Water Heater Coil

Well, got the system set up and it works great. I'm getting plenty of hot water at no extra costs. I am not using a cirulating pump because I'm able to take advantage of therm syphoning to circulate the water. The only problem I had was the hot water tank was one I had kicking around and after about a week started leaking. I don't use a separate hot water tank in my house because I get hot water from my oil boiler. So all I need is a holding tank to replace my leaking one but I'm finding it cheaper to just buy an electric hot water tank rather than buying a tank without the heating elements. Does this sound right? Does anybody know where I can look into purchasing a holding tank at a reasonable price?
Tom

The water storage tanks are not made in quantity like the water heaters are, so the cost is higher.

If you can, stop by a plumbing shop and see if they have a tank, or a heater removed for conversion from propane to Natural gas or ?? Just not removed 'cause it leaked.

If you were nearby I'd give you a used one that I know is good.

Check on the sales at Home Depot, Lowes, and check if they have a dented one!! often you can get a dented one for 1/2 price. A dent doesn't hurt anything, but nobody wants to pay full price for damaged goods

How long did it take to heat the 40 gallons by thermo-siphon?

Hope this helps. Greg L

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Greg,
I hooked up a 30 gallon tank in the morning and in the evening, (about 8 hours later), when I took a shower I noticed a big differance in the amount of hot water I used, or should I say didn't use. The hot water is hotter so I used more cold.
Tom

how do you handle it when the water temps get too hot. is there a pressure valve or something that blows? where does it drain

jimbo970 wrote:how do you handle it when the water temps get too hot. is there a pressure valve or something that blows? where does it drain

Any hot water apparatus will or should have a pressure relief valve, should be one on your current hot water heater. Pressure gets to certain point and it opens, the water released can be directed anywhere via tubing or pipe.

You would always mount the relief valve at the top of the appliance, prefferably in a seperate port. The vent is normally piped down to within 3-4" of the floor to prevent anyone from being scalded.
This is how most boilers and hot water heaters are vented.

That is exactly what I did. I replaced where the pressure relief valve normally is on a hot water heater with a "T". I re-installed the PRV at the top of the "T", and connected the inlet from the stove to the side of the "T". This is the highest and hottest point in the system. Then a line is run from the PRV down to the floor.
Tom

I have two relief valves, one by the stove and the other at the termpering tank. Both are vented to the outside of the house thru the rim joist. If it blows there will be no water in the house. It can also be vented to a drain or slop sink. Would hate to come home or wake up to a mess. So far they have not blown off, that I know of.
Stay warm, Jimmy

Well, I finally got the new tank, (30 gallon), installed and the free hot water is flowing again. This time I installed one that fits and works better for thermo syphoning as opposed to just using what I had available for a tank. This is just amazing. I finished hooking it up last night about 9:00 PM, took my shower and then by 2:00 today the pressure relief valve is ever so slightly opening up. In just 15 hours I have more hot water than I could use.
Tom

rouxzy wrote:This is just amazing. I finished hooking it up last night about 9:00 PM, took my shower and then by 2:00 today the pressure relief valve is ever so slightly opening up. In just 15 hours I have more hot water than I could use.

Pardon my ignorance, but isn't this a bad thing? I mean, aren't you just dumping hot water down the drain every time the valve pops? Water isn't free (well or city) so do you think that you're actually saving money heating with coal? I'm not trying to be rude, but I really am interested in the idea of saving money and having unlimited hot water -- but if it's cost prohibitive, perhaps I'll go with a smaller coil or larger tank and just use it to preheat the well water.

Yeah, but pumping a few extra gallons of water from a well is WAY cheaper than having to heat all that water up.. If you learn when the tanks about ready to start blowing off run the DW or run a load of wash if necessary

Why is the pressure relief valve opening? I have a domestic water heat exchanger also and I don't have that problem at all.

I plumbed it like this.
Hot water continually circulates into the water heat exchanger.
When someone turns on the hot water faucet the cold well water from the well refills the hot water tank. on the way to the hot water tank the well water runs through my heat exchanger, to be heated up by the coal boiler and then into the hot water tank. It isn't scaulding hot because it mixes with the water already sitting inside the hot water tank and my boiler only heats the circulating boiler water to 170deg. and when the cold 55deg +- water only heats up to about 105+-.

I just don't understand why your pressure relief valve is even in the equation.???
Maybe LsFarm can shed some light on this...

Well lets see if I can explain.

The hot water loop is in the coal stove, it collects heat from the coal fire any time there is a fire in the stove. It will collect heat from the coal fire even if the water in the loop is near boiling.

There is no thermostatic control of the water temperature in the hot water loop, it just thermo-siphons the hot water to the water tank any time the loop in the stove is hotter than the water in the tank, which is any time there is a fire in the stove.

Said another way, the hot water loop is transfering heat from the coal fire to the water tank anytime there is a coal fire.

So... any time the hot water tank hasn't been asked to give up hot water for several hours, and the coal fire is burning, the heat collected by the loop can exceed 212* and the relief valve will open.

The advantage to this system is that the water in the tank will always be quite hot if the coal fire is going. Unlike KTM's and my system, where if no hot water was used for say 18-20 hours, the water temp in the tank may drop low enough to trigger the electric or propane heater to raise the water temp up to the tank's minimum setting.

What KTM, myself and others do is run the hot water for a few minutes before going to bed at night, this fills the tank with hot water from our heat exchangers and hopefully the water temp stays high enough through the night that no electricity or propane is used while we sleep.

I think that explains it... Greg L

What I would recommend, is if the PRV opens often, then add a length of radiant baseboard finned tube to the return line from the tank. Then the return will give up a fair amount of heat to the room, less heat with warm water, a lot of heat with very hot water. This will help 'regulate' the water temperature.

Greg L

LsFarm wrote:What I would recommend, is if the PRV opens often, then add a length of radiant baseboard finned tube to the return line from the tank. Then the return will give up a fair amount of heat to the room, less heat with warm water, a lot of heat with very hot water. This will help 'regulate' the water temperature.

That makes great sense. Might as well use that extra heat.

Does the cold water inlet to the hot water coil need to be above the coil for thermo siphon to work?
Chad