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Discuss RCD protection for PV? in the Solar PV Forum area at ElectriciansForums.net

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ak492158

Does a PV system have to be RCD protected?

I did a number of PV installations with a very experianced electrician who said that the PV system had to be RCD protected, but I'm not sure. The AC cable will not be burried in a wall and it's not going into a bathroom, or outside, or suppling a socket. Also putting the PV system on a shared RCD could cause problems if the RCD trips and the Solar is still live for a few seconds.
 

moggy1968

Electrician's Arms
sacked a 'very experienced' sparky off a load of jobs we had because of this. he swore blind that under 17th edition ALL circuits had to be RCD protected and insisted that PV could be put on the same RCD as other household circuits. He said he had done loads of PV installs for other local companies. INteresting as his knowledge of the 17th ed means he shouldn't even be doing general electrics, never mind PV!
 

fiardor

Regular EF Member
Does a PV system have to be RCD protected?

I did a number of PV installations with a very experianced electrician who said that the PV system had to be RCD protected, but I'm not sure. The AC cable will not be burried in a wall and it's not going into a bathroom, or outside, or suppling a socket. Also putting the PV system on a shared RCD could cause problems if the RCD trips and the Solar is still live for a few seconds.
Yes it should be RCD/RCBO protected (DTI guide) (but there are execptions) but definitely not on a shared RCD.


We firstly try to use a 2 way RCD CCU off a henley block.

Failing that we try to use an RCBO on the non RCD protected side of customers CCU.

An inverter can continue to supply voltage into the grid even after the mcb/rcbo/rcd has tripped which (for what its worth) is why we try to use RCD protection in every instal.
 
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infinity

Electrician's Arms
Yes it should be RCD/RCBO protected (DTI guide) (but there are execptions) but definitely not on a shared RCD.


We firstly try to use a 2 way RCD CCU off a henley block.

Failing that we try to use an RCBO on the non RCD protected side of customers CCU.

An inverter can continue to supply voltage into the grid even after the mcb/rcbo/rcd has tripped which (for what its worth) is why we try to use RCD protection in every instal.

How can it supply the grid once the mcb has tripped?
 

BruceB

Electrician's Arms
DTI Guide does not recommend rcd/rcbo, just makes some recommendations about type in those cases where an rcd is required
 

screwdriver

Electrician's Arms
I don't understand the need to fit rcds regardless. I would prefer to do the install knowing that it doesn't require one.
As we generally do an install a day I never ever chase in an inverter feed and in the cases where we have had to run cables through voids within 50mm of the surface of the wall we always use armoured cable. TT systems obviously require them but generally you need to fit a separate consumer unit as most TT systems
around that haven't been changed to pme down our way are seriously old!
 

moggy1968

Electrician's Arms
DTI Guide does not recommend rcd/rcbo, just makes some recommendations about type in those cases where an rcd is required
Agreed
and if your using standard 30ma RCDs when 17th ed regs demand it your probably breaching the regs anyway!
 

fiardor

Regular EF Member
An inverter supplied from a PV array must preferably be installed in adedicated circuit in which:​

no current-using equipment is connected, andno provision is made for the connection of current-using equipment,andno socket-outlets are permitted.An inverter must not be connected by means of a plug with contactswhich may be live when exposed.Where an electrical installation includes a PV power supply systemwithout at least simple separation between the a.c. side and the d.c.side, an RCD installed to provide fault protection by automaticdisconnection of supply must be type B RCD according to BS EN 60898(IEC 60755, amendment 2).
Ah yes, thanks Bruce,

Sorry i knew it said something about TL inverters.
 
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moggy1968

Electrician's Arms
we discussed this at length on here before, as my understanding was that transformerless inverters needed RCD protection, but it was pointed out that most transformerless inverters (SMA, FRONIUS etc) have inbuilt protection that meets the need for automatic disconestion that would require the need of an RCD.
 

BruceB

Electrician's Arms
There is no regulation to my knowledge that requires transformerless inverters to be on an rcd.

However if they are on an rcd for ADS reasons then type b rcd is required by 712.411.3.2.1.2

Except (second para of that reg) if the manufacturer says they are not by design able to feed in dc fault currents then type b not required by the reg.

You could then go on to debate type A or AC by that is not the subject of that reg.

So that's simple then.
 

moggy1968

Electrician's Arms
An inverter supplied from a PV array must preferably be installed in adedicated circuit in which:​

no current-using equipment is connected, andno provision is made for the connection of current-using equipment,andno socket-outlets are permitted.An inverter must not be connected by means of a plug with contactswhich may be live when exposed.Where an electrical installation includes a PV power supply systemwithout at least simple separation between the a.c. side and the d.c.side, an RCD installed to provide fault protection by automaticdisconnection of supply must be type B RCD according to BS EN 60898(IEC 60755, amendment 2).
Ah yes, thanks Bruce,

Sorry i knew it said something about TL inverters.
It kind of depends on your interpretation.
Does this mean an RCD must be fitted to TL inverters, or just that if one is fitted it must be a type B? My interpretation is the latter.
 
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