Discuss How to position CT clamps correctly so solar does not interfere with EV charger. in the Electrical Forum area at ElectriciansForums.net

rwdl1984

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We recently had a solar panel system put it in. The solar batteries were delayed and put in after, at which point it became clear that the CT clamp for the solar system was positioned on the wrong cable. The inverter was reading the power generated by the solar system and including it in the house load, causing the batteries to discharge rapidly etc etc.

The solar company (finally) came back and moved the CT clamp to live 1 between the fuse and meter. This sorted out the issue with the inverter and batteries. Sadly, it has caused issues with our existing EV charger. The EV charger ramps up to around 5.5 kW then cuts out. The electrician from the solar company positioned the solar CT clamp right above the EV CT on live 1. He mentioned briefly at the time that they might interfere with one another.

I'm posting this now because the solar company has gone AWOL and are refusing to come back to fix things. Perhaps there is a simple fix here, without me having to convince a new company to and fix this? Does anyone know the correct position for the solar CT clamp that won't cause the EV charger to cut-out?

I have already tried moving the solar CT clamp further up the cable away from the EV clamp (as suggested in other posts), but this has not made a difference. Please see the attached image. The blue circle at top right shows where the solar CT clamp was positioned originally by the company, but this resulted in incorrect power readings on the inverter. The two CT clamps are together on live 1 now, the EV one is the one below.

Any suggestions would be much appreciated!
 

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Paignton pete

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I was going to sayEasy fix. One can be positioned after meter, but the hendley block takes two feeds out.

where do the two feeds go? one is the main board what is the other. Could it be separate board for pv or car charger?

if the solar pv is wired directly into the main board add one clamp to the main boards feed tail after the meter.
 
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rwdl1984

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I was going to sayEasy fix. One can be positioned after meter, but the hendley block takes two feeds out.

where do the two feeds go? one is the main board what is the other. Could it be separate board for pv or car charger?

if the solar pv is wired directly into the main board add one clamp to the main boards feed tail after the meter.
Thank you so far - please see the wider shot attached below. The units on the left are for our air source heat pump (not currently in use/drawing power). The ones directly above the meter I believe are for the solar/inverter. As you say one feed is going into main board, the other seems to be going into solar and heat pump isolators.
 

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timhoward

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Are you saying it WAS where the red circle is?
How to position CT clamps correctly so solar does not interfere with EV charger. 1660724859873 - EletriciansForums.net

To my understanding, to measure the output from the inverter it needs to be where the green circle is.

My other concern is that you appear to be missing some absolutely essential safety labelling warning of two sources of supply.
 
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rwdl1984

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Yes, originally the CT clamp for the solar/inverter was in the red position - this resulted in the inverter showing a very high load in the house (it was including the power produced by the solar panels in the house load, causing the batteries to discharge to compensate). However, the EV charger worked fine.

Should I move a CT clamp to the green-circled cable, and if so, which one, solar or EV clamp?

I'm not surprised by the lack of stickers - I'm not at all impressed by the company we hired.
 

timhoward

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I should qualify that I have limited experience with solar, having only connected up a couple of Zappi systems.

In general terms I'd expect the EV CT clamp to be where it is, the purpose being to monitor the demand of the whole installation to comply with any grid limits that are set.
I'd expect the solar generation sensor CT clamp to be where the green circle is to monitor the invert output.

The arrow direction matters on the clamps, the EV CT clamp should point towards the consumer unit and the solar CT clamp should point towards the black connection block. So the two arrows should be pointing at each other if you follow along the cable.

At least, that is how Zappi works.
 

Paignton pete

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unfortunately my above idea will not work. Due to solar pv being on separate board, However there is a way, but it will require an electrician to do this it involves fitting another Hensley block to extend the line tail coming out of the meter.
 
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rwdl1984

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Have you tried sliding the upper CT up the cable so it is closer to the meter and not sitting on top of the other one? You could put a cable tie round the cable to stop it sliding back down.

It's always worth trying the simple things first.
Yes, I tried that and it made no difference, I think that was stated in my original post.
 

Paignton pete

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You probably did and I just didn't read it properly.

You could also try putting one on the neutral, just flip it around so the arrow is in the other direction.
Why didn’t I think of that. of course either I was having a senior moment or your a genius. First time I’ve put a creative and not meant it to be condescending.

TBH I think that one was down to my lack of thinking.
 

Paignton pete

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Hang on a moment. My brain is starting to hurt. Would that work?
if the line is in reverse does that nessisarily mean the neutral would be going the other way.

need to think about this one.
 
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rwdl1984

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Thanks everyone for your help so far. Here's what I tried tonight:

I moved the solar CT clamp up to the green circle as suggested. This resulted in a house load reading of 0 kW (even though several things were running in the house), presumably because in that position the clamp is reading the power generated by the solar (it was night time, so nothing). This was the original issue we had with the CT clamp, it was reading the solar generation as house load and causing issues with fast battery discharge.

I then moved the solar CT clamp to the neutral cable after turning it around. I also kept it as far away from the EV clamp as possible. This resulted in a correct house load reading (same as before). However, when I switched the EV charger on, it ramped up to 7 kW and then cut out. I noticed that it did charge for about 20 seconds longer than with the solar clamp next to the EV clamp on live, but eventually cut out.

Is there the option to move the EV clamp somewhere else instead, and if so, to which position? It seems to me that the EV clamp has a less crucial role to play in all this (the EV charger just needs to switch on and stay on), whereas the solar CT clamp is crucial for the functionality of the entire renewable system.

I really appreciate this help guys! If you have any other ideas, I'd love to hear them!
 

timhoward

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It seems to me that the EV clamp has a less crucial role to play in all this (the EV charger just needs to switch on and stay on),
The role is to ensure your total demand from the grid doesn’t exceed your supply’s capacity. It can be very important.
Have you tried turning the solar off and removing the solar CT clamp and then using the EVCP to prove there isn’t a fault with the EVCP?
A lot of CPs are 7kw so is it now reaching maximum power and then cutting out?
As far as I can see the EV clamp has to be there to measure grid import.
 

BenCos18

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The role is to ensure your total demand from the grid doesn’t exceed your supply’s capacity. It can be very important.
Have you tried turning the solar off and removing the solar CT clamp and then using the EVCP to prove there isn’t a fault with the EVCP?
A lot of CPs are 7kw so is it now reaching maximum power and then cutting out?
As far as I can see the EV clamp has to be there to measure grid import.
yep the ct clamp does have to be there for it
It has to be at the point after the meter so it can measure the grid import to limit the supply to the charger if needed
 

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