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Keith671

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Reply with quote  #1 
I sketched up my project with my present system. I would like to use the heat exchanger in my water heater and possibly my boiler, but don't know the best way to hook it up. If I could hook up a circulator pump to the coil in the thermal tank and run it through my coil in the water heater I would have more hot water available than just the coil in thermal tank. When I start drawing hot water it would start circulating and continue until the water heater is back to temp as long as the thermal tank is hot. I hope my attachment is OK.   Any suggestions are welcome.

Thanks Keith R.

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Keith R. in PA.

Keith671

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Reply with quote  #2 
My attachment didn't some up on first post.

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jpeg solar-layout-1.jpg (34.09 KB, 324 views)


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Keith R. in PA.

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Reply with quote  #3 
Hi, Keith !

I wish I had been more explicit in my first reply !

To answer your original question, NO, I don't  consider that you need a tank (you already have one!).

You are looking to produce DHW in summer, without running the central-heating boiler, so unless there's 20 of you in the household, your existing tank should be up to the task...

Your question is, how to get it running on solar.
The answer is HERE:

http://www.brazed-plate-heat-exchanger.com/anwendungen.htm

i.e  a flat-plate heat exchanger, close-coupled to your existing DHW tank. 

This is the cheapest, simplest & logical approach to your problem, & nobody is inventing anything !  If it does not work, OK, go ahead and build your Big Tank by all means...

A FP HEX should cost you less than 200 USD.  You would also need an expansion tank on a separate line out of the DHW tank, in case the system starts overheating... (If purchased big enough, the expansion tank could also perhaps serve as a "backup HW store... although this is not its real aim...).

You thus save on Big Tank, Coil, Valvework... (and maybe even a Pump...) (depending on the location of your collector in relation to your DHW tank).

You can get an idea of the proposed configuration by taking a look at the diagram here:-   http://eecm.eu/?page_id=122

You have to interpret this dwg a bit, of course, to suit your configuration: your existing DHW heater is the big tank in the center, and the tiddly tank on the left would  be your future FP HEX. You also have to redraw the pipe connections: the Solar Collector goes to the FP HEX, and the FP HEX is plumbed in and out of the DHW tank...

Another imprtant thing to consider, regarding your collector, is not to oversize it… I suggest you take a look at this article:- http://www.jradmin.com/hwa/uploads/img4d4acf9f3280e1.pdf

 Don't hesitate to post back & develop the discussion !

Best regards,
G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
Keith671

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Posts: 142
Reply with quote  #4 
I also have a 52 gallon gas water heater that I used before I hooked up the water heater to the boiler. So maybe I could utilize this also. I also have 2 other circulating pumps, one is a Taco 007-F4 and the other is a Bell & Gossett not sure of the number.  Also have a Taco 3 zone control box I don't know if this could be used to control anything or not. I will look at this stuff and get some numbers, so you know exactly what I have. 
Thanks again for the help.

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Keith R. in PA.
Garage_Hermit

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Reply with quote  #5 
OK, Keith, got that...!
I am wondering whether your gas water heater could be used for central heating, using a similar set-up to what I proposed earlier for DHW, namely prewarming the heater thru a FP HEX, with solar, and using gas as a "secondary" energy source (because solar alone would not get the water hot enough for central heating...).

You would also have to consider if there is a price differential between oil and gas...
For example, if gas is a lot dearer than oil, you'd need to study what (if any) potential savings were likely...

If you do this right, you just *might* end up with an OIL-fired boiler, spare, for sale

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
Keith671

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Posts: 142
Reply with quote  #6 
I do not use the propane gas heater as the price was about $2 a gallon more than heating oil.  This is why I installed the water heater to the boiler.  I figured if I am going to have the boiler running I might as well get the DHW at the same time.  I have consider using the gas during the summer, but hoping the solar will work for DHW and adding more for heat later.  I just remembered my boiler also has a domestic coil in it, which is used to preheat water before going to the water heater. I could possibly use this in reverse, circulating my solar water through this to keep my boiler temp up. Thus my boiler would be my thermal tank, although not insulated. If this would work when I draw hot water the circulating pump on the boiler work turn on to heat my water heater. Just thinking out loud.
Thanks Keith R.

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Keith R. in PA.
Garage_Hermit

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Reply with quote  #7 
Keith,

Regarding OIL vs GAS, it might be worth your while taking a look at this...

http://www.scientificamerican.com/article.cfm?id=oil-versus-natural-gas-home-heating

Depending on your location, solar potential etc. it might make sense to consider using solar for both DHW and central heating, and using GAS as your top-up energy source...

That's why I was (albeit jokingly...) referring to the possiblity of getting rid of oil altogether...

G_H


__________________
(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
Keith671

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Posts: 142
Reply with quote  #8 
Garage_Hermit,
I looked at the article you posted and all makes good scents. I am not in an area where I can get natural gas, I have to rely on propane. I believe propane is a product of oil. I do plan on using solar for both as I move forward. I think I am a little old (62)to invest to much, will never see a payback. I just want to supplement what I have and give me something to do as I am planning to retire in a year or so. My brother uses propane to heat his house and it is a little cheaper than oil, but that is because you get a better rate when you buy that much. A lot of people in my area are using the wood fired outdoor furnaces. Then again you have to buy wood or cut your own, plus the expense of the system. I would just as soon let the sun do the work.

Later Keith R.

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Keith R. in PA.
Keith671

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Posts: 142
Reply with quote  #9 
I just found this in a post on another forum that I thought was interesting.

Efficiencies: Assume 85% for heating oil and 94% for propane

Cost per gallon: Assume September, 2011 averages in Maine. Heating oil $3.65 and propane $2.99

Heating Oil BTUs per dollar: 138,690 BTUs X .85 efficiency / $3.65 = 32,298 BTUs per dollar

Propane BTUs per dollar: 91,333 X .94 efficiency / $2.99 = 28,713 BTUs per dollar.

Just for info.

Keith R.

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Keith R. in PA.
Keith671

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Posts: 142
Reply with quote  #10 
Since I have the gas water heater I have redrawn the plan. I would like to get it up and running with minimal investment. I think I can use the gas water heater as my thermal tank to get started. I have been looking into the brazed hex and think this may work. I have attached the new drawing. Please give me your thoughts on this setup.
Keith R.

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jpeg solar-layout-2-flatplate.jpg (59.81 KB, 284 views)


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Keith R. in PA.

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