Measuring flow in a hydronic system

lkstdl

@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.

hot_rod

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

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hot_rod

A PT port with a pressure

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gauge connected to the “needle”

DCContrarian

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.

RPK

https://forum.heatinghelp.com/discussion/comment/1812366#Comment_1812366

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.

fentonc

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?

hot_rod

You can rent ultrasonic flowmeters online. That is the quickest, least invasive way to get accurate readings

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jumper

All zones open gives max flow. Only most distant open, minimum flow.