Kitchen Electrics

[bundybundy]

First post, and a long one, apologies in advance!!

A fortnight ago Currys came to deliver and connect my new washing machine, but on arrival they said that they couldn't connect it because of a problem with the earth.

I had a friend come round and have a look, he does something to do with electrics but I don't really understand what! He did some tests and said there was nothing he could do and that the cable would need replacing for which I would need an electrician qualified for domestic work.

He left me a piece of paper to pass to the electrician;

Supply TNS

Ze 0.37

R1+R2 of 20A kitchen radial 3.67

Checked all socket outlets and FCU's for loose connections (no joy)

All other circuits seem ok.

Today i've had an electrician round who has said that he can just "stick an RCBO in" and it will cure the problem, however I have checked with my friend and he says this is not good enough.

Who is right please???????? I'd rather not have to redecorate if possible.

Many thanks

 

[JohnnyG]

Reg 531.3.1 states:

In a TN system, where, for certain equipment in a certain part of the installation, the requirement of Regulation 411.4.5 cannot be satisfied, that part may be protected by an RCD.

That's probably what the electrician is going with, I think he'd still have to ensure the correct disconnection times are met though.

 

[disinfo]

I'd say have the cable replaced, or at least looked into further. If he's checked all of the accessories for loose connections and found nothing it could be a loose connection in an inaccessible junction box somewhere. Its only going to get worse and could well be a risk of burning.

 

[GaryMo]

The R1+R2 figure is high which indicates an increadibly long circuit or a poor connection. This should be investigated.
Did your friend use calibrated test equipment or a multimeter?

I personally don't feel that an RCD should be used for circumstances where maximum earth fault loop impedances can't be met in a TN system. It's a workaround at best. and your friend is correct by stating that it's not good enough.

Max Zs for a B20 MCB is 2.3ohms or 1.84ohms corrected.
Zs for your circuit is currently 4.04ohms which means that your overcurrent protective device won't trip within the require time.

 

[holmslaw]

..

 

[bundybundy]

The R1+R2 figure is high which indicates an increadibly long circuit or a poor connection. This should be investigated.
Did your friend use calibrated test equipment or a multimeter?

I personally don't feel that an RCD should be used for circumstances where maximum earth fault loop impedances can't be met in a TN system. It's a workaround at best. and your friend is correct by stating that it's not good enough.

Max Zs for a B20 MCB is 2.3ohms or 1.84ohms corrected.
Zs for your circuit is currently 4.04ohms which means that your overcurrent protective device won't trip within the require time.

Hi there, thanks for that

The tester he used, I think he said was a "mega".

I had a feeling it was going to be the more expensive and painful option, but if its going to be safer I suppose its got to be that way.

My friend gave me another option of a type of cable that can be surface mounted, like a thin pipe. Not sure I like the idea of having cables on display but it may be the easier option in my recently decorated kitchen!!!

 

[GaryMo]

There's always the option of mini-trunking to hide surface cabling.

I wouldn't give up looking for the problem unless you're totally sure you've covered all area's - it must be a poor connection somewhere.
Have you lifted any boards above the kitchen?

Is the washing machine just plugged into a socket?
If so, has your friend measured R1+R2 through the socket face or directly via the conductors in the rear of the socket? Ask him if you're not sure.
If it's through the socket face then over time the sockets internal connections can deteriorate thus resistance rises. It may be a simple case of a new socket face.

 

[STI]

GaryMo beat me to it

 

[bundybundy]

There's always the option of mini-trunking to hide surface cabling.

I wouldn't give up looking for the problem unless you're totally sure you've covered all area's - it must be a poor connection somewhere.
Have you lifted any boards above the kitchen?

Is the washing machine just plugged into a socket?
If so, has your friend measured R1+R2 through the socket face or directly via the conductors in the rear of the socket? Ask him if you're not sure.
If it's through the socket face then over time the sockets internal connections can deteriorate thus resistance rises. It may be a simple case of a new socket face.

He did originally use a plug-in type adapter and the meter plugged into this, but when he found there was a problem he removed all of the socket fronts and checked behind them with the meter. Unfortunately above the kitchen is an engineered wood floor which I'm not that keen on lifting up if possible, The kitchen floor is concrete.

I might get him in to have another look if he gets time, but he's a busy guy and I don't think tea and biscuits will work a second time!!!

 

[disinfo]

The R1+R2 figure is high which indicates an increadibly long circuit or a poor connection. This should be investigated.
Did your friend use calibrated test equipment or a multimeter?

189m you never know, they might have a big kitchen!!!

 

[ban-all-sheds]

A fortnight ago Currys came to deliver and connect my new washing machine, but on arrival they said that they couldn't connect it because of a problem with the earth.

I'm amazed they checked anything, given that it just plugs into a socket.

Anyway - FYI - this explains why a high R1+R2 or Earth Fault Loop Impedance is a problem: //www.diynot.com/wiki/electrics:mcb2

 

[bundybundy]

I'm amazed they checked anything, given that it just plugs into a socket.

Well, I suppose as inconvenient as it may feel I'm glad they did.

Anyway - FYI - this explains why a high R1+R2 or Earth Fault Loop Impedance is a problem: electrics:fuses_and_miniature_circuit_breakers:mcb2

Thanks, its kind of making sense to me, my friend did attempt to explain this while he was here, but I was looking a little glazed over!!

It does feel a little frustrating that he can't help me because he's not qualified to do domestic work, even though he seems more in the know that the "qualified" guy.

 

[JohnnyG]

I'm amazed they checked anything, given that it just plugs into a socket.

To be fair to Currys they do state that if you choose their installation service:

Here's what we'll do:
• Check that existing electrical and plumbing connections are safe and appropriate to be used for the new appliance
• Disconnect the existing appliance
• Unbox and check the new product
• Remove transit bolts
• Connect to existing plumbing and electrical sockets plus level the appliance
• Test the appliance to make sure there are no leaks

What we don't do:
• Plumb two waste pipes into one
• Make any alterations to existing plumbing or electrical connections
• We can only install to existing connections

I only know that as we purchased an oven recently and happened to look at the installation options available from high street stores

 

[OwainDIYer]

It does feel a little frustrating that he can't help me because he's not qualified to do domestic work, even though he seems more in the know that the "qualified" guy.

"like for like" replacement of cables and accessories is not notifiable under Part P, even in kitchens and bathrooms.

The fact that someone is employed by a business which is registered under Part P does not mean that that person holds any individual qualifications.

 

[bundybundy]

Evening, just an update.

My friend came round this evening to do some further testing, he think that there is a junction box between the cellar plasterboard ceiling and the parquet in the living room

After explaining my experience with the electrician the other day he has said he is willing to put me in a new circuit using surface mounted cable pyro?

We've come up with a route that keeps it close to floor level so it shouldn't look too bad.

Thanks again for all the advice guys.