Primary & Secondary Loop


Old 12-17-07, 06:12 PM
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Question Primary & Secondary Loop

I am going to be building a new home and was going to install HWBB. I was thinking about using a Primary Loop around the perimeter of the home, and at each zone using a "T". On the primary loop I would use 1 1/4 or 1 1/2 pipe. I thought this way it might take less total pipe and during the winter might be more efficient. Would the heat loss in the primary loop be too much. What might some of the Pros & Cons be. There would be a circulator on each zone. I know it would be more wire to run the circulators.
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Old 12-17-07, 07:05 PM
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This could be a layout nightmare. If you want to do primary secondary with a primary loop all around the basement you need to do a heat loss. Now decide how many zones you want. Calculate the water temperature drop between zones. Now add more baseboard in each zone getting further from the boiler to get the proper heat with lower water temperature if previous zones are running.
The price to run the larger copper around the basement would be more expensive than the smaller secondary loops, which could be pex if you want.
Piping could be easier such as a simple manifold system or manifold system with one set of close spaced tees for hydronic separation.
Old 12-17-07, 08:12 PM
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Running 1.5 pipe to feed a 3/4 inlet to your rad is ridiculous. Your on the right track when you think of inefficiency's tho. Cause this would be right up there with the best of them. You need to save your money and get some help with an effective lay-out.
Old 12-17-07, 08:15 PM
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What you would be describing would be a monoflo setup because you would need to use monoflo tees in order to control the flows through any of the heating branches.

As rbeck says, it would be much easier to pipe this as a home run system. You could run " Pex-Al-Pex from a manifold out to each emitter. That's what I wish I had. I have a monoflo system but the velocity/flow required is quite wasteful of pumping resources and you have to bleed each branch individually if you get air in the system. With a manifold home run set up it can all be purged of air from the basement. It will also allow you to use TRVs on each branch for individual room zone control that is purely mechanical. On a monoflo system, stopping the flow on too many branches would actually make the heating unpredictable on the remaining open branches.

My monoflo loop is 1" with 3/4" branches.

Here's some info on monoflo systems.

If you'll ever be using a high efficiency low temp boiler, this layout sucks because the temps don't drop much do to the high velocity required to make the venturis in the diverters work.
Old 12-18-07, 11:40 AM
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I would still use primary/secondary by connecting the supply and return manifolds together and use one set close spaced tees for the boiler connection.
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