# Sidearm construction



## tuolumne (Mar 4, 2008)

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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## tuolumne (Mar 4, 2008)

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.


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## BrownianHeatingTech (Mar 4, 2008)

tuolumne said:
			
		

> 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?



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


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## tuolumne (Mar 4, 2008)

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


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## BrownianHeatingTech (Mar 4, 2008)

tuolumne said:
			
		

> 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!



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


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## Eric Johnson (Mar 4, 2008)

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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## slowzuki (Mar 4, 2008)

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


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## tuolumne (Mar 4, 2008)

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.


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## slowzuki (Mar 4, 2008)

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.


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## bjleau (Mar 4, 2008)

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?


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## Eric Johnson (Mar 4, 2008)

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.


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## 88rxn/a (Mar 5, 2008)

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



> 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.


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.


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## Eric Johnson (Mar 5, 2008)

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


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## Vtgent49 (Mar 14, 2008)

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


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## Eric Johnson (Mar 14, 2008)

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.


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## tuolumne (Mar 14, 2008)

Eric Johnson said:
			
		

> 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.



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.


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## Eric Johnson (Mar 15, 2008)

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.


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## Vtgent49 (Mar 15, 2008)

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


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## tuolumne (Mar 15, 2008)

Vtgent49 said:
			
		

> Hi,
> 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.



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.



			
				Vtgent49 said:
			
		

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


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.


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## 88rxn/a (Mar 16, 2008)

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?


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## trehugr (Mar 16, 2008)

Eric Johnson said:
			
		

> 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.



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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## Eric Johnson (Mar 16, 2008)

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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## 88rxn/a (Mar 16, 2008)

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


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## tuolumne (Mar 17, 2008)

88rxn/a said:
			
		

> 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?


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.


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## Vtgent49 (Aug 12, 2008)

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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## tuolumne (Oct 19, 2008)

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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## deerefanatic (Oct 19, 2008)

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.


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## Vtgent49 (Oct 19, 2008)

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


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## mpilihp (Oct 19, 2008)

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


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## deerefanatic (Oct 19, 2008)

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..........


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## tuolumne (Oct 20, 2008)

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.


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## Vtgent49 (Oct 21, 2008)

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


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## tuolumne (Oct 21, 2008)

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.


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## Medman (Oct 21, 2008)

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!


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## tuolumne (Oct 21, 2008)

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!


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## Vtgent49 (Oct 21, 2008)

"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


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## deerefanatic (Oct 22, 2008)

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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