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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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    I think my other thread is too long, so I'll ask my question here. I built my sidearm yesterday. I used 1-1/2” outer pipe (boiler loop is 1-1/4) with a 3/4” pipe on the inside. This connects the cold inlet and hot outlets of the indirect storage tank. I had to ream out the stop in the reducer coupling to get it to slide over the 3/4” pipe. The picture at the bottom of the tank shows the cold coming in, the bottom of the sidearm and a drain. At the top you can see the mixing valve to temper domestic water. The valve to the left is to supply untempered water to the dishwasher. The domestic loop still held pressure when I was done, so that’s a good sign! I put a valve at the top of the thermsyphon loop...I was worried that water might jump directly from the cold supply to the hot without going through the tank. Tank outlets are 1-1/2”, versus 3/4” in the sidearm, and the valve will let me sqeeze it down to a very small orifice. Any comments?

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  2. tuolumne

    tuolumne New Member

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    As far as costs....materials to build this sidearm cost around $70 in pipe and fittings. The actual length of the exchanger surface is 46". Assuming that my DHW pump would need to run 1hour each day (is that accurate?) it would cost $17 per year at our current electrical rates. If I can avoid using the pump with this system I will have a four year payback. That is better than I had hoped....I just liked the idea even if it didn't pay back! Also, I will have hotter water available, which hopefully will save kW on my dishwasher as well.
  3. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Throttling down that valve will reduce the thermosiphon effect.

    I'd recommend moving the cold inlet to a separate tapping on the tank. If your tank doesn't have a third tapping already there for water use, you can often remove the anode rod (if there is one) and install a dip tube to diffuse the cold water.

    Joe
  4. tuolumne

    tuolumne New Member

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    This is an indirect DHW tank, the only tappings are the cold supply at the bottom and the hot exit near the top. The boiler tappings are a separate loop. Will the water naturally flow through the 1" pipe into the tank (like I want it to) or bypass the tank through the sidearm which is 3/4". I hate to take things apart...again...but if there is some kind of flow control valve I could put at the bottom to replace the 1x1x3/4 tee I could do that. Maybe it won't be problem at all. I'm hoping someone with a similar setup will give the good news!

    -Hopeful in Vermont
  5. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    I don't typically deal with sidearms, but I'm expecting that the water is going to be inclined to flow straight up.

    Okay, quick brainstorm... there's no real need for a dip tube to go in from the top.

    Remove the female adapter from the tank. Install a 1x3/4x3/4 tee there, oriented like the one you already have. The top (3/4") connection goes to the sidearm. The 1" connection goes to the tank. The other 3/4" connection gets its stop reamed out, and you slide a piece of 3/4" pipe through it, into the tank. Run it up against the opposite wall of the tank, and then back it off an inch or two and solder it in place. That way, the cold water will be injected at the far side of the tank, and will be more likely to mix with the tank water and go out through the top, rather than fighting its way back through the outer portion of the bottom fitting to go up the sidearm.

    Joe
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    Looks pretty good, except that, like Joe says, your water inlets and outlets have nothing to do with the sidearm. Mine is piped into tees in the pressure relief valve tapping and the drain on my water heater. Everything else works like a normal water heater. All the sidearm does is allow water in the tank to circulate through the sidearm and get hot in the process. You really don't need (or want, I don't think) the 3/4-inch lines connecting to the left of the sidearm connections on your setup.

    Here's a simple diagram. You can hook your tempering valve up to the tank's hot water outlet, and create a bypass for the dishwasher from there as well.

    But you built the sidearm right from what I can see. It should work just fine without a pump on the domestic water side. Very similar to mine.

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  7. slowzuki

    slowzuki Feeling the Heat

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    Sorry to jump in but why a sidearm on an indirect tank? It already has a set of hx coils doesn't it?
  8. tuolumne

    tuolumne New Member

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    Eric, I didn't have those tappings available on my tank. Slowzuki, that tank already has coils, but the pump won't kick on unless the temp drops past 110 at center. By always running boiler water past the sidearm it seemed like any easy way to keep the tank at 180 without running that extra pump.
  9. slowzuki

    slowzuki Feeling the Heat

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    Ok so you already have continuous circulation adjacent to the tank for whatever reason. Another option I suppose would have been to move the indirect coil so they were tee'd in but several feet apart so the coil was in parallel.
  10. bjleau

    bjleau New Member

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    Eric,

    So you bring the heated water back into the tank through the pressure relief valve tapping, isn't that on the top? So the cooler water flows from the bottom of the tank though the side arm and then back down into the tank? Just questioning/trying to figure out how the how water dosen't stop at the top of the pipe where it is hottest? Probably some physics thing I should have learned in school?

    All,
    Other question is how hot do you keep your hotwater storage tank? Would it make sense to bring it to like 140 or 150 so you have lots there for AM showers? What about the relief valve and expansion, would I need a tank for that? where would you plumb that in?
  11. Eric Johnson

    Eric Johnson Mod Emeritus

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    You've pretty much got it. It just circulates naturally in a loop between the tank and the heat exchanger. As the water in the inner tube of the sidearm heats up, it rises, pushing the water above it into the top of the tank. That water is replaced by cool water at the bottom of the tank, which rises up into the sidearm and is in turn heated. It works really well, and you avoid the need for a second pump (probably an expensive bronze one). It's just another zone off your boiler. All my boiler water goes through the sidearm before it goes into the house zones. If you have mineral-rich water, like me, you need to drain off a couple of gallons from the bottom of the tank every couple of weeks to get rid of any accumulated lime--it can stop the gravity flow if you don't.

    No need for an expansion tank. You put your pressure relief valve into the tee that the sidearm connects to. You screw the drain back into the tee at the bottom connection. Turn your water heater off, unless you want to try to heat your house with the water heater when the boiler and/or water heater tank temp drops.
  12. 88rxn/a

    88rxn/a Member

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    good, i didnt know i could run it off my tempering valve.

    i think i understand this? so basically the relief valve is just sticking out at the end of the extension (copper line) of where it was originally on the tank then the sidearm below it ?

    my plan was to run the main HOT line from the boiler, to a manifold (for the other zones) up over to the DHW through the exchanger, then back to the other manifold (return lines) and back to the boiler.this is assuming i dont need to temper anything.
  13. Eric Johnson

    Eric Johnson Mod Emeritus

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    In my case it's: tank - brass nipple - galvanized tee - sidearm connection - pressure relief valve.
  14. Vtgent49

    Vtgent49 New Member

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    I have an 80 gal tank, and a side arm off my wood/oil boiler. The side arm is 1.25" iron, wirh 3/4 copper running thru. The 3/4 comes from the tank drain, and returns to T/P valve outlet. The boiler water runs at 140+ when boiiler circulator is on, or less when not on, as I let the wood thermosyphen circulate as the spring/fall seldom needs really hot boiler water. The boiler water has passed thru the house baseboards before it gets to the DHW sidearm.

    The side arm has 37" of contact. I did solder some 12 ga. wire on the bare 3/4" straight tube, to incease surface area and turbulance. This things works so well that the whole 80 gals can be warmed from 50-120 in 8-12 hours, way more than I need.

    Search side arms on ebay for some ideas, if you aren't familiar with them.

    Al
  15. Eric Johnson

    Eric Johnson Mod Emeritus

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    Welcome to the Boiler Room, Al. I just got back from a trip to Vermont. As always, there's a lot of wood being burned in the Green Mountain State. Lot of frost heaves on the secondary highways, but nothing like Maine, which has incredibly bad roads made worse by the heaving.
  16. tuolumne

    tuolumne New Member

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    It's been a rough year here for the roads Eric. We've had lots of really warm days followed by really cold days. The extreme in Pawlet went from a near record of -20 one day to low 50s a few days later. We've mastered the pothole slalom. Where we're building is more like backwoods Maine; don't get cross threaded!

    Al, that's a great idea about the copper wire to increase turbulence. I guess we're a lot smarter as a group. Thanks for the tip.
  17. Eric Johnson

    Eric Johnson Mod Emeritus

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    I drove Route 2 from Bethel, ME to Montpelier, and the only really bad spots were right outside of Montpelier. Then I took Route 7 from Burlington to Bennington, and that was all good. But the country roads in between were heaving pretty good today.
  18. Vtgent49

    Vtgent49 New Member

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    Hi,

    Re: the wire. I spiraled 2 pcs. of 12 ga. house wire around the 3/4, then soldered it where I could, maybe 50%. I doubt it's needed on this set-up, as there is plenty of heat transfer, but it a more marginal syatem it is.

    The T/P valve dead ends a Tee as close to the tank as possible. I wouldn't go without one, and the T probe should be immersed in the hottest spot.

    These side arms need to be super-insulated, or they will reverse flow when boiler is cool, and cool the tank. I just found a super light resistance check valve (gravity only, no spring). I might try that to eliminate the reverse thermosyphen cooling effect.

    My home dirt road is 5 mph max in a few spots now, and the mud hasn't even started yet.

    Al
  19. tuolumne

    tuolumne New Member

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    I plan to manually close the valve as needed for now. There are a lot of places on my system where I am interacting at this point...I need to go down there to tend the fire anyway. Maybe someday I'll be fully computerized like nofossil. Tinkering is fun.

    Yep. We're building the last house on a class 3. They take care of it pretty could. The class 4 past our house also goes out to the blacktop, and most of the time it's in better shape. The natural drainage is better and it doesn't get as much traffic.
  20. 88rxn/a

    88rxn/a Member

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    i was wondering if i could get a parts list? im going to try and make my own side arm.
    looking on the first page and the pics provided by tuolumne, how do i run the 3/4" through the 1 1/2" (example sizes) and seal the ends off? i see the 1 1/2 just T's off on each end for entry and exit of the boiler, i just cant picture it in my head how the ends are sealing between the 3/4 and 1 1/2?
  21. trehugr

    trehugr New Member

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    Geeze Eric, You were in Bethel ? When ? I work in Bethel, and live in Greenwood. Let me know when your rollin through here and ill make sure you eat and sleep at the right places. If you break your car in our craters I can fix that too.

    Did you see this goofy thing on your way through ?

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  22. Eric Johnson

    Eric Johnson Mod Emeritus

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    I didn't see that, so I must have bypassed it somehow. I sure would have noticed. Thanks for the invite. I was there on Thursday. Wasn't sure I was going to get there at all. I started out in down in Baldwin and must have taken a wrong turn somewhere along 117, because I wound up in Denmark, and then had to backtrack 20 or some odd miles back to 117 over those absolutely awful roads. Good thing it was a nice, sunny day.

    88: You use 1 1/2" to 3/4" reducers. You need to file out the little stop in the 3/4" passage so that you can slide the tube through. Then just solder everything together. Note that once you get it put together, I don't think there's a way to take it apart, other than with a hacksaw.

    Here's what mine looks like:

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  23. 88rxn/a

    88rxn/a Member

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    OIC, thanks. maybe sometime soon ill make one and post some results.
  24. tuolumne

    tuolumne New Member

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    As Eric said, just file off the stop in the reducer so the 3/4" pipe can slide right through. Then solder the 3/4" pipe to the small end of the reducer. This solder joint prevents water in the the 1-1/2" pipe from continuing on out, forcing it to take a turn and head out the side of the tee.
  25. Vtgent49

    Vtgent49 New Member

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    I want to add that I did put a gravity type check valve in my system to stop the reverse thermosiphon flow. With that and a lot of the very good insulation I can now just leave it open all summer, when the boiler water is cold. Without the check valve, the tank would cool in just 1 day.

    My solar syatem is online and working fine. BUT the crappy weather has caused me to turn on my electric backup once in July and so far once in August. It only takes 10 mins of electric to raise the temp from 85 to 105, enough for two showers. Then I turn it back off at the breaker.

    The side-arm/boiler set up works so well, that I don't care if the solar works during heating season.
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