RCD protection for PV?

[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.

 

[BruceB]

Ask him to cite the regulation the requires pv to be on an rcd.

 

[moggy1968]

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]

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.

 

[infinity]

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]

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

 

[BruceB]

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

Because it is allowed up to 5s in most cases to shut down on loss of mains.

(which I know is not supplying the grid, but is energising the installation)

 

[screwdriver]

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!

 

[fiardor]

Because it is allowed up to 5s in most cases to shut down on loss of mains.

(which I know is not supplying the grid, but is energising the installation)

Thanks Brucey baby thats what i meant LOL

 

[moggy1968]

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]

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.

 

[moggy1968]

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]

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.

 

[fiardor]

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.

It was LOL

 

[moggy1968]

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.

 

[fiardor]

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.

Transformerless inverters mean they dont have galvanic isolation between ac and dc so i would say that you should provide rcd protection and bond the array for TL inverters

 

[BruceB]

You can debate whether you should have an rcd with transformerless and I would be interested in the reasons. I am not sure I know enough about the internals to argue from a position of strength though.

What I can say, I think authoritatively, is that there is no regulation requiring an rcd with transformerless. The requirement in 712.411.3.2.1.2 refers to 'rcd to provide fault protection by ADS' which would apply for:
- TT
- Zs too large at inverter (unlikely for voltage drop reasons on non-TT)

 

[fiardor]

The DTI guide as moggy says can sometimes be open to interpretation.

In fact so can the regs LOL

And my misssus come to think of it...........

She says dont touch but i know what she really means :53:

PMSL

 

[GaryM]

Can we talk about what deems somebody to be competent? PMSL

Formal qualifications and experience

 

[SibertSolar]

The excerpt from the DTI guide assumes that you are assessing the need for and RCD for ADS. If you do, and IF you do not have galvanic isolation (simple separation) between the DC and AC circuits, then you should choose a Type-B RCD. It is not a definitive "you must use a Type-B RCD for any TL inverter installation". I believe Bruce has it right in his post above. The debate starts from there really as to whether the TL inverter manufacturer's statements regarding the need for a Type-B RCD or not are all-encompassing or not..... the outcome of such debate can have an impact on the general use of Type-B RCDs for all TL inverter installations, regardless of the need for ADS or otherwise.

 

[fiardor]

Formal qualifications and experience

EH ERRR

Sorry Gary but that was my point,

The regs make no reference to formal qualifications in their definition of competent only technical knowledge and practical skills are enough to qualify as a competent person.............apparently.

 

[ak492158]

Thanks very much for your help guys.

The supply was TNCS with good Ze, so I used a Garage unit with 20A MCB and a built in generationn meter.

 

[moggy1968]

EH ERRR

Sorry Gary but that was my point,

The regs make no reference to formal qualifications in their definition of competent only technical knowledge and practical skills are enough to qualify as a competent person.............apparently.

The regs may not, but the courts will. In the event you have to defend yourself in court you would be expected to provide evidence of competence.

Training+qualifications+experience=competence

 

[fiardor]

The regs may not, but the courts will. In the event you have to defend yourself in court you would be expected to provide evidence of competence.

Training+qualifications+experience=competence

Not really the point i was making but thanks moggs LOL

 

[infinity]

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.

do you know where we can find information as to weather SMS for example, has built in protection negating the need of an rcd for the tl range?

 

[solarsavings]

The regs may not, but the courts will. In the event you have to defend yourself in court you would be expected to provide evidence of competence.

Training+qualifications+experience=competence

Guys that have ended up in court in the past have sometime found that despite having the training, qualifications and experience they are judged as incompetent and locked up. As we see on here you can do your best, do what you believe to be right and someone will still drag the **** out of you. Get two "experts" together and it's Harry Hill time.

 

[moggy1968]

very true. Whenever 2 or more electricians are gathered together there will be an argument about the regs! (just see some of the posts on here :0) )
SO- get yourself in court with 2 'expert' witnesses and if their interpretation is different to yours your in the mire.
Your own credentials are part of your defence though. Try standing up in court and saying, 'well actually I don't have any qualifications and this was my first install' and they probably won't even need those witnesses.

 

[solarsavings]

TBH that's also true

 

[Dan]

Don't mind me while I bump some threads in the solar PV forum. If they're not current or applicable topics, just ignore the threads; they'll drop off the page. If they are, feel free to chip in and chat solar stuff in the solar panels forum.