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Central Outdoor Wood Boiler/ Oil Boiler Tie in

Carl PE_2
Carl PE_2 Member Posts: 42
1. Probably doesn't make that much difference. As long as your piping is well (pre- ?) insulated, it should do fine. I'd be more concerned with the pipes freezing when the outdoor boiler is off.

I'll bet you that's why they run the circ constantly.

2. See (1). I don't think transmission loss is going to be too bad, IF you have decent insulation. We bury hot and chilled water piping all the time.

If you plan ahead, you can run the piping underneath your sidewalk. Whatever losses you have then are "snowmelt".

3. Are you referring to the water side being open? No, most of them aren't. A stainless hx or copper-fin model will be fine, though..

4. "negligible" would not be a word I would use to describe it. Show me the numbers.

If it were mine, I'd want glycol in any pipe that goes outside. Either separate the indoor and outdoor portions with a hx, or fill the whole system w/ glycol and pipe the outdoor boiler in parallel with the indoor.

How do the controls work on this system?

Comments

  • Robert O'Connor_6
    Robert O'Connor_6 Member Posts: 299
    I've

    seen a few of these combo's and have a number of questions / concerns. These are stand alone outside and inside units tied together.

    1) Supply and return specified to be buried 12 - 18"below grade. Would seem burying them below frost would reduce transmission loss.

    2) Boiler runs to 190 and supplies heat to house. Most houses around here are designed for 180 avg water temp. Trans mission loss' seem to prohibit supplying adequate supply temp to system

    3) Are the average oil fired or gas fired boilers listed for use as a system that is open to the atmosphere?

    4) The pump on the wood boiler constantly circulates to the the oil/gas boiler. If there is no wood fire the oil/gas boiler is keeping the wood boiler warm.Local dealer says energy consumption for this is negligible.


    Appreciate any comments



    Robert

    ME
  • Carl PE_2
    Carl PE_2 Member Posts: 42
    ok, here goes..

    1. Probably doesn't make that much difference. As long as your piping is well (pre-) insulated, it should do fine. I'd be more concerned with the pipes freezing when the outdoor boiler is off.

    Maybe that's why they run the circ constantly.

    2. See (1). I don't think transmission loss is going to be too bad, IF you have decent insulation.

    3. Are you referring to the water side being open? No, most of them aren't. A copper-fin should be ok, though..

    4. "negligible" would not be a word I would use to describe it. Show me the #'s.

    If it were mine, I'd want glycol in any pipe that goes outside. Either separate the indoor and outdoor portions with a hx, or fill the whole system w/ glycol and pipe the outdoor boiler in parallel with the indoor.
  • Dave_38
    Dave_38 Member Posts: 8
    OD units

    To reply to your questions

    1-- If the pipe is PROPERLY insulated 18 to 24" will not be a problem. The fact that the gound freezes around a properly insulated pipe will supply that answer.

    2-- See above, a PROPERLY insulated pipe will have a heat loss of less than 2 degrees up to about 200 feet.

    3--No, no closed system can be hooked with an open system, a heat exchanger must be used or a closed or semi-closed wood boiler must be used. Most open wood boilers will rust out in as little as three years unless STRICT water treatment procedures are adhered to.

    4-- No, the heat loss is not negligable but is necessary to prevent freezing, if the outdoor unit is to be left unfired for over a day or two it must be protected with the proper anti-freeze and the pump controled by an aqua-stat. Also the heat exchanger MUST be on the return side of the indoor boiler for obvious reasons.
  • Eb Barth
    Eb Barth Member Posts: 7


    I have installed a number of these boilers. What I like is that they are simple and come with stand alone controls. We always try to put the piping below frost and have had the best success with a pre-insulated piping product. The downside is that this is a very inefficient boiler and seems to run at about 60% effeciency which means cutting a lot of wood that goes up in smoke.
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