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Help with system layout

I would like to get some advice on a system I am building for my house.

I have read a huge amount and my brain is crazy spinning now.

Here are some details.

The house is off Grid with no power lines for miles.

There is an advanced solar photovoltaic system installed so though using huge amounts of power is a problem the power itself is very clean and reliable.

The house has an open radiant floor system so must be separate from the boiler.

The boiler is a wood gasification boiler, BioMass 40 from New Horizon and will produce 140K BTU.

There is a 1300 gallon insulated stainless steel water tank for use as thermal storage that can be pressurized to 12 psi.

The heat load for the house was calculated at 66K BTU

I plan on heating a swimming pool from this system.

I plan on heating a 1200sq foot shop with this system.

The domestic hot water needs to be heated from propane in the summer.

There needs to be a propane boiler backup for vacations (hah, as if I ever get one.)

Money is tight.

I found a design at

<a href="http://contractormag.com/columns/eatherton/alternative_energy_interfaces_3/">http://contractormag.com/columns/eatherton/alternative_energy_interfaces_3/</a>

by Mark Eatherton that I like and modified to fit my situation. I hope

he does not mind.

I have included the modified drawing. I would like your opinions on what I have done. I have a mixing valve with a question mark and was wondering if I could by pass the thermal storage tank (buffer) when the tank is not being heated enough to heat the house i.e. if the tank is below 130 degrees and the propane boiler kicks on then the heat from the propane is traveling the primary loop without entering the buffer? I would also think that in the summer and the solar was working well then the heat would get above 130 and start diverting to the buffer tank.

In the drawing Mark says "many components have been omitted for drawing clarity" Can you fill me in on what some of those components are?

Thanks in advance for your help.



  • ErikAkia
    ErikAkia Member Posts: 2
    bigger picture

    I noticed that the picture is very small and could not figure out how to make it bigger.

    Here is a link to my flickr page with a bigger picture.



  • Gordan
    Gordan Member Posts: 891
    Sure, you can bypass the tank.

    You could pipe in an electrically actuated diverter valve to bypass the whole tank and mixing valve (with question mark) assembly, and tie it into a differential control which activates the diverter valve if the temperature at the top of the storage tank is lower than the temperature at the inlet to the storage tank. That would be a simple alteration to your diagram but probably not the most elegant one.

    You could do the same with a 3-way zone valve that gets actuated by the same control that decides that the boiler should get a call for heat. This is even simpler, but you're not extracting the maximum of BTUs out of the tank (when the tank is cooler than your needed supply temp, but warmer than the return temp.)

    Is it necessary to have so many plate HXes in the whole scheme? Could you simplify? For instance, you're not heating DHW when you're away - could that be supplied by a separate set of tappings directly from the storage tank? What's the deal with solar - where is its storage? Basically, I think that you need to think about various operational modes and think of the simplest way to accommodate them. All those pumps and controls consume power.
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