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Please help me design my hydronic system.

Krash Member Posts: 17
We are building a 2100 sq. ft., plus 400 sq. ft. garage, home in the mountains of Colorado. The elevation is over 8,000 feet, and it gets darn cold. We are in climate zone 7.

I know the first question is have we done a heat loss calculation. The answer is we have done several of them, but they have all been a crap shoot because of our particular situation. I will explain. Here is a picture of our home just as we were being evacuated because of fire. The home survived.

Not easily seen is that the left rear corner of the house is almost completely buried in the hillside. Here is a view of the foundation just before being poured. All the walls here are 8” concrete and there is 3.25 inches of foam on both sides of the concrete. This is called ICF’s, or insulated concrete forms.

When backfilled, the left and back ground floor wall will be almost completely buried. Kind of a ½ walk out basement I guess.

All framing on the house is 2x6 and the R value of the framed walls is R 20, and the roof is R 49. This is a non vented roof, and using closed cell foam, will be extremely tight.

Having said all this, most of my heat loss calculations have resulted in 42-50,000 Btu’s. I am not sure this is even close to accurate, so I intend to size the boiler to be a little oversized.

The ground floor has 4 loops of ½ OX barrier PEX. One of the loops is in the garage at 300 ft, the other 3 loops are 250 ft each.

The second floor will be staple up with aluminum plates. (sheet or extruded)

All equipment will be in the ground floor boiler room under the stairs.

I was going to use tankless water heaters, but you guys have all scared me about that idea now. I reluctantly submit my design below using a two heater design to avoid the heat exchanger and to provide redundancy if one fails. I also have not used a primary secondary loop here. I have read that in small systems, it may not be necessary.

There are two things that puzzle me right off the bat??

1) If the supply and return on the heater is ¾”, what is the purpose of going to 1” in other parts of the system?

2) I understand the need for a primary and secondary, with mixing valve when high and low temperatures are required, but why would it be needed for a system where the whole system uses say 100-120 degrees?

Anyway, please feel free to re-design to your heart's content, and provide me with an education in the process.

One last thing, where I am building it costs a fortune to get tradesmen to work, and they rarely will show up anyway as they are working on multi-million dollar homes, so please don’t tell me to hire a professional. My wife and I have built this entire home by ourselves so far, and we will continue to do as much as we can.



  • hot_rod
    hot_rod Member Posts: 22,387
    Need to know the type of boiler, most like primary secondary piping or a hydraulic separator. If it is 3/4 it sounds like a tankless heater?
    If you can design around one low temperature that would be ideal..
    After the heat load comes a design, it tells you how many loops, spacing, supply temperature, gpm flow rate, etc.

    If nothing else hire out a heat load and design, then you can buy and install the pieces.
    If you use a high efficiency boiler, might be worth having a pro do a combustion analysis and get it all dialed in. Most factory warranties want that step completed.
    Look for Steve Minnich here, he does design work.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream