washing machine and dishwasher supply

amstel · 28 Oct 2013

Good afternoon all,
I have a separate kitchen ring main, the washing machine and dishwasher are both pluged into different 13amp switched sockets on this ring, both of these sockets are underneath the worktop and behind the said appliances, the circuit is protected by a 32amp RCBO.
My question is this,...is the plug top fuse and rcbo enough protection? or should there also be 20amp dp switch involved above the worktop?
Thanks.

riveralt · 28 Oct 2013

amstel said:
My question is this,...is the plug top fuse and rcbo enough protection? or should there also be 20amp dp switch involved above the worktop?
Thanks.

Yes the 13A plug fuse(s) are sufficient to protect the washing machine and dishwasher cable. The RCBO is there to protect you.
Adding a DP 20A switch does not add any level of protection although it could make it easier to isolate the appliance for maintenance purposes.

amstel · 28 Oct 2013

riveralt";p="2921512 said:
amstel said:

My question is this,...is the plug top fuse and rcbo enough protection? or should there also be 20amp dp switch involved above the worktop?
Thanks.

Click to expand...

Yes the 13A plug fuse(s) are sufficient to protect the washing machine and dishwasher cable. The RCBO is there to protect you.
Adding a DP 20A switch does not add any level of protection although it could make it easier to isolate the appliance for maintenance purposes.[
/quote] Thanks Riveralt, this is what I dont get about these 20amp dp isolators and fcu's above the worktop,...if the appliance needs maintenance, you would have to pull it out from under the worktop anyway, switch off the socket and pull the plug.
Like you say, the rcbo and plug top fuse are adequate. cheers.

EFLImpudence · 28 Oct 2013

riveralt said:
The RCBO is there to protect you.

And the cable.

amstel said:
this is what I dont get about these 20amp dp isolators and fcu's above the worktop,...if the appliance needs maintenance, you would have to pull it out from under the worktop anyway, switch off the socket and pull the plug.

It's true that you do not need a second 13A fuse and a switch does nothing except switch.

However, it may be useful to isolate the appliance before the repair man arrives and pulls it out.

PrenticeBoyofDerry · 28 Oct 2013

amstel said:
My question is this,...is the plug top fuse and rcbo enough protection? or should there also be 20amp dp switch involved above the worktop?

Is a normally set up for free-standing appliances and quite safe.
If the appliance were integral, then for ease of isolation it would be wise to have above worktop isolation. But as already stated a 20A DP isolator is not going to offer you any more protection than what you already have.

PrenticeBoyofDerry · 28 Oct 2013

amstel said:
this is what I dont get about these 20amp dp isolators and fcu's above the worktop,...if the appliance needs maintenance, you would have to pull it out from under the worktop anyway, switch off the socket and pull the plug.

But if for any reason the machines casing had become live or you did need to isolate the machine quickly, then above worktop isolation would mean you did not have to handle the machine to isolate. But that being said you could isolate at the consumer unit if needs be.

amstel said:
Like you say, the rcbo and plug top fuse are adequate.

Indeed they are

amstel · 28 Oct 2013

PrenticeBoyofDerry said:
amstel said:

this is what I dont get about these 20amp dp isolators and fcu's above the worktop,...if the appliance needs maintenance, you would have to pull it out from under the worktop anyway, switch off the socket and pull the plug.

Click to expand...

But if for any reason the machines casing had become live or you did need to isolate the machine quickly, then above worktop isolation would mean you did not have to handle the machine to isolate. But that being said you could isolate at the consumer unit if needs be.

amstel said:

Like you say, the rcbo and plug top fuse are adequate.

Click to expand...

Indeed they are

Thanks, just say for instance, there was a earth leakage fault, and the appliance casing had become live, would the rcbo sense this and trip, even if the appliance was not in use? cheers.

PrenticeBoyofDerry · 28 Oct 2013

It should, providing the RCBO was working and not faulty.

ban-all-sheds · 28 Oct 2013

And provided the appliance and its circuit are wired correctly.

EFLImpudence · 28 Oct 2013

PrenticeBoyofDerry said:
It should, providing the RCBO was working and not faulty.

If it was faulty the fuse would blow (not technically earth leakage but an earth fault current).

EFLImpudence · 28 Oct 2013

To clarify if the OP is not aware -

RCBOs protect against

earth leakage - Live to Earth and Neutral to Earth - and

overload and

earth fault current, L to E, and short circuit current, L to N.

PrenticeBoyofDerry · 28 Oct 2013

EFLImpudence said:
If it was faulty the fuse would blow (not technically earth leakage but an earth fault current).

That would depend on the nature of the fault and how it was introduced, but that is a side issue.
My point is that you cannot rely on the RCBO to be working as it is expected to.

EFLImpudence · 28 Oct 2013

PrenticeBoyofDerry said:
EFLImpudence said:

If it was faulty the fuse would blow (not technically earth leakage but an earth fault current).

Click to expand...

That would depend on the nature of the fault and how it was introduced, but that is a side issue.
My point is that you cannot rely on the RCBO to be working as it is expected to.

Mmm.

I presume you mean the RCD part - well, everything fails.
The only precaution would be more than one device.

Do you suspect the overload aspect as well?

JohnW2 · 28 Oct 2013

EFLImpudence said:
PrenticeBoyofDerry said:

My point is that you cannot rely on the RCBO to be working as it is expected to.

Click to expand...

Mmm. I presume you mean the RCD part - well, everything fails. ... The only precaution would be more than one device. ... Do you suspect the overload aspect as well?

That's the (essentially unanswerable) $64,000 question, isn't it? Whilst there are some concerns (and a very limited amount of data) in relation to in-service (un)reliability of RCDs (which may also apply to the RCD part of an RCBO), since they are effectively untestable in service, we really don't have a clue about the in-service reliability of MCBs (or the over-current part of an RCBO).

Kind Regards, John

PrenticeBoyofDerry · 28 Oct 2013

I recently went to property regarding a power-loss to the cooker.
The fault was not related but while investigating, I found a DP RCBO in the open position but still powering a circuit. The test button did not function nor did the RCD trip on testing. I thought it pointless introducing an overload fault to the unit, but I suspect that to would have failed also.

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washing machine and dishwasher supply

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