can someone please explain?

[leckyant]

Beats me man. Why don't you suggest 1/2 a dozen 1 milli amp RCDs in series

 

[spark 68]

The only time it may need to be larger CSA that I can think of, is if it is a combined CPC and bonding conductor for PME/TNC-S, and you are extending the zone

 

[telectrix]

the way he said it was along the lines of: if water from jacuzzi was to splash onto motor, then water would have a potential which may not be enough to operate mcb/rcbo/fuse, therefore a larger earth is required, typically 16mm or 25mm

which would seem to suggest that he reckons that copper less than 16mm has a higher resistance than water.

 

[Engineer54]

the way he said it was along the lines of: if water from jacuzzi was to splash onto motor, then water would have a potential which may not be enough to operate mcb/rcbo/fuse, therefore a larger earth is required, typically 16mm or 25mm

Total hogwash!! lol!!

 

[Inteificio]

the way he said it was along the lines of: if water from jacuzzi was to splash onto motor, then water would have a potential which may not be enough to operate mcb/rcbo/fuse, therefore a larger earth is required, typically 16mm or 25mm

So if water (which is a lousy conductor), splashes on to a motor (which would be IP rated), the difference of a few milliohms of conductor width will be affected but the few thousand ohms of water path.

Seems implausible to me, but then again i often overlook stuff.

 

[Engineer54]

The only time it may need to be larger CSA that I can think of, is if it is a combined CPC and bonding conductor for PME/TNC-S, and you are extending the zone

PME is Not recommended on swimming pool and Jacuzzi installations.... TN-S or TT system!!

 

[Darkwood]

The only time it may need to be larger CSA that I can think of, is if it is a combined CPC and bonding conductor for PME/TNC-S, and you are extending the zone

Exactly what i said but in simpler form, this is the only reason i can see it and as OP has said the designer has done larger scale swimming pools etc too possible in buildings with larger csa supplies hes applying said bonding/earthing rules to lower scale installs.

 

[spark 68]

PME is Not recommended on swimming pool and Jacuzzi installations.... TN-S or TT system!!

I was referring to when the Earthing conductor may be larger than the supply cables, but thanks anyway for pointing that out:wink_smile:

I realise it has no bearing on this thread, and I should not really have added it.

 

[leckyant]

Dean.
Just ask the guy for a small beer in a local pub. tell him you want a little chat about leccy.

 

[Engineer54]

I was referring to when the Earthing conductor may be larger than the supply cables, but thanks anyway for pointing that out:wink_smile:

I realise it has no bearing on this thread, and I should not really have added it.

Your explanation is as good as anyone else's at the moment, apart from PME not being recommended for these types of installation...lol!!

Can't really see that being used to larger pool installations as being an excuse either as virtually all pipework, filters etc etc are all PVC/glass fiber installs these days. So as long as the pump motors are earthed with a suitable sized earthing conductor, then they shouldn't need frame bonding....

 

[spark 68]

Just out of interest, what does a Jaccuzi fall under ?, would it be under swimming pools and other basins ?, or just under normal bathroom regs ?

A look though GN7 suggests you can use PME for swimming pools and other basins (Zone 2), but with a requirement to have an earthmat or earth electrode 20 ohms or less to be installed and connected to the protective equipotential conductor. 702.410.3.4.3

 

[Darkwood]

Good point, its a Bath with bubbles but could fall under 'other Basins' .... a strange one really cos if i let rip in my bath does it change the reg's requirements to which it falls under as it becomes a jacuzzi.

 

[Jimmy Boy]

Just out of interest, what does a Jaccuzi fall under ?, would it be under swimming pools and other basins ?, or just under normal bathroom regs ?

A look though GN7 suggests you can use PME for swimming pools and other basins (Zone 2), but with a requirement to have an earthmat or earth electrode 20 ohms or less to be installed and connected to the protective equipotential conductor. 702.410.3.4.3

Regs say 'Recommended' something you should do..'Requirement' is something you must do very interesting reg tho I will bear that one in mind when looking at PME's

ATB S

 

[Engineer54]

QUOTE=spark 68;539568]Just out of interest, what does a Jacuzzi fall under ?, would it be under swimming pools and other basins ?, or just under normal bathroom regs ?

A look though GN7 suggests you can use PME for swimming pools and other basins (Zone 2), but with a requirement to have an earth mat or earth electrode 20 ohms or less to be installed and connected to the protective equipotential conductor. 702.410.3.4.3[/QUOTE]

I'm taking the meaning of ''Jacuzzi'' as being an exterior installation, not a bath in a bathroom with bubbles!! ..lol!!

I personally wouldn't connect PME earthing to an outdoor swimming pool, or an outdoor Jacuzzi installation unless it stopped at a remote or distant plant room. Frankly i'm surprised that BS767 would consider that a 20 ohm rod connected to the MET/EMT would be sufficient to protect persons with bare feet on bare wet ground or wet concrete!!! In fact, the vast majority of S/pools will have a Ufer earth via the concrete/rebar construction that should be connected to all metallic pool accessories such as ladder/steps and spring boards etc... I'd have no problem with connecting that Ufer earth to a TN-S earthing system... I wonder how many Swimming pool contractors or Jacuzzi manufacturers would recommend a PME connection to their equipment??

 

[spark 68]

Hi E54,

Re: rod/Earth mat, It wasn't even a requirement, lol, as Steve pointed out to me, it was a recommendation.
This was poor wording on my part.

Steve Breeds: Regs say 'Recommended' something you should do..'Requirement' is something you must do very interesting reg tho I will bear that one in mind when looking at PME's

ATB S

So it is worse than you thought lol, I wasn't arguing with you btw, just pointing to the GN which says you can .