Estimating KWh electicity billing using clamp-on amp meter

Home Guy · 2011-05-28T00:17:01+00:00

I have a small commercial building with a 3-phase, 120/212 400 ampservice.The billing meter is in a locked cabinet (for which the local utilityhas a key) and out of this cabinet run 4 large cables (each about 1 or1.25 inches in diameter) that run to their own insulator or terminalblocks where smaller cables (3/8" diameter) connect to them and run toseparate panels and switch boxes.All of these large cables are black, and one of them is (I believe) aneutral or ground (it has a white stripe running down it's length).A voltage reading from this neutral wire to each of the other 3 terminalblocks is 120 vac, and voltage readings between the 3 terminal blocks isabout 212 vac.I have a hand-held amp meter (Fluke 31 true RMS clamp meter) which looksexactly like this: don't know exactly how old this meter is, but I believe it's at least10 years old and quite possibly 15 years old.The electrical devices in the building are typical for an office withsome very light manufacturing. About 15 desktop computers, many withsmall UPS backup, telephone system, some networking switches androuters, a few printers, flourescent lighting, a few soldering irons,microwave, coffee maker, fridge, water cooler / distiller. At this timeor year neither the building's furnace (forced air natural gas) or ACunit is running (the breaker powering the outdoor AC unit is off). When I put the meter clamp around each of the 4 large cables, I readanywhere from 10 to 20 amps on them during normal day-time electricalusage inside the building. During a test when all computers, monitors,printers and lights are turned off (but all UPS's are still turned on) Iread a total sum of about 4 or 5 amps across all 4 power cables.So my questions are:1) when coming up with a total current measurement, do I include thecurrent flowing on the neutral line? Should I indeed measure anycurrent on that line at all - or should the current on the neutral beequal to the sum of the currents on the other 3 lines?2) I am not...