German Electrician refuses to fit Current Transformers inside dist panel

[J_Redman]

Hi, I just wondered whether anyone had any experience in this area.

Background:
I am in Germany and operate out of a large shared rented building. We have 3 distribution panels in our offices and want to measure the amount of energy we are using with a view to driving reduction and saving resources. The building only has one main supply and does not measure what we use - we just pay a share on the rental.

Issue:
I have asked the building electrician about fitting the clamp monitors around the neutral inside the panels. He has taken a look at the clamps and says that as they do not have ‘VDE 0100’ written on them he cannot fit them. I pointed out they have the CE stamp but he said that under Germany law he can only fit things that have that on them. Is he right? If so is there a clamp we can use in Germany? There is a chance that he just doesn’t want to do the job hence the question.

Thanks in advance for any suggestions.

[Robert.Wall]

I don’t know German installation practice, so I cannot comment about whether he is right or not. I’ve looked here http://www.batt.co.uk/upload/files/din_copy2.pdf and from that, I seems that VDE 0100 is a standard for the erection of electrical equipment and the measures for protection against shock. It does not appear to be a standard against which equipment is manufactured, so my reading is, it would not be appropriate for the current transformer to be certified to that standard. But without reading the standard, I cannot be certain.

Provided that the extra low voltage cable out of the c.t. is adequately segregated from the other wiring, I don’t see where the problem is. The c.t. itself is CE marked, tested to 1 kV so it’s possibly against EU law not to fit it.

The SCT-013-000 data sheet says:
Dielectric strength(between shell and output) 1000V AC/1min
Fire resistance property: In accordance with UL94-Vo

You could try a German manufacturer of electrical instrumentation (Siemens springs to mind) and see if you can find a c.t. that either has a 1 V output (i.e. the burden resistor is inside the c.t. housing) or has a reasonably low current output, ideally 50 mA at your maximum current, though we can handle other currents with a small component change (though not 1 A or 5 A - due to the 3.5 mm jack connector).

[Edit]
I’ve looked at a few German c.t. manufacturers. C.T’s with 1 A secondary windings seem to be readily available. One of those would be usable, but you would need to arrange a 1.2 Ω burden resistor external to your emonTx (or emonPi) that’s rated at at least 2 W. You’d be able to leave the internal 22 Ω burden in parallel, the effect of that will be to give a resulting burden value of 1.14, which should be OK as far as the input is concerned, but will need a slight adjustment to the calibration (the difference from the nominal calibration is about 3.45%).