ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Unexplained Power Consumption

Thanks for the replies. I've been to the job today.

I found the following problems: a fridge inside the cellar that was been refridgerated; chiller door seal broken; immersion heater on all the time (you get cheap rate electricity at night in the UK); vents blocked in air con units; food parcels blocking fan in walk in freezer; convector heater left on in room which is heated by LPG central heating; recent introduction of clothes dryers where use of washing line was used before.

Although none of these problems would explain the increase as described by the client I suspect that the increase business and attitude of the staff are the most likely causes.

There was a lot of electric equipment been used such as 9 microwave ovens, an oven keeping pre heated food warm, tea urn etc.

TSUK,
I'd go for a Data Logger on the Incoming Mains.
I've used these before to good effect logging Voltage, Current, PF and Max Demand.
They give a real-time "look" at what is happening in a circuit.
Your output is on a laptop.
Is this place spread over 3 Phases, with a Neutral?.
Refrigeration is a constant current once the compressor is started, only thing that would upset that would be if the thermostat was set too low or the contacts were welded shut.
The compressor would go out on high pressure after a time though

I suggested a Data Logger but it was a no go. The client was looking for one specific thing that was causing the problem and he was monitoring the units on the meter every day.

The installation was 2 phases with a nutral (the third fuse at the service head didn't have any tails coming out). One thing I haven't noticed before was the meter was the type with the spinning disk with both phases going into it. I've usually seen a meter on each phase.


[This message has been edited by TeesdaleSparkUK (edited 02-10-2006).]

Oops, a three-phase meter with only two phases connected? Could that unbalanced load cause trouble too?

I've never really thought about the typical 3-ph meters here, but are the voltage coils in them usually connected phase-to-neutral or phase-to-phase?

As long as all the voltage coils are energised the meter will be very accurate.
If one voltage coil is de-energised the voltage flux from the missing phase, its braking effect at light loads, may make the meter go a little faster in the order of around 1 to 1½ %.
This only applies to genuine 3Ø4Wire meters.
e.g. 3x230/400 Volts or 3x120/208 Volts with a Neutral.

Some 3Ø meters have the BØ PT coil wired with 3 wires in (not 100% sure) Scott type connection between the PT coils, so that these can also be used on 3Ø without Neutral as well e.g. 3Ø3Wire or 3Ø4Wire ccts.

In my days in meter calibration I have proved it on the test bench with a 3 phase meter running at 2Ø or even 1Ø. As long the other PT coils are live, the meter will be very accurate to within its class.

In New Zealand when with tariffchanges in the early 1990's, some older pumpsheds were converted from 3Ø to 1Ø it was not always warranted to fit a new 1Ø meter. ( Usage in some of these pumps is sometimes less than 100 kWh / Year). We left the 3 Ø meter on site and put PT jumpers in to the other 2 phases to keep the coils energized and the meter accurate. A lot of these meters were the Sangamo S 301.2 type, 66 2/3 rev kWh,
3 x 10 / 60 Amps, clockdial type

Lots of different meter pics thanks to Ray now posted in the Photos area here:

kWh Meter Types

If that were the case, they wouldn't be using a single 3 phase meter for domestic use here. The first house I lived in, built in 1967, had a single 3 phase meter, so they've been around at least that long. Obviously in a residential situation the current draw on each phase is seldom going to be equal. Older houses here have a separate meter for each phase and the kw/h are merely added together for billing purposes.

Well, I wasn't talking about current draw but about voltage at all. As said, if one voltage coil is not energized the meter will be off.

One other cause of short-cycling and no real cooling is a leak in the refrigerant lines.
or a shortage of gas in the lines altogether.
Until you get some gauges on the equipment, you have no idea what is happening inside the system.
A set of Refrigeration Gauges is like our Volt-meter.
And to a degree a Current meter too.
System Pressure is a big part of Refrigeration.