storage tank?

Propane tanks and anhydrous ammonia tanks are popular. Inexpensive large compressed air tanks turn up from time to time. Any large dome-end steel tank is generally suitable. Check scrapyards, call farm equipment dealers and anhydrous ammonia suppliers for leads on used/obsolete anhydrous tanks. Unpressurized storage is viable.

https://www.google.com/search?num=2...0.msedr...0...1c.1.62.serp..2.0.0.If0mptqv2No

I have an American Solar Technics unpressurized tank, it works great. Comes in pieces that can be carried through any door and was relatively easy to assemble. Pressurized tanks tend not to fit down through a standard door. Both should solve your creosote problem. If you are in a state that requires a code vessel, the cost for pressurized storage tank goes up as you need a stamped tank. Once you go with storage you will never go back. There is a good reason why tarm and other firms will not guarantee an install unless there is storage.

I used passive storage, just built a 4x8 plywood box and lined it with foam insulation and EPDM (a form of sheet rubber). The expensive parts are the two copper heat exchangers, 240' in the primary and 180' for DHW.

Lots of choices for storage , buy one, make one, it works either way...search this forum and do a general google search under "Solar Hot Water Storage"....Storage will get your system back on track.....good luck.

deerslayer699 said:

I found a 500 gal converted propenat tank from smokeless heat for $1000.Or would it be better to try and find a used one and convert it.What would have to be done to tank.Also do you always need heat exchangers and how did you guys insulate the tank.Thanks

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Depending on what you can find, you might not have to do anything to it. Main needs are top & bottom tappings - preferable 1-1/4" or bigger. If none there, you'd need ot get some welded in by a competent welder preferable pressure certified.

Propane tanks or the like (pressurized storage) don't need heat exchangers but they need expansion tanks. Open or non-pressurized like the boxes mentioned above need heat exchangers but don't need expansion tanks. Generally speaking.

Insulate however you can - no magic there. I built a box around mine & used foamboard & fiberglass.

I will try to get some photos up. I do have 550 gallon unit. I have standard baseboard so like any storage tank I don't get as much useful capacity as someone with radiant or low temperature emitters. I.E. I heat my tank to 190 deg F and it puts useful heat out the radiators down to 130 at its best. If I had radiant, I could run it down to 90 degree F. Thus someone with radiant can store more heat in the tank which extends the length they can go between firings but when they fire it will take longer.

You might be able to fit a 500 gallon propane tank through a door. I forget the dimensions, but I think I could do it if I removed the door frame.

My 110 & 330 gallon tanks are 30"dia., a 500 was 36" I believe.

I think you should note we all are trying to keep the bias out of our responses because pressurized versus non pressurized storage can turn into a Ford vs Chevy debate

I expect we can agree that either way is major improvement over what you have now.

How far East in PA are you located? I bought a few a few 220 gallon tanks that fit through a 30" opening and are <7' standing up from just outside Philadelphia.

I used 2 air tanks, took door frame off,
They are 400 gallon verticals, which are
36"x93".

They are also ASME stamped, but expensive if you buy new. Hard to come by used.

Scott

A couple comments on tanks.
Cost is always a consideration. Deals on used pressure tanks are around. Of course, there is handling and sweat equity that are also factors with used or new pressure tanks.
Unpressurized tanks can be installed anywhere that you can walk (or crawl!) into.
They do function similar to pressure tanks, with a top and bottom tapping, the difference being that these are heat exchanger connections--one at the top of the tank and one at the bottom.
I normally heat my tank to about 190F in the cold weather, with no issues. The use of a heat exchanger, in any form, does not lose energy, it just means a circulator might operate a few minutes longer.
My testing indicates our heat exchangers operate in the 90-95% efficiency range. There are a lot of variables here, but that seems to be the norm.

We make our standard tank 4' tall since that helps contain costs. We have made them up to 8 feet tall. And also can easily "sister" tanks together without major cost compromise when necessary.
What makes or breaks these tanks are the liners. Having been around a long time and made most stupid mistakes that one can make in business over the years, we still use the same liner we started out with.
It is rugged and stands up to heat. It will degrade by becoming brittle if exposed to too high temperatures. I have not seen that problem yet, after 30 years. A brittle liner will still hold water, you just cannot move it.
A liner can be replaced easily if needed. Also heat exchangers can be added if necessary. Or tank water can be pumped in an unpressurized scheme if desired.

deerslayer699 said:

I am just on the border of nj up near Delaware water gap.Where are you located my wife is originally from Bordentown nj,if not to far from that area would possibly like to come see your set up.

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I'm about half an hour north of Bordentown.... welcome to come by if you want to see the EKO 40 in my basement (not yet hooked up) and three 220 gallon steel tanks in the backyard (likely annoying neighbors).

Is one difference between pressurized and non-pressurized tanks is that the water chemistry must be monitored in non-pressurized tanks, while this is not required in pressurized tanks?

Not necessarily. If your boiler is non-pressurized, chemistry should be done, but if the boiler is pressurized & it & the system uses HXs between them & storage, the storage itself shouldn't matter. Depending what its made out of, that is. A plastic lined tank as described above, no.

jeffesonm said:

I'm about half an hour north of Bordentown.... welcome to come by if you want to see the EKO 40 in my basement (not yet hooked up) and three 220 gallon steel tanks in the backyard (likely annoying neighbors).

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you need to take care of water chemistry in both, but in a pressurized, once the oxygen is used up there is no more introduced to the system so chemicals don't need to be added near as often and there shouldn't be any make up water introduced to a pressurized system unlike unpressurized. If water chemistry is neglected in both types the pressurized is sure to last much longer.

Unpressurized plastic lined tanks require no water treatment if the tank water is not being used as a circulating fluid.
If you circulate tank water into a steel boiler, you need to treat the water. If you are using a heat exchanger to interface a steel boiler with an unpressurized tank, not treatment is needed.
BTW, a single heat exchanger is used to put heat into the tank and that same heat exchanger also removes the heat. We do this with a single coil for boilers that are up to 150k btus/hr. Larger than that we parallel the coils.

I have the 820 gal american solar technics tank. Works very well.

Couldn't the water in plastic tank eat at the heat exchanger from the outside if left untreated ?

Only real downfall I see with unpressurized storage is the cost of the heat exchanger. This may or may not apply to you depending on the price you find pressurized tanks to be in your area.

I recently replaced a 1200 gallon STSS unpressurized storage system with a 750 gallon pressurized (3 - upright 250 gal propane tanks).

The original system made it 15 years but the copper heat exchangers ultimately failed. I only ran boiler water through them and they failed in several places - internal pipe joints and support brazes. This resulted in several pin hole leaks and an overflowing storage tank. The water chemistry was maintained and it was impossible to service after the failure. I tore the whole thing out.

The EPDM liner was in good shape but I also had some good control logic to prevent overheating of the tank. This has been a problem for users in the past.

I have a Tarm Solo 60 and it takes a lot of $ copper to get all of that heat into and out of the water!

My experience with unpreassurized vs preassureized are summarized below:

Unpreassureized pros
Large tank through small door
Odd shaped tanks in tight spaces
Low system volume - no expansion tank
Easy to insulate
Can go larger then pressurized in equivalent space
HXs eliminate tank mixing and promote stratification

Cons
Expensive heat exchangers
HX prone to eventual failure
Delta T across HX at higher flow rates
EPDM prone to eventual failure
Higher pump head due to HX
Difficult to service
HX placement can physically be difficult to get good stratification results
Can overheat tank and damage liner reducing it's useful life

Preassureized pros
Tanks can be inexpensive
No HX!
No delta T at any flow rates!
Very long life
Simplified plumbing
Perfect stratification if done correctly
No tank liner to worry about
Can operates at higher tank temperatures and store more BTUs/gallon

Cons
Tanks can also be expensive
May require sweat equity to keep costs down
Difficult to handle and to fit in tight spaces
Typically lower capacity then unpreassureized due to space constraints (rounded tanks vs square)
Requires a substantial expansion tank
Tank insulation more involved