New Mira shower 10kw Ask questions and find answers to many subjects relating to electrics and electrical work

[huckfynn]

Hi how can I test a new 10 kw shower is safe? Its connected radially back to the CU which is a ''Basics'' via a 50 amp mcb, the cable is 10mm, How can I make it ''trip'' as a test? It would put my mind at rest. I'm unemployed at the moment and really can't afford electricans at £30 an hour. Your help would be most appreciated though. regards to all, and what a great site frequented by great and clever people. peace out x

[ericmark]

The meter required to test a RCD is far more than the £30 you would pay an electrician. They cost around £200 each. There are 6 tests done. Because AC has positive and negative half cycles all three tests are done twice once on + and once on -. There are three tests.
1) Check it does not trip at 15ma
2) Check it does trip at 30ma
3) Check it trips within 40ms at 150ma
Without special meter the latter is impossible.

However although only designed to mechanical test the RCD to ensure it is not stuck the built in test button is normally a good indication as to if it will work.

The MCB is for over current only and is not normally tested. There were some bogus ones around but any electrician would realise at once as they were much lighter than real ones and did not feel right when switched so unless some DIY has been done very unlikely you would find one.

So really it is only the RCD that needs testing. So unless you have some reason which you have not talked about in your post for thinking there is something wrong then if the RCD trips when you press button I would not really worry.

There was a time when RCD's were not required on showers but that was a long time ago. I have not found a shower in many years where the manufacture did not say it should be RCD protected so if you don't have a RCD then you should be thinking about getting one fitted.

I have been surprised over the years on how many faulty new RCD's I have found so I would not consider fitting one as being a DIY job.

[huckfynn]

Hi EricMark,
Thanks for your reply, that was really useful. The trip button worked ok. What we've got here is a ''Basics'' CU with 6 mcb's lights, ring, hob, oven, immersion and shower. I am worried about the electrics here as we've just bought this little cottage.

Inside the shower unit the incoming electrical connections seem awfully easy to get damp, if you know what I mean. They're about 2 inches or so from the top and just don't seem protected. I expected to see a completely closed off electrical system. What exactly would happen if dampness somehow got through and settled around these? Thanks again, for any advice. Peace x

[ericmark]

Normally the RCD will trip before it get to stage of being a danger. However you are right to worry a little. The IET who are regarded as authority and write the regulations say that the electrics should be tested every 10 years or on change of occupant. So if you have just moved in then they should have just been checked.

Main point is of course you don't know what a previous occupant may have done. And testing ensures nothing daft has been done. You would not believe what we find. Many houses have not been tested in last 30 years never mind last 10 and it is common to find originally it used water pipes as earth which is no longer permitted (They still connect to earth though) and over years the water main has been changed to plastic.

For me to say don't worry there's no problem would be therefore wrong. And to be certain it does need testing. However it is very likely there is no problem. Hermetically sealed units have a habit of each time they heat and cool drawing in water so the more open approach is often better and any small drops of water that do enter are free to run out again.