Power meter

The one you point to above measures kWh, according to the posting and the 5th photo.

The terminals don't look like they're rated anywhere near the 20A or 30A claimed max current though. In one place it implies it uses an external current transformer, but the wiring diagram doesn't show one.

on 12/09/2016, rick supposed :

You can get 13amp plug in units, which can measure various things - volts, power factor, current, Kw, KwH. Might one of those do?

But the picture does doesn't it?

Cheers, T i m

Some of the energy monitors "given away" by the utility companies had memories to store usage over a week/month. Some had USB interfaces where you could plug them into a computer and as long as the computer was on would log the power usage.

These types uses a remote current transformer/sender which normally clips on to the household incoming mains cable and a seperate receiver which displays usage etc.

Depending on application, something such as

Various different models on Ebay with more/less functionality.

The OP didn't tell us what kind of range they need, so it's difficult to tell how accurate they need to be. I suspect those aren't very accurate for measuring things in the tens of watts or below.

I recently looked for a plug-in monitor with remote data capability and the best I could find was this:

adding a 4 pound Raspberry Pi Zero if needs be.

Theo

unfortunately no

OK ... should have explained. I have a PV array on my roof and it dumps any spare generated power into my immersion heater. Just thought adding a kwh recording device would be useful for me to see how much I am 'storing'

So measuring between 0 to 3kw power supplied.

The cost of such a device will almost certainly exceed the value of the electricity stored in a year.

Probably so. Unless you have twenty people in the house bathing daily.

It has been providing all my hot water 'for free' for past 3 months .... so it will soon be paying for itself.

I want to measure the power 'dumped' so I can get accurate record.

I have generated 3.95MWh so far this year .... so plenty to store.

What is it with all these left brainers and everything being down to 'cost'. Why couldn't someone just be interested in seeing what is going on and not mind spending some money [1] to see / measure that?

Cheers, T i m

It sounds as if your PV array is connected only to your immersion heater and feeds it DC. If so, a suitable kWh meter would be expensive.

I have a thermal store - so the stored energy is available for heating as well as DHW. Dish washer, Washing machine use the HW as well as also use the free leccy.

The cost of power meter is only £7 .... and as you say it is my interest to see what is actually going on, rather than just assume.

No, never mentioned DC. To clarify the PV is connected to a normal DC-AC inverter ... connected to my consumer unit. I use the output of that to power anything in the house .... the excess is detected by a Solar diverter switch and dumped into the immersion in my thermal store. This avoids exporting anything out to the grid.

The immersion heater is a purely resistive load, and its resistance can easily be measured. Therefore you do not need a power meter; you only need to log the root mean square voltage applied to the load by the PV array, and then do a little arithmetic.

If it happens that, when the PV can supply the heater, it always does so at a particular voltage, you only need to measure the amount of time for which it supplies.

until you have all the hot water you can use....

So this 'Diverter switch' 'diverts' as much as our money as possible into your bank account via the FIT scheme? [1] ;-)

Cheers, T i m

Correct ... but due to size of my thermal store very rarely reach maximum temp.