Dual rcd board tt system

[dnjr]

Dear all
Wonder if anyone can enlighten me
I've just changed a board to a dual rcd board. TT system with ze of 100 ohms
All circuits test ok and everything fine for 2 days . Had a call to say that while the customer was out ( so nothing in use) both rcds tripped at same time , they know this as two timer clocks ( one on each rcd side stopped at same time)
As far as I know it's only happened one , customer has asks what would cause it and I don't know so thought I would ask. I'm guessing it's something external but would appreciate anyone who can enlighten me
Cheers


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[dnjr]

How do you know it tripped at 10.30?

Both time clocks stopped at same time


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[dnjr]

Dear all
Wonder if anyone can enlighten me
I've just changed a board to a dual rcd board. TT system with ze of 100 ohms
All circuits test ok and everything fine for 2 days . Had a call to say that while the customer was out ( so nothing in use) both rcds tripped at same time , they know this as two timer clocks ( one on each rcd side stopped at same time)
As far as I know it's only happened one , customer has asks what would cause it and I don't know so thought I would ask. I'm guessing it's something external but would appreciate anyone who can enlighten me
Cheers


Sent from my iPad using Tapatalk

Dear all
Just thought I would update this one
Surprise suprise. Owner had done sone diy after I left and borrowed a neutral for his garage lighting so when turned on a light inside it tripped both rcds. Gota love em. Cheers for replies

 

[Leesparkykent]

Phew. I'm almost a TT virgin so was worried I'd missed something. Cheers


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Ideally there should be an up front 100mA S type RCD to provide fault protection for the links between the main switch and RCD's.

 

[dnjr]

Hi lee. I though s type were not intended for Personal shock protection as they are slower to react and could allow current to flow for an unacceptable period of time. Is this not the case ?

 

[Leesparkykent]

will still provide fault protection through ADS and protection against the risk of fire. Just not suitable for the requirements of additional protection. Your scenario is described on page 20 of the on site guide.

 

[Risteard]

30mA time delay

I don't believe that they exist.

 

[Midwest]

Ideally there should be an up front 100mA S type RCD to provide fault protection for the links between the main switch and RCD's.

Would only need up front s type, if the installation has a distribution circuit, simple tails and and bespoke gland would suffice, I believe.

Lee's correct again, when using A3 Dual RCD CU on TT . Apart from I thought the page number was 32-35 yellow OSG (haven't got a yellow one yet myself), which advices using s type as main switch.

 

[Leesparkykent]

Lee's correct again, when using A3 Dual RCD CU on TT . Apart from I thought the page number was 32-35 yellow OSG (haven't got a yellow one yet myself), which advices using s type as main switch.

Pages 32-35 show the pictures but page 20-21 goes in to a little more detail.

 

[Midwest]

Pages 32-35 show the pictures but page 20-21 goes in to a little more detail.

Arrrgh, must purchase a new osg, once they get the amendment's done, they say a picture paints a thousand words.