Water jacket/coil on cookstove for hot water?

[bholler]

Water is circulated with pumps all the time and has been found to be very safe.

unless the power goes out or the pump dies. To me it is a big risk not worth taking why not just raise your tank so you dont need a pump?

 

[Rusnakes]

Real rough numbers if you heat 50 gallons of water up 50 degrees there is about a cubic foot of expansion. You already should have an expansion tank on your water heater, add another one for the preheat tank. If you are not going to use a preheat system (it is generally one of the better ways to plumb it) you can use your exiting water tank. You need to lower the thermostat setting as low as possible and use a tempering valve to prevent scalding if you go this way. It will not be as efficient if you do not use a preheat design, but it can be done. Your water temperature coming out of the faucet will tend to very in temperature without a preheat tank. With the preheat tank the water is warmed to operating temp, then it flows through the main tank, generally the elements will stay off, they should only come on when it is sitting and has thermal loss.

So for your preheat tank, you are just using a standard water heater? As in this setup?:

Cold line into house---> preheat water heater with expansion tank (to whatever temp you said above...something like 60*?)--->woodstove + coil--->secondary storage tank, with expansion tank (and overflow drain)--->main hot water line to fixtures in house

Our water temp is about 46-48* in the winter months.

 

[bholler]

So for your preheat tank, you are just using a standard water heater? As in this setup?:

Cold line into house---> preheat water heater with expansion tank (to whatever temp you said above...something like 60*?)--->woodstove + coil--->secondary storage tank, with expansion tank (and overflow drain)--->main hot water line to fixtures in house

Our water temp is about 46-48* in the winter months.

You really really need to have someone who understands this set it up. Doing it wrong can be catastrophic. Or use a pre-engineered system

 

[electrathon]

unless the power goes out or the pump dies. To me it is a big risk not worth taking why not just raise your tank so you dont need a pump?

House configuration. The stove is in the fireplace, no nearby (or upper) place that a tank could reside. There is a basement under the house there the furnace and instant hot live, so it a was natural place for it. I agree, higher is better. A lot simpler design that way. Overpressure can be controlled through expansion and pressure relief. I have two relief valves (one on the water heater and one on the woodstove set-up) and an expansion tank.

 

[Rusnakes]

You really really need to have someone who understands this set it up. Doing it wrong can be catastrophic. Or use a pre-engineered system

Oh, we will. I'm no plumber (my specialties are in all things wood). Just trying to imagine how this would flow to plot out the course through the house and the possible equipment needed.

 

[electrathon]

So for your preheat tank, you are just using a standard water heater? As in this setup?:

Cold line into house---> preheat water heater with expansion tank (to whatever temp you said above...something like 60*?)--->woodstove + coil--->secondary storage tank, with expansion tank (and overflow drain)--->main hot water line to fixtures in house

Our water temp is about 46-48* in the winter months.

You heat the water in the preheat tank. The water is already hot when it goes into the water heater that way. This is done for both safety and comfort. If you use an instant hot water heater there is no energy used when the preheat water is hot. With a tank, only energy used is to maintain the water temp when not using water. Use a lot of water, you will have 100 gallons of hot water instead of 50. The expansion can be anyplace in the system, as long as there is no check valve between the tank and the stove.stopping expansion. I am not the best at drawing but I will draw up a basic diagram.

 

[electrathon]

This s the basic concept.

 

[Rusnakes]

This s the basic concept.

Electrathon, thanks so much for taking the time to draw that out. I see your preheat tank is also your storage tank, which is interesting and something I hadn't considered.

 

[electrathon]

Rusnakes, You do not have to do it this way, but it is a far better functioning system. By preheating the water it enters the domestic water heater at temperature and it becomes nothing but a storage tank. You have twice the amount of water, if needed, that way. It is more efficient too, so there is a better energy savings. It also can be used as a solar water tank in the summer time. I often turn off my water heater in the winter time and just use the preheat tank as the water heater.

 

[Rusnakes]

Rusnakes, You do not have to do it this way, but it is a far better functioning system. By preheating the water it enters the domestic water heater at temperature and it becomes nothing but a storage tank. You have twice the amount of water, if needed, that way. It is more efficient too, so there is a better energy savings. It also can be used as a solar water tank in the summer time. I often turn off my water heater in the winter time and just use the preheat tank as the water heater.

Almost exactly what I was envisioning, just different on the thermal siphoning loop and ordering of the storage tank first. I appreciate all the info and the drawing was very helpful.

 

[electrathon]

I found this online. It is a very old book on water heating. Written about 100 years ago, it talks about how it was done and things that both worked and did not work. If you read through there is even a place that talks about an explosion that happened from improper use of the system.
http://www.archive.org/stream/kitchenboilerco00unkngoog#page/n44/mode/2up