500 gallon gas tank for storage

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Can I clean and use an old gas tank

 

[ewdudley]

Can I clean and use an old gas tank

Yes except fuel tanks aren't normally capable of being pressurized, so you wouldn't be able to have pressurized storage.

Which means you'd need a heat exchanger to get heat into or out of storage.

Then again there is one possible workaround for avoiding a heat exchanger, which is to use an 'open expansion vessel', which is an expansion tank that is open to atmospheric pressure, situated a couple feet higher than the highest point in your entire system.

--ewd

 

[pybyr]

Can I clean and use an old gas tank

Yes except fuel tanks aren't normally capable of being pressurized, so you wouldn't be able to have pressurized storage.

Which means you'd need a heat exchanger to get heat into or out of storage.

Then again there is one possible workaround for avoiding a heat exchanger, which is to use an 'open expansion vessel', which is an expansion tank that is open to atmospheric pressure, situated a couple feet higher than the highest point in your entire system.

--ewd

Excellent suggestion, but depending on how tall the overall hydronic system is, even such an "open" system may have a fair amount of pressure down at the boiler/ tank. I am too faded out right now to pull the formulas and do the math, but I think I recall that if you had a boiler in a cellar, and two floors above with hydronic zones, and then the "open expansion tank" above those (as it would need to be), you could easily get up into the 10+ PSI range at the bottom end of the system, just from the 'head' of the vertical column of water. That level of PSI is tiny for components that are built for pressure, but it might be significant for a vessel that had never been designed to contain any pressure. Perhaps a fuel tank is thick enough to handle it- just pointing out that this is a factor to consider.

 

[ewdudley]

Can I clean and use an old gas tank

...

one possible workaround for avoiding a heat exchanger, which is to use an 'open expansion vessel'

...

...

depending on how tall the overall hydronic system is, even such an "open" system may have a fair amount of pressure down at the boiler/ tank. I am too faded out right now to pull the formulas and do the math, but I think I recall that if you had a boiler in a cellar, and two floors above with hydronic zones, and then the "open expansion tank" above those (as it would need to be), you could easily get up into the 10+ PSI range at the bottom end of the system, just from the 'head' of the vertical column of water. That level of PSI is tiny for components that are built for pressure, but it might be significant for a vessel that had never been designed to contain any pressure. Perhaps a fuel tank is thick enough to handle it- just pointing out that this is a factor to consider.

Right, should have noted the water column factor: 1 foot water = 0.433 psi. So 10 psi would be a good working estimate for many two-story situations. Doesn't sound like a lot but it's nine tons pushing out on the flat end-disk of a typical four foot diameter oil tank. I was actually considering using an old four foot diameter 12 ga fuel tank for my system, and I filled it up with water and took it up to 12 psi. It held OK but the ends bulged a little and were stressed. I couldn't figure out a way to work an open expansion vessel into my system so I abandoned the used fuel tank idea, but if I had gone ahead with it I would have added four or five rods welded in the length of the tank to serve as insurance against a hot flood. In the end I took my time and scrounged up some LP tanks. I did consider an open storage tank with a heat exchanger, but not for long.

The other thing I neglected to mention is that if a system does use an open expansion vessel, there needs to be a fat pipe going from the boiler to the top of the expansion vessel for over-pressure blow-off. This could be a real pain to work into the design depending on the location of the expansion vessel.

--ewd

 

[bigburner]

I use an open storage with a probe type heat exchanger, that enters a 4000 gal [old fuel tank standing on end] It has a three way thermo mix valve that holds off the boiler until it hits temp to charge. The biggest issue is water treatment for a steel vessel. I would recommend a pressurized tank if possible, it takes a lot of hassle out.

 

[in hot water]

Can I clean and use an old gas tank

...

one possible workaround for avoiding a heat exchanger, which is to use an 'open expansion vessel'

...

...

depending on how tall the overall hydronic system is, even such an "open" system may have a fair amount of pressure down at the boiler/ tank. I am too faded out right now to pull the formulas and do the math, but I think I recall that if you had a boiler in a cellar, and two floors above with hydronic zones, and then the "open expansion tank" above those (as it would need to be), you could easily get up into the 10+ PSI range at the bottom end of the system, just from the 'head' of the vertical column of water. That level of PSI is tiny for components that are built for pressure, but it might be significant for a vessel that had never been designed to contain any pressure. Perhaps a fuel tank is thick enough to handle it- just pointing out that this is a factor to consider.

Right, should have noted the water column factor: 1 foot water = 0.433 psi. So 10 psi would be a good working estimate for many two-story situations. Doesn't sound like a lot but it's nine tons pushing out on the flat end-disk of a typical four foot diameter oil tank. I was actually considering using an old four foot diameter 12 ga fuel tank for my system, and I filled it up with water and took it up to 12 psi. It held OK but the ends bulged a little and were stressed. I couldn't figure out a way to work an open expansion vessel into my system so I abandoned the used fuel tank idea, but if I had gone ahead with it I would have added four or five rods welded in the length of the tank to serve as insurance against a hot flood. In the end I took my time and scrounged up some LP tanks. I did consider an open storage tank with a heat exchanger, but not for long.

The other thing I neglected to mention is that if a system does use an open expansion vessel, there needs to be a fat pipe going from the boiler to the top of the expansion vessel for over-pressure blow-off. This could be a real pain to work into the design depending on the location of the expansion vessel.

--ewd

A good rule of thumb is to have 5 psi at the uppermost radiator or point in the system.

Boiler fill valves are set at 12 psi from the factory this provides enough pressure for a 2 story building with some positive pressure. This assures good air removal.

Systems with problematic air issues can be cured by increasing the pressure to 15 maybe 20 psi. Increasing the pressure makes the air bubbles smaller so the fluid can carry them back to the air eliminators.

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