Manufacturer says 15A fuse needed for 2.79kW oven

[Taylortwocities]

You cant get 15a fuses that go in plugs.

Au contraire! See this set of beauties readily available on a well-known auction site!

 

[ericmark]

As has been said so many times, if a manufacturer believes that their product requires protection which may be greater than that provided by the device protecting the cables which supply it, then they should provide that protection within the product.

I would agree with a domestic appliance one would expect that to be the case, however with commercial equipment often the protective device needs to be where there is access to service it, this is not always possible inside the appliance, and I am sure you have fitted many a motor starter which is a different make to the motor, I know I have.

So the installer and commissioning engineer have to decide where to place the protective equipment, clearly an extractor fan fitted in the ceiling 20 foot in the air will not have the starter built into the fan, but on the ground where it can be serviced.

The same rules apply be it a commercial piece of equipment to domestic, although seen them ignored with domestic, know I had to return a whole batch of angle grinders as the on/off button could be latched on, i.e. no no volt release. As a DIY user latching on the on/off button may be considered as a good thing.

However be it industrial, commercial, or domestic same rules apply. So protective devices do not need to be built into fixed equipment, the manufacturer can stipulate they are fitted else where.

 

[ericmark]

Au contraire! See this set of beauties readily available on a well-known auction site!
View attachment 365454

But not to BS 1362 the last 2 do not comply, yes you could get 15 amp plugs where the pin was a fuse, but not seen them for some time now.

 

[JohnW2]

I would agree with a domestic appliance one would expect that to be the case, however with commercial equipment often the protective device needs to be where there is access to service it, this is not always possible inside the appliance, and I am sure you have fitted many a motor starter which is a different make to the motor, I know I have.

If the manufacturer installs a protective device in an 'inaccessible' location,then they are, at the least, plain daft - it could easily be rendered 'accessible for servicing' (often on the front panel' of the equipment).

In any event, this is a DY forum, so I don't think we should be particularly concerned about practices in relation to 'commercial equipment'.

 

[AndyPRK]

And we would all assume they were fakes?

Or not to British standard.

Better than a nail I guess

 

[AndyPRK]

Au contraire! See this set of beauties readily available on a well-known auction site!
View attachment 365454

Do you have a link for them ? Tempting.

 

[Taylortwocities]

Do you have a link for them ? Tempting.

A simple google search was all that was needed.

 

[JohnW2]

And we would all assume they were fakes? ... Or not to British standard. ... Better than a nail I guess

I have some

Obviously not to BS1362, although they claim to be (see photo), but I would be far from surprised if they actually 'do what it says on their tin', in the same way that do the (BS1362-compliant) ones from 1A to 13A. The unknown, of course, is whether BS1363 plugs and sockets would be 'up to' currents above 13A, although it would again not surprise me if they were (at least as far as 15/16A)

 

[AndyPRK]

The good thing about them is that they should would generate Less heat.
And let the MCB trip before the fuse which is typical.

The plug would be up to it. It’s more the socket I worry about

 

[JohnW2]

The good thing about them is that they should would generate Less heat.

True.

And let the MCB trip before the fuse which is typical.

Possibly, but certainly not necessarily, at least in relation to fairly modest 'overloads.. We obviously don't have any data on the "20A" fuses, but if one extrapolates from 13A BS1362 fuse, it could take something like 34A to blow a 20A one - which, in theory, should not cause a B32 to operate (which should take at least 36 to trip. In the case of a very high fault current then, yes, it would be pretty likely that the MCB to probably operate first (with any fuse rating).

The plug would be up to it. It’s more the socket I worry about

Maybe, but it wouldn't surprise me if the socket was also happy, at least with 15A. Don't forget that the BS1363 'temperature rise test' is done with 14A through one of the socket outlets.

 

[morqthana]

As a DIY user latching on the on/off button may be considered as a good thing.

Until suddenly it isn't.

 

[morqthana]

I would be far from surprised if they actually 'do what it says on their tin', in the same way that do the (BS1362-compliant) ones from 1A to 13A.

Calling Big Clive.

Big Clive, come in please.

 

[Ragnar_AT]

The fusing current of a BS1362 fuse is 1.9*In, i.e. 38 A for the 20 A one. The fusing current of a B-curve MCB is 1.45*In or 46.4 A for a B32. So in case of an overload it’s likely that the fuse blows first - provided this plug is the only load on the circuit. In case of a short, the MCB is most likely to trip first with at least a 13 A fuse.

Looking at a BS1363 plug I suspect the weak spot is the fuse holder. All other parts seem quite likely to withstand much higher currents, possibly up to 32 A (nominal current, not under overload conditions) if you managed to cram 4 mm2 conductors into the terminals.
The sockets are a bit of an unknown. I don’t doubt they could be made to warrant a 32 A rating but I‘m not sure they actually are. The contact surface between plug and socket is probably equal to that of a 32 A industrial socket, which is a good start. The questionable bits are the connections between the screw terminals and the contacts, and of course the switches.

 

[JohnW2]

The fusing current of a BS1362 fuse is 1.9*In, i.e. 38 A for the 20 A one.

That's not much different from the "at least 36A" I mentioned I suspect that 1.9 * In is the 'average';, or maybe the maximum. If you look at the curves for a 13A BS1362, the minimum current which should blow it is around 22A - which is what I extrapolated from to get my "at least 36A" for a 20A one.

The fusing current of a B-curve MCB is 1.45*In or 46.4 A for a B32.

Well, the magnetic threshold is. However, relevant to 'moderate' overloads (i.e. not 'shorts') a B-curve MCB should operate (thermally), eventually, for any current above 1.13 x In - i.e. about 36.2A for a B32.

So in case of an overload it’s likely that the fuse blows first - provided this plug is the only load on the circuit. In case of a short, the MCB is most likely to trip first with at least a 13 A fuse.

Yes, that's essentially what IO wrote. However,there is some 'hit and miss'about it, and I've seen examples of both the things that "one would not expect" - a 13A fuse, but not a B32 operating in the face of a high current fault ('short') or an MCB, but not a 13A fuse, operating in the face of a 'moderate overload' - so one can never be certain (and, of course, sometimes both will operate).

Looking at a BS1363 plug I suspect the weak spot is the fuse holder. All other parts seem quite likely to withstand much higher currents, possibly up to 32 A (nominal current, not under overload conditions) if you managed to cram 4 mm2 conductors into the terminals.
The sockets are a bit of an unknown. I don’t doubt they could be made to warrant a 32 A rating but I‘m not sure they actually are. The contact surface between plug and socket is probably equal to that of a 32 A industrial socket, which is a good start. The questionable bits are the connections between the screw terminals and the contacts, and of course the switches.

I largely agree with all that - but, as I've said, I'd been far from surprised if a 13A plug + socket could (at least usually) cope with 15/16A, and maybe also 20A (or more).

 

[gavman99]

So the oven model from the OP arrive today. Was expecting no plug but wasn’t expecting no cable. Manual says nothing about how to connect cable other than consult a qualified electrician.

I’m quite able to wire a plug to a cable, but wiring a cable to the oven, I’m less sure about. I’m assuming it’s this black plate ?

Any advice appreciated !!