Loop lenghts

ALH_3

It depends on how the system is piped also.

Dont forget to take into account differences in lengths of distribution piping to manifolds.

If I'm running comomon supply, common return with the manifolds running in parallel, I shorten the loops farther from the mechanical room relative to the closer manifolds. Account for everything in the circulation loop.

Most manifold manufacturers have balancing built into their supply manifolds. Keep in mind if you use them you'll be pinching back every loop to match the one with the most head loss.

Using a delta-p valve will help you balance things better.

-Andrew

Andy Morgan_2

Loop lengths

When laying out tubing, what do you guys consider to be acceptable as far as the difference in lengths from loop to loop? We all know its nearly impossible to have identicle lengths in actual installations, although we try to. For reference, say on, a 4 loop zone, with supposed 250 loop lenghts.

Andy Morgan

Riverside Mechanical, LLC

hr

10% is the number

I have always used. 250, 275, or 225. I use 300 foot 1/2 PAP most often. I do my best to use that roll to the exact length.

For example, as I roll out I keep an eye on the footage. As I near the end of the roll I take the end back to the manifold and connect. Sometimes this loop ends mid slab somewhere. Then the next loop doubles back to fill in where the 1st loop ended. Make sense?

So in a large room with multiple loops you should always be able to use exact loop lengths. If the last loop is looking like more tube than you need just tighten the spacing a bit. Better than an odd length loop.

With PAP we can actually lay out the entire zone, with as many 300 foot loops as needed, before we tie any tube. This allows us to shuffle tube spacing to get that exact fit.

Of course small, 1 loop rooms that would not take a 300 foot loop would need to be cut.

hot rod

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WPH2205

This is for Hot Rod: I've only been on "The Wall" a short time, but I've been reading Plumbing & Mechanical for many years. During this time, I have come to realize that you are a radiant heat expert. I have worked in the trade for 22 years, and I am just now doing my first radiant job. I have some questions that I know you can answer, and I was wondering if you would be willing to help me out. Thanks in advance.

hr

I'm still learning also!

But I would be glad to share any knowledge I have. Ask away, or call 417-753-3998.

hot rod

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Tim Doran

Considerations

There are a few things that I consider when designing a system.
1) Are the loops all on the same zone?
2) Do they serve different rooms or spaces?
3) Are the loads the same (btu/sqft)?

When all thigs are equal it is nice to work with equal loop lengths and the rules of thumb that Hot Rod gave you work well. I would also suggest that you use a reverse return configuration to help eliminate balancing issues.

If the loads vary from one loop to another or if the loops service different zones a "dynamic" balancing approach should be used. This means that balancing by pressure drop alone may not be the best answer. Dynamic balancing takes into account not only the pressure drop but the flow required to support the design load and the characteristic curve of the selected circulator on a loop by loop basis. A bit more complicated but there is good data available to help make it clear.

Tim D.