house buying and electrics

[ban-all-sheds]

I seem to remember you saying white twin and earth which may mean it is thermal setting not thermal plastic cable and thermal setting is rated 90°C not 70°C so reference method C for 2.5mm² is 33A table 4E2A.

Personally unless marked on the cable I would assume it to be thermal plastic and use BAS list but what I am pointing out your electrician could be correct without seeing how installed and having a bit of the cable to inspect or test I would certainly question 32A with 2.5mm² but would still accept it once shown it is thermal setting cable.

In 2005 it was probably just white thermoplastic.

But even if it is thermosetting cable with a 90° rating, the accessories it's connected to won't like that temperature, so you're back to 70° and the current carrying capacities in the table I posted.

 

[ericmark]

Likely you are right but I am wary about criticising another electricians work when we don't know all the facts and it is possible what he is proposing is OK.

 

[masamune]

If I install a new cable what would be the best option for Neff?

Most single neff ovens seem to be in the 3.5kW plus range. Although that is full total load (oven and grill at the same time if I understand right?)

Since we are fitting floor, I asked the sparkie to fit a spare cable/dedicated MCB for the cooker anyway, to connect at later date. That is so we won't have to lift the floor again.

Of course he asked me the oven specs in order to decide which cable. I don't have a clue, one of the installation manuals I checked online states H05VV-F cable. These appear to come in different sizes.

So the key questions are, how can I make it forwards compatible with most neff ovens in terms of wattage? What fuse and wiring is needed?

edit: the cable around the ring is most likely old PVC, black/red, or standard grey 2.5mm. I will open a socket to check.

 

[ban-all-sheds]

Most single neff ovens seem to be in the 3.5kW plus range.

Yup.

They are designed with the rest of Europe in mind, where 16A socket circuits are the norm, and where an oven like that could simply be plugged in. 16A equates to 3.68kW @ 230V.

Of course he asked me the oven specs in order to decide which cable.

Just ask him to install a 32A circuit.

one of the installation manuals I checked online states H05VV-F cable.

That will be the cable to connect the oven to the cooker outlet plate, not what is used between the CU and the outlet plate - that will be twin & earth.

//www.diynot.com/wiki/Electrics:harmonized-wire-code

So the key questions are, how can I make it forwards compatible with most neff ovens in terms of wattage?

Ask him to install a 32A circuit, i.e. one which could supply a 32A load if required. That will be enough for any domestic cooker up to 15kW.

What fuse and wiring is needed?

You may find that to comply with Neff's instructions, and to make it easier to use a sensible sized flex to connect it, that you actually need a 16A breaker in the CU.

 

[masamune]

Just ask him to install a 32A circuit.

i.e. one which could supply a 32A load if required. That will be enough for any domestic cooker up to 15kW.

So what cable would that require to fit (pro-actively)?

You may find that to comply with Neff's instructions, and to make it easier to use a sensible sized flex to connect it, that you actually need a 16A breaker in the CU.

Sorry a little confused, are you saying the cable should be able to take load 32A but the breaker in CU should be 16A?

The electrician is a bit anal with standards, so when I asked to fit a cable that is forwards compatible with above 3kW ovens he said it doesn't work like this. All I want to do is isolate the oven from the ring downstairs

 

[ban-all-sheds]

So what cable would that require to fit (pro-actively)?

• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.htm
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://web.archive.org/web/20070327014113/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  
  The references above which are in italics are out of date. The principles are still valid, and you can absolutely learn valid things from them, but you will need to refer to the latest edition of the Wiring Regulations to get the correct data.
  

Sorry a little confused, are you saying the cable should be able to take load 32A but the breaker in CU should be 16A?

It might need to be 16A.

The electrician is a bit anal with standards, so when I asked to fit a cable that is forwards compatible with above 3kW ovens he said it doesn't work like this.

I sympathise with eric's POV, but it really does sound as if your electrician is broken, and should be replaced.

Of course it works like that.

Of course you can have a 32A cooker circuit installed if that's what you want.

 

[masamune]

[/size][*] http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

Thanks you, the link is really useful, not sure about the cable type though.

We have a plastic trunking going to the CU under the floorboards and onto the wall. The oven position is about ~6 meters from the CU considering the cable running down the wall and under the floor.

What should I enter in the fields?

Should I enter higher power than required?

 

[EFLImpudence]

Ask him to install a 32A circuit, i.e. one which could supply a 32A load if required. That will be enough for any domestic cooker up to 15kW.

As your cable is in conduit (trunking) you will need 6mm² cable.

 

[ban-all-sheds]

... not sure about the cable type though ... What should I enter in the fields? ... Should I enter higher power than required?

Who will be signing this?:

I being the person responsible for the design of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2011 except for the departures, if any, detailed as follows:

because I don't think you can....

 

[masamune]

... not sure about the cable type though ... What should I enter in the fields? ... Should I enter higher power than required?

Who will be signing this?:

I being the person responsible for the design of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2011 except for the departures, if any, detailed as follows:

because I don't think you can....

Sorry I am not following you?

The questions above are about the link you sent to calculate the type of cable required.

What are you referring to?

 

[ban-all-sheds]

In order to comply with the Wiring Regulations the act of designing a circuit (and the acts of installing it and testing it) require that the person doing the work signs that declaration on an Electrical Installation Certificate. Complying with the Wiring Regulations is really the only practicable way of complying with the Building Regulations, which is a legal requirement.

You do not appear to be qualified or competent to sign the declaration, so I asked you who will.

There are similar declarations to be signed by the person who installs the circuit, and by the person who tests it before putting it into service. If the same person does all three acts then there's a combined declaration he can sign.

I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2011 except for the departures, if any, detailed as follows:

If I install a new cable what would be the best option for Neff?

Don't forget that before you install it you are required to apply for Building Regulations approval.

Just ask [your electrician] to install a 32A circuit.

Ask [your electrician] to install a 32A circuit, i.e. one which could supply a 32A load if required.

 

[masamune]

I never implied that I will be doing the work myself. All the work is to be carried out by a certified electrician.

 

[JohnW2]

I never implied that I will be doing the work myself. All the work is to be carried out by a certified electrician.

I know you didn't imply that. In at least four posts, including in the very first sentence of your initial one, you mentioned your electrician.

Some people seem to do a lot of 'assuming' (of the worst) around here!

Kind Regards, John

 

[masamune]

Anyway

I just want to fit a sodding cable "lying" there pro-actively for my future cooker. As no dedicated MCB existed before for the cooker.

My electrician should of course know, but ...well he has his views and I'd rather he fitted it than talk about it forever. Besides the cable need not be live, so nothing to certify about it.

Can we all agree what that should be for:

1. Running through a plastic trunking from the CU, then chased into wall to oven socket

2. About 6m distance

3. 3.6kW+ oven

He keeps asking me for the manufacturer's spec, I cannot find any further info other than the wattage load really. The manual does not refer to the power supply cable, only the appliance connecting cable.

Thank you

 

[ericmark]

If you don't have paperwork certifying what has been done then no point in doing anything as I would not connect up a cable I could not inspect whole length of without some paperwork telling me how it was installed.

Yes in my mothers house I have placed cables ready for new ring main. But unless I do the work then those cables would not be used any other electrician worth his salt would want to install new cables.

Cables with power on them are something different. Having a cable from consumer unit to a cooker isolator and from cooker isolator to cooker connection unit all live and ready to use is what one would expect again paperwork is required. If for example it states 45A cooker supply fitted but fused down to 16A as this was requirement for oven. At a latter date another electrician would not worry at changing the MCB to 40A for new cooker. Without that paperwork likely he would not want to use it.

On forums like this it is common to see posts where they say they are getting an electrician in often they claim he's on holiday but we know that will not be the case. In the main this is apparent by the questions asked. We have got use to reading between the lines and so will give advice accordingly. When being fitted by an electrician we do not need to remind him of the RCD requirement for new circuits for example but we often will talk about this as we expect it is not going to be fitted by an electrician.

Today in the main I would use 10mm² cable for a new cooker feed to make it future proof and on the paperwork I would call it a 45A feed fitted with a B16 MCB to match installed oven. I would hope then any electrician would swap the B16 MCB for a larger one if required in the future.