the indoor boiler alltogether and at the same time allows for the addition later on of different add on heat sources such as solar thermal when it becomes affordable. If you are having problems with your heat exchanger it is either not plumbed properly, plugged up or not sized right.

 

[war-wagon]

If you are having problems with your heat exchanger it is either not plumbed properly, plugged up or not sized right.

fairly certain the addition that is on a closed system the HX is undersized, since there is no heat loss between OWB and HX. just doesn't cut the mustard. so pre-existing manifold that is an open system would need a HX too. are these sized by sq footage being heated, number of loops in the radiant, or?

 

[war-wagon]

Do you have duct work now or is it all a hot water system?

If you have no ducts now & are thinking A/C, there is no way I would undertake retrofitting the ductwork needed for central A/C with the mini-split technology that is out there now. It could do your A/C & give you back up heat. And could even do all your heat in the shoulder seasons which would then reduce the wood you need to cut every year.

And are you saying that your heating circs run 24/7 - even when the OWB goes cold? That should be an easy one to overcome.

QUOTE]

there is no existing duct work, all pex radiant heat. i'm looking at heating 5000sq ft, how many min-splits is that? I did some checking and found units that have up to four heating/cooling units but my concern with that is now i have a bunch of conduit on my outer walls and bulky units on my interior walls. also i think with our high ceilings the radiant does a good job of heating everything evenly.

yes the pumps on the OWB run constantly, so if the fire goes out i'm pumping cold water through the house. kind of a pain to reheat the place. how do i go about having the pumps shut off when the fan quits because the temp has gone to low

 

[Richard@PM]

Why does your fire keep going out on the wood boiler? Yes it is possible to shut off the circs to the wood boiler but possibly you can remedy the whole situation by simply using what you have already by keeping the boiler running, you should be getting a 10-12 hour burn per filling with it, is that not possible.

 

[war-wagon]

Typically there is no issue with the fire going out. I figure if I'm going to bite the bullet and spend some money on a backup system, why not rig it to work in tandem with the OWB for those long days of hunting