Adding PV array into existing circuit?

[DomB]

Hi all,

Do you have any thoughts on hooking a PV array's inverter onto an existing circuit, say a ring final? Obvioulsy as long as the cable was good (2.5mm for instance) I wonder what issues there are with doing that..

Cheers for any replies!

 

[Markc]

That's a no no! PV must be on a dedicated circuit and not in with an existing. If no spare way fit a stand alone board. It's not going to cost that much.

 

[SolarCity]

Are you sure about that, Mark? It was my understanding that doubling up onto an existing breaker was permissable.

To be honest, even though I believe it is accepted, I would say it is bad practice and like Mark says I would strongly recommend fitting a seperate CU for the new circuit.

 

[DomB]

So I've looked at the MCS doc on Solar PV and it says "all double-ticked items in the DTI guide are mandatory".

The DTI guide (http://www.bre.co.uk/filelibrary/pdf/rpts/Guide_to_the_installation_of_PV_systems_2nd_Edition.pdf) then says (and this part is double ticked):

"An inverter supplied from a PV array must preferably be installed in a dedicated circuit in which:
no current-using equipment is connected, and
no provision is made for the connection of current-using equipment,
and
no socket-outlets are permitted"

So I guess it's a dedicated circuit.

Mine is not to question why...

Cheers

 

[JulianC]

"An inverter supplied from a PV array must preferably be installed in a dedicated circuit ..."

Hmm, as ambiguous as ever with the use of the word preferably. There is a guide from ESC that says it's OK to connect into an existing circuit providing the wiring can handle the combined current of that from the PV system and that capable of being pulled through the breaker. I would imagine this would be difficult to confirm in many real world scenarios.

I agree that it doesn't seem like good practice and I wouldn't entertain the idea. A new circuit on a new breaker everytime, on a new CU if necessary.

 

[Markc]

I love that Preferably. I can't see how anyone could be criticised for keeping it on a dedicated but might be over doubling up. May be putting MUST in my post was a mistake. Sorry.

 

[edexlab]

I read that ESC guide and looked into this , ( i tend to fit a new Cu just for pv as standard ) but my thinking was more geared to using existing submains ie outbuildings etc
and this term of existing final circuit allows this, subject to cable size/load .

 

[bigbob1]

G83/1

Small Scale Embedded Generator (SSEG)​

A source of electrical energy and all associated interface equipment, rated up to and including
16 A per phase, single or multi phase 230/400 V ac and designed to operate in parallel with a​

public low voltage distribution Network.

5.2 Installation Wiring and Isolation​

The installation that connects the SSEG to the Supply Terminals shall comply with the
requirements of BS 7671. All wiring between the Supply Terminals and the SSEG shall be
protected by a suitably rated protective device; and shall be of suitable size and type for the​

rating of the SSEG.

I say go and do it, then on your test sheet write down 32A mcb and see what happens! and then go get a socket rated at 16Amps blah blah blah

 

[edexlab]

perhaps i did'nt explain my last post very well ,what i should have said was a dedicated pv circuit, connected into a consumer unit off a suitably rated submain .
I've had a good chat with Niceic and two separate DNO's talked about 1% vd limit and they were happy with this although they agreed this may be difficult to achieve.
As for connecting into an existing circuit i agree not a good idea!

 

[bigbob1]

if you just follow dti guide, mis 3002 and G83/1 you can't go wrong.

 

[Energetic]

Have come across this recently, what i thought would be an dedicated submain to a garage seems to be coming off an unknown circuit. Only at the initial enquiry point so have not installed anything, the CU is right up the other end of the immaculate cottage, no chance of running another circuit in... Would only be a small system and not worth the hassle...

Any way to get round it?

 

[Worcester]

View attachment Best Practice Guide 5.pdf Well the NIC EIC reckon it's OK (pages 11-13)

 

[bigbob1]

anyone can install a pv system on a property, as long as it is part P'd. If your not MCS accredited the customer will not get the feed in tariff. You must install the system in accordance with the dti guide to installing photovoltaic systems 2nd edition, and IEE Guidance Note 7 to BS 7671 - Special Locations, Section 12 SolarPhotovoltaic (PV) Power Supply Systems (ISBN 0 85296 995 3, 2003). Also attention must be paid to section 2.3.1 which states An inverter supplied from a PV array must preferably be installed in a
dedicated circuit in which:no current-using equipment is connected, and
no provision is made for the connection of current-using equipment,
and no socket-outlets are permitted.
An inverter must not be connected by means of a plug with contacts
which may be live when exposed.
Where an electrical installation includes a PV power supply system
without at least simple separation between the a.c. side and the d.c.
side, an RCD installed to provide fault protection by automatic
disconnection of supply must be type B RCD according to BS EN 60898
(IEC 60755, amendment 2).
a.c. cables are to be specified and installed in accordance with BS 7671.

A manual a.c. switch-disconnector must be provided located in an
accessible position within the Customer’s installation as in G83/1 (e.g.
adjacent to the consumer unit or main distribution board), which is
in accordance with BS 60947-3

must switch all live and neutral conductors.

must be securable in the OFF position only. It must be simple to secure

using a standard padlock
So unless you follow those rules, which plainly states no to "hooking up to anexisting circuit" and follow the rules set out for industry, if i was you i wouldn't do it!

 

[bigbob1]

As an electrician there is no hassle in doing it correctly and running a 4mm cable in from the inverter to the fuseboard and putting it on a 16A mcb (rcd protected). Then you can use that job to get your MCS as long as you've followed the rules.

 

[bigbob1]

Also the system must be registered within 30 days to the local Distribution Network Operator and fully comply with engineering recommendation G83/1....... Get reading!