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Old 12-04-2008, 07:27 AM   #1
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DIY Heat Exchanger


Hi guys I'm looking for some help from all you D.I.Y. guys out there or pros for that matter. I'm in the process of installing a coal stoker with a boiler in my shop and I priced out wall hung heat exchangers. Holly cows are those things salty $$$$ ouch. Well I'm thinking that there's has to be some kind of way to convert car radiators and gang them together. Then install a fan behind them to force the heated air into the shop. I sure could use some help... has anyone pulled this off?

Thank in advance!!!


Pat

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Old 12-04-2008, 10:27 AM   #2
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DIY Heat Exchanger


I remember in Alaska I had a shop that was cold in the winter (probably because it was 30 below outside). I had a lot of oil from oil changes in 55 gallon barrels.

So lots of fuel and a need for heat.

I converted an old wood stove and welded some pipe to it for the heat exchange. The pipe was connected together and ran up the wall to an old truck radiator and back down to the stove. There was a check valve on one side of the circuit to allow the hot water to go up to the radiator and the cold to fall back to the stove.

I connected the barrels to a small drip system into the stove that had sand in the bottom for the oil to drip into. Once it was ignited it would stay lit as long as there was oil dripping onto the sand.

A fan at the back of the radiator would blow the heat into the shop. On good days I could get that place up to a warm 40 degrees. When it was really cold out and the wind was blowing I could get to 20. But that was better than the 30 below outside.

You could also use some duct work and surround your boiler with it. It would heat up the air inside and you could route the ducting to the ceiling. Have a fan blow into the duct work at the bottom to force the warm air out the top. Nothing more than a furnace does in the house.

Water is more efficient though but then you have to have safety devices like a T&P valve and good solid connections to prevent leaking. Much more complicated that the air method.

Bottom line and short answer is that you can do almost anything you want to if you have the knowledge and skills to make it happen.

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Old 12-04-2008, 10:37 AM   #3
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DIY Heat Exchanger


Hi Marvin and thank you for your response. Do you think that a car/truck radiator will stand up to the operation pressure needed in a boiler system, 20 to 25 lbs?

Thanks

Pat

P.S. skills I have, knowledge I'm working on :-)
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Old 12-04-2008, 11:49 AM   #4
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DIY Heat Exchanger


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Originally Posted by geoman View Post
Hi Marvin and thank you for your response. Do you think that a car/truck radiator will stand up to the operation pressure needed in a boiler system, 20 to 25 lbs?

Thanks

Pat

P.S. skills I have, knowledge I'm working on :-)
By the time you are done you will have both.

Truck radiators are made for 15 psi and I am sure there is some percentage of tolerance there. I can't say for sure that they will handle 20-25. You could ask around. Try asking a radiator shop. They fix radiators and as a test pressurize them in a tank of water and look for leaks.

Another component you will need is a recirculating pump. They run about $75 to $200 depending on where you get it. I have gotten several at pexsupply.com for pretty cheap (no affiliation, just a customer). The Taco 007-F5 was a nice buy at $60. I have several of these on my solar hot water system and they are quiet and move the 1-2 gpm I need.

If you go with a water system you will need all the components like an air scoop, T&P valve, bladder tank for equalizing pressure and a pressure gage.

I would also consider adding an old water heater to store hot water. You can get these for cheap on craigslist. No need to hook it up. It will just store hot water for you when the boiler is not on. Either electric or gas is fine as you will not be using the power source.

Copper pipe would be the way to go since it can handle over 200 degrees and higher pressure. Pex will not stand up to temperatures over 200 degrees. Use 1/2" copper for the supply and 3/4" for the return.

The system should have a pressure of 12 psi at rest with cold water.

If you are in freeze country use antifreeze to protect the pipes.
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Old 12-04-2008, 04:57 PM   #5
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DIY Heat Exchanger


Not trying to be negative, but do you have insurance on the shop and will they continue to cover you with this type of heater if there is a fire? They charge a heck of a premium for wood stoves where I am.
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Old 12-04-2008, 05:00 PM   #6
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Not trying to be negative, but do you have insurance on the shop and will they continue to cover you with this type of heater if there is a fire? They charge a heck of a premium for wood stoves where I am.
I'll check but these heaters are UL approved.

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Pat
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Old 12-05-2008, 06:42 AM   #7
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DIY Heat Exchanger


The coal stoker is UL approved.
But the automotive rads are not UL approved for whatyou want to do.
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Old 12-05-2008, 04:51 PM   #8
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DIY Heat Exchanger


Even a low pressure steam boiler (under 15 psi) can destroy a building if the pressure relief valve fails. Be careful out there.

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