# Added thermal mass to wood stove



## Clifton73 (Jun 18, 2007)

I was thinking about burning less wood this winter...got to thinking about thermal mass...then thought about a couple of water heater tanks I have around the place....idea...put'em next to the stove and fill em up. Thats what I did...not the prettiest things to look at but lets just see what happens. Any opinions?


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## OntarioMan (Feb 11, 2007)

I suppose the "million dollar questions" are (assuming all things are equal - similar heating season, same species of wood, etc.) : 

- will he burn less wood, and if so, why?

- will he burn the same amount of wood and why?

- will he burn more wood and why?


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## WisJim (Jan 14, 2004)

You might burn less wood because the heat stored in the water tanks would keep the room warm longer between fires, but I suspect that the main result would be more even heat and more comfort.


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## wy_white_wolf (Oct 14, 2004)

I think He'll burn about the same. 

1. While he doesn't say what size I really don't see them as enough thermal mass to make much difference.

2. It takes the same amount of energy to warm the tanks up as you get when they cool down.

3. The only way it would save is if he was over heating the house when the fire was burning.


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## Clifton73 (Jun 18, 2007)

Both are 40 gal tanks. 

If that amount of thermal mass won't make much difference, then why do we put fire bricks in our wood stoves?

Also, I forgot to mention before that both have their inlet/outlet pipes open allowing humidity into the room.


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## Ross (May 9, 2002)

fire brick is to shield the steel from extreme heat. Glad the tanks are open, super heated water can be a probem. I think you'll save some wood, as you should be more comfortable avoiding the fast burning fires to re-warm a cooled room.


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## ET1 SS (Oct 22, 2005)

I installed three 55-gallon drums in our crawlspace for use as a thermal-bank.

However when we began using them in the hot water loop, the pressure in the system [20psi], caused the drums to change shape.

The normal flat tops bulged into rounded dome shapes, and the plumbing fixtures got distorted and leaked.

So I took it all apart, and we are playing this week with running the system with a low pressure.

Good luck.


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## MELOC (Sep 26, 2005)

i agree with wolf. i doubt your usage changes much, but your house will be more comfortable.


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## OntarioMan (Feb 11, 2007)

Are these just the water heater tanks or the entire water heater?


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## zant (Dec 1, 2005)

Would the tanks need blowoff valves and some way to vent outside??


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## ET1 SS (Oct 22, 2005)

Not sure who this is addressed to;

My thermal-bank tanks are just tanks to hold a capacity of heated water, during times of high heat availability and to give off that heat to the radiant loop during periods of lower heat.

All systems need to have a pressure relief valve installed.


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## Clifton73 (Jun 18, 2007)

just tanks, metal jacket and insulation have been stripped off. The tanks are not connected to the water lines just sitting behind the stove with both the inlet and outlet pipes open in the event it would get too hot the steam would just come out the top...no danger of bursting.


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## Yukon Mike (Nov 25, 2004)

A thermal mass is the way to go for reasonable all night heat. If you get tired of the water tanks do what my friend did.

My friend in Wisconsin heats only with a wood stove and for years put up with adding wood in the middle of the night and putting up with the temperature fluctuations as the fire cycled up and down. What he finally did was add brick around the wood stove (about a foot and a half thick) on three side. This did the trick plus and now he stays in bed at night. :zzz:


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## blue gecko (Jun 14, 2006)

Just make sure your floor joists can handle the load.


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