Measuring power use via circuit breakers at the switchboard

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timmmay

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#165579 13-Feb-2015 21:38

So, trying to work out where my power is used. Is there a safe, practical way to put something between the switchboard and the circuit breaker to measure power? That way I could measure lighting (it's on a circuit), hot water, my bathroom underfloor heating, etc.

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Vocus

#1237641 13-Feb-2015 21:47

There's inductive loop meters you can get, if you can access the L wires coming out from the breakers

hyperman

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#1237642 13-Feb-2015 21:51

Are you looking for a temporary measurement

if so as long as the circuit breaker is removable you could remove it and complete the circuit using a multimeter.
most multimeters are rated to 10A @ 240V

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SumnerBoy

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#1237643 13-Feb-2015 21:51

To get accurate readings you need both a current sensor (as mentioned by ubergeek) and a voltage sensor.

If you are the tinkering type, check out www.openenergymonitor.org. They are UK based but ship to NZ. There are a few GZ'ers who are using their system and they are a very friendly bunch.

You can buy the EmonTX which has 4 current sensors + 1 voltage sensor, so you can measure 4 different circuits very accurately.

Worth a look if you are happy to fiddle around a bit with Arduino sketches and the like.

ubergeeknz

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Vocus

#1237646 13-Feb-2015 21:56

hyperman: Are you looking for a temporary measurement

if so as long as the circuit breaker is removable you could remove it and complete the circuit using a multimeter.
most multimeters are rated to 10A @ 240V

DC only though. Also do not do this, it is very dangerous :) Most cheap meters are not rated for mains voltage and may not safely isolate you.

Jaxson

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#1237647 13-Feb-2015 22:00

Schneider do one like this. Basic, but works.

Oncop53

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#1237648 13-Feb-2015 22:01

Legally of course you cant modify the switchboard. If you have the old ceramic fuses though you could put a multimeter across the terminals.

k1w1k1d

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#1237651 13-Feb-2015 22:05

For temporary use you could get a clamp multimeter.

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Niel

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#1237655 13-Feb-2015 22:14

You actually get a multimeter lead set which plugs into a fuse holder, but it can be expensive (small market).

A clamp meter is clamped around a cable without having to break the connection.

Multimeters have a fuse, but be cautious of cheap ones. Only use ones that feel like they actually have the isolation rating (like Fluke).

Yes you need to measure true (and RMS) power as that is what you are paying for (in a residential setting), but if you want a good indication then a current reading by itself is fine. Power meters takes the phase in account. Companies also pay for the reactive (out of phase) power, but residents only for the real (in phase) power. Consumer goods do not use that much power, and they are tested to use little reactive power. The heavy users (stove, hot water, heaters, etc.) use virtually only real power.

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hyperman

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#1237656 13-Feb-2015 22:15

ubergeeknz:
hyperman: Are you looking for a temporary measurement

if so as long as the circuit breaker is removable you could remove it and complete the circuit using a multimeter.
most multimeters are rated to 10A @ 240V

DC only though. Also do not do this, it is very dangerous :) Most cheap meters are not rated for mains voltage and may not safely isolate you.

sorry to tell you but any HALF pie decent meter will handle 10A AC
this is also less dangerous than opening the back of the board to put on a clamp meter.

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Bung

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#1237663 13-Feb-2015 22:41

Very few circuits only carry 10A. Your meter could be restricted to measuring 1 of several loads.

gzt

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#1237709 14-Feb-2015 02:36

I'd have to say there are a variety of dangers when using a multimeter inline for mains current measurement. It is not something you want to use for any length of time. Quality of the meter and connecting equipment are primary, but there are other safety issues.

timmmay: Is there a safe, practical way to put something between the switchboard and the circuit breaker to measure power? That way I could measure lighting (it's on a circuit), hot water, my bathroom underfloor heating, etc.

I'd suggest taking a look at DIN rail kwh meters and asking for an electrician's opinion on legality on the switchboard. You must have these installed professionally. Most of these meters have pulse output available for future projects.

RS has a good quality example for $120. Same model could be half that price elsewhere in NZ.

Also there are cheaper brands available but some research is required to ensure you are getting equivalent quality with similar accuracy over power factor etc. Edit: For standard lighting or heating there is no power factor so maybe there is an economy to be found for those circuits, and pf may well be near enough to unimportant elsewhere anyway.

Throwing in a crazy example @$20(!) on ebay but maybe there is a happy medium in quality and supplier reputation somewhere else.

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richms

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#1237712 14-Feb-2015 02:49

The din mount meters I got off trademe work great. Board is too small to fully equip it but when it's upgraded I will get a mammoth one to take them and all the breakers to split off different zones of the house to get different amounts.

Richard rich.ms

richms

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#1237713 14-Feb-2015 02:50

Richard rich.ms

gzt

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#1237715 14-Feb-2015 03:05

richms: The din mount meters I got off trademe work great. Board is too small to fully equip it but when it's upgraded I will get a mammoth one to take them and all the breakers to split off different zones of the house to get different amounts.

Cool. How close does the total line up with your supplier meter for those?

richms

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#1237718 14-Feb-2015 03:10

I don't have them on everything. Just a circuit in the garage. Agrees with plug in meters to about 1-5 on pc type loads. It was measuring the meter too which is a pretty budget capacitive dropper power supply so poor power factor.

Negatives are a small cheap lcd which needs a torch to read because it's so dim where it is. Backlight would be nice. Also no amps, powerfactor, instantaneous power or volt display, just kwh

Richard rich.ms

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