Planning for Future DHW Coil on the Keystoker 90

gitrdonecoal · Post by **gitrdonecoal** » Thu. Jan. 02, 2014 8:58 pm

My hot water tank is 20 ft from my stove. I have read here that anything over 10 ft needs a water pump to properly circulate water. This is all well and good, but is it more expensive to supply electricity for a pump vs 220 for the hot water coils?

blrman07 · Post by **blrman07** » Fri. Jan. 03, 2014 5:12 am

An Alaska that I looked at had the tank 15 feet away from the stove and it did just fine I don't think it really cares as long as the tank is higher than the stove. Warm/hot water rises and cold/cool sinks. That's what gives you the circulation.

Maybe we need some of the calculators to chime in on this?

Rev. Larry

blrman07 · Post by **blrman07** » Fri. Jan. 03, 2014 5:51 am

The only regs I could find were British. They require that any solid fuel boiler be able to operate and circulate using thermosyphen to move the water in the event of a power failure that took out the circ pumps.. The only reg I found was a Recommended max lift of 25 Meters using thermosyphen and it had to have all the bells and whistles such as pressure relief valves, anti-scald valves etc etc. Pretty interesting reading in that they even have a system of piping called "up and over." This allows hot water to rise to the attic and then down again to upper floor radiators. Pretty neat. It appeared to be very touchy and the article described how most plumbers won't install it.

Maybe someone has something more definitive other than rule of thumb.

Rev. Larry

philthy · Post by **philthy** » Tue. Jan. 14, 2014 10:03 pm

I'm in the same boat. My water heater is about the same distance (20ft). I'd rather not rely on a pump for safety reasons but worried thermo syphon won't be effective. I'm also considering a storage tank closer to the stove to ensure it will syphon correctly. I wanna move forward with this project but temporarily held up by too many choices.

Within the next week I'll make my decision and move forward.

I do have a dumb question though; what moves the water from the storage tank to the water heater? I'm sure this sounds funny to some put a question I have been wondering. . .

McGiever · Post by **McGiever** » Tue. Jan. 14, 2014 11:34 pm

In response to a couple of the questions, effective thermosphion distances are a factor of at least 4 things, receiving tanks height above coil, distance laterally between both coil and tank and the resistance to fluids to free flow (pipe diameter size, total number degrees of all bends in pipe routing)

HIGHER
SHORTER
BIGGER
STRAIGHTER...all make it BETTER

If you start fudging here and there the results will dwindle.

Electric WH tank is typically 4500 watts, whereas a small circ pump may be 40 watts.

Water moves from near buffer tank to the DHW tank at the same time and by the same way as when any hot water is flowing out at the fixtures.

blrman07 · Post by **blrman07** » Wed. Jan. 15, 2014 9:48 am

philthy wrote:I'm in the same boat. My water heater is about the same distance (20ft). I'd rather not rely on a pump for safety reasons but worried thermo syphon won't be effective. I'm also considering a storage tank closer to the stove to ensure it will syphon correctly. I wanna move forward with this project but temporarily held up by too many choices.

Within the next week I'll make my decision and move forward.

I do have a dumb question though; what moves the water from the storage tank to the water heater? I'm sure this sounds funny to some put a question I have been wondering. . .

The water moves by convection. Hot water rises, cool water falls. As the water is heated in the coil it will move along the rise. Cooler water flows down to replace the hot water that went up. The length of piping can be a factor if you don't have it heavily insulated. If the hot water looses to much temp on it's way to the water storage tank the flow will stop.

Rev. Larry
New Beginning Church
Ashland, Pa.

SMITTY · Post by **SMITTY** » Wed. Jan. 15, 2014 10:20 am

Just an FYI post - I found the following observations interesting ......

When I had the coils in my Mark III connected to the boiler, they circulated by convection no problem at all. Sometimes they would be a bit sluggish when warming up, resulting in a few seconds of water hammer until things got moving. After that there was never an issue. I installed a circ that I didn't even need. Luckily it was laying around from an old HW tank that was here when we moved in, so it didn't cost me anything. The stove is about as close as you can possibly get to the oil boiler.

Now, when I hooked up my stoker boiler to the oil boiler, I figured it would circulate by convection as well, especially since I was using 1-1/4" pipe vs. 3/4" pipe for the coils in the Mark III. Lucky for me, Rob R. suggested I install a circulator. I balked because I'm a cheap bastard ... but he insisted, so I got a used one off eBay. THANK YOU ROB for that one!! He saved me a MAJOR headache .... because once I got the system all hooked up and lit the boiler, I had forgotten to turn on the circulator I installed. The safety valve was blowing off on the stoker from overheating, while the oil boiler water wasn't even 120°. The water wasn't moving at all! If I hadn't installed that circ, I'd have been doing the job twice!! Guess the stoker was just a foot or 2 too far away for convection.