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hi all, I've been asked by a chippy mate to install an extractor in his workshop. Had a look at the spec and its 2.2kw so nothing major. Spec say to install on a 16a socket protected by a 30a d type mcb.

Ideally then a 2.5mm radial and 16a cform.
I understand the 30a d type is for start up and being a fixed load short circuit protection is achieved either way (the great shower debate) but in this instance if we are saying we need a bigger mcb then surely I'm installing cable and sockets that aren't upto the job. Am I being over cautious here??
 
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  • #3
i'd question the 30A type D. seems way over the top.
Yeah I did mate, I've spoken to "technical" and they just say for sart up. I could either follow manufacturers instructions or put in something like a c20 or run a 4mm to a 32a c form which seems crazy
 

telectrix

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a 20A C feeding 2.5mm cable would be fine. loads of 2.2kW motors on compressors come with a BS1363 fitted. on a 1.5mm flex.
 

davesparks

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Did you point out to them that 30A is not a standard rating for a 60898 MCB?

This in itself suggests to me that someone who doesn't know what they are talking about is responsible for that specification.

The regulations allow the omission of overload protection where the load is not subject to overload faults, not just for any 'fixed load'. The extractor should have overload protection built in to it which will allow the omission of overload protection for the circuit feeding it, but you need to check this.

I would not personally accept a circuit designed with a socket in it as being exempt from the requirement for overload protection as the socket can easily be used for anything else. If you are going to omit overload protection then, in my opinion, the equipment should be hard wired.
 
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Agree with both of you, its one of those things where most people say you must follow manufacturers instructions but in this case I'm just not doing it. I would like to put a socket for flexibility in his workshop. I'm going to sticking on a 20a and keep my fingers crossed
 

telectrix

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regulations state that MI should be taken into account, not blindly followed. this would appear to allow for incorrect MIs, esp. those that are from China.
 

davesparks

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I would like to put a socket for flexibility in his workshop. I'm going to sticking on a 20a and keep my fingers crossed
That implies that this socket is expected to be used for other appliances? If so are you installing 30mA RCD protection?

A single 16A socket, especially one for general use, should be provided with overload protection at 16A, that's just simple common sense.
 
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  • #9
No I mean flexibility for me when the chippy decides something else is going there, it will be dedicated for the extractor and marked up as such
 

pc1966

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For a 16A socket I would assume a 16A MCB for protection, but a D-curve would make perfect sense for a motor with big start-up current.
 

Wilko

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Hi - as per Dave and PC, if you’re installing a socket it can’t be assumed what the load will be. And if the socket is 32A or less it will need a 30mA RCD as the labelling up option has been deleted from the 18th, if I recall correctly.
 

davesparks

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No I mean flexibility for me when the chippy decides something else is going there, it will be dedicated for the extractor and marked up as such
Being marked up as dedicated to the extractor does not negate the need for an RCD (though it could be one of multiple measures put in place following a risk assessment)

How does having a socket provide flexibility for you? You are an electrician so you should be capable of changing a hard wired appliance easily. Having a socket adds flexibility for anyone to replace the appliance or use it for multiple appliances via a multi-way adaptor.
 
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  • #13
Being marked up as dedicated to the extractor does not negate the need for an RCD (though it could be one of multiple measures put in place following a risk assessment)

How does having a socket provide flexibility for you? You are an electrician so you should be capable of changing a hard wired appliance easily. Having a socket adds flexibility for anyone to replace the appliance or use it for multiple appliances via a multi-way adaptor.
I didn't say there wasn't rcd protection, simply that I was going to mark it up as for that appliance. As for flexibility this isn't a standard customer but a mate of mine that I've worked for for years so it helps that when he calls me in 6 months to say that machine is moving to an opposite wall and being replaced with something else I'm not having to muck around and can simply plug and play. And yes I am an electrician. I highly qualified and experienced one but by no means perfect hence the reach out to fellow sparks for a bit of support.
Post automatically merged:

Hi - as per Dave and PC, if you’re installing a socket it can’t be assumed what the load will be. And if the socket is 32A or less it will need a 30mA RCD as the labelling up option has been deleted from the 18th, if I recall correctly.
Absolutely agree mate, thats why I started this thread
 
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