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Additional side arm exchanger

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Bugzapper, Sep 29, 2009.

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  1. Bugzapper

    Bugzapper New Member

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    I have a single side arm plumbed into a tempering tank then into the gas water heater. Would I get more efficiency or faster recovery if I added another side arm next to the first using the same water line from the boiler? 6 ppl in the house seems too much for just one side arm. The gas has to kick in once in a while...

    A second question and I would probably never use it, but could an automotive radiator be used as a heat exchanger for use with a fan? The only problem I can see would be the small lines, and maybe that wouldn't be a problem.

    JB

    Man's Prayer:
    I'm a man. I can change. If I have to. I guess. Red Green Show

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  2. MrEd

    MrEd New Member

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    I personally wouldn't hook up a radiator to a pressurized heat system, but it theoretically would work.

    In fact, in college we rented an apartment where you had to pay for the heat, but hot-water was free...so we ran hot water from the faucet into a radiator and then down the drain with a fan behind it and heated a good portion of the apartment...a tremendous waste of water I know - (what can I say I was young, stupid and poor), but it did throw some heat. :>)
  3. Bugzapper

    Bugzapper New Member

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    Well, the heat exchanger for the furnace is basically the same as a radiator isn't it?. What would be the difference other than the tube size? I have a Central Boiler OWB if that means anything.

    Thanks for the reply.

    JB
  4. MrEd

    MrEd New Member

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    I'm not telling you not to do it, I just wouldn't. My system is pressurized and I would have no idea how much pressure an auto radiator could handle.
  5. rowerwet

    rowerwet Minister of Fire

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    CB OWBs are all unpressurized, so a car radiator would make a great HX, not sure if the size of the passages in a car radiator would be to small, since there are many passages to go from one side to the other. I actually heard that someone had set up a few rooms in their house with this systems, and even saw a picture a home inspector took of a set up like that. Also figure a car radiator is meant for about the same temps an OWB system will hit.

    adding a second side arm in parallel with the first would do what you are looking for, what you would be doing is increasing the surface area in the HX, you may run into the restriction on the in and out ports of your hot water heater unless you have another set of ports for the second side arm Hx.
  6. taxidermist

    taxidermist Minister of Fire

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    I have seen people use a bus rad. for heating a polebarn. I think a auto rad. is under more pressure than my EKO.....15psi
  7. Gooserider

    Gooserider Mod Emeritus

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    The numbers I have seen are that an automotive system is designed to run normally at around 12-15 psi, and will start to get damaged around 25-30... I have a copper heater core that I plan on using for a water cooled PC if I ever get the funds to build it. When pressure testing it, I would get visible swelling at around 20 PSI, and didn't take it any further.

    My feeling is that in an open system it might be OK, though I'd worry about oxygenation damage and possibly dissimilar metal corrosion issues. However I am not sure it would be safe in a pressurized system as you would be running really close to the pressure limits, if not over... Seems like normal closed system pressure is around 15psi, with the PRV letting loose at thirty... If the numbers I've mentioned above are correct, you'd really be pushing things towards the high end at normal pressures, but would be OK. However if you ever had an over-pressure situation, it would seem like you would have NO margin of safety, and the radiator might well blow before the PRV did.

    I believe truck and bus systems are designed for higher pressures, and they might be OK for that reason...

    Gooserider
  8. flyingcow

    flyingcow Minister of Fire

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    Only thing I'll add is a truck rad holds about 8, sometimes 10 gals of liquid, a car hold what 2 gals?. Obviously a much bigger area. We run filters on the truck cooling system, this helps to keep the junk from plugging it up(also keeps the system conditioned properly). These usually get changed every service. Would a rad plug up quicker than a side arm?
  9. Gooserider

    Gooserider Mod Emeritus

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    I would expect a rad to plug up faster than a sidearm simply because you have smaller passages in it, however I would expect that the two would have totally different uses - a Radiator is intended as a water / air HX, while a sidearm is intended for use as a liquid / liquid HX.

    Gooserider
  10. woodak

    woodak New Member

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    i use a large truck radiator with my homemade boiler( non-pressurized) and it works great. use a 3 speed box fan set up with an aquastat. that thing will pump out the hot air. hooked up with pex. radiators usually set to run at 15# and temps to 230 or so, but not sure maximums. might be close to your t/p valve settings. might not hurt to give a call to radiator shop for maximums.
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