Power metering

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danfaulknor

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#171796 1-May-2015 11:43

If I wanted to put some current probes around the cables coming into my power meter (as that's where they're exposed the best) am I going to hit any issues with that?
Say if my house burns down and the fire inspector spots the device where the meter was, am I going to get denied my claim?

Places like Jaycar sell them, but the one I have in mind is not wireless.

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#1294987 1-May-2015 12:33

This thread touches on power metering slightly. Interested if you could link to the product you're considering.

danfaulknor

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#1294993 1-May-2015 12:48

I'm looking at using the Ubiquiti mFI current sensors, plus the V meter from my UPS to give me a vague measure. I know it won't be perfect but I don't feel like buying a real power meter and trying to wire it in safely (because they need a power socket to get the power read)

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SumnerBoy

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#1295005 1-May-2015 13:18

Check out openenergymonitor.org. They have just released an all-in-one device (just recently been funded on Kickstarter). Or you can roll-your-own using an Arduino plus their EmonTX shield. I am using one with great results.

You chuck current clamps around the circuits you want to monitor (the EmonTX shield supports up to 4 CTs) and then plug a voltage adaptor into your mains to get the V readings. The EmonTx sketch does all the calculations and they have a pretty sweet server solution, EmonCMS, for storing and graphing the results.

Very helpful community if you get stuck. Worth a look IMO, relatively cheap and very customisable if you are that way inclined.

Aredwood

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#1295011 1-May-2015 13:27

I will be building one of the open energy monitor systems myself soon. As it is one of the very few that can calculate power factors. Any current clamp only unit will give incorrect readings for power used by electric motors and electronic devices.

SumnerBoy

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#1295039 1-May-2015 13:57

Keep us posted Aredwood - I would be happy to help with the setup/EmonCMS side of things if you are planning on a local server. You know far more about the electronics/power side of things however...

danfaulknor

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#1295077 1-May-2015 14:54

I guess the annoying bit about the real power monitoring is the AC socket requirement. I would either have to get a sparky in to add one right next to the external meters or have some very long cables between the clamps and the power cable I'm metering...

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SumnerBoy

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#1295080 1-May-2015 14:57

Yep - that is a problem often. But it is the only way you will ever get accurate power measurements. I was lucky enough to get my solar inverter installed right next to my distribution board so got them to wire in a socket when they did their connections etc.

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#1295083 1-May-2015 14:58

I just got one of these devices

http://www.neur.io/

Haven't installed it yet, but it does power monitoring down to individual appliance just by clamping your incoming power feed.

danfaulknor

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#1295087 1-May-2015 15:03

Sounddude: I just got one of these devices

http://www.neur.io/

Haven't installed it yet, but it does power monitoring down to individual appliance just by clamping your incoming power feed.

Too Cloud-y for me I'm afraid

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danfaulknor

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#1295088 1-May-2015 15:05

SumnerBoy: Yep - that is a problem often. But it is the only way you will ever get accurate power measurements. I was lucky enough to get my solar inverter installed right next to my distribution board so got them to wire in a socket when they did their connections etc.

Yep indeed. The only place I can put the clamps without putting them behind the switchboard is outside where the power goes into the meter, and you can't put a mains socket out there...

Is it just voltage it measures or something else?

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SumnerBoy

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#1295094 1-May-2015 15:23

Just voltage. I put my clamps behind my internal distribution board. Was pretty easy to pull off the plastic cover and put a clamp around the incoming mains feed from the external switchboard/meter. Any chance you can access that?

danfaulknor

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#1295098 1-May-2015 15:33

I can but then I'd be breaking the law doing something behind the switchboard (see my original post)

How horribly inaccurate would it be if I measure current and voltage in different places and do the calculations myself? I'm not using this to challenge a bill, just to make us more aware of power usage so we can cut back.

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SumnerBoy

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#1295099 1-May-2015 15:35

FWIW - I have run my install past both the solar PV installer, and my local electrician and they both seemed to think it was fine. But yes, you would want to be confident it was safe/legal!

Have a read up on the OEM site, there is plenty of info about what is best practice etc. Ideally the V and C are measured at the same point, but I am not sure what sort of error you will introduce by doing the measurements separately.

Aredwood

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#1295181 1-May-2015 17:23

The voltage feed is used for phase angle calculations. They want the power point close to the meter box only so other loads on the same circuit won't affect the readings as much. I don't see any reason why you couldn't just have the 12v transformer inside. And run a long cable to the meter box. Just use at least 1mm2 cable. Just chop the plugs off an old extension cord and use that. And use a power point that doesn't have much other load on its circuit.

raytaylor

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#1295868 2-May-2015 20:16

danielfaulknor: I guess the annoying bit about the real power monitoring is the AC socket requirement. I would either have to get a sparky in to add one right next to the external meters or have some very long cables between the clamps and the power cable I'm metering...

I have never trusted those clamp sensors
You can buy plug-in meters from mitre 10 or the warehouse for $10 each.
They look like a digital timer - except they show various figures like watts currently used, this month, max/min bla bla bla.

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