Hot Water Heating Idea

[CT-Mike]

I am in the process of installing an insert and a full SS liner. I was thinking about wrapping a coil of copper tubing around the liner as it exits the stove before it hits the damper plate. Putting that in-line with my hot water heater to help minimize the DHW heating bill (oil-fired water heater). Anyone see any reason not to do this? Would it be worthwhile?

Thanks,

Mike

 

[Valhalla]

Good idea! There are many ways to recover waste heat. As long as you don't have a pressure problem with the temperature rise, it sounds fine. I would possibly put a simple over pressure valve in it, as a safety.

Let's see what the pros say next.

 

[KeithO]

You will more than likely need to add a recirculation pump to keep the water moving. Coldest water from the bottom of the tank to the coil and the heated water dumps in the top of the tank. With this type of system, safety is always an issue. You have to be sure it can never run dry or boil off, else you will generate steam. I hope that your insert is at a physically lower level than the hot water tank, else this is unlikely to work without constant vapor locks. An ideal configuration may be an electric water heater installed in the loft (under a bed of insulation) with the pipes running down to the wood stove / insert. This is the best configuration for passive circulation and avoidance of vapor lock.

 

[begreen]

Maybe not so good. There needs to be multiple safety valves and contingency systems in case of power failure, etc. I'm not saying it can't be done, but the risks of steam explosion are not trivial.

Also, if too efficient, it may cool down the flue gases to the point of affecting draft or creating a creosote issue. Some things to think about.

https://www.hearth.com/econtent/index.php/forums/viewthread/236/

 

[gpcollen1]

Maybe just do the wood boiler thing?? Do not think this will do anything substantial. What design were you thinking??

 

[burntime]

Hate to say it but it is a good way to fill the chimney with creosote. You will cool the gases and get a build up. You may also drasticly reduce the heat output of the unit. Better to save on heat and pay to heat your water than create a hazard. Not to say that it can't be done because it is a good concept, just one I would not explore.

 

[wellbuilt home]

I think you would be better off with a coil in the fire box or a SS water box on the side or rear of the stove that would be plumed to the water heater with a safty valve. I want to do the same thing but have not started on it yet.

 

[CT-Mike]

Well,

As I said it was an idea, and not necessarily a good one. I did not think about the possibilities of steam formation, and creosote build up.

Thanks for the input,

Mike

 

[gpcollen1]

Nothing wrong with ideas Mike...

 

[Adios Pantalones]

I'd also add that heating hot water is an inefficient way to recover heat.

Anyone know how long it takes to freeze ice?

 

[polaris]

I have seen hot water tanks on e-bay that surround the flue pipe. With just a tap to dispence hot water and a fill bung on top. I agree it not worth the risk of steam build up or creosote formation but for occasional hot water use in a remote location,maybe. Even so think I would want redundant blow off/pressure relief valves.

 

[Jags]

Anyone know how long it takes to freeze ice?

Depends if you started with cold ice or warm ice.

 

[billb3]

I'd also add that heating hot water is an inefficient way to recover heat.

Anyone know how long it takes to freeze ice?

My wood stove doesn't fit in the freezer.

 

[Valhalla]

I am in the process of installing an insert and a full SS liner. I was thinking about wrapping a coil of copper tubing around the liner as it exits the stove before it hits the damper plate. Putting that in-line with my hot water heater to help minimize the DHW heating bill (oil-fired water heater). Anyone see any reason not to do this? Would it be worthwhile?

Thanks,

Mike

I still believe that you could receive an easy advantage of warming your incoming town/well water of approx 40+ degrees to about 100+ degrees, thereby saving some oil to heat your DHW.

Smartly and simply done, this could work. It is your choice.

 

[Adios Pantalones]

Valhalla- I'm hoping to see you in about 60 years

Anyway- a preheat tank is not an uncommon way to put some heat in the source water (room temp) before the heater. It's nothing new, but putting it next to a woodstove might give it some bonus heat. I just don't want one in my livingroom

 

[billb3]

I've considered putting a preheat tank in the attic.

I'd have to drain it sometime between November and March.

 

[tradergordo]

I was thinking about this recently also. The main issue I think is the incoming water coming in at 40F and being stored in my hot water tank in the 55F basement. My cost (nat gas) for hot water heater alone actually triples from summer to winter. A small pre-heater tank, just sitting mostly out of sight, BEHIND the woodstove seems like a good idea to me, possibly with a grid of copper coils (pulled heat exchangers from junk air conditioners?) to further capture heat from behind the stove. I wasn't thinking of actually wrapping anything around the stove or flue, there would be no direct contact, its a mush safer, passive design with the goal of just trying to eliminate the tripling of energy use in the winter for the hot water heater by at a minimum just getting the incoming water up to room temp before it hits the water heater. Obviously if the cost of materials is high, its probably not going to be worth it - anyone know what to use for an inexpensive small storage tank? Is the tank really needed if I use the heat exchangers (grid of copper tubing) yanked from free/junk air conditioners? I guess I'd have to measure how much water would be held inside the heat exchangers. Also the cost of copper pipe to run from the stove area to the hot water heater in the basement I know would be very high - would using PVC for that be a good/bad idea? I know some people that have all PVC plumbing - not sure how easy it is to go from copper to PVC though (or how reliable those connectors would be).

 

[d.n.f.]

I've considered putting a preheat tank in the attic.

I'd have to drain it sometime between November and March.

Wow that is a good idea. I wish I would have thought of that idea when I had an attic.


My friend looked into this hot water woodstove idea (running a coil into/around the stove) and found some kits. He also found a lot of talk of explosions and such. Steam is a powerful thing.

 

[JustWood]

I was thinking about this recently also. The main issue I think is the incoming water coming in at 40F and being stored in my hot water tank in the 55F basement. My cost (nat gas) for hot water heater alone actually triples from summer to winter. A small pre-heater tank, just sitting mostly out of sight, BEHIND the woodstove seems like a good idea to me, possibly with a grid of copper coils (pulled heat exchangers from junk air conditioners?) to further capture heat from behind the stove. I wasn't thinking of actually wrapping anything around the stove or flue, there would be no direct contact, its a mush safer, passive design with the goal of just trying to eliminate the tripling of energy use in the winter for the hot water heater by at a minimum just getting the incoming water up to room temp before it hits the water heater. Obviously if the cost of materials is high, its probably not going to be worth it - anyone know what to use for an inexpensive small storage tank? Is the tank really needed if I use the heat exchangers (grid of copper tubing) yanked from free/junk air conditioners? I guess I'd have to measure how much water would be held inside the heat exchangers. Also the cost of copper pipe to run from the stove area to the hot water heater in the basement I know would be very high - would using PVC for that be a good/bad idea? I know some people that have all PVC plumbing - not sure how easy it is to go from copper to PVC though (or how reliable those connectors would be).

I'm gonna try this this winter. I have a 20 gallon air compressor tank I scavenged out of a dumpster that I will fasten to the ceiling in my furnace room. Also going to hang a small loop on the back of furnace where there is no jacket. Using a short section of insulated pex left over from my dads OWB install to get to the water heater.

 

[VTSR5]

I'd also add that heating hot water is an inefficient way to recover heat.

Anyone know how long it takes to freeze ice?

If you are having trouble freezing your ice, try unthawing it first.

 

[Adios Pantalones]

I'd also add that heating hot water is an inefficient way to recover heat.

Anyone know how long it takes to freeze ice?

If you are having trouble freezing your ice, try unthawing it first.

Unthawing is just freezing... How long does that take for ice?

 

[egghead2004]

, possibly with a grid of copper coils (pulled heat exchangers from junk air conditioners?) to further capture heat from behind the stove.

I would be carefull about using old evaperators or condensers. Refrigerant oil is pumped through that copper tubing, make sure it gets thoroughly cleaned out before heating potable water through there. As for how to clean it? I'm not sure how you would go about it and be safe.

 

[tradergordo]

, possibly with a grid of copper coils (pulled heat exchangers from junk air conditioners?) to further capture heat from behind the stove.

I would be carefull about using old evaperators or condensers. Refrigerant oil is pumped through that copper tubing, make sure it gets thoroughly cleaned out before heating potable water through there. As for how to clean it? I'm not sure how you would go about it and be safe.

I'd just flush it to clean, maybe with a degreaser/detergent solution. My family doesn't directly drink our hot water heater water, its used for doing the dishes, showers, washing hands. I doubt any oils would stick around for long but its easy to tell if oil is in your water (rainbow colors on the surface).

 

[Adios Pantalones]

Most AC units have small tubes for more surface area and better heat exchange, but maybe that would create a back pressure and therefore a drop in available pressure in the shower/sink/etc. You can get bendable copper pipe and it's not terribly expensive. I have used it to make a chiller for making beer, others use it for exchangers in boiler heat storage systems- look in "The Boiler Room".

 

[gpcollen1]

, possibly with a grid of copper coils (pulled heat exchangers from junk air conditioners?) to further capture heat from behind the stove.

I would be carefull about using old evaperators or condensers. Refrigerant oil is pumped through that copper tubing, make sure it gets thoroughly cleaned out before heating potable water through there. As for how to clean it? I'm not sure how you would go about it and be safe.

I'd just flush it to clean, maybe with a degreaser/detergent solution. My family doesn't directly drink our hot water heater water, its used for doing the dishes, showers, washing hands. I doubt any oils would stick around for long but its easy to tell if oil is in your water (rainbow colors on the surface).

And you don't fill a pot with hot water before putting it on to boil? Happens in my house sometimes....