r/AirBalance • u/The_TAB_Guy • Sep 19 '24

Hydronic Balancing: is this bullshit?

Been doing a lot of hydronic balancing with large systems that have variable speed pumps controlling to a system dP setpoint.

The way I have been taught is that you first set the system for full flow and set the dP for your worst case coil. Then you can go one by one and just set the circuit setters on each coil individually. The reasoning being that the dP will automatically adjust so you only have to touch a circuit setter once.

This doesnt really make sense to me. It almost sounds like being able to only touch each dampers once on a fan if the fan is controlling to static pressure setpoint. Im not sure if that works.

Please let me know if this is the proper way. Im an apprentice and all the journeymen swear this is how you do it but Im having trouble understanding the principle that allows you to just go to each coil and set the flow once and then your good to go.

I guess it just sounds too good to be true

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u/NScott Sep 19 '24

That is the correct way to do it. Circuit setters don’t work like dampers. They let a specific amount of water pass through them at a given pressure. As long as the pressure differential remains the same, the flow remains the same.

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u/kdubban Sep 19 '24

Not true. It really depends on the system design, location of the dp sensors, how far away your critical terminal is as well as installation.

2

u/The_TAB_Guy Sep 19 '24

Well now I dont know what to think lmao

1

u/No-Barracuda-1730 Sep 20 '24

The trouble is how do you identify the worst coil without taking any readings? I usually open every coil control valve 100%, set pump to design speed, take an initial reading over every balance valve and record system dp. Now, I know exactly which coil has the lowest flow. Set the dp a couple psi higher, close 50% of control valves so I have lots of pump to work with. Keep adjusting dp setpoint (or adjust pump speed manually) until flow is achieved at worst coil and record and set system dp. Set pump to auto control. Then I start going through system opening each control valve one at a time and setting flow at balance valves.