Energy audits and BTU measurement
Thermal energy is flow multiplied by delta-T. Measure only one of them and you have an estimate. Rent a meter that measures both and you have a number you can put in a measurement and verification report.
What the energy kit adds
Surface-mounted temperature probes on supply and return, read by the meter alongside flow. The instrument then reports instantaneous thermal power and totalised energy, so your log file already contains the answer rather than three columns you have to combine in a spreadsheet afterwards.
This matters for M&V work because the totalisation happens at the measurement interval. Multiplying an average flow by an average delta-T over an hour gives a different and worse answer than integrating instantaneous power at 1 Hz, particularly on a system with variable speed pumping.
Typical audit deployments
- Chiller plant efficiency. Flow and delta-T on the evaporator side, compared to electrical input, gives real kW per ton rather than nameplate.
- Boiler and heating loop load. Same measurement, other direction. Useful for sizing a replacement rather than copying the old nameplate.
- Heat recovery verification. Measuring both sides of a heat exchanger tells you what is actually being recovered.
- Sub-metering feasibility. Two weeks of logging tells you whether a permanent BTU meter would pay back before you buy one.
Getting the temperature measurement right
Surface probes measure pipe wall, not fluid. On an insulated pipe with reasonable flow velocity the difference is small, but it is not zero, and it is worst at low flow. Two practical rules: insulate over the probe after fitting, and do not trust delta-T readings taken in the first fifteen minutes after installation while the probe and pipe are still equalising.
Deployment length
A day of data tells you about that day. Most audit work wants at least a full week to capture the weekday and weekend load pattern, and a month if there is a seasonal question. The UF801-P will log for up to two months on internal power using the sleep function, which is why it is the audit meter rather than the ProLite.