# Heat Storage and Exchangers



## SteveJ (Nov 19, 2007)

I have a Seton W-130 and a propane 225kBtu for a 3700 sqft off grid house at 9000ft

Since the house is off grid, I am trying to minimize electricity - shut off as many circulator as possible.

The Seton cycles on and off many times during the transitional periods (60 degree days and 30 degree nights).

So, I would like to add a storage tank to the system.

Currently the Seton uses a flat plate exchanger to pre-heat the DHW and then keep the existing gas boiler warm to minimize propane use and to use existing zone controls.

There are three zones of radiant heating for the house.

I was planning on building a tank like this

Then I was going to use 3/4" L type copper for the heat exchange - 200 ft top to bottom for the Seton and bottom to top for the heating.

I will probably add solar collectors later.


Questions

1. Tank storage location - Seton is in garage and propane boiler and DHW 40 gal tank in basement. I would like to have the tank in the garage with the Seton. Is there any convection issues with the tank one floor above the propane boiler?

2. Tank structure - is anyone using a plywood tank with and EPDM liner with success?

3. pH values - should the pH for the tank be in the range of 8.2 to 8.9 for the copper Hx?

4. Has anyone used KiTec (Pex) as a successful water to water heat exchanger? If so, is about 3x the length of copper required?

5. How do I minimize the electricity requirements of the system? Can I avoid the always on circulator pumps without using a differential controller?

6. Any additional suggestions would be appreciated.

It seems that the ultimate setup is the tank system from Sven at STSS - Does anyone use this system?

Thanks,
Steve


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## pbvermont (Nov 19, 2007)

I installed one of the STSS tanks and a Tarm for someone.  I  was so impressed with the tank that I went home and....built one  for myself.  I don't know why folks would build a rectilinear tank. Generally a round tank makes more sense.   Spiral heat exchangers in a box?  Cold corners?  Skip the plywood and 2x4's.  I built my tank in a day, including the trip to the store for materials.  Its really just an above-ground swimming pool, built to whatever size you want...limited to some laws of physics of course.


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## Eric Johnson (Nov 19, 2007)

There ar a lot of different ways to skin a tank, but I think pbvermont has the best DIY solution.

On your questions:

1.) If you're pumping water, I don't see any issues. If you're planning to rely on convection, then it's way more complicated than I can get my mind around.
3.) Don't know.
4.) My understanding is the pex and kitek need 3x as much length as copper.
5.) I use circulators because of their response time, but I considered constant circulation and zone valves. But I'm not sure if that's more efficient.

Why Type L copper? It's a lot more expensive, doesn't transfer heat any better (I don't think) and might or might not last longer than Type M.


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## pbvermont (Nov 19, 2007)

answer to ph question:  you are right on with the 8.2-8.9 range.  Check the tank water in beginning and once a year using a ph meter.  adjust using a 2 lb. box of baking soda usually (to raise ph of water in the 7 and under range).


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## Eric Johnson (Nov 19, 2007)

Another thing to consider, especially if you have cast iron radiators, would be constant circulation and a four-way mixing valve. It works off a room stat (or an outdoor stat, if you prefer), and keeps the room at a constant temp by varying the flow through the zones. And uses almost no electricity.


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## SteveJ (Nov 19, 2007)

Thanks everyone for the knowledgable responses.

Type L because that is the spec from STSS. But I am always open to cheaper alternatives.

Eric - the pump question - right now I have a Grundfos UPS15-58FC on until the Seton goes under 130 - so basically always on.

I have on low speed so the draw is 0.5A or less. But off-grid anything that is always on is much worse than a bigger draw over a shorter period.

So, I am playing around with my dump zone to get the heat away before boiling over - lots of knobs and adjustments without a storage tank.

Also, I chose a rectangular storage over round storage due to foot print in the garage - round storage is much stronger and works better with spiral coils but the space issue will no work for me. Maybe a propane tank on end - but then there is not enough tank bottom area for the coile exchangers.


Question

With a storage tank the idea is to run the gassification boiler at full capacity until the tank is charged. How do you determine that point? That is, how do you prevent boilover when the storage tank reaches say 180 (tank will be about 650 gallons).

Thanks again,
Steve


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## Eric Johnson (Nov 20, 2007)

Not having used one yet, I don't really know, but people I've talked to say that you quickly figure out how much firing it takes to get the tank to where you want it to be. They say things like, "The tank was 130 when I got up this morning, so I ran a load and a half of wood through the boiler to get it back up to 180." So I think you get a feel for it. Plus, your boiler isn't going to boil over when everything gets satisfied. If it's like mine, it will go into idle and you'll get a little smoke and lose some efficiency. So you can play around with it.


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## trydave (Nov 20, 2007)

Hi,
I was looking at buying a Seton.  DO you like it?  How much wood do you use in a winter.  Does it smoke alot?  Basicaly are you happy with it?  Thanks


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## SteveJ (Nov 20, 2007)

tryDave,

This is my first winter with the Seton so I am not sure how much wood I will use.

Several neighbors have Central boilers and went through 10 cords last winter.

Smoke - not that much - like Eric said smokes in off cycle and right now mine is cycling too much.

I am happy with the boiler. I am still trying to determine the ultimate setup and currently have the configuration shown below.

Have you talked to Fred Seton? He is extremely knowledgeable and helpful and quick to repond.

I am looking foward to the ThermaVolt add on from Fred when available. Should be about 1000W during the heating cycle - my batteries would love that.

Steve


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## trydave (Nov 21, 2007)

Steve, 
Thanks for the reply.  How many times a day are you loading?  How much wood are you curently using(60 day-30 Day)?  I would like to try and compar to my usage.  I currently have a smoker but would like to upgrade.  I have talked to Fred Seton but would like to hear from someone with one of his stoves.  
Dave


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## SteveJ (Nov 21, 2007)

Dave,

I have had the W-130 hooked up since November 1 this year. So I don't have a good usage number.

For instance from a cold house and cold start, today, I have used about 1/24 of a cord of beetle kill pine. 15 degrees F outside now.

I have only been loading a few logs at a time to get a feel for it. So, right now I am loading about every four hours but could probably do a full load every 16 to 24 hours.

What boiler do you currently have?

Let me know if you have an idea of how to perform a good comparison.

Steve


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## antknee2 (Nov 21, 2007)

trydave said:
			
		

> Hi,
> I was looking at buying a Seton.  DO you like it?  How much wood do you use in a winter.  Does it smoke alot?  Basicaly are you happy with it?  Thanks



The Seton boiler is a amazing boiler once you understand that it works best when you start out with a full load of wood and a full heat load . After the boiler and wood are up to temperature the boiler has no problem of shutting down and extinguishing the fire completely ,it could stay that way for hours and then re-lite and burn clear in in a couple of minuets.My Seton boiler was bought used it had a major design flaw. It  had so many air leaks ,that the original owner probably produced more steam than hot water, major bummer .I made custom door and draft damper gaskets and used high temperature silicon on other leaks . The good news is the Seton boilers refractory are cast in six separate pieces with steel reinforcing rods they seem to be built like tanks . The boiler really loves big unsplit logs cut to the width of the fire box,  right from the forest floor , I don't see the need for seasoning with this type of boiler , never thought I say that . You will not believe how much hot water it produces per load of wood . PS my Seton has 360 gallons of heat storage capacity ,works like a dream. Anthony


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## SteveJ (Nov 21, 2007)

Anthony,

Do you have pictures?

Especially detailing your air leak fixes?

How did you hook the Seton to the tank and to the house?

Thanks,
Steve


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## ISeeDeadBTUs (Nov 21, 2007)

So Anthony, how easy is it to obtain and replace individual firebox sections?


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## antknee2 (Nov 22, 2007)

SteveJ said:
			
		

> Anthony,
> 
> Do you have pictures?
> 
> ...


These little fixes totally tamed the beast . You could check for negative air leaks by using anything that generates smoke , I put the in-line induction blower on at full speed and have the high limit damper closed .Check around the entire boiler any ware the smoke gets sucked into the boiler is a leak that should be sealed , if you like perfect shut downs and complete control over water temp.  I talked to Fred Seton he said has refractory sections in stock and there very easy to cast yourself .My piping arraignment is to hard for me to explain right now , but I will get to it. Any body know the secret to uploading pics?
Happy Thanksgiving
Anthony


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## Eric Johnson (Nov 22, 2007)

If make a post in "Fast Reply," you need to go into "edit" mode after the post is made to attach the pics. If you choose "Post Reply" when replying to a post, you can do it before you send it in.


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## antknee2 (Nov 22, 2007)

Eric Johnson said:
			
		

> If make a post in "Fast Reply," you need to go into "edit" mode after the post is made to attach the pics. If you choose "Post Reply" when replying to a post, you can do it before you send it in.


Thanks Eic


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## antknee2 (Nov 22, 2007)

SteveJ said:
			
		

> I have a Seton W-130 and a propane 225kBtu for a 3700 sqft off grid house at 9000ft
> 
> Since the house is off grid, I am trying to minimize electricity - shut off as many circulator as possible.
> 
> ...


How Cool living off grid , your way ahead of us on the east coast . I would love to know more about your system.
  Anthony


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## SteveJ (Nov 22, 2007)

Anthony,

Thanks for the pics...Nice sealing job

What is the material you used around the damper and door?

Maybe we should start a Seton Thread.

What would you like to know about my system?
- I am using the Seton to pre-heat my existing propane boiler (which now never uses propane) - hooked up per instructions from Fred.
- I am having boil-over issues using the main floor as the dump zone - I have the damper set at 180 and the dum set at 185 to prevent boilover.
- I am sure I have air leaks - around the door hinge and damper - smoking during the off cycle
- The system cycles a lot after the house is up to temp.

_ I would like to seal like yours and am adding a storage tank to reduce the cycling.

As far as off-grid
- I have a 4.4kW Solar array and a 4kW inverter and a 3500AH 48 V battery bank


Thanks again for the great pic and I am looking forward to your piping explanation!
Steve


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## antknee2 (Nov 23, 2007)

The gasket material you could find in any well stocked wood stove supply store , I bought a whole range of sizes an had to experiment with then for best fit . I used high temperature silicon to set the gaskets .As far as my setup I have two separate heat exchangers one is a flat plate 30 plates that feeds the main house an bypass's the tanks .The other heat exchanger is built into the 120 gallon Super Store stainless storage tank . The three tanks are hooked up in series with each other, with a separate circulator and low limit aqua-stat . As it turns out every part of the system mixes together and only needs to fired once a day[ so far ]. There are two unused heat exchanger in other two tanks , I will use them for solar backup and domestic hot water in the summer.PS the Seton has so much output that it heats the house and the tanks at the same time  without even missing a beat. Hope this info is useful .


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## wouldchuckwood (Dec 4, 2007)

Anthony D said:
			
		

> trydave said:
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What brand of sealer did you use to hold the gaskets in place?   Seems to me the door would be way too hot for the standard high-temp silicon we have at our local hardware store.  I have a Seaton W-100, and it's about as air-tight as a mini-skirt.

Thanks.


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## antknee2 (Dec 4, 2007)

wouldchuckwood said:
			
		

> Anthony D said:
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I hear you !   So far high temperature silicon with some sort of copper additive seems to hold the best , very easy to use . How long have you had your Seton in service ? Anthony


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## Tarmsolo60 (Dec 4, 2007)

SteveJ said:
			
		

> It seems that the ultimate setup is the tank system from Sven at STSS - Does anyone use this system?
> 
> Thanks,
> Steve



I just put the 957 gallon STSS tank online today. Mine came from tarm when I bought my boiler, I don't know if I overpaid. Looks like something you could build and save some money. I had pretty low wood consumption today compared to when I wasn't using storage. I think I'm going to like it.


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## wouldchuckwood (Dec 4, 2007)

Anthony D said:
			
		

> wouldchuckwood said:
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Thanks for the information.  Well, "had in service" is the appropriate tense.  I installed it last year, and loved the way it performed, but had a bit of a disaster last Thursday (see link).  I'm waiting to hear back from Fred.  

Seton, Adobe, and Greenwood all use this same design, and I can't believe none of them use any gaskets at all!?!  With such catastrophic consequences for having a smoldering fire, I would think they would be more concerned about eliminating the air leaks.


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## Eric Johnson (Dec 4, 2007)

Tarmsolo60 said:
			
		

> SteveJ said:
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New Horizon, the importer of the EKO, claims up to 45 percent less wood usage with storage. That's a pretty big number. I hope it's accurate.


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## Nofossil (Dec 4, 2007)

Eric Johnson said:
			
		

> New Horizon, the importer of the EKO, claims up to 45 percent less wood usage with storage. That's a pretty big number. I hope it's accurate.



I'm totally skeptical about that claim. Granted that there is some loss during startup and cooldown, there's no way that storage makes that much difference. If anything, our wood consumption increased slightly. I attribute that to keeping the house and hot water warmer with the storage, but there's no way that there's a 45% difference.

Hard numbers: 

3.2 cords November 21 through March 15 without storage.
4.5 cords November 1 through April 15 with storage.

I haven't counted up degree days and compensated for hot water load, but perhaps there's a small efficiency boost with teh storage. I do know that comfort and convenience improved dramatically.


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## Donl (Dec 4, 2007)

nofossil said:
			
		

> Eric Johnson said:
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Interesting observation Nofossil. Do you think maybe the resulting higher efficiency gained through a steady hot burn is negated by heat storage loss through the storage tank?

Don


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## Nofossil (Dec 4, 2007)

Don L said:
			
		

> Interesting observation Nofossil. Do you think maybe the resulting higher efficiency gained through a steady hot burn is negated by heat storage loss through the storage tank?
> 
> Don



No - there is some loss from the storage tank, but it's less than 10,000 BTU per day as close as I can figure it. For an indoor installation, I can think of only a few sources of boiler-related efficiency losses that would be affected by the presence of heat storage:

1) Incomplete combustion during startup - less than ten minutes for me.
2) Incomplete combustion and / or excess chimney losses during idling.
3) Heat loss up the chimney from excess air blown through the gasification chamber as the fire dies.

Heat storage allows you to have fewer fires, so startup and shutdown losses would be reduced. If you have half as many fires, you'd reduce those losses by 50%. However, I don't think that either one is a very big loss.

Idling losses may be a bigger deal, but the EKO seems to idle pretty well - very little smoke, cool stack temps, and gasification resumes instantly coming back off of idle. Heat losses out the sides of the boiler just heat the house anyway.

I just can't see where losses would come from that would lead to a big increase in efficiency from using storage. I'd but 10% or maybe even 20% if you twisted my arm a lot, but my own data shows a very small difference if any.

I'm still a big storage fan - infinite hot water and and a warmer house are wonderful. I just don't see any justification in my experience for the efficiency claims being made.


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## Eric Johnson (Dec 4, 2007)

I think there are a few more factors that you aren't taking into consideration, nofossil, mainly tied to your setup, which sounds pretty efficient to me to begin with.

I think the bigger the boiler, the bigger the efficiency gain with storage. There are a couple of reasons for this. First, those of us with big boilers and no storage tend not to fill our fireboxes. Instead, we make a series of smaller fires, since we don't want the boiler to idle too much, and our output exceeds our load most of the time. That's less efficient for a number of reasons, including: 1.) Incomplete fuel 'preparation,' since the boiler is designed to burn full loads and we're only filling it, say, one-third full; 2.) Losses every time we go out there and stoke the boiler up. I open my boiler room door and let cold air in, I open the main loading door and let cold air in and sometimes, smoke out. I open the gasification chamber door just to watch it work. Sometimes I open the bypass damper and get the new load of wood burning good before initiating gasification. This all robs efficiency. 3.) And at least at first, we tend to run around the house turning up thermostats to keep the boiler from going into idle mode. This behavior tends to diminish when we realize that idling isn't such a big deal after all, but by then, everyone is used to having the house at 80 degrees, and they groan when it 'cools off' to the mid '70s.

Add it all up, and it's a pretty big number. Add that to your observations, and it's even bigger. 

Contrast all this (which is actually a pleasure, since it gives me an opportunity to play around with the boiler) with setting the zones at 72 or 75 and forgetting about it, and firing the boiler once a day, and in my case at least, I don't think that 45 percent would be a big surprise. A welcome one, to be sure. Although it's not like I'm worried about running out of wood.

I've tended conventional wood-fired boilers for around 12 years. Even without storage (it's almost a reality, I promise) this boiler is a lot easier to operate and get results from in a hurry. And even in its compromised state, it burns less wood overall, and a lot less wood for the heat produced.


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## SteveJ (Dec 5, 2007)

Eric,

You described my situation perfectly - lots of small fires and messing around with thermostats. I am racing you for storage but have all but conceded!

Another issue with idling has been reported in this thread where idling equated to creosote which almost put an end to all heat demand for wouldchuckwood. Thank God he was home and caught the early stage of meltdown.

So, I think that storage seems to be great regardless of the efficiency claims (I am slowly coming around to not beleiving everything I read :bug: )


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## Eric Johnson (Dec 5, 2007)

I don't have any creosote buildup to speak of, surprisingly enough. I checked the chimney a couple of weeks ago and found only a thin layer of soot.


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