Hot Water Coil Project

I lit the furnace Friday night, just been burning it low and slow with the mild temps. I'm really excited about my water coil installment I'm monitoring the temperature on the high side of the coil about 2 feet from the furnace. I stuffed a meat thermometer in between the pipe insulator and the copper. My cold water out of the ground is just under 50 degrees.. This temp is after heating thru the night with a very low fire. I wonder whats gonna happen when I gotta rev her up Electric company ain't getting money outta me for hot water for the next 6 months

130 degrees on the preheated water tank this morning!

I got another meat thermometer to monitor the water temp going into the coil. The black thermometer is reading the pipe coming out of the bottom of the tank on its way to the coil. The white one is out of the coil and back to the top of the tank. Looks like a 25 to 26 degree raise, thats with an idling fire. Its just natural water convection. No pumps circulation water thru the coil. Hard saying what the flow rate is though. Any way to even guess??

How do you intend to control the temperature of the water once the stove is running hard?

This tank flows out to my electric tank so that the electric tank's input is preheated.. The only way I can control the temperature of the preheated tank is to watch it and try to keep up with it demand wise so it doesn't over heat. So far, I've only seen it reach 140 degrees..

Thought I'd post an update on the water coil project..
When factoring the draw of the blowers, I'm saving around $100 a month on my electric bill per month with the water coils!


My preheated tank is usually around 120 degrees. I've seen it get up to 150, then I tell the woman to do a load of laundry with warm water. Not used to that either lol...

All I did with the hot tub side is cut a jet line and splice the coil loop into it with pex pipe running the water to and from the furnace with a tiny 12 volt water pump. I used a jet line so I wouldn't have to cut holes in the hot tub.. IN the summer I'll just couple the jet line back together and drain the loop. My hot tub was last used on New years eve and has lost 8 degrees since then (6 days) in sleep mode. In sleep mode the heater won't activate until its 20 degrees below preset temp. Without the coil loop to the furnace its hard to say how much heat it would have lost. Probably 8 degrees the first day!

I still think there is room for improvement with the hot tub side by using a small temper tank in the basement similar to the DHW system. Even though I tried hard to insulate the lines running to and from the tub, I'm sure there is still some heat loss going on there

Lightning wrote:Thought I'd post an update on the water coil project..
When factoring the draw of the blowers, I'm saving around $100 a month on my electric bill per month with the water coils!


My preheated tank is usually around 120 degrees. I've seen it get up to 150, then I tell the woman to do a load of laundry with warm water. Not used to that either lol...

All I did with the hot tub side is cut a jet line and splice the coil loop into it with pex pipe running the water to and from the furnace with a tiny 12 volt water pump. I used a jet line so I wouldn't have to cut holes in the hot tub.. IN the summer I'll just couple the jet line back together and drain the loop. My hot tub was last used on New years eve and has lost 8 degrees since then (6 days) in sleep mode. In sleep mode the heater won't activate until its 20 degrees below preset temp. Without the coil loop to the furnace its hard to say how much heat it would have lost. Probably 8 degrees the first day!

I still think there is room for improvement with the hot tub side by using a small temper tank in the basement similar to the DHW system. Even though I tried hard to insulate the lines running to and from the tub, I'm sure there is still some heat loss going on there

I'm sure it's not gonna heat it all but,it seems to be helping alot and saving $$

Dennis wrote:I'm sure it's not gonna heat it all but,it seems to be helping alot and saving $$

Yeah man!! Its kinda funny to look at it this way... but if I spend $800 on coal and save $600 on electric for the 6 months I'm heating.. How much was my coal really lol $200.00? So I heated thru winter for $200!

Lightning wrote:

Dennis wrote:I'm sure it's not gonna heat it all but,it seems to be helping alot and saving $$

Yeah man!! Its kinda funny to look at it this way... but if I spend $800 on coal and save $600 on electric for the 6 months I'm heating.. How much was my coal really lol $200.00? So I heated thru winter for $200!

Your right on that. I save $2500.00 a year burning coal,I just can't seem to find that $2500.00 anywhere,it would help pay the bills

Lightning wrote:I fixed the leak finally. Its a pain to drain and heat pipes back up!! I replaced the female adapter over the stainless and wrapped more teflon tape and tightened it even harder. All set to heat water now! Just need some cold weather to fire it up

Tinning flux is your friend. It's makes sweating copper easy for those that don't do it regularly. On the threaded connections, wrap them with tape and then use this and you'll never have a leak again: http://www.pexsupply.com/Hercules-15515 ... ant-1-2-pt

Be sure to take Kerosene or diesel fuel and wipe down the joints after using an oil based flux - eventually it will corrode the pipe and joint away.

Wear gloves if you use that GRRIP thread sealant.

Oatey tinning flux is nice stuff.

Berlin wrote:Tinning flux is your friend. It's makes sweating copper easy for those that don't do it regularly. On the threaded connections, wrap them with tape and then use this and you'll never have a leak again: http://www.pexsupply.com/Hercules-15515 ... ant-1-2-pt

Be sure to take Kerosene or diesel fuel and wipe down the joints after using an oil based flux - eventually it will corrode the pipe and joint away.

By the way Berlin, thanks for shedding new light on my old block and mortar chimney last year.. Its working fantastic since I rebuilt the top and started using it.. And to think I was considering building a new chimney!!

Rob R. wrote:Wear gloves if you use that GRRIP thread sealant.

Oatey tinning flux is nice stuff.

Thanks guys Thats good to know! I had an awful time with just a few of them!
But, It coulda been worse since I only had a couple leaks out of all those connections..

Hi all and Happy Easter!! .... I thought I would do an update on the water coil project since I have about a month at most left this season. They performed better than expected! I was worried that my coils would either produce too much heat or not enough, but turns out it was just right. My preheat tank thermosiphon on the DHW did get kinda hot a few days during the winter when I was pushing the furnace hard. It got up to 160 a few times. To bring it down, we would fire up the clothes washer or something. The preheated tank feeds the electric tank. I left the primary electric tank powered up so I never had problem with not enough hot water. I'm sure the electric tank used a small amount of power but by sending water to it that was between 120 and 160 degrees (instead of 50) it didn't need to work very hard.

For the hot tub, I just recently replaced the tiny 12 volt circulator with a real one ..(pic below).. It works much better.. I thought I would end up needing a small temper tank for the hot tub because of heat loss back and forth to the tub, but the bare bones loop did just fine. I kept the hot tub in sleep mode so the internal heater wouldn't activate unless it got cold. The tub rarely got below 90 .. I would activate the internal heater when I wanted to get in it to get it up to 102, which turned out to be once or twice a month in the winter. Just yesterday I drained and refilled the hot tub (should be done every few months) and overnight it went from 60 to 69 degrees just from heat off the coal furnace water coil

The trip back and forth from the furnace to the hot tub is pretty lengthy. Its about 80 feet with 50 feet of it outside. I did a cheap insulating job just for experimental. I ran the 1/2 pex lines together thru a 1 1/2 inch electrical conduit. Then I wrapped it with the foam pipe insulators then wrapped it with duct taped then wrapped it again with a layer of fiberglass insulation then wrapped again with plastic sheeting so the whole mess couldn't get wet ... The pipes run under the 6x6's then up into the floor of the hot tub where I spliced into a jet line.. It looks bad but I plan to do something more permanent and maybe even bury it for next year.

I can only estimate my savings on electric since there is other variables using power during the winter months. I'm certain of a few givens to work out the estimate. I'm thinking I saved $90 to $100 per month with the coils..

Also below is a pic of what the hot tub looks like with 10 kids in it. That was last summer lol. I drained it and did a refill after that event too for obvious reasons hahahaha....