Are you replacing type AC RCD's with Type A?

[HappyHippyDad]

Just looking for a bit of clarification regarding RCD's.

A type AC RCD is no longer acceptable for offering additional protection for socket outlets. If you are (for example) adding one socket to an existing circuit are you all updating the RCD to a type A? I can see this being a bit tricky sometimes. It's ok if its a brand of consumer unit that does type A RCD's but this will not always be the case.

Do the regulations mean that if you are extending an existing socket circuit you cannot use an existing type AC RCD?

 

[Lucien Nunes]

Yes, because a pulsating DC fault that is sufficient to blind the upstream type AC won't necessarily be high enough to trip the downstream type A.

 

[happysteve]

Yes, because a pulsating DC fault that is sufficient to blind the upstream type AC won't necessarily be high enough to trip the downstream type A.

Well then, we're stuffed.

If the additions and alterations require that the circuit is protected by a Type A RCD because there's the possibility that something plugged in to the bit you've added would blind a Type AC RCD, and there is an upstream Type AC RCD that we can't remove and which also protects other circuits.... There's no option but to change the board (or at least split the tails and add a second board), because any additions and alterations can't make the existing installation less safe...

Or am I barking up the wrong tree?

 

[timhoward]

I’m not worried about adding Type A RCD socket or RCD spur and sockets being added.
It complies with letter of regs as far as I can see and while a dc leaky device could be plugged in and blind an upstream device they could equally choose any other socket in the house and achieve the same thing so I don’t think it makes the installation less safe.

I actually see more issues with lighting circuits as adding LED down lights is more certain to add permanent dc leakage.
I can imagine convoluted testing reassuring me, e.g measure dc leakage of lights and then check upstream RCD tolerates that much leakage. But more likely a board change if no RCBO is available.

Maybe TT systems deserve more respect as it’s not ‘only’ additional protection we are jumping through hoops to comply with.

 

[HappyHippyDad]

Well then, we're stuffed.

If the additions and alterations require that the circuit is protected by a Type A RCD because there's the possibility that something plugged in to the bit you've added would blind a Type AC RCD, and there is an upstream Type AC RCD that we can't remove and which also protects other circuits.... There's no option but to change the board (or at least split the tails and add a second board), because any additions and alterations can't make the existing installation less safe...

Or am I barking up the wrong tree?

There have been a few discussions about a 'lower grade' RCD being upstream of a 'higher grade' (poor wording but couldn't think of anything else). All the literature states that you should not do this.


However, @pc1966 did a homemade test which seemed to indicate 'blinding' was pretty unlikely. I cant find his thread though.

 

[Lucien Nunes]

The question I suppose, is whether the existing parts of the installation are made less safe by the addition. If you are adding a socket-outlet, you might argue that in its absence, whatever would have been plugged into it would have been run from an existing socket-outlet via an extension lead. Therefore any DC leakage from that load would still have been drawn through the original type AC. OTOH If the new circuit is specifically for a known possible DC leakage source that could not otherwise have been used, then in theory the existing installation is indeed less safe.

 

[telectrix]

i fit whatever i got on the van. type A, AC, even Z. sod it.

 

[Mike Johnson]

Now I am confused, I don't have a van, what should I fit?

 

[Julie.]

Now I am confused, I don't have a van, what should I fit?

In that case you don't need to fit any as it's an acceptable departure under 123.45.6.7.8.9.a. part iv

 

[Electro-tech]

If you have a Type AC RCD at the D/board & decide to install an extra circuit or spur with a 13 Amp 2 Gang RCD Socket.
Are the RCD sockets Type A now as I guess there are old stock AC types about ? According to this diagram co-ordination is vital.

 

[timhoward]

If you have a Type AC RCD at the D/board & decide to install an extra circuit or spur with a 13 Amp 2 Gang RCD Socket.
Are the RCD sockets Type A now as I guess there are old stock AC types about ? According to this diagram co-ordination is vital.

Yes, you can get Type A. One example:

13A 2 Gang 10mA Type A Passive RCD Socket

Type A RCD complying to BS 7288-2016

www.cef.co.uk

You are right about coordination, but sometimes we may have no choice. Points have been made above regarding the load being plugged into an extension lead or into another existing socket anyway , so actually any DC leakage will exist in the installation whether or not you install the new socket.

 

[Markyd]

I think amendment 1 will be withdrawn on 28th September, so AC still valid for the time being

Yes

 

[Markyd]

Been fitting type A for a good 18 months now

 

[Mike Johnson]

Why would you fit anything else now days, and while where at it, fitting non fire rated downlighters, why would you, just to save a bit of money.

 

[Welchyboy1]

Why would you fit anything else now days, and while where at it, fitting non fire rated downlighters, why would you, just to save a bit of money.

Obviously reasonable new works it’s a no brainier but there is a huge issue ahead with small works/alterations and additions to existing installations

On older boards and obsolete brands already installed with a/c type RCDs its going to have massive pain and cost implications for customers and installers

Even matching compatibility with mcbs Is a headache in this regard, but at least you have old ones floating about you can get hold of with a bit of effort

Not so with type A rcds or rcbos, it’s gonna be alot of ‘satellite’ mini consumer units or rcd spurs added around existing consumer units again like when RCD protection became the norm for most circuits

I can do three or four small jobs in a day where additions to one or two circuits on each job at least is fairly usual

There really needs to be some allowance for this!

Then the next update will be for afdds to be protecting every circuit and the whole merry-go-round starts again!

 

[Mike Johnson]

Old ones floating around, and I still fit Cross-ply tyres to my car.