New oven & washing machine tripping RCD!

keystone

lisal0u wrote: »

Well the BC told me that I could do a re-wire this way and they would provide me with the certification, cost £175 for the privilage!

They have done the first and second fix checks then will send an electrician in at the end to do the final tests.

I think you will find that this covers the necessary works to be able to issue Part P Documentation. Electricians will usually refuse point blank to issue 17th Edn Certs for a system that they haven't completely designed, installed and tested themselves from start to finish. You could get a PIR done after the event I suppose but it isn't the same.

It seems the advice given in March 09 in your other thread has gone unheeded. I really do suspect you have an electrical problem and no disrespect to your dad but industrial and domestic are NOT the same. It really would be worth your while IMHO after all the investment in time, money, sweat and heartache you have made in this property to get a recommended, trusted (friends, neighbours etc) domestic installer to give this installaton the once over properly before you go much further.

Not being critical you understand. I really am trying to be helpful.

HTH

Cheers

lisal0u

Hi keystone,

I do appreciate your comments. Ill be very annoyed if we dont get the correct certification as that is what I have paid the council for. They have been and inspected first and second fix and had no problems. It states specifically that a competant person or qualified electrician not a member of an electrical body can carry out the installation.

I do realise that industrial and domestic are different but he did used to be a domestic installer, obviously a while ago hence making sure we had a copy of and used the 17th edition and part P documentation.

He's going to test the earth leakage then we will know what is causing the problem. Im definately going to be having a chat with building control tomorrow!

Lisa

Canucklehead

Hi,

If the oven is on it's own circuit then that would suggest the oven has a fault.
The washing machine might be a separate problem.

GSR.

lisal0u wrote: »

Hi,

Not sure what you mean?

We changed the plans and the kitchen has it's own ring. The cooker has it's own fuse, not part of the ring. Is that what you mean?

We also changed the consumer unit for a larger one so now there are 2 spares. The council have ok'd first and second fix just need to do the final test once the garage is finished.

Lisa

Homersimpson

". I really do suspect you have an electrical problem and no disrespect to your dad but industrial and domestic are NOT the same. "

I'm sorry to disagree but the principles for domestic, commercial, industrial etc. are all the same, there all covered under BS7671:2008 17th edition. If you are competent to wire a commercial or industrial ringmain then a domestic ringmain which works in exactly the same way should pose no problems. In commercial installations the use of twin and earth cabling for ringmain circuits is widespread and has been for years. I wouldn't be so confident with a domestic electrican wiring a commercial or industrial job though....

To the OP

If you have a problem with an RCD tripping its either:-

A faulty piece of equipment
A faulty RCD
A cable fault

If you consumer unit only has one RCD then consider swapping the consumer unit for one with two RCD devices (all the new 17th edition consumer units should be like this now). This allows you to spread the circuits out so that the cumulative effect of the earth leakage current is reduce and hence nusance tripping can be avoided.

My first port of call would be to try replacing the RCD as its not unknown for these to be faulty.

Happy fault finding!

keystone

I have a nagging feeling in my water that some of your problems are related to having your sockets all on a single ring. But I've just seen that you've made the kitchen a separate ring and that the oven is now on its own circuit. Is it an single oven or is it a cooker (ie double oven)? I can't find that info anywhere either in this thread or in your other one (or am I just missing it?) If its a double one it needs a proper cooker circuit with a large double pole switch near the cooker rather than a 2.5mm TC&E but I'm sure you know that. It may be that an RCBO would be more appropriate for this circuit if the cooker / oven is nuisance tripping which may not necessarily be an oven / cooker fault.

Is the washing machine still tripping the RCD now that the kitchen has a separate ring?

I'd be tempted to be thinking about splitting the upstairs and downstairs ring into separate circuits as well if you now have spare ways.

Cheers

keystone

Homersimpson wrote: »

I'm sorry to disagree but the principles for domestic, commercial, industrial etc. are all the same, there all covered under BS7671:2008 17th edition. If you are competent to wire a commercial or industrial ringmain then a domestic ringmain which works in exactly the same way should pose no problems. In commercial installations the use of twin and earth cabling for ringmain circuits is widespread and has been for years. I wouldn't be so confident with a domestic electrican wiring a commercial or industrial job though....

Don't be sorry - there is no reason to be. I'm more than happy to be shown to be wrong (and at least I am prepared to admit it) or be challenged if it means that the OP gets the help they need to solve their problem. Its what this forum is about n'est pas?

Cheers

eco-friendly_2

My first port of call would be to try replacing the RCD as its not unknown for these to be faulty.

Particulary for the intermittent/delayed tripping of the oven.

lisal0u

Thanks for your help, it’s much appreciated!

We completely changed the re-wire after the advice we had last time and through thorough reading of the 17th edition.

There is now an upstairs ring, downstairs ring, kitchen ring and the cooker has it own double pole switched circuit. The consumer unit has a RCD on both sides. The cooker is a single oven and is only 1.1kw. I decided I wanted to put the cooker switch in in case I decided to upgrade to a double oven in the future.

The dishwasher, microwave and tumble dryer are all using the kitchen ring the same as the washing machine and they do not cause any tripping.

My Dad is going to try a few things at the weekend to try and find the fault. He’s suggested swapping the oven to the other side of the consumer unit and see if it still trips and also check the earth leakage from the appliances.

I am fairly sure the washing machine has a faulty element as it trips when you start to hear the element heating the water. Same point every time! It was also given to us so it’s not new and may have been knocked about a bit in transit. The rinse spin cycle is completely fine which is another reason for thinking it’s the element.


Thanks again for the advice,

Lisa

Homersimpson

The usual way in a house is that one (or now two) RCD devices serve a number of MCB's. Bear in mind that an RCD will never trip because of an overload, an RCD simply measures the current flowing out on the live against the current flowing back on the neutral, if the difference is more than the devices rating then it trips as the missing current must have been transfered to earth.

As an side if you wanted an RCD with overload protection then you would use a single device called an RCBO but generally these are more a commercial thing (but can be used in houses without and problems, its more for cost reasons that we don't tend to use RCBO's in houses).

Lets say for arguments sake that you have one main 80A/30mA RCD feeding the following circuits each with their own MCB

10A MCB Lighting
32A MCB Ringmain general
32A MCB Ringmain kitchen
45A MCB Shower
32A MCB Cooker

The total of the earth leakage current on all of these circuits must be less than 30mA otherwise the RCD will trip. Electric cookers, washing machines and electronic equipment (especially PC's) are notorious for earth leakage.

If you can't reduce your total earth leakage current then you need to split it up so having two RCD devices configured as follows would be a good idea (and is how it should really be done under the 17th edition).

80A 30mA RCD
10A Lighting Circuit
32A Ringmain General
32A Cooker

80A 30mA RCD
32A Ringmain Kitchen
45A Shower

As an alternative (and more costly option) you could dispense with the main RCD devices and put every circuit on its own RCBO as mentioned above.

Before you get to heavily involved with this I would test the RCD with a proper RCD tester to see how sensitive it is and change it as necessary. The fact that so many appliances are upsetting it would lead me to check this first.

Best of luck!

lisal0u

Thanks ever so much, your posts are really helpful and I can understand them :-)

The current consumer unit has 16 fuses and is a Wylex NHISS8704

The first side has:
1 spare
lights - says 06 on it, 6A?
lounge underfloor heating -10
Kitchen underfloor heating - 10
Garage - 16
Kitchen ring - 32
Downstairs ring - 32
cooker - 32
RCD - 80A 30mA

Second side has:
2 spare
outside lights - 6
lights - 6
Bathroom towel radiator element - 10
Bathroom underfloor heating - 10
upstairs ring - 32
RCD - 80A 30mA

I will get my Dad to check the RCD first!

Thanks again for all the helpful advice,
Lisa