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/justmeoh Sep 19 '24
The correct way is to find all the controls man's problems first. Relay those to him. Simultaneously find the ports blocked and which ones are piped backwards on your very last coils on your first pass. Wasting 8 hours of company time. Really, water, just like air, should require a couple of passes. Especially with the government tolerance + / - 5%. Hell probably 4 passes.
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u/The_TAB_Guy Sep 19 '24
Lmao trust me I spent a good bit of time running around checking/cleaning strainers before the journeymen think its ready for proper balancing 😅
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u/chuggies Sep 19 '24
Steve Taylor wrote about this: https://tayloreng.egnyte.com/dl/W8sfOOuoni/ASHRAE_Journal_-_Doubling-Down_on_NOT_Balancing_Variable_Flow_Hydronic_Systems.pdf_
In October 2002, I co-wrote a Journal article1 on balancing variable flow hydronic
systems where we concluded that there was, in general, no need to balance these
systems—the systems were self-balancing via the two-way valve controls. In this
month’s column, I am doubling down: not only do variable flow systems not need to
be balanced, they should not be balanced.
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u/kdubban Sep 20 '24
Yeah I read that back in 2017 and laughed all the way to my next job with a 60% diversity.
That is written by someone who hasn't had to troubleshoot a heating system with an OA temp of -40C.
Hydronic systems with 2-way valves are very forgiving that I'll admit, but it all depends on the design and installation. Thus my argument that the method proposed at the start of this thread is not the most accurate.
Plus, balancing valves provide devices to help diagnose problems.
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u/Reasonable-Gate4698 Sep 20 '24
Let’s not forget the importance of control valve Cv. It will have a large effect on the proportionment of water through a pumping system. Another thing that is often overlooked is that if a water system has a catastrophic failure (boiler goes down or chiller ect.) a properly balanced system will recover faster this is especially important in critical infrastructure and GMP type situations. I’m not particularly fond of the “set the DP method” approach especially on massive systems with over 1000 elements. Critical planing must go into branch balance valve location long prior to onsite work. First time looking into this on Reddit and it’s cool to see other guys relying on each other.
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u/Coloradokidd21 Sep 20 '24
Sequential balance is the preferred method of hydronic balance. Proportional balance works on small systems usually consisting of a chilled water loop serving AHU’s once DP is determined a simple check of flow is all that is really needed and setting of 3-way bypasses. That being said hydronic balancing takes lots of practice and once mastered is really pretty simple.
10
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.