HW Suggestions Needed...

HW Suggestions needed...

PostBy: BurninCoalInRI On: Fri Dec 08, 2006 12:55 am

Hot water suggestion needed...

I saw the hot water coils on here. I have a mag Stoker, and use 50 gal electric hw heater. I'd like to make my HW with the harman, flow into the 50 gal electric so when the stoves off in summer, im back on that.

any suggestions on best way to do this? where to get a hw tank etc?

PostBy: coaledsweat On: Fri Dec 08, 2006 10:08 am

You have a Harmon, right? You would need a coil in your stove and a circ pump to move the water to your existing water heater, pretty simple stuff really. I think if you use the search function you will find oodels of info on this one, it is popular.
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

PostBy: LsFarm On: Fri Dec 08, 2006 1:14 pm

BCinRI, here is a links to informative threads on a couple of HotWater coil installations.

Tell me it was worth it.

SF-250 hot water coil

Coal Stoker Coil Question

The basics are:
A Coil in the stove to collect heat
Piping to a tempering tank or to your HW tank
A circulating pump or natural gravity circulation

For a tank, you can buy a stand-alone storage tank, but if you can find one, many of us have used a discarded hot water heater's tank. Often for free. Or you can tap into your current electric tank if there are enough extra ports. Moving the overtemp/pressure relief valve usually gives you one port, and you can move the tank drain valve for another. Move the two items into the new piping you install.

If your stove is below the water tank, a loop for hot water out [it rises] and cold water back [it sinks] will provide natural [but slow] circulation.
If your stove and hot water tank are on the same level, just add a circulating pump, they cost about $80, and burn 100watts.

Hope this helps. Greg L
Last edited by LsFarm on Fri Dec 08, 2006 10:22 pm, edited 1 time in total.
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

PostBy: BurninCoalInRI On: Fri Dec 08, 2006 2:40 pm

OK, my stove is on the basement floor, and the 50gal elec hw heater is about 10 feet to the side. it does have a drain valve at the bottom as well as a pressure relief valve near the top.

i would rather use another tank that feeds the elec. so I guess I would need a hw tank. and if im understanding this, if I get, say, a shorty and place it hjigher than the stove (how much higher should the bottom be?) then I can rely on thermosiphon?

also, I wonder how often would the thing boil over and vent?

so far it looks like I need the HW coil, a tank, and some simple plumbing/piping supplies (i can sweat pipes etc no prob)

also, which Hilkoil model would I need for the Mag Stoker? is that prety much the best brand to get?

Length Width Hole Center Thread Length Tank Size
18S 18" 7" 6" 3 1/2" or 4 1/2" 30 gal. or less
24S 23" 7" 6" 3 1/2" or 4 1/2" 30 - 60 gal.
16T 16" 10" 9" 3 1/2" or 4 1/2" 60 - 100 gal.
18TL 18" 10" 9" 3" 80 - 120 gal.
21T 21" 10" 9" 3 1/2" or 4 1/2" 80 - 120 gal.

thanks to all for the advice...

PostBy: coaledsweat On: Fri Dec 08, 2006 3:21 pm

Try to avoid using a seperate tank, you don't need it and it will just complicate the project. You should be able to trigger the pump with the thermostat on your water heater.
The key is the ports on your HW tank.
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

PostBy: BurninCoalInRI On: Fri Dec 08, 2006 3:33 pm

heres what im thinking... I want to keep the elec hw off, but be available for summer and high demand.

to my way of thinking, a holding tank would be (almost) perfect for that, since I could get another 40gal shorty, mount it at the right height to use thermosiphon (what height is that?) and it would feed the elec tank. the elec element would only come on to maintain the tank but since the feed water would be warm or hot depending on stove usage, the elec would either not come on at all, or come on much much less.

also, I would not have to move the elec tank, just stick the 40 gal next to the stove and feed its hot water to the elec.

to me, this is easy, and adds redundancy etc.

now, im new at this so thats why im asking for ideas. really wanting to avout a circ pump, I *could* build a stand for my current elec 50 gal and get the bottom of it about as high as the top of the stove, run the hw coil to the dran and pressure valve ports, and rely on thermosiphon. presumably, the elec element would not come on for maint, and only when using hw from it and the temp drops below the set point. I imagine the tank would stay at a temp much higher than its (prob 120f) set point and thats the buffer that keeps it off.

does anyone know how hot it would be, generally? also how often would the pressure relief valve blow? (i could send that outside)

PostBy: coaledsweat On: Fri Dec 08, 2006 3:54 pm

Seems to me like more work. There are many ways to make it up, just take it slow and look at it from a few different ways to see what would be best for your application.
Most PRVs are set at 30#, some (rarley) are adjustable.
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

PostBy: BurninCoalInRI On: Fri Dec 08, 2006 4:07 pm

my city water pressure is over 80# so the prv must be higher than that... no?

PostBy: BurninCoalInRI On: Fri Dec 08, 2006 4:27 pm

so, essentially I need first to know what coil to use. for a few extra bucks, could I put a double loop oin there?

im looking at the 21t... would that make too much hw and open the prv too often?

PostBy: coaledsweat On: Fri Dec 08, 2006 4:50 pm

80# seems like an awful lot of pressure, you may have a reducing valve somewhere in the system. But I may be mistaken, Boilers run at 30#, perhaps you have a 90# on your water heater. It should be labled clearly or stamped on it somewhere.
The longer the coil the more surface area, more surface = more heat transfered.
It shouldn't blow at all unless you go way over on the temp (boil).
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea


PostBy: endinmaine On: Fri Dec 08, 2006 7:43 pm

I wrote about my experiences , in another thread , with a small wood/coal stove that my dad used to heat a 30 gallon DHW tank. Even though the stove was quite small and he used only wood to take the chill off the kitchen , the 30 gallon tank would frequently blow after a little more than one hour. The coil he used was hand made , seamless 1/2" copper about 8' long heated and bent into circles then place inside the stove. Since the stove was a top fed type he just place the small wood pieces inside the copper circle. He mostly use cut up pallets and since the 30 gallon tank was within 10' no circulating was used.
I will be using a 2nd 80 gallon tank heated by my Mark III to compliment the 40 gallon propane gas DHW , using a circulating put.

Hand Fed Coal Stove: Margin Gem Cook Stove and Harman Mark III
Stove/Furnace Make: Harman and Margin Gem
Stove/Furnace Model: Mark III and CookStove

PostBy: LsFarm On: Fri Dec 08, 2006 8:28 pm

Hot water boilers have a pressure reducing valve in the fill line, reducing house pressure to 6-8psi. The 30 psi relief valve is just for overpressure from heat expansion, there usually is an expansion tank on a boiler too.

A hot water tank has a Watts valve, that will blow off with either over heat, or overpressure, or both. The water that comes out is dangerously hot sometimes it's steam, that is why building code says a hot water heater PRV must have a pipe on the outlet down to within a few inches of the floor.

BCinRI, I think you will find that buying an extra tank costs more than a circulating pump. And the simplest way is to hook the loop into your existing tank with a circulating pump. A gravity or thermosiphon sounds neat, but it circulates slow, and will have a very slow recovery rate. The system will probably thermosiphon through the circulator pump anyway, so you don't have to run the pump 24/7.

Another thing to think about is, if you have a preheated tank, or tempering tank feeding your electric water heater, the water heater's stored water is not going to stay hot unless the electric element is powered.

IF you don't use any hot water for 8 hours, like at night, then the water in the electric heater will cool off, even though the tempering tank is getting really hot from the coal stove all night long. You need to keep the stored water in the electric heater hot too.

I'd hook up to the electric heater either with a circulating pump, or thermosiphon. This keeps the water hot that you will use first. If you desire to have more capacity, then an additional tempering tank can be added at any time.

I'd recommend a simple system first, and if it doesn't work well enough, then add an additional tank. What is your hot water use pattern or habit? Do you have many people taking showers in the morning, needing more capacity?

Greg L

In my system, I have a hot water heat exchanger in the cold water line feeding my propane hot water tank. The heat exchanger heats the incoming water to about 150*. The propane tank's thermostat is set to keep the water at 110*. At night, just before going to bed, I will run hot water into a bathtub, leaving it there overnight. This does two things. The volume of water in the bathtub is replaced in the propane heater by 150* water, so the water will not likely drop to the 110* threshold and trigger the propane valve overnight. And the second thing is the tub of hot water helps humidify the house.

Last edited by LsFarm on Fri Dec 08, 2006 8:37 pm, edited 1 time in total.
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

PostBy: Jerry & Karen On: Fri Dec 08, 2006 8:31 pm

Go to my web page, Leisurelinestoves.com and at the bottom of the product page there is a link to the coil site. It shows the different ways of hooking up a coil to your hot water.
Good Luck
Jerry :)
Jerry & Karen

PostBy: Cap On: Fri Dec 08, 2006 9:45 pm

Hey Rhode Island--

I built a coil this season from scratch. Read the thread under the hand fired stoves. Greg offered a link but here it is from the top:

SF-250 hot water coil

If I really let my stove rip, I will easily exceed the 200F mark and unload the safety relief valve. Right now I maintain a very warm 140F but I have my unit designed so I can isolate the coil when I need to fire up the stove for a really cold night . Like tonight! But durning the day and early evening I let the stove simmer at 130-140F. Be sure to install a tempering valve. I will need to install one at some point.
Hand Fed Coal Boiler: Harman SF 250, domestic hot water loop, heat accumulator

PostBy: BurninCoalInRI On: Fri Dec 08, 2006 10:16 pm

thanks guys, for all the good advice. now a circ pump scheme may sound better, what grabs me with that is the thermosiphon being slow.

perhaps a bigger tank would also be good down the line, maybe 80 gal (my "5 year" elec hw heater is like 10 years old ...)

so I will try to design a circ systm of some kind. for safety sake, my design will include a tempering valve, and a prv (maybe 2)...