Replacement oven - incorrect switch?

[luckyNot]

Hi,

I just moved in to a new house and have encountered a number of 'interesting' wiring scenarios, but for now I will focus on the only one I think is ok ..

I have a 20A MCB, 4mm clip direct running 10 meters to oven isolator switch. The oven is 4Kw, so about 16A. There is 1 mtr of 2.5 flex between the oven and mounting plate - so rating 25A.

I need to replace the isolator switch. From what I can see a standard cooker switch is 45A, but isolator switches at 20A are available though not labelled 'cooker'. Is there a best practice here e.g. is putting 45A switch on a 2oA circuit misleading, or using a 20A for a cooker wrong?
Thanks

 

[telectrix]

you can fit a 45A isolator no problem, as the 45A is the max. rating of the isolator, any thing under a 45A load will just mean that it's not being overloaded.

 

[Strima]

20 amp will be fine as the MCB is rated at 20 amps.

 

[DJ Ovengloves]

The fact you’re askjng the question means you shouldn’t be changing it!

How many hundreds of thousands have you just spent, but yet you’re trying to save cash on something that could kill?

 

[telectrix]

or buy a labeller machine and label the existing switch.

 

[luckyNot]

The fact you’re askjng the question means you shouldn’t be changing it!

How many hundreds of thousands have you just spent, but yet you’re trying to save cash on something that could kill?

I am confused, but it may be I phrased my questions poorly. I wanted to know if the current install, using a 45A switch was wrong given the rating of the circuit. The responses here confirm that a 45A is ok (and not misleading), so I can replace like for like.
I am replacing the switch due to it being dirty and cracked.
Given this, is your view that I require an electrician to do this? If so, why?
Thanks

 

[DJ Ovengloves]

Not once have you mentioned cracked switched, more “interesting wiring”, with a load of pseduo spark speak and then misunderstood something basic in regards to ratings of the switch, which points to an amateur.

Why is the switch cracked..excessive heat, physical damage etc? How are you measuring that the cpc is viable etc?

 

[Wilko]

Hi - if there any issues with making the connections then there is risk of fire due to ohmic heating for example. It's very important for the earthing to be correctly carried through too.

 

[luckyNot]

Thanks for the quick response. I think we can agree my opening post was poorly worded/described
Pseudo spark speak it is. I looked on the forum and saw these were the sorts of details that people ask for, so I provided them.
What I was trying to understand, with regard to switch rating, was whether or not it was misleading putting a 45A switch on a circuit that did not appear to be be capable for running 45A. The responses suggest this is common practice and not misleading. So it seems I have indeed misunderstood something basic.
I am an amateur and this is a post in the DIY forum. I have chosen to ask here before acting for just this reason.
Following your question regarding damage, I have opened the switch and looked inside. There is no burn/electrical damage, the face plate is cracked but not heat marked.
I had to Google 'CPC' and I cannot make full sense of what I found. I think what you are asking is whether the earth feed is big enough for things to be safe. From what I can see in the switch the feed is using earth from the 4mm cable. Is this a concern?
Thanks again

 

[Deleted member 26818]

CPC = Circuit Protective Conductor, which is the earth wire you see in cables.
45A is fine, anything else and you run the risk of having to change the back box, which could mean chiselling out the old one and then filling a gap, etc.
Make certain all the conductors are terminated correctly.

 

[FatAlan]

Ignore some of the patronising responses. I think the general consensus is that replacing like for like is ok with the proviso that their are no underlying issues that have resulted in the damaged switch.

 

[DJ Ovengloves]

..and you would test for underlying issues by visually inspecting and?

I have no problem with anybody doing electrical work, however even a like for like change where you’re releasing / tightening / creating connections need basic testing to be sure that what you have done is safe - anything else is guesswork and can get you or someone else killed.

Dramatic / worst case yes. Scaremongering, I don’t think so. Patronising, no way mate.

Great name btw!

Ignore some of the patronising responses. I think the general consensus is that replacing like for like is ok with the proviso that their are no underlying issues that have resulted in the damaged switch.

 

[FatAlan]

The fact you’re askjng the question means you shouldn’t be changing it!

How many hundreds of thousands have you just spent, but yet you’re trying to save cash on something that could kill?

Patronising. Yes

 

[DJ Ovengloves]

No careful. Hopefully your training will teach that.

Also, lookup th definition of patronising. At worst I was rude based on how stupid I feel the op is being to safe a few quid. I can handle that.

Op - it’s nothing personal mate, but imho if you’re doing anything with electricity (except changing a bulb, plugging in a plug) it needs testing or you are potentially asking for trouble.

 

[FatAlan]

Feeling a bit provocative I’m afraid DJ. I know your posts like a lot of others on here are well meaning but they do I do cringe at some responses when DIYers come on here asking for advice. I also appreciate a little knowledge can sometimes be more dangerous than none but the OP was aware of equipment loads and the need to have appropriately rated switches, cables and fuses to raise the question.

 

[luckyNot]

Thanks all and thanks for the different perspectives and weighting thereof.
After considering what was written here, and the originally referenced 'Interesting wiring' I am seeing around the house (1920s built with 1980s extension), I have decided to get a local sparky in to give me an 'overview' of the house as a whole. From there hopefully I can make some informed decisions on what is within my abilities and what is not.

Risks of testing, or not, by amateurs is a good challenge. I have a B&Q plug thing that tests plug sockets. Other than that I only have multi-meter. Whilst from what I have read and tried on a lighting circuit I can verify connectivity between two points and voltage difference between points I would struggle to verify anything more. Does this mean I should never do DIY? As noted, the consequence of getting it wrong is potentially fatal, but is paying £120 for someone to undo and redo 5 screws just a case of modern 'nanny state' thinking?

In my old house a Pro installed my kitchen circuit and tested one of my RCD. It did trip but did not respond within tolerance. This scared the sh*t out of me, as yet is something I can never test.

It is late and I am rambling.
Good night

 

[Des 56]

If you are unaware of the standard or the safety of your installation,it is worthwhile having a condition report done on the installation,it involves using and being familiar with instruments that are not normally available to the general public

Once you have the whole picture,any like for like changes or minor additions to the wiring can be done by yourself,most people with a little care are quite capable of carrying out simple domestic electrical tasks
As long as care has been taken with the task,this ongoing maintenance should hold no issues

 

[DJ Ovengloves]

It’s meant to be provocative, but not from a sense of superiority but trying to get people to focus on what is important. The op doesn’t have the tools to ensure what he is doing is safe and has effectively put a price on £120 on his life and in regards to the “its only five screws” comment...yes, it is a silly amount (which I would contest btw) to REPLACE the accessory, the trick is testing the change and ensuring it’s safe!

FYI - I am not an electrician - I am a keen DIYer who has 2394 and 2395 (amongst others) and a calibrated tester I know how to use, but the best things I’ve learnt is not to simply trust your confidence (I.e “it’s only a couple of screws etc), test EVERYTHING and most importantly, know your limitations!

All the best Alan in your training and I hope you keep safe op!

 

[FatAlan]

It’s meant to be provocative, but not from a sense of superiority but trying to get people to focus on what is important. The op doesn’t have the tools to ensure what he is doing is safe and has effectively put a price on £120 on his life and in regards to the “its only five screws” comment...yes, it is a silly amount (which I would contest btw) to REPLACE the accessory, the trick is testing the change and ensuring it’s safe!

FYI - I am not an electrician - I am a keen DIYer who has 2394 and 2395 (amongst others) and a calibrated tester I know how to use, but the best things I’ve learnt is not to simply trust your confidence (I.e “it’s only a couple of screws etc), test EVERYTHING and most importantly, know your limitations!

All the best Alan in your training and I hope you keep safe op!

Hi DJ. I meant I was being provocative. FYI I’m a 50+ grumpy old fart in a different profession having completed 2494/5 like you plus the other domestic type C&G courses etc. These SM forums like emails and texts are easy to take out of context.

 

[FatAlan]

PS. Not saying that you are a 50+ grumpy old fart!