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Sidearm construction

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by tuolumne, Mar 4, 2008.

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  1. tuolumne

    tuolumne New Member

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    It is about time that I follow up on this thread! We hope to move into oue new home in a few weeks. The sidearm works fantastic as constructed. Today I fired the boiler to fill and test my radiant wall panel loops. Boiler temps were running around 155 as I was filling the radiators and introducing a lot of cold water to the system. During the first two hours, water in the primary loops (and sidearm) took 80 gallons of DHW up to 150 degrees. Once I was done adding cold water, boiler temps rose to 175 and the DHW was around 165 when I left. I had 3 zones drawing water off the loop prior to the sidearm. What amazes me about this primary/secondary configuration is how hot the primary water stays for all of the zones. Supply drop after those three zones (40,000 btus worth of wall panel radiators) is typically only 3-6 degrees. What also suprised me was how quickly the thermosyphon allows the DHW tank to aproach nearly the same temperature as the supply water.

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  2. deerefanatic

    deerefanatic Minister of Fire

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    Ok, is it just me or what... I have a sidearm on both the house and barn DHW tanks..... They can run all night and not get my tanks up to even 120........ And that's with 170F+ boiler water.......... What gives?

    I have them plumbed as follows:

    Remove drain valve
    Attach 3/4 inch pipe fitting to old drain valve connection. Add short nipple. On end of nipple, attach a tee. On one end, a 3/4 ball valve, on the other end, the sidearm.
    Run sidearm vertically.
    Run top of sidearm outlet up to top of tank, then across the top of the tank.
    Another 3/4 tee, one end heads down to the hot water outlet of the water tank, the other connects to the DHW piping..

    The sidearms are 1.5 inch copper shell with 3/4 inch copper inside that's been run through a pipe threader to add a spiral groove to the outside. Approx 48" long I believe. Piped with hot boiler water entering top, and exiting bottom. Bought them here: http://cgi.ebay.com/SIDE-ARM-HEAT-EXCHANGER-OUTDOOR-WOOD-FURNACE-BOILER_W0QQitemZ390001508698QQcmdZViewItem?hash=item390001508698&_trkparms=72:1205|39:1|66:2|65:12|240:1318&_trksid=p3286.c0.m14

    Also, the anti-convection check valves in the tops of both heaters have been removed from the Hot water outlets.
  3. Vtgent49

    Vtgent49 New Member

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    Matt,

    How and where are you measuring the tank temp? I ask that because I think you may have water flowing thru the side-arm and out the Tee at the top of the tank, when you draw water. Thus your DHW is actually a blend from both the top and the bottom of the tank. Unless I didn't understand your description?

    My sidearm returns water to the T/P valve outlet that is near the top. The T/P is teed in the same opening.

    Al
  4. mpilihp

    mpilihp Feeling the Heat

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    Hi tuolumne how about a picture of your setup on your indirect hot water tank, im confused as to how the connections are to prevent drawing DHW from the side are and only form the tank.

    Another question for all. My planned storage tank will be about 15 ft away from where my indirect DHW tank is. Can a side are be used and if so should the side are be closer to the storage tank or the indirect DHW tank? Im thinking closer to the storage tank and then insulate the pipes...

    Phil
  5. deerefanatic

    deerefanatic Minister of Fire

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    Al, I was measuring my temp 2 ways. First, on the Barn Hot water tank, the tee that the sidearm goes into on top has another tee above it. On the top of that tee is a thermometer and off the side of that tee is the hot water outlet.

    On the house DHW, I have an old hot water heater that the sidearm is attached too. That dumps into the gas hot water heater. After running all night, the relief valve on that sidearm tank was barely warm, meaning that the top of the tank was not all together all too warm..........
  6. tuolumne

    tuolumne New Member

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    Pictures are in the first post. I wondered if cold (bottom) would be tempted to run up the sidearm instead of through the tank. However, real use has proved otherwise. Apparently the 1" straight ahead route is the easier path than turning 90 through the sidearm.
  7. Vtgent49

    Vtgent49 New Member

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    OK Going back to middle pic on post 1:

    I can't see any reason why the thermosiphon should cause any hot water to enter the tank. You seem to have a way for it to loop around (up and down) and bypass the tank.

    Secondly, drawing DHW will definately bring some from the bottom of the tank, as well as from the top. Maybe less than 1/2, but still enough to cool.

    Additionally, the mixing valve may actually prevent the thermosiphon from having any chance of looping/moving any water at all. Youre trying to force hot water thru the cold side of that walve. Can't imaging that will work.

    Going out on a limb since your setup is so different from mine, but I'd say even going direct from the top of the sidearm to that cold return won't work. The top of the sidearm need to go to the tank.

    Maybe another pic of sidearm and the tank will help us understand this one. As of now, I see no reason for this setup to heat water.

    Sorry if this sounds rude. You could just easily be way over my head :)

    Al
  8. tuolumne

    tuolumne New Member

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    Well friend - mine is the one that was working well despite the pictures! Another poster was having issues. My setup heats the tank very quickly and draws hot water off the top only. I know this because my tank temp at the middle can read 100 degrees and I will still be getting 110 at the upstairs faucets.
  9. Medman

    Medman Feeling the Heat

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    What brand/type of gravity check valve works to prevent reverse thermosyphoning? I would like to add this to my system when I install - hopefully in the next week or so.
    I also have a Hy-vent air remover at the top of the sidearm, to prevent air lock from stopping heat transfer. I am thinking I will also add a small expansion tank to the hot water piping, because we have some very high demand days, like weekends, where we can empty the tank. I'm worried about the pressure increase while bringing my tank from cold 40* to hot 180* overnight. Could make my monday morning shower excitingif the pressure spikes to 90 psi due to expansion of the water in the DHW tank!
  10. tuolumne

    tuolumne New Member

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    I have a pressure relief valve and did not feel the need to add an expansion tank to the DHW....maybe I am wrong...after all, 80 gallons is a lot of water. Wouldn't any time of check valve tend to inhibit the thermosyphon effect? It takes water velocity to move even a swing type. I put a ball valve on mine, so I always have the option of manually turning off the sidearm to prevent reverse thermosyphon if the boiler is cold. Then again, we have no source of heat in the house but the wood, so when will the system ever be cold once we move in!
  11. Vtgent49

    Vtgent49 New Member

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    "Well friend - mine is the one that was working well despite the pictures!"

    My apologies, Tuolumne, late night post I suppose. Still that set-up seems less than ideal, but then again, these sidearms don't need ideal when the wood heat goes 24/7, as mine is starting to do, since this is October. Cranking 80 gals up to 120 is so easy all winter.

    Medman _ I added a swing-gate check valve to mine after running all winter without it. It's really the off season that matters most. It has to be mounter horizontally to have the least resistance to flow. I believe it's needed but then again I'm a trial and error guy.

    Al
  12. deerefanatic

    deerefanatic Minister of Fire

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    Ok, update on mine. I replumbed the side-arm in the house so that it taps off the drain fitting on the bottom of the heater and returns to a T where the pressure relief valve goes. Seems to be working MUCH MUCH better as now my thermosiphon is faster and it's actually heating the tank within a few hours time tonight... It's currently up to about 120 at the top before showers... (I'll have to check it and see now that we're done showering.)
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