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Hydronic Radiators which accept DHW......

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by webbie, Jan 3, 2008.

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  1. webbie

    webbie Seasoned Moderator Staff Member

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    Anyone have any sources for some decent looking radiation that can take DHW as an input?
    This is needed when you power radiation off a gas or oil hot water heater.

    I have a kickspace (blower) type unit which does this, but I am looking for something silent. My bedroom is right above our furnace, and the noise from the ductwork in there is annoying - I looked and there is really no way to quiet it down, since it is more air noise than furnace noise, and the furnace is right under that floor. So I am thinking of pluming in a radiator and hooking that to it's own thermostat in there.

    I could use a heat exchanger if I can't find anything, but I would rather use the DHW directly.

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  2. Bartman

    Bartman Member

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    You can use any copper baseboard for DHW but then you would have to lower the pressure somehow. Commercial baseboard usually is heavy walled copper, possibly L grade.
  3. Bartman

    Bartman Member

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    Embassy, Argo, and HydroTherm are some manufacturers of commercial baseboard, but none list the wall thickness of their copper tubing, just the enclosure, and fin specs.
  4. Eric Johnson

    Eric Johnson Mod Emeritus

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    The stuff I tore out of my kitchen (and replaced with cast iron radiators) sure wasn't no Type L. More like bored out Type M with slip connections.

    I'm trying to think of how you could reduce the pressure that much. A shell & tube or flate plate hx is starting to sound more attractive. You'd save more than the cost of the hx by going with a cast iron circulator instead of bronze. Then you could use a beautiful cast iron radiator, Craig. Oooh--can I come over and help?

    EDIT: I forgot about the pressure relief valve, expansion tank and air scoop. More fun stuff!
  5. Bartman

    Bartman Member

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    If you check on eBay you may be able to get a bronze circulator cheap(er). If you can get the commercial bb it would certainly be a lot less work. Standard residential bb is made of copper foil, at least that's what it feels like.
  6. Bartman

    Bartman Member

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    You wouldn't have to add an air scoop, flow check etc., since it would be an open system. It's just piping with fins. Although I would put an expansion tank (potable), I always use an expansion tank with DHW.
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    You're talking about using the DHW, not a separate loop with an hx, right Bartman?

    Because I'm planning to put a glycol loop in my greenhouse with a flat plate hx off the wood boiler, and somebody told me that I should treat the hx just like a little boiler, with the tank & relief valve, scoop, etc. piped into the loop. And, if I eventually put in an infloor radiant glycol loop, would that stuff be necessary, too?
  8. webbie

    webbie Seasoned Moderator Staff Member

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    I installed a large expansion tank already on my DHW tank because of varying pressures. A tube in shell exchanger would require two pumps (I think) which is a down side - although they could be really small pumps. The unit I have is rated for DHW and the pressure, as are many fan coils meant to go into furnaces and exchange heat from water heaters.

    I have a:
    http://www.beacon-morris.com/html/duct_furnace_fan_baseboard_faqs.asp#29
    Twin Flow...... for my office.

    I guess I do run into the problem of lower temp water also, although I can crank the thing up to about 150 easily...I will have to oversize the radiation.
    This looks like what I need:
    http://www.greenheat.com.au/radiator.html

    But that is on the other side of the world.
  9. Bartman

    Bartman Member

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    Eric,
    The original question posted by Craig addressed using baseboard radiation for DHW. Correct me if I'm wrong, but I took that to mean that Craig wants to run the potable DHW through a baseboard unit if the DHW demand is low. That is something I have never heard of doing but anything is possible. If I'm way off base, then maybe the WAF slipped something in tonight's dinner.......it did taste exceptionally good......
  10. webbie

    webbie Seasoned Moderator Staff Member

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    Bart, this is something that is done quite often. We installed kick space heaters 30 years ago to take excess heat from DHW heaters that we installed (with solar and woodstove backup heating the water)....

    Our gas DHW heater is 70,000 BTU's per hour, and could easily heat our entire house! We have only two of us using DHW, and we are not taking showers overnight - so it would work out perfectly.

    Today, they call these combination systems, and they are often used as the total house heating in temperate areas:
    http://www.dulley.com/docs/f934.htm
  11. Bartman

    Bartman Member

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    You guys are just fountains of knowledge! It's great to have others to chat with about this stuff. When I try to talk to people here about this stuff, all I get is this.... :eek:hh:
  12. webbie

    webbie Seasoned Moderator Staff Member

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  13. Bartman

    Bartman Member

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    Looks expensive.
  14. Eric Johnson

    Eric Johnson Mod Emeritus

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    I bet you've given more than you've taken, Bartman. It's good to have you aboard.

    I can't speak for anyone else, but if I don't know the answer to a question, I don't hesitate to make something up.

    Seriously, the first I ever heard of using a DHW heater for hydronic heat was from Craig when he set on up a few years ago. It's an intriguing idea--kind of a poor man's boiler. Not to suggest that Craig is anywhere near impoverished, of course. The one knock I've heard is that some people object to the idea of putting potable water through a hydronic heating system. But most people don't drink DHW, and I don't see the difference between a regular piece of copper pipe and a piece of finned tube baseboard.

    BTW, I have inadvertently tried to heat my house with an electric hot water heater through unintended theromosiphoning. I don't recommend doing that.
  15. webbie

    webbie Seasoned Moderator Staff Member

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    I think some modern gas DHW heaters are actually heater rated....and, as mentioned, used in combo with an air conditioning systems with a fan coil. The perfect heating system for places in temperate weather because of one appliance instead of two. As to the copper, I think you still want to meet certain codes, such as the lead content in the solder, and that is how units like the Beacon Morris Twinflow get approval.....

    Also, these kickspace heaters are designed to get decent heat out of lower temp water, which is why they are perfect for solar, wood and my (DHW) use. If nothing else, at least you hydronic folks will have an option for those hard-to-reach areas. Example: these are often used under kitchen cabinets where it is hard to fit baseboard.
  16. Bartman

    Bartman Member

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    Typically water heaters weren't as efficient as boilers, but a lot cheaper. Just by design they're simpler, but I've heard of people doing it, and for larger applications they would be used in tandem. The company Hydrotherm did some stuff with that theory, and they make sequencing controls for commercial boilers. They made a gas unit called the Hydropulse, it was a condensing uit rated @ 90K btu, (I think), if you needed more, just add another, the units looked like DHW heaters. Of course copper is copper and you can always use it for potable water, it's the pipe thickness on hydronic heating components that is the problem. Since hydronic systems max @ 30psi you don't need a heavier wall tubing, by add some pressure like 75psi+ and the thin walled tubing will split under domestic water pressures. As long as DHW mixes with cold, you're drinking it. Do you ever temper your tap water by mixing cold and hot?
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