Lowest acceptable IR

[alchemist]

That was an option I gave them, but they were already thinking about a new CCU. I believe you can get standalone RCD enclosures for adding protection to an existing circuit.

 

[NozSpark]

Sorry and one question I forgot to answer.. yes I disconnected all conductors to keep them separate when testing. Originally I did a global IR and found it low so went on to do circuit by circuit.

Remember, when you do this you should leave the earth connected to make sure that a cable isn't shorting out through pipework or similar.... got picked up on this during an assesment once

 

[PC Electrics]

That was an option I gave them, but they were already thinking about a new CCU. I believe you can get standalone RCD enclosures for adding protection to an existing circuit.

Wylex Fully Insulated RCD Shower Consumer Unit - Screwfix.com, Where the Trade Buys

But check out equivalents at your wholesaler, they may be cheaper.

Simply mount the unit next to the old board and wire it in so that the circuit 'passes through' the RCD on its way out of the fuseboard.

If you've got to do this with more than one circuit, use the same enclosure but fit two RCBOs which can be fed by just one of the old fuseways with an appropriate sized fusewire.

 

[batty]

On older installations I use RCBO consumer units although generally I only use RCBO consumer units only. Less chance of nuisance tripping.

 

[Manator]

I have just completed a little job, installation of a new circuit, no way was I going to use the exsisting circuit. I used an eight way main isolator board fitted with the 20amp rcbo for my installed circuit. This gives the client the option of staged rewire without the need to shut down, or a new DB to be fitted.

2.5mm radial fitted hence the 20amp rcbo.

 

[Bane]

1MOhm is acceptable but anything less than 2MOhm should be investigated.

Or has this already been established?

 

[spinlondon]

There is no Requirement in BS7671 to install RCD protection in CUs.

There is also no requirement to rectify any defects in the existing installation.

Regulation 131.8 requires you to ensure the earthing and bonding arrangements are adequate for whatever protective measure is installed for the safety of the adition or alteration.

Just what defects are you allowed to record when commenting on the existing installation?

Regulation 633.2 requires you to record any defect where reasonably practicable, there is nothing to suggest that certain defects should be rectified before re-energisation.

As alchemist has stated the requirement of Regulation 610.4 is to verufy that an addition or alteration does not impair the safety of the existing installation.

Could someone please furnish a Regulation that requires you to upgrade existing installations, or existing circuits when conducting an addition or alteration?

Perhaps the Regulation requiring one to rectify defects in existing installations and circuits would be usefull.

 

[Zeespark]

The BRB isnt the be all and end all spin, merely a guide as you well know.

Andy

 

[binky]

The cooker circuit I am sure is the cabling, no loads were connected when I did the last IR test. The immersion circuit L-E was tested with the FCU switch to the immersion off, so the test would not have included the element. The water pump was connected still though.

If cooker hood and pump are still connected to circuit, then it is still posiible that these items are causing low readings - I would suggest retesting but between L&N together to earth with circuits disconnected at CU. This helps protect appliances from 500V, and is an acceptable means of testing where items are hardwired to circuits. As for 3Meg, the official position as I understand it is that any circuit that passes test is good for ten years (domestic property). Personnally I would not be happy with these numbers, and would suggest re-testing at a lower timer interval, but if customer cannot afford re-wire at the moment then this is one way to proceed. Changing CU would improve protection of cables, and protect customers better. If you decide to continue with this I would however state on certificate that in your professional opinion that the property would benefit from additional works (ie re-wire or intensive test/fault finding) given the low IR readings obtained.