IR low on site office

[pc1966]

Yesterday discovered that the RCD had tripped in the board on our new site. Those sockets feed a hired site office cabin, and that in turn feeds a hired chemical toilet. A quick bit of investigation revealed the main reason for the trip was the commando plug/socket for the toilet had filled with rainwater, so RCD did its job.

But...when checking things out I did an IR test on the feed to the hired office and found it disturbingly low. Both L-E and N-E around 0.2M, and if I checked the individual lives by isolating circuits with the MCBs found the internal sockets (with everything unplugged and/or removed) was 0.5M for L-E, the two heaters about 1.5M, and lights about 1M.

It is dry inside, is only 10m x 3m in size, and only has four double socket outlets.

Any ideas why it is so utterly crap? For comparison I was getter marginally better IR on the water-filled toilet lead after opening and shaking out the half-cup of water it has accumulated!

It is hired so not really our business to monkey with it, but for now we are powering it off when not on site just in case

 

[Lucien Nunes]

There wad a thread a few weeks back about T+E with partially conductive 'insulation'. If the fittings are dry it seems the most likely cause. Unless they have been on power while wringing wet and started to develop tracking internally.

 

[pc1966]

After I posted this I remembered that case of the crappy low IR cables, though in this case no real sing of moisture, etc. But it is quite possible they had the same batch of dodgy cable.

Otherwise it is hard to explain all circuits being rubbish without any obvious reason.

IR was fairly constant, much the same on 500V as 250V, and a slight increase in R with time if I held the tester energised.

 

[Strima]

Is this a Portakabin or trailer mounted style office?

 

[pc1966]

It looks like a shipping container, basically a corrugated steel box but with two shuttered windows and a door (instead of the double end-doors that shipping containers use).

 

[Strima]

It looks like a shipping container, basically a corrugated steel box but with two shuttered windows and a door (instead of the double end-doors that shipping containers use).

Quite possibly the vibration of it being transported around has started to affect the insulation on the cables and we all know how well hire kit is looked after.