sidearms

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coolidge

Member
Dec 16, 2008
218
Maine
Got the propane bill today for our hot water. EXPENSIVE $3.83 per gal. So i need a sidearm to install and the he double hockey sticks with propane. Any good advice on where to purchase one? I have seen them on e-bay and such, but figured i check with all of you before the purchase. Planning on hooking up two 80 gal tanks to cover our overusage of hot water. Pros/cons too two tanks? Four showers and at least two loads of laundry/plus the dishwasher per day.
 
what is your set up right now? OWB, gasser ect? I am doing away with my side arm as it is to slow to recover for me. I am installing a 30 plate HX and making a on demand system.

Rob
 
Taxidermist,

How are you accomplishing your on demand system ?

I was reading Siggy newest edition of Hydronic heating and he uses a flow switch that detects DHW usage on one side of the plate exchanger which will turn on small circulator on the other side of the exchanger that draws hot water from a buffer tank which will heat the DHW.Siggy doesn't show any kind of mixing valve ,but it seems like one should be incorporated
 
How low of storage temps will the on demand setup still heat dhw?


I want to set up my dhw water the same way. Small potable water pump on domestic side and a pump on my primary/secondary set up as another zone.

I have slightly acidic water so copper sidearm and thermo-siphon is a bad idea.

gg
 
Jeff S said:
Taxidermist,

How are you accomplishing your on demand system ?

I was reading Siggy newest edition of Hydronic heating and he uses a flow switch that detects DHW usage on one side of the plate exchanger which will turn on small circulator on the other side of the exchanger that draws hot water from a buffer tank which will heat the DHW.Siggy doesn't show any kind of mixing valve ,but it seems like one should be incorporated

That is the way i am setting mine up to. Any chance I could get a copy of that?

Rob
 
Taxidermist is right about slow recovery compared to a roaring flame. My sidearm is home made and works well but at 155*f it takes about 3+/- hours for a full recap. At 170*f it's about 2 hours. My circ runs 24/7 and is always trying to keep the dhw at peak. 40 gal tank.(very primitive set up)
I built my own sidearm for a little less than an outright purchase of a pre built but with a few extra valves and unions for quick maintenance and my outer pipe is large enough to more than accomodate the water flow from my circ. (1 1/2" black pipe with a 3/4" core). There is usually enough hot water and when there is not it is because lime deposits in the tank have followed the convection flow and began building a blockage. The extra valves and unions make for a quick flush and I'm back in business. A personal side note is you usually find out there is a blockage when you thought you had the day off or the wife wants to really soak for a spell.
I don't understand your set up but it sounds like you may want to think of two sidearms. In any case you need a tempering valve as it will prevent hazardous scalding and will seem to "extend" your usable hot water.
 
Setup is a OWB I have the P and M Optimizer 250, I am thinking with two tanks about installing some solar hotwater next year. I did have an extra supply and return stubbed into the piping when installed just for this but havent used it yet. The on demand seems really interesting. I do have my boiler hooked to a 330 gal propane tank for extra btus.
 
Heres another thought, I have a 250 gal propane tank that i had the end cut off and 100 ft of 1/2 inch refrigeration copper coiled inside of it and stubbed out the top, pressure tested, good to go. Do you think if that tank is 180-190 that i could get on demand DHW that way.Mightt make one hell of a preheater before the Rinnia.
 
If you are using a OWB and your pump runs 24 - 7 then with a flat plate you should have unlimited hot water. My friend has this set up and he has 4 girls and a wife and has never ran out of hot water.

The difference with mine is i have storage so no need to run a pump 24- 7 that is why i am calling mine a "on demand" system. I turn on my DHW and a flow switch turns on a pump to pump water thru the HX. No need to put a pump on DHW side because of the pressure from my well pump and pressure tank.

Rob
 
taxidermist said:
If you are using a OWB and your pump runs 24 - 7 then with a flat plate you should have unlimited hot water. My friend has this set up and he has 4 girls and a wife and has never ran out of hot water.

The difference with mine is i have storage so no need to run a pump 24- 7 that is why i am calling mine a "on demand" system. I turn on my DHW and a flow switch turns on a pump to pump water thru the HX. No need to put a pump on DHW side because of the pressure from my well pump and pressure tank.

Rob

My setup is an OWB with a plate heat exchanger. I have run 2 showers, the washing machine and dishwasher simultaneously and have always had unlimited hot water at my mixing valves set point of 125. It seems that the critical part of this is getting the plate exchanger sized right but if you do that, it works wonderful.
 
coolidge said:
Heres another thought, I have a 250 gal propane tank that i had the end cut off and 100 ft of 1/2 inch refrigeration copper coiled inside of it and stubbed out the top, pressure tested, good to go. Do you think if that tank is 180-190 that i could get on demand DHW that way.Mightt make one hell of a preheater before the Rinnia.

That's a Tom in Maine question, but I wouldn't be surprised if you could get reasonably hot DHW at 5 gpm with a hundred feet of copper with tank temperatures down to 130 or lower, based on my experience with fifteen feet of the finned copper.
 
Has anyone ever tried using a regular copper sidearm with an additional "potable" circ circulating the water through the DHW part of the sidearm? I would think the recovery would be vastly improved over thermosiphoning. Fins might even help more. I already have a 80gal electric and spending $1k on a Superstor is not in the cards. When we built a couple years ago, I'm not sure they even sold them with electric backup elements but I do see they have versions like that now made for solar use. Fuel oil heating and boilers are almost non-existent in homes in this part of the country so the builder, plumber, and inspectors would probably have all balked had I requested one. For an OWB, the plate exchanger with water circulating continuously sounds like a great idea. For those of us with boilers and storage, I figured the cooler water temps would not keep up with demand or is still because the plate is oversized. I know the plate exchangers require periodic cleaning. Do sidearms also need cleaning if you have soft water?
 
huskers said:
Has anyone ever tried using a regular copper sidearm with an additional "potable" circ circulating the water through the DHW part of the sidearm?

I have a homemade DHW heater made from 20' 3/4" and 1" copper with a taco 006 on the domestic side (I think, it's buried in a heat pump attached to the desuperheater and pressed into extra service). I get no where near endless hot water, but that's why it's hooked to an 80 gal tank. With solar heat it works fine if it's the only load, that is if the solar/boiler water can get up to 140-150 without the floor loops sucking out all of the heat. If the floor is on, then the temp will never get hot enough to make hot water. I get very roughly 30-40,000 btu/hr with 3-4 gpm rising from 120 to 140 with the solar water entering around 150-160. More btu/hr when the tank is cold and tapering to zero approaching boiling.

If the boiler is running it will keep up even better.

If you have storage inside, then a coil inside the tank (e.g. Tom in Maine, Gary's builditsolar) is a no brainer, storage tank optional.

With an OWB or any system that circulates constantly (I'll include solar in this) then a non sidearm DHW circulated "sidearm" with adequate DHW storage makes sense to me, or a straight thermosyphon sidearm with more storage if you have hot enough boiler water circulating often enough anyway.

If you're thinking about DHW, don't forget to check out nofossil.org especially the hot water subsystem.
 
You may also consider a differential controller as a low-temperature lockout so when the temperature of your boiler dips to below the temperature stored in the DHW tank (or storage tanks) then you are not removing heat from the DHW and putting it back into the boiler loop. Unless, of course, you want that as a back-up feature should your boiler fail for some reason ..?
 
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