Making a External DHW Coil

KLook · Post by **KLook** » Sat. Dec. 01, 2012 6:41 pm

And i'm sure it has been mentioned in another thread but have the magnets held up in the heat? I thought they lost their magnetic properties when heated.

Kevin

bug512 · Post by **bug512** » Sat. Dec. 01, 2012 8:56 pm

Couple of reasons.
WIth a internal coil it must be flooded all the time.
And cost, most of the items were laying around

KLook · Post by **KLook** » Sat. Dec. 01, 2012 10:24 pm

I would think anything in the firebox would be affected by corrosion also.

kevin

bug512 · Post by **bug512** » Sun. Dec. 02, 2012 7:46 pm

KLook wrote:And i'm sure it has been mentioned in another thread but have the magnets held up in the heat? I thought they lost their magnetic properties when heated.

Kevin

Everything is still holding strong.

bug512 · Post by **bug512** » Sun. Dec. 02, 2012 7:48 pm

KLook wrote:I would think anything in the firebox would be affected by corrosion also.

kevin

If it is made out of a good quality stainless I'm sure it would be fine.

Halleys5 · Post by **Halleys5** » Fri. Dec. 28, 2012 3:42 pm

I appreciate your annual follow ups on this project. Gives me confidence that it is worth it long term.

What suggestions would you make if you were starting this project today, as in, what would you do differently?
Horizontal heat tubes? Different tubes? More tubes? I read one blog where a guy took a coil of flexible copper and embedded it in plaster of Paris and stuck it to the side of his stove for heat exchange. I am thinking about being slightly more elegant than that....

I love your magnet idea, where did you find them?

I want to tee into my domestic tempering tank so I am not sure if the floor register type tubes would be a good idea (solder?). Possibly just a matrix of 1/4" copper that I could layout myself.

Just looking to benefit from your experience. Appreciate it.

bug512 · Post by **bug512** » Sat. Dec. 29, 2012 3:28 pm

Hello, as far as what I would do different is a tough answer because I do not know is the outcome would be desirable or not. My recommendation to someone would be to build it like I did. We had 117 degree water in the tempering tank this morning. This gives my "normal" furnace little work to do to top off the temperature.

Would I do it again? Absolutely. Especially with the cost of oil. I am looking into switching out my oil fired boiler and going with natural gas for the 2013 heating season. I did the calculation and for the tonnage I use (four @ $266 per) if you convert that over to what they charge per therm ($1.04) of natural gas it comes out less expensive. So we will see what rebates New Jersey will offer for 2013 for switching to natural gas.

I will always keep the coal stove and might use it to keep the basement at 72 during the winter months.

And magnets can be purchased at Grainger. Link Here

Best of luck and post questions if needed.

michaelanthony · Post by **michaelanthony** » Sat. Dec. 29, 2012 7:45 pm

bug, I think your hot water coil is awesome and want to do the same. What are your thoughts of my coil on the exterior of the hot air jacket of my stove, I'm reading 260* to 300* when cranking on the exterior or should I cut out a panel, ( in turn I would make this a hinged door ) and do as you and apply coil directly to the stove body. Also my HW tank is a 32 gallon oil fired approx. 10 ft. from my stove, do you feel I would require a tempering tank for strictly thermosyphon, or could I get by with a circulating pump?

bug512 · Post by **bug512** » Sat. Dec. 29, 2012 8:07 pm

Hello, I would mount it on the side / top of the stove. If you have temperatures in the 200+ range you will definitely get some heat transfer.
Personally I would not cut, drill, or modify a stove in any way shape or forum.

I would get a tempering tank and her is my reason. If you use your exiting 32 gallon water heater as a storage tank you might "give up" heat. With this setup you be basically installing a radiator on your current water heater. When your coal stove is not running at a high fire you could then "dump" heat out of your water heater.

With a tempering tank before your "normal" water heater you will bring in cold water form your well or city water supply, circulate this water via thermosiphon or pump to a heating source (your coal stove) then sent it to your water heater. No energy is lost. Even in the summer months mine runs (with the stove off) and gets the temperatures in the low 70's (from 58 from the city) and then we send it to the boiler.

I hope I explained this well, if not let me know. Oh as far as thermosiphon or pump? Give the thermosiphon a try, less cost and nothing to stop working.

michaelanthony · Post by **michaelanthony** » Sat. Dec. 29, 2012 9:02 pm

bug512 wrote:

I would get a tempering tank and her is my reason. If you use your exiting 32 gallon water heater as a storage tank you might "give up" heat. With this setup you be basically installing a radiator on your current water heater. When your coal stove is not running at a high fire you could then "dump" heat out of your water heater.

Thank you Gene, makes sense, it took a few minutes to sink in I am on the hunt for a second hand water tank!

bug512 · Post by **bug512** » Sat. Dec. 29, 2012 9:23 pm

Please let me know if you have any more questions.

Joeski · Post by **Joeski** » Mon. Jan. 07, 2013 12:36 am

I can not wait to start this project this next weekend

Thank you so much bug512 for putting this info on here.

hotblast1357 · Post by **hotblast1357** » Fri. Feb. 20, 2015 9:20 pm

Bug how are things going?

bug512 · Post by **bug512** » Sun. Feb. 22, 2015 7:45 pm

hotblast1357 wrote:Bug how are things going?

Great !

Sorry to say but I have switched to natural gas and replaced my steam boiler with new. That has let to selling the coal stove.

I hope the new owners get the same amount of years of warmth as I did.

hotblast1357 · Post by **hotblast1357** » Mon. Feb. 23, 2015 12:42 am

Well I am sorry too hear that! Hopefully prices stay cheap for you.

Making a External DHW Coil

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