Some questions about heat storage ...

[patch53]

Guys, after only running my Seton for a few weeks, and reading a lot of valuable info on this site, I have decided that I will be adding storage next year. The one thing that I have a hard time grasping is how the flow thru the tubes is able to move the heat off fast enough without shutting down and refiring repeatedly, until the storage is up to temp.

I would be doing unpressurized storage, perhaps up to 1000 gallons, but probably closer to 500.

If my Seton 130 is cranking at say 1500F, I find it hard to imagine that it could run like that for 4-5 hours without shutting down. That would seem to require a phenomenol flow rate thru the tubes to keep from getting too hot and shutting down the air. Yet most of you guys seem to be saying that is exactly what you do. What am I missing here?

thx. Pat

 

[Nofossil]

You do need a good deal of surface area in the tank. I have the equivalent of over 100' of 3/4" copper in the storage tank.

 

[in hot water]

When the tank is cool and the boiler 150 °F or more you transfer a lot of BTUs (wide Δ T).

As the tank temperature approaches the boiler setpoint the transfer will slow down and you may have cycling of the boiler (small Δ T).

There is a way to size heat exchangers as "close approach" where the B side can run almost, within a few degrees, of the A side, but it takes a lot of surface area to be able to do that small Δ T exchange.

The companies that build un-pressurized tanks and supply copper coils bundles for them have a very good formula that is workable without breaking the bank Too much surface area could keep the boiler in condensing mode indefinitely, so you find the middle ground.

hr

 

[patch53]

Thanks guys. So what you're saying is that by having a lot of coil you will be able to transfer enough heat to the tank without overheating the boiler? And yes, I would imagine that the closer the tank water gets to shut off temp, the slower the rate of transfer and hence the probability of having the boiler cycle a few times before finally reaching full temp (190F or so)

Another question. The one thing I would like to avoid is to have the Seton run completely out of fire. I doubt that would happen with only a 500 gallon tank. I do NOT want to have to make a new fire every day. So, is it possible to have the Seton run for say a 2 hour burn, then cycle off for an hour or two, and then run again for 2 hours, etc.? I don't want to have to worry about excessive creosote build-up when not firing, however, wouldn't a hot 2-hour burn elimintae any small amounts of creosote that might accumulate during an off cycle?

I am burning only well seasoned red oak, mostly large splits with some medium rounds.

Like everyone else, I am trying to get to a point where the boiler will perform at peak performance with as little maintenance and effort as possible. My only cornerns are having the Seton idling too much and having to make a new fire every day or two. There has got to be a happy medium here somewhere I would think?

thx

 

[flyingcow]

The seton is a different animal than what i have. But I'd offer 2 suggestions.
I talked to fred seton last year, nice guy to talk to, if he's still available, call him. i got him thru his website, his site had some good reading. He'd have some good advice, obviously it's his design. He was very accessible last fall.


Also, contact american solar technics. The link is in my signature. The owner is Tom, he could answer your heat transfer questions. If you decide to build your tank, his HX coils work really good. He might sell them seperately. Good way to contact Tom is thru emails. I have his tank, works very very well. In the summer , I bring the tank up to about 165ish, and usually get 5 days for DHW. 2 adults, 3 kids in teens. Thats about as high as I bring it, kind of a waste to drive it up to 180. I do drive the temp up to 180 in the winter time., thats about the limit, without wasting wood, and idiling.

 

[patch53]

The seton is a different animal than what i have. But I'd offer 2 suggestions.
I talked to fred seton last year, nice guy to talk to, if he's still available, call him. i got him thru his website, his site had some good reading. He'd have some good advice, obviously it's his design. He was very accessible last fall.


Also, contact american solar technics. The link is in my signature. The owner is Tom, he could answer your heat transfer questions. If you decide to build your tank, his HX coils work really good. He might sell them seperately. Good way to contact Tom is thru emails. I have his tank, works very very well. In the summer , I bring the tank up to about 165ish, and usually get 5 days for DHW. 2 adults, 3 kids in teens. Thats about as high as I bring it, kind of a waste to drive it up to 180. I do drive the temp up to 180 in the winter time., thats about the limit, without wasting wood, and idiling.

Thanks Bro, I'll check out the link.

hey, do you happen to have a phone number for Fred? It's not on the site anymore.

thx, Pat

 

[flyingcow]

no number

 

[tom in maine]

It's on the website.
207-548-2148

 

[patch53]

Thanks Tom, I'll try calling Fred tomorrow after work. I haven't talked with him for about a year when I bought the plans for the Seton from him.

I'll be looking for some HX material next spring also, I'll keep you in mind.

thx again, Pat

 

[Rory]

I have 670 gallons of storage heated via 240' of copper coils (2 120' coils in parallel). It's able to take all I can crank out of my Tarm Solo 30.

 

[tom in maine]

Oops, my bad. I gave you our phone number, not Fred's.

The number for Bethel Engineering is 866-372-6287.

I get confused too easily!

 

[patch53]

I was wondering about that because I was just on the site as few days ago and couldn't find Freds # . I will probably call John at Bethel, I would think he has Freds #.

Thats good to know about the coils, my run will only be about 30 feet from storage tank to the Seton.

Pat