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Help hooking up circulation pump. Jean Pain mound.  RSS feed

 
zeek mcgalla
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I have an existing electric hot water tank.  I am making a Jean Pain mound to heat my domestic water...I have a Taco pump to circulate but how do I hook it up? 
Thanks
Zeek
 
Travis Johnson
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zeek mcgalla wrote:I have an existing electric hot water tank.  I am making a Jean Pain mound to heat my domestic water...I have a Taco pump to circulate but how do I hook it up? 
Thanks
Zeek


I don't think you can.

An electric hot water heater has only one tank and electric elements slip inside it and heat up the water. The key word there is ONE. You really need a hot water tank that has two tanks...one inside the other...or a coil inside it. The only thing you could do, is dismantle the metal jacket from around the electric tank, take off the insulation, wrap the water jacket on the outside with copper tubing, and then plumb that back to your circulator. Then put back the insulation and redo the metal jacket to help try to hold that heat in. It would be inefficient at best however.

You still; for SAFETY SAKE, have to have a 12 pound relieve valve so that if the compost pile gets too hot (while unlikely to flash to steam) must have a way to be released. You will need to have some way to control the circulator as well, or you could overheat the electric hot water heater. If that happens the water would flash to steam and your relief vale on the electric hot water heater will release. Please vent this to the outside and realize relief valves are mechanical in nature, and thus can fail. This would be bad, but probably not as bad as your family having scalding burns.

To deal with that you should have a PLC and Relay control set up with priority settings so that the circulator only comes on when there is a need to maintain the hot water heater at a certain temperature. When it does not call for heat, it would shut off the zone valve going to the hot water tank coil and open up another what is known as a dump zone. This could be as simple as an old cast iron radiator...anything that will dissipate heat quickly. That is the BEST way, but an expensive option as plc's and relays are not cheap. Normally I would just suggest a programmable 120 volt timer to pump the water around the hot water heater only when you need it, but the problem is, unless you use copper or steel pipes in the compost pile, plastic pipes will melt if water is not constantly being pumped through it.

Interesting though; I was just talking today to my wife about doing a compost heating system this year for us. We got the plc, zone valves and relay system, so for us it is just a matter of hooking up the circulator and lots of pex pipe. Like you, we only have an electric hot water heater, so to get the double tank we need, we are using a wood/coal boiler primarily for the water jacket. It has a domestic hot water coil so that will heat our domestic hot water. It will also give us 25 gallons of storage capacity and relief valve for the compost pile side of things.
 
Kevin Derheimer
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Location: Fort Myers, fl - Durango CO
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In my house in Florida, I had a heat recovery system hooked up to the condenser of the air conditioner.  It was a commercially available system that had a taco pump in the box outside as well as a heat exchanger.  The hot line from the Condenser was routed to one side of the heat exchanger and contained refrigerant.  The other side of the heat exchanger was a loop that went from the bottom of the water heater thru the heat exchanger and back to the top of the water heater.  I have worked on a number of these systems when replacing water heaters, and what I did was to first remove the cheap boiler drain at the bottom of the heater, install a brass nipple of appropriate length to extend just past the outside of the metal, then add a brass tee. One side of the tee gets a street ell, close nipple, full port ball Valve, and hose adapter.  The other side gets fittings to connect to loop running to heat exchanger, usually 1/2" soft copper, but I have seen pex used, but worry about high temps. On the top of the tank, you have to remove the plastic heat trap, this is usually a flap inside an insert, if you don't remove this, the water has a hard time flowing back into the tank.  A simple tee at the top allows connection to heat recovery loop.  The box outside has a thermometer attached to the lines to control operation.  My experience with the one on my water heater was great, I shut off the breaker in the summer and never had a problem with lack of hot water.  I will say this tho, I have replaced a fair number of pumps, but most repairs were to replace the pipes on the water loop side, for whatever reason, the pipes on the heat exchanger loop failed whereas the rest of the house plumbing was fine.  So, there is a commercially available product out there that may work for you.  It's not designed for your application, but may work.  The way I see it, is you would need a loop in the mound with a pump to circulate fluid on the side normally used for refrigerant, this is normally a passive side since the AC condenser pump moves the freon.  The loop to water heater would function as designed, the pump inside the unit moves water In the water heater loop.  All of the systems I have seen were on a conventional water heater, taking cooler water from the bottom and dumping hotter water back in the top.  I always provide a full port ball valve on the bottom so the heater can be flushed, important when sending water through the heat exchanger.  Some units I have seen have a filter to trap sediment before the heat exchanger, not one customer had any idea how to service the heat recovery system, and a couple were never even turned on because the plumber had no idea either.  So, flush heater regularly, and inspect and replace anode rod if necessary.

Travis is correct In stating the need for controls, but if you can find a heat recovery unit, they are built in.  This is definitely a project for someone with advanced diy experience!  I have worked on these systems and used one myself, so I would be very comfortable adapting one for an alternative energy project, but would recommend caution to anyone who has never touched one, or with little plumbing experience.

One other thing, with the efficiency of AC systems increasing (high seer ratings), I don't see heat recovery systems on water heaters any more because of less waste heat being seen at the condenser.  You won't see these units at a big box store, I'd look online if you go this route, unless you can buy from a supply house.  Search for "AC heat recovery".  If you are really handy, you could look for a used unit and take it apart and refurbish it.

Good luck, and let us know how you ended up making this work.
Kevin
 
zeek mcgalla
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hmmm so it seems like I have been told I can't do it...and then how to do it.  It is totally possible with just a circ pump, and there is a T&P valve installed on the hot water tank.  I am simply trying to hook up a circulation pump to keep water moving through the mound.  Typically this is a loop that moves water into the top of the tank (cold water inlet), then out the bottom, through the compost mound and back into the tank.  I am thinking I could put a Tee in the cold water inlet that is connected to city water with a check valve above the Tee and run the loop that way.  My main question was there is pressure in the tank at all times so when you open the hot water faucet hot water flows, will the pump be able to circulate despite the pressure?

Go here, http://compostpower.org/node/24, and look at step 10 and let me know what you think.  There are many examples about hot water re-circulation pumps that do not use anything but a pump.
 
Travis Johnson
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We are telling you that it cannot be done the way you are want it to, then explaining other alternatives (workarounds) to the problem that will net you the same result.

Heating water is VERY easy, heating water so that it does not flash to steam and blow up is another thing altogether. Heating water up so that it does not scald your family and cause third degree burns is yet another.

That means controlling the water and there is a lot to that. Kevin and I are basically describing the same thing, just with different applications. I was suggesting each component required and he was describing a unit with all the controls already in place.

Basically what you are suggesting is turning two systems, the Jean Pain mound heating system, and your families domestic hot water needs into one, and that just cannot be done. What you need is a boiler mate hot water tank, which is two tanks in one. Even then you need the controls to efficiently operate it.

It does not matter if heating the water is done with a Jean Pain mound, a propane boiler, or a rocket stove, you cannot drink water from a closed loop system, nor fail to protect it by pressure relief valves. If you ever smelled rancid boiler water, you would know why. However in a lot of ways a propane, natural gas, electric, or oil heating system is FAR easier to plumb because the appliance itself can be regulated. I can shut down any of those units in an over-heat situation which cannot be done in a Jean Pain mound. It is just going to remain hot for months, probably hotter than what you or your family wants.

Doing what you want is entirely possible because hydronic systems can do so much. I am ideally situated for it at my own house, but it is VERY expensive. My boiler was only $1800, my entire system with all the controls was $10,000. In other words $8200 went just to control everything. There may be some cheaper alternatives, but here is a link to show the power of water getting too hot in an electric hot water heater. As I said, they can, and do fail...

webpage

 
zeek mcgalla
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I currently do what you suggest is impossible with my Hardy H4, see pic.  The water flows through the 75 foot  3/4" copper coil that sits in water in the Outdoor wood boiler (OWB) which is about 185 degrees.  When the hot water is opened in the house the cold flows through the coil in the boiler and comes out hot and fills the hot water tank in the house; this is standard for many domestic water loops in outdoor boilers...well boiler is the wrong term as it is not pressurized.  All I am going to do is add the compost loop in series with the existing coil in the OWB and as I think about it I probably do not need any pump as my current system does not have one.  I would imagine that after the water flows through 400 feet of pipe that is buried in compost it will come out warm to hot.  Isn't that exactly what the tank-less systems do?  In fact I could totally bypass my how water tank in the house and basically have a tank-less water heater and I have done that in the winter when the OWB is fired.
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Kevin Derheimer
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Location: Fort Myers, fl - Durango CO
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Zeek - as to your main question, there is no problem with the circulation pump continuing to function properly when you open a faucet. Yes you are reducing pressure, but you are not introducing air into the system.  The circulation pump will function as long as you don't break suction, with the pressure being atmospheric or 60 psi.  Hot water recirculation loops function under the same conditions.  There is no need for the check valve at the top of the water heater, water will flow through the tank in the proper direction due to the action of the pump, pump may have check valve in it.  I would put a tee at the bottom of the heater to allow flushing.  i would sanitize the loop going to the mound since it will be part of domestic hot water.  Do you have any danger of freezing? Either insulate lines between house and mound, or bury below freezing depth, I would insulate anyway so you are not loosing heat to ground during circulation.  Step 10 mentioned a pressure tank, you mentioned city water, so you should already have a small pressure tank installed close to the water heater, if not, I would install one, it serves to dampen pressure fluctuations from city water supply as well as pressure fluctuations from heat from the mound.  If you had a well, the well pressure tank would service that concern. 

The system described on compost power is very simple, I don't see a problem with their simple loop.  You will be running the pump 24/7, but it draws very little current.  Only issue I see is the target temperature, compost power said you could expect temps of 110-140,  if you only use the mound to heat water, you may not get hot enough to prevent bacteria growth in the tank, legionella needs min 140 degree to kill it, water treatment industry thinks min 22k cases of legionella per year and maybe 1/2million cases of pneumonia are legionella misdiagnosed as pneumonia because hospitals don't test for legionella.
Our municipal water treatment plants dirty little secret that doesn't get talked about, is that most do not sufficiently treat for bacteria and virus.  Most are still running on 50's technology, and are not forced to change unless there is a highly publicized problem, like with Los Angeles or Milwaukee.  So, this is probably more than you wanted to hear about water safety concerns, but sounds like you are using city water, so just a word to the wise.  If your loop was for hydronic heating, then no problem, but domestic hot water use brings up safety issues.

Will you put thermometers on supply and return lines to measure heat gain or loss from mound?
Kevin
 
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