Domestic hot water off thermal storage tanks

[Rob186]

I am installing a vedrolux 37 with 2 500 gallon storage tanks and want to put a coil for my hot water in the top one I am tri g to find a coil to go into the tank and I can only find one from boiler supply I am a commercial hvac tech so I was thinking of making one if I can find something reasonably priced anyone have any input on we're I can purchase or ant information on making one

 

[woodsmaster]

http://www.boilersupplies.com/tankheaters/index.html

 

[maple1]

It's not on their web site, but Ahona (they advertise here) sells them. They're just under $400. You'll have to call or email them for the poop on it - I think they fit into a 4in. female pipe thread fitting you'd weld on your tank.

Now for some McGyver input: call me crazy but I am going to try packing & spreading out a couple 100' coils of 3/4 pex in around the top of my tanks, under the insulation. Maybe even 4 of them, 2 on each tank. I figured there's a couple gallons capacity in each roll, that would give me almost 10 extra gallons of hot DHW - plus a heat exchanger. I have found the hard way that, in my world at least, it is best to keep tank welding to an absolute minimum & preserve original tank integrity as much as possible. I hate chasing leaks I can't easliy fix. I'm not sure anyone has tried this - don't think I've read about it on here anyway. It might end up a total failure - only one way to find out though.

Plus pex coils are a heck of a lot cheaper than in-tank DWH copper coils.

 

[woodsmaster]

maple one said
Now for some McGyver input: call me crazy but I am going to try packing & spreading out a couple 100' coils of 3/4 pex in around the top of my tanks, under the insulation. Maybe even 4 of them, 2 on each tank. I figured there's a couple gallons capacity in each roll, that would give me almost 10 extra gallons of hot DHW - plus a heat exchanger. I have found the hard way that, in my world at least, it is best to keep tank welding to an absolute minimum & preserve original tank integrity as much as possible. I hate chasing leaks I can't easliy fix. I'm not sure anyone has tried this - don't think I've read about it on here anyway. It might end up a total failure - only one way to find out though.

Plus pex coils are a heck of a lot cheaper than in-tank DWH copper coils.[/quote]

woodsmaster says
For less than $100 more than 400' of 3/4 pex cost you could buy a 30 plate hx and have something you Know will work. Metal to pex isn't going to be a fast heat transfer.

 

[maple1]

Wouldn't a plate HX also require at least one additional circulator - plus associated wiring & controls for it?

 

[woodsmaster]

Wouldn't a plate HX also require at least one additional circulator - plus associated wiring & controls for it?

Yes it would so it would take and additional circulator or zone valve and control depending on your system. It would be more like $200 more. But I'd hate to waste the money on the 400' of pex if it wont do the job. Steel to pex is going to be a much slower transfer rate than water to copper.

 

[woodsmaster]

Maybe it will work for you ,but sounds risky. 10 gallon is a lot of hot water though so .....

 

[maple1]

I'm also incorporating a sidearm exchanger that will gravity flow, and using an electric hot water tank so we'll have hot water when the wood fire & storage goes cold - after away for a few days, or when I get lazy.

Can always sell the pex on Kijiji too if it doesn't work out. I'll be letting people know how it works, good or bad, once I get things put together. Just got a call from my welder, he's coming tomorrow to fix my leaks - then it'll be full speed ahead. Or at least hopefully ahead.

EDIT: BTW, good to see another Varm going in. I've got a 40 sitting here waiting for me to get my act together.

 

[woodsmaster]

With a side arm I bet it will work good. Are you saying you bought a varm? If so congrats!

 

[maple1]

Yes I did. Unloaded it a month ago & parked it in the barn. I didn't even unwrap it yet - shame on me, but I had (have) a lot of getting ready to do. Finally got the last major component on the weekend (new electric hot water tank), and my tanks should (finally) be good to go after tomorrow.

I think I severely underestimated the cost of fittings though - everytime I'm in town I'm coming home with another hundred bucks worth. In a small bag. Not looking forward to the final tally when done.

 

[Rob186]

Ok I think I am going to try to make one using a spring bender and a peace of 3" PVC to wrap it around I'm thinking 40-50 ft of copper should absorb enough heat I need my min working temp to be around 130 that way I can burn less in the winter I'll take pics if it works

 

[Hobartian]

In winter I heat my domestic hot water by using the same water that circulates through my hydronic radiators. I installed three heat exchangers inside my hot water cylinder and fitted an external circulation pump, Y filter and flow switch. The hydronic heating water only flows through one of the heat exchangers and other two are connected to air conditioning condensing units and are used for summer heating.

I only need to heat my domestic hot water every second day and it doesn't take long to bring the water up to temperature when the hydronic water is above 80 C

Stainless steel heat exchangers are not expensive and are highly efficient. In my case I could have installed the units externally which would make them easy to service but I liked the idea of having them inside the cylinder to reduce heat losses.

 

[stee6043]

A year or two back I did some math on wrapping my two tanks with pex to pre-heat my DHW. Ultimately, if I rememeber correctly, I could heat my hot water for 20+ years for what it would cost me to implement the setup even using the cheapest pex I could find.

Keep in mind that you SHOULD install a mixing valve on our hot water heater output if you're going to do any kind of preheating. My tanks reach 180 almost every night. Sending that water straight up to the shower in the morning would be bad, bad news. Mixing valves are $100+. Budget buster in my case.

 

[Clarkbug]

Not necessarily relevant to the conversation, but Im glad to see there are more Varm owners showing up here on Hearth... Im curious to see what everyone else has to say this heating season when they get to fire it up!

Related, I would like to get my DHW put on my system also, but I think Im going to go sidearm on the hot water heater and just pump it as a separate loop run off of an aquastat. That might have to wait a season or two, but its still a possibility out there...

 

[goosegunner]

A year or two back I did some math on wrapping my two tanks with pex to pre-heat my DHW. Ultimately, if I rememeber correctly, I could heat my hot water for 20+ years for what it would cost me to implement the setup even using the cheapest pex I could find.

Keep in mind that you SHOULD install a mixing valve on our hot water heater output if you're going to do any kind of preheating. My tanks reach 180 almost every night. Sending that water straight up to the shower in the morning would be bad, bad news. Mixing valves are $100+. Budget buster in my case.

You must have Natural gas for hot water? I have propane and I hope to use my boiler soon. I think I will use a small buffer tank with a flat plate exchanger both very close to the water heater.

gg

 

[woodsmaster]

You must have Natural gas for hot water? I have propane and I hope to use my boiler soon. I think I will use a small buffer tank with a flat plate exchanger both very close to the water heater.

gg

Didnt mean to quote your post gg

I bought a used side arm and use the same circ. as is use for the radiators. My DHW setup paid for its self in 2 months. Now its money in my pocket each month !