Chilled water balancing
Balancing valves tell you what the valve is set to. A clamp-on meter tells you what the pipe is actually carrying. On a system that has been rebalanced three times over fifteen years, those are rarely the same number.
What you are actually chasing
Most chilled water complaints resolve to one of three things: a branch taking more than its share, a coil that has fouled and is passing less than design, or a bypass that somebody opened in 2011 and nobody closed. All three show up immediately as a flow number that does not match the drawing.
Reading a loop with a clamp-on meter
- Start at the plant room. Total system flow first, then work outward. If the total is wrong, individual branch readings will send you in circles.
- Insulation. Chilled water pipe is almost always insulated. You need to cut back a window roughly 18 inches long to clamp the sensors, then reinstate it. Factor that into your time on site.
- Condensation. A cold, sweating pipe surface fights the coupling gel. Wipe it dry immediately before clamping and expect to re-gel if the sensors sit for hours.
- Small copper. On 1 inch and under, use the 4 MHz sensor pair. The 1 MHz pair will not resolve it.
Delta-T and thermal load
Flow on its own tells you half the story. If the deliverable includes tons of cooling or a delta-T diagnosis, rent the UF801-P with the energy kit and take supply and return temperatures at the same time. Low delta-T syndrome is a flow-and-temperature problem, and measuring only one of them is how it goes undiagnosed for years.
Common measurement errors on chilled water
- Measuring within five diameters of a balancing valve, which is a deliberate flow disturbance
- Entering nominal pipe size instead of actual outside diameter on copper
- Ignoring internal scale on old steel, which changes the effective bore
- Trusting a reading taken while a variable speed pump is ramping