Non-PV electricity monitoring

[Eddieboy]

Hi,

I have a 2.9 KW system which is going great guns in the recent sunny weather, but I thought it would be helpful to monitor my non-PV electricity usage 'real-time' to make sure I didn't exceed my PV electricity supply when running appliances. I bought a CC128 monitor which I clipped onto the power feed going into my meter which works fine when the PV isn't working, but when it is the usage figure actually goes up, like its also including the PV electricity in the total. I've spoken to the installer and they said to try the other 3 cables coming out of the meter but I just get a similar effect. I'd appreciate any advice on how to sort this out or if its just not possible. Thanks

 

[steptoe]

you need to clamp your monitor onto the cable just as it enters your consumer unit(fusebox),

is your PV on a seperate consumer unit(fusebox) from your normal supply?

 

[ProDave]

A simple current transformer cannot determine the DIRECTION of current flow, so it's reading your exported power as if it were consumed power.

I have a thread running in the solar PV section of a project I am building that hopefully will be able to determine the direction, and automatically switch on a dump load.

 

[Eddieboy]

Thanks for the help. I had a feeling it would be something like this, I'm just surprised it occurs whichever cable I attach the monitor to. I assumed the exported power would get into the grid via the negative cable, not the positive as well, but if thats how it works I guess I've had it. If you come up with an affordable solution let me know.

 

[Eddieboy]

I've tried that but I still get this problem. The PV has a mini consumer unit. I've attached the wiring plan if it helps

 

[steptoe]

mmmm,

can you take a picture of your PV consumer unit, and your normal consumer unit,

I think the problem here lies in the fact your PV CU seems to be fed from your normal CU, is that correct?

thats how your diagram shows it to be,

BTW, that is a very poor schematic if that is what your installer left you, please ask him to come round so I can slap him.

 

[Eddieboy]

Hi, I've attached a photo of all the connections etc. My mains power comes in top left and I assumed if I attached the monitor to the red cable going from it to the meter bottom left it would pick up my mains usage. IBut when the PV system is operating the surplus gets back into the grid through the red and black cables somehow and whichever I connect the monitor to I get a cumulative reading. The PV CU is the grey box on the far right and the cables go into the black box in the centre which has wires leading into the two main fuse boxes. I can't see any way to overcome this problem but I'm happy to try any safe suggestions!

 

[NozSpark]

As you have 3 (2 x non pv & 1 x pv) consumer units and they are all connected into a single (DP) henly block then there is only 1 way to do it cheaply and I'm afraid it's not something I'd recommend as a DIY job.

 

[Phoenix]

If the monitor you have is anything like the OWL one i've seen, it supports upto three clamps (to enable it to be used on 3ph), so you could buy an extra clamp and monitor the two wylex standard boards as two separate readings.

Or see if the monitor manufacturer offers a 'rope' style CT, which could go round both live tails to the boards

 

[Eddieboy]

Many thanks everyone. I'm going to see if there are any other monitors out there which might sort this out. I understand that its not a DIY job, but would this be something a competent electrician to sort out for me at a reasonable price?

 

[NozSpark]

I'd have thought that it shouldn't cost more than

 

[steptoe]

where are you located Eddieboy?

---------- Post Auto-Merged at 21:55 ---------- Previous post was made at 21:53 ----------

personally I would split the Line tails as well, and boy oh boy do I hate those DP ISCOs, unless you are really pushed for space with a lot of tails being connected.

 

[NozSpark]

Yes, those DP henlys are horrible, especially some of the older types

I was thinking of just breaking into the neutral tails because it should be safer and you shouldn't need to call the DNO out to isolate

 

[Eddieboy]

I'm in Ferndown in Dorset, about 7 miles from Bournemouth. If anyone's in the area...