MCD tripping with oven

[liddelljohn]

When i use the oven the MCB trips out whole house ,

Had this problem before turned out to be Door bell getting moisture in  , we replaced it and sealed that unit 3 years ago but now same problem again ,

 

The breakers are correct Amperage  the 30amp circuit RCD for OVEN  is separate   and nothing else trips the system RCDs ever ,, only The Oven  and that causes MCB  to trip but not the RCD

 

disconnecting doorbell and  all outside electric  does help , but its not a viable solution and the Thai electricians are all out of their depth.

 

any solutions , because I use my oven a lot , but I need outside lighting and doorbell

The oven is in perfect order  its not very old , and works perfectly  when disconnected from Earth , but thats  not a safe option  I just did it to make sure the oven was fine ..

 

[bluejets]

1 hour ago, liddelljohn said:

The Oven  and that causes MCB  to trip but not the RCD

 

1 hour ago, liddelljohn said:

and works perfectly  when disconnected from Earth

 

These two comments contradict each other.

Are the above part of the one breaker or two independant units...??

Photos thanks.

 

Other than that I'd say you are sufferning from effect of voltage drop and your disconnecting the earth is simply nothing to do with the situation.

Get PEA to check any and all connections at the pole/meter........(twist and tape territory in Thailand..........aluminium mains capital as well)

Use gas where mains cover long distances and you insist on using undersize mains as per Vdrop calculations.

[OneMoreFarang]

Did you try a new MCB?

[digbeth]

are you sure the mains wiring to the oven is big enough, 4sq mm at least for oven

[liddelljohn]

5 hours ago, OneMoreFarang said:

Did you try a new MCB?

yes  we have done that   , but no difference ,,

[liddelljohn]

4 hours ago, digbeth said:

are you sure the mains wiring to the oven is big enough, 4sq mm at least for oven

yes wires are  4sq mm,, all the houses here in out village are built with ovens  and have  30amp 4sq mm circuit  for it

[degrub]

A/C cycling on when mcb trips and oven on ?

same for water heater ?

or other motor driven device ?

water well pump ?

 

just some ideas.

[OneMoreFarang]

MCBs trip if more current flows through them then their max current rating (i.e. 16A).

RCCBs and RCBOs trip because of leakage (mostly max 30mA = 0.03A).

 

Maybe something is wrong with the wires or the outlet (if there is one).

 

One common problem is that people connectors with low power ratings to connect wires together.

Many of them are rated maybe for 10A or 16A, which is not enough for many hobs (which are maybe part of your oven).

 

 

 

 

[bluejets]

16 hours ago, OneMoreFarang said:

MCBs trip if more current flows through them then their max current rating (i.e. 16A).

RCCBs and RCBOs trip because of leakage (mostly max 30mA = 0.03A).

No...combo's will trip from either and usually there is a trip indicator showing whether over current or earth leakage.

The earth leakage may be 30mA but the trip current would depend on many conditions including current rating and class of breaker.

 

Still waiting for photos of sw board setup from OP to make further educated comment.

[OneMoreFarang]

26 minutes ago, bluejets said:

No...combo's will trip from either and usually there is a trip indicator showing whether over current or earth leakage.

The earth leakage may be 30mA but the trip current would depend on many conditions including current rating and class of breaker.

 

Still waiting for photos of sw board setup from OP to make further educated comment.

Thanks for your correction. You are of course correct. I tried to make it simple, but my explanation was a little too simple.

[liddelljohn]

we have checked all visible wires , no damage at all the cable choccy bloc connector is not plastic  but an industrial ceramic one rated 100a ,

 

No other  equipment a/c, pumps cycle , and when all other circuits in house disabled  the oven still makes MCB trip,, the only thing that affects this is the doorbell circuit  that seems live all the time unless bell is disconnected ,,

 

without the oven I cant cook the food I like .. all my neighbours have same system thats 209 houses and no one has reported any issues with oven and I have asked dozens .

PEA  have checked and said nothing wrong ??????

[degrub]

Reading your original post again, oven works when not safety earthed, no trip and trips when earth is connected ( to frame i assume), it would appear there is a fault or leakage to frame  ? 
Do all of the other surveyed working ovens have a safety earth connected ? 

Do i understand correctly that there is no issue if the safety earth is disconnected from the oven ?

 Either that or the circuit is overloaded as indicated by the statement that removing the doorbell and outside lights “helps” ?


 

 

[Liquorice]

Sounds like an earth leakage fault with your oven appliance.

[liddelljohn]

5 hours ago, Liquorice said:

Sounds like an earth leakage fault with your oven appliance.

Yes definitely earth leak fault  ,, but all tests indicate the OVEN itself is OK  the old oven which had same fault  is now in a friends house  and is ok  ,, the fault is baffling everyone I have had round ,,no on can isolate it ???

 

5 hours ago, degrub said:

Reading your original post again, oven works when not safety earthed, no trip and trips when earth is connected ( to frame i assume), it would appear there is a fault or leakage to frame  ? 
Do all of the other surveyed working ovens have a safety earth connected ? 

Do i understand correctly that there is no issue if the safety earth is disconnected from the oven ?

 Either that or the circuit is overloaded as indicated by the statement that removing the doorbell and outside lights “helps” ?


 

 

Without the earh the oven is unsafe  as its live  all over , when earthed its not live to touch but it trips out the system,   Its a new oven the old one was doing the same  , but is now in a friends house  and is working fine ....?? 

 

all tests on Oven wiring circuits  are inconclusive , I had PEA, some electricians  etc

[liddelljohn]

Real issue is i cant get anyone here who is able to find , solve  or isololate where the problem is exactly

 

I cant cook now without an oven whole thing is farcical

#

just need a competent electrician with correct tools and diagnostics

[degrub]

Is this an issue that was not there, then appeared suddenly after a change in the house electrical - something was added or changed ?

Or was this present from the beginning- initial construction ?

 

is this issue present no matter if it has rained or not ?

you say it gets better when the doorbell and outside lights are turned off or is it when they are physically disconnected from power ? How and where are those physically connected to the oven wiring ?

i would think that the oven would/should have dedicated wiring from the breaker box to the oven with the only cross connect at the N buss bar and Safety Earth buss in the breaker box.

 

Does the oven require 3 wires (L,L2, N) or 4 (L, L2, N, S) by design ?

 

 

either way, it sounds to me ( not an electrician and US  based, Thailand is not the same electrical implementation), like the Neutral or possibly safety earth has been crossed with a Neutral return somewhere or a Load supply. Has anyone measured the voltage differences between L-S, N-S, L-N, L2-S, L2-N  at the wall connection with the oven physically disconnected ?

 

if the outdoor lights and doorbell were somehow spliced into what should be a dedicated circuit for the oven…… could be  a nail or screw, cut in wire insulation within conduit, device fault, a miswiring, etc. 

 

just some ideas.

 

[Liquorice]

2 hours ago, liddelljohn said:

Real issue is i cant get anyone here who is able to find , solve  or isololate where the problem is exactly

 

I cant cook now without an oven whole thing is farcical

#

just need a competent electrician with correct tools and diagnostics

Send a PM to @Crossy

He's a competent electrician working in Thailand.

[Liquorice]

1 hour ago, degrub said:

i would think that the oven would/should have dedicated wiring from the breaker box to the oven with the only cross connect at the N buss bar and Safety Earth buss in the breaker box.

It's quite common in Thailand to find appliances of higher amperage to be connected directly to the incoming tails from the meter unit.

The meters are on poles erected externally to the house.

[liddelljohn]

the system in my house has dedicated wiring and breaker just for oven with4sqmm cable  all conected to MCB and then to meter with all other wiring its a standard setup for here same as previous house ,, but this problem is so odd it makes no sense .

32 minutes ago, Liquorice said:

Send a PM to @Crossy

He's a competent electrician working in Thailand.

yes but he is in Bangkok im in Sattahip??? but i will ask him .

[Crossy]

OK let's try and sort this one out once and for all.

 

First thing we need @liddelljohn is some photos: -

• The device which is tripping, after it has tripped - So we know exactly what we are looking at.
• Your CU / distribution board with the lid off (care please).
• The rating plate of your oven.

Have you tried an appliance of similar rating (kettle, toaster) in place of the oven?

Can you try the oven on a different circuit?

Have you re-checked that the doorbell/outside lighting hasn't got the damp in again?

 

I'm suspecting some sort of earth leakage but let's gather some evidence.

 

Note:- The oven being live-case when the ground is off isn't necessarily a fault, elements do tend to leak somewhat, and of course, any switching power supplies will have mains filters.

 

Also, do you have any test gear (multimeter)?

[liddelljohn]

I have a multimeter,,will take some photos  and upload

the oven was taken to my friend house and it works fine  there ,,no tripping

[liddelljohn]

how do I load photos here   from phone

[Crossy]

33 minutes ago, liddelljohn said:

how do I load photos here   from phone

 

• Start a new reply to the thread.
• Click on "Add Files" at the bottom of the window.
• Click "My files"
• Click "images"
• That should open your Gallery where you can select images to add
• Click "Done"

 

EDIT Forget to add, you need to "insert" each photo into your post where you want them before submitting the post, if you don't I think it just lumps them all together at the end.

[liddelljohn]

Photos  uploaded. Oven mcb outdoor  Bell etc

 

[terryq]

May be nothing but there is a view that the problem is earth leakage related.

 

From your photo of the distribution board notice that the trip is set to only 5mA.

 

This may be too sensitive. Try setting  to the standard 30 mA and check if any improvement

 

 

.

[Crossy]

As @terryq suggests, first try your RCBO at 30mA, it's no less safe than 5mA is really.

 

Are you really feeding mains through that doorbell push? Those things are surely not IP65 or better which they ought to be when outdoors in the wet. I'd really look to modifying that to a low-voltage doorbell system.

 

Can you show a close-up photo of the RCBO section after a trip so we can see the indicator flags please.

[liddelljohn]

Thanks guys ,, upping the MCB trip and removing and changing doorbell circuit seems to have sorted the oven it stays on for  more than a hour ,, girlfriend says  her son turned the MCB down ???

[Crossy]

RCD problems seem to be en-vogue at present, at least that's one off the list