Earth bonding to bath tub.

[richardg]

Hi - Good evening.. I've just completed an EICR in a domestic property. A larger number of defects have been noted and actioned.
There were two issues which I would like some sage advice to help clarify.

The bath has been connected directly to the MET and bonded with the sink. A seperate equip-potential bond is visible on the bath pipes. I believe this method was legal at one point - should it be highlighted as a area of concern? (Seems like a risk could be present if an exterior fault developed)
What era was this method used??

When testing the house ring main variable Zs readings were present. After a little investigation a section has been found wired in 1.5mmT+E The owner cannot afford a part rewire this month. My scheme operator recommended fusing down the ring with a upgrade to the BS3871 30A fuse to a modern 10A 600898 type B and write a very good cover letter to protect myself

This is a very temporary patch - i would like to know how to work out what the maximum current a 1.5mm ring can safely handle. I know there are extra limits due to the 1mm Earth and will look at the equation tomorrow.

- Any help gratfully received

 

[ImpededLoop]

There's no problem with the bonding to the bath and basin. In fact it's only been relaxed in the 17th Edition of BS7671 if an RCD protects the bathroom circuits.

With regard to the ring final circuit, how much of it is wired in 1.5mm? If it's only one leg near the middle of the ring, you could split the ring into two radials and protect the 1.5mm leg with a 13A fused Spur.

 

[Deleted member 26818]

It's unlikely that an MCB would fit.
It would be better to just de-rate with a 20A fuse.

 

[richardg]

Hi Spin London - surprisingly my local wilts had a box of retro pushfit 600898 MCB. Amazing what they can keep in stock. The 1.5mm is present on at least 2 legs. Some more investigation needed soon. Breaking the ring down might work depending where the 1.5mm has been spliced in.
Cheers

 

[davesparks]

Nothing surprising about that, the plug in MCBs for Wylex boards are still in production and any half decent wholesaler will be able to supply them.

 

[davesparks]

It's unlikely that an MCB would fit.
It would be better to just de-rate with a 20A fuse.

The MCBs are more commonly available than the HRC fuseholder a for those boards

 

[Deleted member 26818]

Be careful with the plug in MCBs, some don't fit the rewireable fuse holders, and only fit the cartridge fuse holders.
I am surprised though that your scheme suggested this option, usually they wouldn't countenance such an idea.

 

[davesparks]

Be careful with the plug in MCBs, some don't fit the rewireable fuse holders, and only fit the cartridge fuse holders.
I am surprised though that your scheme suggested this option, usually they wouldn't countenance such an idea.

The MCBs are supplied with the correct bases which replace the rewireable fuse bases.

 

[Deleted member 26818]

The MCBs are supplied with the correct bases which replace the rewireable fuse bases.

Sounds just like what happens when you buy a rewireable fuse.

 

[tony mc]

I would just do the EICR and report your overall assessment of the installation along with any observations that you come across!

I would not consider the 1.5 to be a C1 where immediate action is required IMO and on the covering letter with the report cover all your points including replacing the 1.5 with 2.5 for the RFC.

I would have a look at reg 433.1.103 while looking at your equation!

 

[davesparks]

We've been talking about changing fuses for MCBs, but looking at the OP again it already has bs3871 MCBs in it do it's changing MCBs out for MCBs!

 

[ian.settle1]

We've been talking about changing fuses for MCBs, but looking at the OP again it already has bs3871 MCBs in it do it's changing MCBs out for MCBs!

My thoughts exactly a bs3871 is an MCB not a fuse

 

[D Skelton]

What is earth bonding?

 

[HappyHippyDad]

Its when it gets together with Mars, Jupiter and Mercury and they all take a fishing trip to the sun!

 

[Silly Sausage]

Its when it gets together with Mars, Jupiter and Mercury and they all take a fishing trip to the sun!

And Venus gets left behind at home to do the housework.