Primary/secondary piping

Jason_13

Am I wrong? I was always told that he primary pipe is the pipe the close spaced tees were mounted on and the secondary came off the bulls or branch to the tees.

Others say the primary is always the boiler piping.

Which is correct.

jonny88

[piping

go to the tool bar on top of page,click on systems scroll down to hot water and there you will find everything you need to know

RJ_4

primary

Seen it both ways, as long as your consistant when describing it and you fully understand the concept.

Paul48

True

It really doesn't matter how you refer to them.If you apply them by the book, you get the same results.....circs that can pump at different flow rates in a system without interfering with each other.

Ironman

Clarity

I have found that it helps to clarify the situation if we classify the primary as the loop where the expansion tank is connected and has the PONPC.



I've heard it both ways, but Siggy and every other manual that I've seen I.D. it that way.

SWEI

hydraulic separation

http://www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_1_us.pdf does a very good job of explaining.

Jean-David Beyer

I have found that it helps to clarify the situation if we classify the primary as the loop where ...

I find it clarifies the situation if the loop where something is is specified, and that something is also specified. It is my impression that most people (but by no means all) use the loop with the boiler in it as the primary. It is OK with me if, instead, people use the loop with the expansion tank.



But there are systems with what I might call tertiary loops as well -- where there is a loop with a lot of closely spaced Ts in it and the boiler is in one such loop  and the loads are some of the other loops. And when there is one of those load loops that is divided up with closely spaced loops ..., and the expansion tank could be in any of the loops...



At some point, the idea of primary and secondary may be less useful and drawing out the system and labelling the components is the only way to be clear.



By changing the definition of primary loop from the one with the boiler in it to the one with the expansion tank in it would change which of my loops is called primary. But it would not change how my system works at all.

CMadatMe

I Look At It

As the heat source is my "Primary Side" and the distribution as the "secondary side" taking away the btu/hr/gpm flow rate that it needs. There is no wrong or right answer.

HDE

Works both ways

Boilers are often the secondary flow injecting heat into the primary flow. This is mostly done when system flow (now the primary) can/will exceed boiler (now the secondary) flow. This often works better because a primary loop on a small boiler can see elevated return inlet temps affecting fire rate which lowers supply outlet temps.