Un-Answered Question??

Dan Peel

from a "trinity", Dan

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Dave_22

I've asked this question before and never really seem to get a straight answer back..... Here goes- On a prim/sec system with close T's and no crossover bridges, the loads are supposed to be set up a certain way with the lowest temp loads at the end. Agree? Now what about when they are the only loads calling for heat- they are not low temp anymore because they will get the full boiler water temp. How do you protect them? Mixing valve? Thanks for "learnin" me!

Unknown

Yes

Usually the loads each have a mixing control on each pair of tees, unless they are baseboard with a thermostat.

Injection controls, or mixing valves are common.

I favor not putting the Indirect water heater on the primary loop, at all. As a separate pumped zone out of the boiler, the primary pump never has to run in the off season, and the primary loop never gets hot in the off season. No ghost flow potential in warm weather. Cheaper to run.

Noel

hr

It would depend

on what those zones are. If you had a slab with vinyl, or other temperature sensitive floor coverings, then it would be best to have a accurate mixing device. For small loads I think a 3 way thermostatic works fine.

Remember, if the loads are small enough based on the boilers total output the boiler return temperature shouldn't be a problem. I think 1/4 of the boiler output is a good rule of thumb.

In other words , if the boiler is a 100,000 output, then a 25,000 load would be okay for a single zone without return protection, as the boiler could stay in a safe temperature mode with that size load.

You are exactly right, there will be times when not every load (zone) will be calling to provide that graduated temperature drop along the primary circuit.

For a fun exercise play around with the various sceniros on Siggys Design Studio. Model the system and then drop off, or switch on, various zones and watch how the flow and temperatures to others zones are changed.

hot rod

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jim f

I favor not putting the Indirect water heater on the primary loop, at all. As a separate pumped zone out of the boiler, the primary pump never has to run in the off season, and the primary loop never gets hot in the off season. No ghost flow potential in warm weather. Cheaper to run.

Noel



like this noel??