Measuring flow in a hydronic system
Comments
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@jumper That's a good method when we know the curve. In my case many of the zones don't have a published curve (e.g. arbitrary amounts of PEX in a slab, with multiple loops that are approximately but not exactly equal).
What are people using for differential pressure measurement? I'm familiar with the one from Grundfos but haven't tried any of the cheap ones on Amazon.
Luke Stodola1 -
a good quality 15 psi gauge is all you need, valve it to both sides of the pump
PT ports allow you to check temperature and pressure, so you come up with all the actual data, GPM from the pump curve, delta T from actual temperature readings.
You need to run until thermal equilibrium is reached, steady state operation, then read the temperature delta.
A refrigeration manifold works also to valve either side. This example shows the pressure differential on a small circ.
The next Caleffi Idronics will detail how this device works. Remove the pump, insert this assemble to measure and define any circuit
This helps determine the ability to use a HP in a retrofit, by measuring the circuit as it exists
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
A PT port with a pressure
gauge connected to the “needle”
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Just to clarify the question, this is for a floor radiant heat system. I know the total system flow and heat output, I'm trying to figure out a way to calculate the heat output of each zone.
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This is a great method and good way to get a reality check if a balancing valve reading seems questionable. Just need a pressure drop and corresponding flow. Can be misleading if the device is fouled/plugged though.
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Do you know what the nominal output is at a given temperature? Or do you have no idea what the output of any given zone should be?
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You can rent ultrasonic flowmeters online. That is the quickest, least invasive way to get accurate readings
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
All zones open gives max flow. Only most distant open, minimum flow.
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