Can my electrician use an existing cable for a solar feed?

[suntrap]

Hello. I'm having solar PV installed (2.75kWp), with the electrician due to arrive in the next couple of days. What they tell me they do is install a separate consumer unit for the PV, in order to comply with Part P without certifying the whole of the existing installation, and use surface wiring to the inverter or they charge more. Now, I have an old electric shower feed which is a 4mm^2 (?) T&E, from adjacent to my existing CU to the loft. This cable is disconnected at both ends, and has no joins (although I can't prove that to the electrician as some of it is hidden, nor can I prove that part of it isn't inside a Thermos flask). Does Part P allow use of this old cable, presumably after passing insulation/resistance tests? It is of course in the old colours, and is stranded rather than solid core (but yes, it is PVC, not cotton and gutta-percha!).

Many thanks.

 

[malcolmsanford]

Hello. I'm having solar PV installed (2.75kWp), with the electrician due to arrive in the next couple of days. What they tell me they do is install a separate consumer unit for the PV, in order to comply with Part P without certifying the whole of the existing installation, and use surface wiring to the inverter or they charge more. Now, I have an old electric shower feed which is a 4mm^2 (?) T&E, from adjacent to my existing CU to the loft. This cable is disconnected at both ends, and has no joins (although I can't prove that to the electrician as some of it is hidden, nor can I prove that part of it isn't inside a Thermos flask). Does Part P allow use of this old cable, presumably after passing insulation/resistance tests? It is of course in the old colours, and is stranded rather than solid core (but yes, it is PVC, not cotton and gutta-percha!).

Many thanks.

There I'm afraid is the crux of the whole situation, he can not in accordance to part P sign off that the cable is installed to the current building regulations, ie route of cable, erection method etc. So Officially he can not utilise that cable.

The installation of a new single consumer unit for your PV installation is in fact not Part P driven but a recommendation of the DTI, which all PV installers have to adhere to.

Yes they have no responsibility to test the existing installation but what they have to do is as per the regulations and Reg 131.8 is assure that the PV installation is not detrimental to the existing installation and that all earthing and bonding is current to the Regs

 

[suntrap]

OK, thank you very much for your clarification. I won't press the electrician on the matter, and I'll have to have some ugly surface wiring then - the only bit in the whole house.

I get the impression from the thread about controlling immersion heaters to maximise use of PV that some installations don't have a separate consumer unit (making it harder to find somewhere to put current transformers to measure the output) but I may be mistaken there.

I won't ask any questions about the wider implications as it will be covered by discussions and FAQs ad nauseam!

 

[Lecky Leon]

I'm a PV installer. He is not allowed to put the inverter in the loft. Otherwise what is he intending to use the cable for ??. If it's for the strings the cable must be fated at up to 600 volts and each cable double insulated as class 2 insulation.

Lecky Leon

 

[truckster]

Leon

Why cant the inverter go in the loft?

 

[suntrap]

There's nothing to stop an inverter going in the loft, provided it is installed as per the manufacturer's instructions. Are you thinking about temperature or ventilation issues? My roof is not lined with felt so has plenty of ventilation and although it gets hot it doesn't reach 60C which is what the inverter can handle. The cupboard under the stairs which contains the consumer unit would have too little ventilation for my inverter (dissipating about 150W max).

The installer did specify an AC disconnect switch to go at each end, presumably as the cable is connected to a voltage source at both ends.

So yes, the whole point in talking about this cable is because it would be used for an inverter in the loft.