TT System 100ma S Type Housing

[saspm]

Hi,

Got a Domestic TT system which needs a new 100ma S Type RCD. What are your thoughts on this being placed in an Insulated or metal enclosure?

It is not in an external meter cupboard so falls under 421.1.201 (within domestic).

Thanks,

 

[SparkyChick]

When you say new, is it a replacement for an existing one (i.e. is there already an enclosure) or is it an addition to the installation?

If it's the later, I'd go with metal if it's not in a non-combustible enclosure and if it's the former I might give the customer the choice.

 

[saspm]

When you say new, is it a replacement for an existing one (i.e. is there already an enclosure) or is it an addition to the installation?

If it's the later, I'd go with metal if it's not in a non-combustible enclosure and if it's the former I might give the customer the choice.

It doesn't even have one. It has an older 16th edition board so half the circuits are 30ma protected

 

[SparkyChick]

Metal

 

[Wilko]

I go mental metal these days too

 

[saspm]

Cheers guys, that was my thought too.

 

[Des 56]

It doesn't even have one. It has an older 16th edition board so half the circuits are 30ma protected

So why don't you change the main switch for a time delay Rcd in the existing board

Also if it has half the circuits not on an RCD
The mcbs will not be adequate on their own

 

[saspm]

So why don't you change the main switch for a time delay Rcd in the existing board

Nice idea, saves buying an enclosure!

 

[saspm]

I'm actually now thinking of just putting a standard 30ma RCD on the other side of the board as there is room to convert it to a 17th edition and move some circuits around. They are thinking about having some work done on the lighting circuits anyway. Would this negate the need for a time delayed RCD?

 

[Des 56]

I assume its a plastic unit so no special protection for the supply tails are needed
The Rcds being double pole will do just fine without a S type

 

[saspm]

I assume its a plastic unit so no special protection for the supply tails are needed
The Rcds being double pole will do just fine without a S type

Yeah it is an old Wylex plastic 16th edition board. Not too sure why it didn't have an RCD in front though, wasn't this a requirement of 16th edition boards?

I believe that a time delayed RCD would be required in front of a non-combustible consumer unit, like the amendment 3 ones.

Thanks for clarifying!

 

[Des 56]

Yeah it is an old Wylex plastic 16th edition board. Not too sure why it didn't have an RCD in front though, wasn't this a requirement of 16th edition boards?

I believe that a time delayed RCD would be required in front of a non-combustible consumer unit, like the amendment 3 ones.

Thanks for clarifying!

Your welcome

Most all TT systems have always required a Rcd for earth fault protection
A 16th board on TT with half the circuits minus Rcd protection would not have complied at the time it was installed

As long as further protection ( shrouding the entry and securing the tails) is applied,there is no absolute need to fit a Rcd before the metal board

 

[saspm]

As long as further protection ( shrouding the entry and securing the tails) is applied,there is no absolute need to fit a Rcd before the metal board

Thanks!

That's one for the memory banks! I put a 100ma S type RCD in a insulated Wylex ip enclosure on the last 17th ed board I did which was used for a surveillance visit. Nothing mentioned by them about it

 

[westward10]

Your welcome

Most all TT systems have always required a Rcd for earth fault protection
A 16th board on TT with half the circuits minus Rcd protection would not have complied at the time it was installed

As long as further protection ( shrouding the entry and securing the tails) is applied,there is no absolute need to fit a Rcd before the metal board

To say it would not have complied at the time is not correct, both 16th and 17th Editions state an rcd (incorporating overcurrent protection) or an overcurrent protective device may be used for fault protection. Both state the rcd is the "preferred" option.

 

[saspm]

To say it would not have complied at the time is not correct, both 16th and 17th Editions state an rcd (incorporating overcurrent protection) or an overcurrent protective device may be used for fault protection. Both state the rcd is the "preferred" option.

Providing disconnection times are met with a low Zs on all circuits not protected by RCD?

Surely this would be all catered for in the initial design anyway!

 

[Des 56]

To say it would not have complied at the time is not correct, both 16th and 17th Editions state an rcd (incorporating overcurrent protection) or an overcurrent protective device may be used for fault protection. Both state the rcd is the "preferred" option.

Quote
Most all TT systems have always required a Rcd for earth fault protection


Well,the reason I used the term "most" at the start of the reply was precisely because of the reason you state
But I agree if anyone was to state "it would not have complied" I too may have posted a similar response as yours

 

[westward10]

Quote
Most all TT systems have always required a Rcd for earth fault protection


Well,the reason I used the term "most" at the start of the reply was precisely because of the reason you state
But I agree if anyone was to state "it would not have complied" I too may have posted a similar response as yours

What are "most TT systems" are there different types.

 

[Des 56]

What are "most TT systems" are there different types.

Most TT systems is used as a numerical term to portray the overwhelming number of TT sytems that need Rcd protection (when compared to those that can rely on the Mcbs only) and you know "exactly" what was meant by myself

Why are you pushing for conflict of opinion,you and I know exactly what is required
Nothing I posted has sought to cause mischief with yourself or anyone else

 

[westward10]

Sorry Des no conflict intended

 

[Deleted member 26818]

Not aware that either the 16th or 17th edition mention "incorporating overcurrent protection" in relation to RCDs?
My understanding, is that an RCD incorporating overcurrent protection is an RCBO.

 

[westward10]

Not aware that either the 16th or 17th edition mention "incorporating overcurrent protection" in relation to RCDs?
My understanding, is that an RCD incorporating overcurrent protection is an RCBO.

I slightly reworded Reg 411.5.1 to save it being "wordy".
Note 2 of said reg says where an rcd is used for fault protection the circuit should also incorporate an overcurrent protective device. So this could be an rcbo or mcb and separate rcd.

 

[saspm]

I have called the Niceic help line today as to weather a 100mA S Type RCD is required on the TT system and can confirm that:

In my case:

If the 16th edition board is converted to a 17th board using the original plastic casing it will not require a 100ma time delayed RCD, as long as the meter tails are short enough. This also applies to the new metal consumer unit.

Thanks for everyone's input