Between the Tees

radiconnection

If the flow rates are the same on both sides, say 10 GPM, is there any flow between the CSTs? Or, is it stagnant, for lack of a better term. I alway thought both flows passed each between the CSTs, but does the flow instead go directly from primary to secondary in that case??

One other stoopid question: why do I see it stated that the diameter of the piping between the CSTs should be larger that used on either loop if The max. flow in the between the CSTs will never be greater than the difference of the GPM flowing in both loops?

What goes in must come out, but it has two ports to choose from :) It starting to clear up in my mind a bit..

radiconnection

Understanding flow between P/S CSTs

is the flow between closely spaced Tees the sum of both flows, and do both flows occur simultaneously in the space between the tees, or just the difference? I'm getting confused.

S Ebels_2

What goes in must come out

The confusing part of P/S is that you have 2 in's and 2 out's. One set on the primary and the other on the secondary side.

Let's say we have a primary flow of 20
GPM entering the P/S tee arrangement.

10 GPM leaves that flow and goes out to the secondary loop

The flow is now only 10 GPM in the primary between the CST's

At the point where the secondary dumps back in to the primary, the flow rate is back up to 20 GPM.

Now assume that the primary flow is 10 GPM

20GPM leaves the primary and heads out to parts unknown on the secondary. Where did the additional 10GPM come from?

It got stolen from the 20 GPM return flow on the secondary, actually reversing the direction of the primary loop inbetween the two CST's.

Meanwhile, 10GPM of the secondary return heads back down the primary wondering the the H*** just happened

Mark Eatherton

Simple math...

In your last scenario, the flow betwixt the tees would be ZERO.

Where did you see that the common piping had to be larger?

I've never seen that.

ME

radiconnection

Anedoctal information, and I can't from whom or where I heard it from at this point! But, all of this pretty much clears up the misconceptions, I can see how the flows work now.

Pete

s.brown

pipe diameters

Any drawing schematic that I have been given always mentions on a p/s system is to not exceed a max. 4 pipe diameters between the TEES

radiconnection

Shane, that would be the cross sectional pipe diameter between the CSTs, as in going to 1-1/2" diameter pipe between the CSTs, when the supply and return pipes to the outside tees are 1-1/4". That's what I was trying to say...

Pete

NRTDave

Better hydrinic separation...

Using larger diameter piping in the area of the closely spaced tees should result in less velocity there and therefore less chance of the flow from one circuit affecting the other.

Steve Ebels_3

Uni

That would be true but it's the pressure drop or rather the lack of it that makes P/S piping work. That being said, I usually make a practice of doing what you described using a WebStone P/S tee one size larger than the pipe or tube.