Domestic Consumer Unit.

[Grizzly]

:off topic:Sorry Guys I know my subject matter is somewhat off Topic.
It's just that I know we have some very knowledgeable sparkies on the forum.

I was wondering if they could Help?
My Son has moved into his first house and I am helping him with some of the decorating etc.
His consumer unit is probably not more than 3/4 yrs old.
Of the split board type with a 80a 30ma rcd.
Basically when the grill on the electric oven has been on for a while.
The rcd trips I am assuming that it is the stat operating that is causing the trip.

I have not yet investigated further but was wondering how common this issue could be?
Can anyone advise.
Many thanks Grizzly

[B G Scott]

Second go at doing this post.
Got to the end and it went into the ether.
Check that the neutral from the cooker has not been crossed over to the Non RCD protected N bar on the consumer unit, this will cause a problem.
Easy mistake to make at the consumer unit end.

[Grizzly]

Second go at doing this post.
Got to the end and it went into the ether.
Check that the neutral from the cooker has not been crossed over to the Non RCD protected N bar on the consumer unit, this will cause a problem.
Easy mistake to make at the consumer unit end.

Brilliant advise thanks BG.
Basically yesterday whilst dropping the dinning area lights prior to scimming the artexed ceiling over.
I discovered the light was controlled on and off via a dimmer switch through the live only.
With no nuetral being used on the light fitting! Discuss!
I have now rewired it correctly with a new ceiling rose.
But i am begining to wonder what over suprises I am going to find?
Cheers for the Help.
Grizzly.

[frank]

I would suspect that the heating element in the cooker grill is faulty leading to an earth leakage fault.

If the neutral was wired to the non rcd side of the board, the rcd would trip the minute you switched the cooker grill on, not after some time in use.

Aren't domestic electrics fun ;)

[chemi-cool]

Hi Grizzly,

You can "dry" heating elements by disconnecting the ground for a short while, switch them on for 20 minuets and then connect it again and check. [wait for them to cool....;)]

We do not wire the lights through the RCD, don't know why but I have seen it in many homes.

[Grizzly]

Another good point to check out Frank.
Thanks for the advice,
So how would you advise metering the Heater element?
i am assuming what you are describing is the insulation to earth diminishes as the element gets hotter?
Am I correct in thinking using a Megga would not detect the gradual insulation breakdown?
I knew as soon as I saw the fact that the recently installed Condensing boiler was powered by a 13amp plug.
We were going to have fun!
Grizzly

[Grizzly]

Hi Chemi.
Its been a long time since I was involved in Domestic installs.
But I believe it is common practise to ensure the lighting circuit.
that provides light to where the consumer unit is.
To not be on the rcd side so that when the rcd trips, "You" can see what you are doing.

My reference to the lighting was an indication as to the state of how things are electrically.
Not a direct reference to the RCD issue.
But thanks all the same.
Grizzly.

[monkey spanners]

I've had water heater elements do this and crank case heaters also, they only trip the rcd when hot. If you are lucky you can megger it while still faulty.

Or get a nice gas cooker :p

[frank]

The only way to check the element is to carry out an insulation test at 500v DC.
If the element passes the test, i.e. remains above 1Mohm then you need to look elsewhere for the fault.

Then again, its not unknown for the rcd to be faulty. Do you have access to an RCD tester?

[Grizzly]

Nah! Sold my rcd tester and loop impedance tester probably 10 yrs ago when I stopped being site based.
But I may well have a spare RCD lurking in one of my sheds?
And I have a good friend who is an electrical wholesaler.
So all is not lost!
MS I am told this is the best option
the same as Mrs Grizzly has Electric fan assisted Oven and grill.
With Gas hob!
And I have not survived 27 yrs of marriage by disagreeing with her!
Grizzly

[Peter_1]

I have for these kind of problems a leak current clamp meter from Meterman.
You connect the clamp direct over all the wires (earth excluded) and you read immediately the leak current
Few knows that this meters excist.

[Magoo]

Hi Grizzly.
The RCD's these days are fine as a nano difference and super sensitive, see if you can borrow a tester and a loopp impedence tester as well. Electric cookers are prone to leakage to earth and usually the largest power consumer in the house. Perhaps a singular RCD for the cooker would save a lot of frustration, specially if you can find and older one as they are less sensitive. The service boards here used to have earth and neutral bares linked, which smoothed things out so-to-speak.

Chemi-cool tell us more on the clamp test idea.

[Grizzly]

The only way to check the element is to carry out an insulation test at 500v DC.
If the element passes the test, i.e. remains above 1Mohm then you need to look elsewhere for the fault.

Then again, its not unknown for the rcd to be faulty. Do you have access to an RCD tester?


Thanks Guys for the sound advise.
Frank I megga'd the heater element as you said with
500v and the element was straight down to earth.
Just to prove my point I megga'd the Oven element, which is known to be good.
This went to infinity.
Just under £33.00 on the Internet for a new one!
For the good advise... Priceless!
Scotty. I checked the consumer unit Neutral bar and all were common on 1 bar.
So I would not be able to separate them.
Cheers Grizzly.:D

[frank]

Nice to hear that you got it sorted. Well done. :)

[casstrig]

If you have electrical knowledge and a megger meter give the element a leakage test if the reading is low the element could still be ok, heat the element to red hot and test again if the reading goes up you had a moisture problem within the element.If you don't have the test equipment or if this sounds beyond you get a professional and go no further.

[Grizzly]

If you have electrical knowledge and a megger meter give the element a leakage test if the reading is low the element could still be ok, heat the element to red hot and test again if the reading goes up you had a moisture problem within the element.If you don't have the test equipment or if this sounds beyond you get a professional and go no further.

You cannot get much lower than 0Mohm's
Please read the posts again!
The problem has been sorted.
Grizzly