mobile home.... wtf?

itchy · Apr 7, 2011

How do you test these things?
I'm trying to get readings for one home, but the site has one main box feeding about 80 homes. They've been installed on what I can only assume to be a giant final ring circuit. Where each one spurs off with a fuse board with an rcd. This then has about 20 meters of cable leading to the fuse board for the lighting circuit, ring main boiler etc in the home home. Which in turn has a fuse board next to it for the shower radial and kitchen ring.

How do you do live tests when one rcd trips down from the one you are testing. And secondly, ze?

Thanks, help me as my brain cannot cope today... I know i'm missing the obvious.

Deleted member 9648 · Apr 7, 2011

Are you just testing the mobile or right back to the origin?.....not sure what you are asking,it's no different to any other test???

itchy · Apr 7, 2011

Just the mobile. Its a tns system but I'm getting a ze of 1.35... Or should that test be done in the main box that feeds the site, jot the distribution board in the home?

topquark · Apr 7, 2011

There is often a sub box outside the home (often with a meter) that feeds the home via SWA to a normally CU (mcb's or old fuses). As for testing as wirepuller says and there is a section in the BRB for park homes.

Liamsparks · Apr 7, 2011

Note additional test results down on the "notes" section in the schedule of test results

itchy · Apr 7, 2011

The brb says under 721.1 'they do not apply to the electrical installations of mobile homes, residential park homes and transportable units. note 1: For mobile homes and residential park homes, the general requirements apply'.
To me that means that ze on a tns system should be under 0.8? Not the 1.35 im getting?!
Also the sub box us where im getting nuisance tripping when testing the rcd's.

itchy · Apr 7, 2011

just note the ze is too high and walk away?

IQ Electrical · Apr 7, 2011

itchy said:
just note the ze is too high and walk away?

How can you measure Ze in the mobile home when you have a ring main distribution circuit?

Your Ze measurement (from what you have described) will be at the origin of the installation.

Your measurement in the home will be the Zs of that particular distribution board.

If there is no discrimination between upstream and downstream RCD's then you will note that as a code 4 defect.