SF-250 hot water coil

Hi Dave, you can use both tanks or just one. You could have your stove and tank thermo-siphon if you want, and save the expense of a circulator pump.

I see no reason that you couldn't have a pipe on the side of the firebox instead of on the top.

To setup the system to thermo-siphon, you would want to have an upper and lower fitting for the tube in your stove, and an upper and lower fitting in your tempering tank.

You probably would use the normal in and out connections at the top of the tempering tank for the water in and hot water out to your new electric tank. Just put the tempering tank in series with the cold water line.

In the tempering tank, use the side outlet where the overheat/overpressure watts valve comes out as the stove water inlet, and the drain valve fitting at the bottom of the tank as the outlet to the stove's loop. The heated water in the stove will rise, and the cooler water from the bottom of the tempering tank will migrate into the bottom of the heat loop, and 'round and 'round it will go.

Or of course you could add a circulator pump in the system. And if the water gets too hot add a length of baseboard finned tubing to the loop and you will have more 'free' heat in the basement.

Hope the above makes sense.

Greg L

I modified my hot water coil to allow the hot return to enter the second or other remaining port on the hot water tank. Oringinally I had it entering the same port as where the main tank relief is piped.. With only two ports, I would perfer the return enter the tank away from the hot water to the house BUT I have no choice but to share this connection. See images. Keep in mind, the relief has an 8" plastic stem so it must enter directly into the tank of water. The second port actually curves up through the insulation feeding directly into the top of the inner tank thus not allowing the 8" plastic stem to screw into the fitting. I also have shutoff valves and a bleed valve if I need to isolate the coil from the stove heat. I haven't turned on the electric to the hot water heater in over two weeks.

I haven't removed my fire box reducer yet so I am only heating at 50% and I can maintain 150F - 170F on the return line. The temperature in the tank is about 160F. A mixing valve may be in order yet, we'll see in a few weeks when temps drop into the lower 20's.

Here's an article I found very useful about everything we have been talking about here. Thought I would share it.

Finally got mine hooked up and have been running it for a week now. Mine runs into the return line of the baseboard behind my stove, 10 feet from boiler. I have that zone wired on all the time, and I shut off the oil boiler. It was 24 last night and the water coming out of the stove was 110, enough to keep the lower rooms in my house toasty, in addtion to the convection heat of the stove. It's not hot enough to take care of the tankless hot water coil in the oil boiler, so I've been turning on the oil in the morning for showers and then shutting it back down again.

I have about 16 feet of 3/4" stainless in my stoker, I squared off the coil to keep it out of direct line of fire from the coal bed, to not get it too hot. I think I can bend one or two of the loops into the fire area to pick up more direct heat, now that I know what it will and wont do.

Then again, the stove is not running its strongest yet.

Over all, I'm happy with the results, and there's still a good chance it wil perform better with the coil tweaking.

I ordered a Groundfos water circulator pump to add to my hot water coil. The system I put in has been working to a satisfactory level but once the water at the top of the 80 gal water tank gets very warm ( above 160F. ) , the natural migration tends to slow. My thinking, if I install this 1/25 hp pump which is on the very small side for a Groundfos, I should be able to heat almost 100% of the water in the tank rather than just the top 33% which is what I believe is occurring now. I hear complaints from family members of the water becoming cold after back to back to back showers.

As of now, I am always on the look for the domestic water becoming overheated as the tank will relief at 200F. So I cannot fire the stove on high without shutting off the water. This pump should allow a longer heating period since I should be heating considerably more water.. I'll let the list know how it works next week.

You may have long term problems with your pump if you ordered an ordinary boiler water circulator pump. What is the pump casting material? Circulator pumps are designed for closed loop use. That is they circulate the same water over and over. In an ideal situation this boiler water is non corrosive and inert. When it's not, over time the cast iron pump casting will be eroded. It's usually not a problem in boiler use because the oxygen in the water is removed by the air purge scoop and the boiler water is eventually self neutralized. Pumping hot domestic water is the worst case use. High temperatures and continued fresh water with lots of oxygen in it. The solution is a pump casting make of bronze (expensive) or stainless (very expensive).

A better solution has two stainless heat exchangers one in the stove and one in the bottom of the tank hot water tank. The pump is then always pumping the same water. As expected these water tanks, known as indirect hot water heaters, are expensive.

Yanche

Yanche has a point about the corrosion of an iron body pump. BUT I have used these iron pumps with almost 100% success in fresh-water oxygen-rich systems for years.

The Taco 007, the Grundfos, and other small iron pumps can be bought for ~$50-70. About a third to a fifth of a bronze or stainless pump.

I treat the iron pump as disposable, but have had to throw away none over the last 10-15 years. I had only one fail to start up after sitting for two years unused. I opened it up and used a small wire brush to clean off some rust on the pump body, reassembled it and had it back in service in about 30 minutes. I currently have seven small iron pumps running in my various heat systems at the farm.

I would plan on removing the pump, drying it out each summer. this should take about 30 minutes if you put shut off valves on each side of the pump. You could just remove the motor and circulator, opening up the pump for a wipe-down and spray of rust inhibitor, or remove the whole pump and blow it out and let it dry. Either way I believe you can get many, many years from an iron pump if treated well.

So the Bronze or Stainless pump are best, but the iron pumps will work for many years from my experiences.

Hope this helps. Greg L

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Yes, I am aware the cast iron are for closed loop, SS & bronze versions are very expensive and NOT in the scrap dumpster. I'll be installing a strainer after it to catch any particles. Will 100 mesh screen be too fine? 100 mess flows lin & lox so it should flow water unless it gets crudded up.

Hi Mark, I don't know that a filter is necessary, not a bad idea though. I've never installed one. The clearances in these pumps are pretty big, they can be measured with a tape or ruler.

The one pump I had stick just had a few rust spots that got be about 1/16" tall and touched the pump impeller. This happened when the pump was not running. These motors have virtually NO torque, so the motor just couldn't start moving. I just scraped the rust spot with a pocket knife, and brushed it with a wire brush and reassembled it.

I don't know how much a filter would slow down the circulation, I have no experience with them. I think since you are pumping fresh water from your water system, it should be free of sediment?

Looking forward to the results of the pump install.

Greg L.

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Like Greg says you don't need a filter screen. All my experience is all with Taco 007 pumps. In closed loop circulator use they last forever. In a solar hot water application cast iron pumps would fail. A bronze replacement did not. I use cast iron 007's in primary-secondary piping systems to direct water flow. A pump is much cheaper and more reliable than a solenoid valve. A word of caution though. The rotor cartridge has a water lubricated ceramic bearing. If it's been used and then removed from service it may seize up. Maybe it's my acid water ph = 5.7 but it has happened to me several times. Now if I making plumbing changes and the pump will be open for more than a few days I remove the cartridge and put it into a closed container of water. BTY you can buy replacement cartridges cheaper than a pump. The high end Taco 007 controllers cycle on the pumps in the off season, 10 seconds every three days to prevent seize up.

Yanche

Maybe it was the ceramic bearing that siezed on my Taco 007 pump! When I took it apart, I thought it was the rust spots, but it could have been the bearing, I just gave it a spin and returned it to service. It could have been either or both.

Yanche, you had a 007 pump fail from corrosion? Did the housing rust through? or grow so much rust it siezed the rotor??

I guess I've been lucky so far with my pumps. I keep two spares in stock, they were bought real cheap off of Ebay so I don't have a lot of money sitting there.

Greg L

Greg, Yanchi--

The reason for the strainer? I have very hard water. I see lime buildup around one fitting that leaked just a few drops for over one week. This leak was on the hot side.

Maybe someone understands the reaction that takes place? When water in my area is heated close to a boil, the lime silt will be left behind. You can find it in tea pots on the stove too. If I steam off water for humidifying purposes, lime sediment will build up in th container.

Is the bottom of my 80 gal tank building up with sediment too?

( This may need a whole new thread. )

The strainer will blind over time, but is not a bad idea, it will require periodic cleaning or it may cause problems.
Most well water is fairly hard, some is very hard and can cause a lot of problems. A simple test, put a large pot of your water on your heat source, when the water is gone and you have a fair amount of white crap left in the pot, you have a "hard water situation".

Mark, I grew up in the Lehigh Valley (Alpha) so I know the lime deposits you are talking about. While I'm no expert as I understand it the lime results when you change the water from a liquid to a vapor. This can be done in two ways, raise temperature to boiling or lower pressure so that the water boils at room temperature. In either case since you have gotten rid of the water only the minerals are left behind. When you are using a pump to transfer heat from the stove heat exchanger to your hot water heater there is no evaporation of the water, therefore no lime deposits created. Now if you run your stove so hot that the water boils and the steam is released by the safety valve you have the conditions for lime build up. I once removed galvanized hot water tank that was heated by a coal boiler. When I cut it apart there was some lime but nothing to worry about. It had be in service for 40 years using public water that comes from the same underground aquifer as your water. I think the lime protected the tank from internal rusting!

Yanche

Greg, I've had two types of 007 pump failures. The first was in a solar hot water heater application. A cast iron pump was used to pump potable hot water from a heat exchanger to the hot water storage tank. The casting rusted around the pipe threads. After years of experience with my acid water I have some theories. A pipe tread joint is nothing but a leak with a circular path. You fill that joint with pipe compound or teflon tape. Over time the joint filler starts to fail. A leak develops, hardly seen at first, especially if it's hot water because it evaporates. My acid well water, when hot and when open to oxygen in the air is especially aggressive. It just eats all metals except 316 stainless. I now use GE high temperature silicone RTV rubber as a joint sealant. I apply it carefully to both male and female threads.

My other 007 failures were in closed loop circulator heating applications. Seized rotor shafts. Impossible to free up using force and/or industrial strength penetrates. I suspect it my be unique to my water. Solved by never allowing a used pump to be dry. I also now neutralize my boiler water. Another whole story.

Yanche