Circuit Setters

Don Robertson

I am trying to balance some parallel primary loops and can't seem to get my head on straight. If you see the attached pictures the system balances just how I want it when there are no circuit setters. I can't figure out why the gpm through the branches goes down so much when the CV rating is added to the circuit setter. I thought it was the pressure drop that increased as you tried to get more flow through the valve. I have a 0013 and the loop has virtually no head loss but I need the GPM through the 1-1/2" 3/4" and 1" branches. These branches have closely spaced tees coming off of them which you can't see in the pictures. I'm not sure if my question is clear. Let me know and I can clarify.
Thanks
Don

Brad White_9

When the Cv is imposed

that essentially is placing resistance in the path which is why the flow goes down, especially when the other branches have no restriction. The N/A category in the drop down really toggles the balancing valve "off" and out of the picture. This explains the drop in flow.

The only purpose of a balancing valve is to impose additional resistance in circuits of otherwise lower pressure drops such that the pressure drops in all circuits are equal. In a perfect world, your defining circuit would not need any balancing valve and the one's closer to the pump or with fewer restrictions by nature, would have them.

Did that answer your question, Don? Let me know.

Brad

Don Robertson

Thanks

Yes Brad it does. My system is essentialy already balanced the way I want it. I think the problem I am having is I can not set the CV to 26 on the HDS simulator for the 1-1/2" branch. If I do the math according to the chart that came w/ the circuit setter I would set all of them to zero (fully open) because they all have the same press drop. I wonder if I should leave them in the job (just in case) or just take them out. How much will they restrict the flow if they are all open?
Thanks again
Don

Brad White_9

Cv if all are open

Check the charts for those, Don, in the 100% open position. That is your core (minimum)Cv.

You of course understand that this represents the flow rate at a 1.0 psi pressure differential. If you know your flow rates (and you seem to) your pressure drop will be calculable. Hydronic Design Studio, which you seem to be enjoying, has a Cv calculator built in as part of the Hydraulic Resistance Calculator module.

Of course if they are balanced, why mess with perfection?

Brad

Don Robertson

Thanks again Brad.

Thanks again Brad. I just needed a refresher. I've got it now!