Poor ir on when connected to mcb

[joehat]

As above says, when testing ir on three circuits I put each circuits neutral into the line into the mcb and tested from mcb terminal to earth, each result below 1M, I then tried connecting the line and neutral in a terminal block , and the results shot up?????

This consumer unit is in a cold outdoor cupboard as per pics I will post, it did the same on all 3 mcbs on the right hand side, all mcbs where switched down in case anyone asks.

My thoughts where dampness or something wrong with mcbs?

 

[joehat]

 

[joehat]

 

[Lucien Nunes]

My thoughts where dampness or something wrong with mcbs?

Remove MCB, IR test across it. If low, try blow-drying it and see if the result improves. If so, is cupboard suitable location for CU?

 

[joehat]

Remove MCB, IR test across it. If low, try blow-drying it and see if the result improves. If so, is cupboard suitable location for CU?

Thanks will do, have you had any issue with this?

 

[Octopus]

Are you absolutely sure that everything is unplugged?

 

[joehat]

Yes, triple checked and its 2 socket circuits and a light circuit having the same issues.

 

[Octopus]

So you IR'ed the circuits with the MCB's switched on and connected to the RCD?

 

[joehat]

.......

 

[joehat]

So you IR'ed the circuits with the MCB's switched on and connected to the RCD?

All switched off so basically I used the mcb to connect the line and n together, then tested l-n to Earth

As described above

 

[joehat]

When I tested with the method of l-n in the mcb to Earth 250v was hovering just u under 1M and at 500v was about 0.05 and when disconnected from mcb and used block to connect it shot up to about 30M each circuit was similar in results on the the last 3 mcbs to the right of the pic

 

[Midwest]

Isn't the maximum voltage for rcd/mcb's 500v?

 

[Midwest]

In terms of dampness, there are quite a few CU's installed in garages and isolators in meter boxes, without issue. But I guess if the ventilation is poor, condensation can form. I've seen a CU in an integral garage, with corroded neutral/earth bars.

 

[joehat]

Isn't the maximum voltage for rcd/mcb's 500v?

I don't see your point?

 

[joehat]

In terms of dampness, there are quite a few CU's installed in garages and isolators in meter boxes, without issue. But I guess if the ventilation is poor, condensation can form. I've seen a CU in an integral garage, with corroded neutral/earth bars.

So the question is I guess, this can happen inside an mcb

 

[Midwest]

I don't see your point?

I'm just wondering, depending on how you carried out your test, if using 500v and conditions inside MCB/RCD were damp, you could get reading through devices, even if they were turned off?

 

[joehat]

I'm just wondering, depending on how you carried out your test, if using 500v and conditions inside MCB/RCD were damp, you could get reading through devices, even if they were turned off?

I tested all at 250v getting about 1M with n-l connected in mcb switched off and when tested at 500v I got about 0.05 yet when connected in a terminal block out of mcb I was getting 30M plus

 

[joehat]

Teste across one of the mcbs at 250v and then 500v and at 250v it came up at 81M and at 500v it came up at about 62M

Thoughts?
Should this be above what the tester can read?
If so would this be the damp getting in and would you cod this c2 or c3 in an EICR?

 

[Octopus]

Teste across one of the mcbs at 250v and then 500v and at 250v it came up at 81M and at 500v it came up at about 62M

Thoughts?
Should this be above what the tester can read?
If so would this be the damp getting in and would you cod this c2 or c3 in an EICR?

why would you code anything? The readings in your example above are way above what is ok

 

[joehat]

why would you code anything? The readings in your example above are way above what is ok

I'm not sure, it's just why would this be giving a poor reading if connected in a mcb terminal rather than a terminal block ect