13A supply to 16A (3.2kW) machine. It works fine, but is it illegal?

Question

Hi, 
 I'm working with a machine that has a data plate for 3.2kW but this is peak, when all elements are running. I have it running on a 13A RCD protected supply with no problems, but it has been suggested this is illegal. I could understand a small machine running on a large supply, but the fact that it draws less current than the data plate surely means it is safe, although maybe running closer to the current limit. 
 In service testing regs talk about fusing of circuit to protect, but never the other way round. 
 Can anyone quote me a reg saying either way?

gkenyon · Accepted Answer

Dena Thompson said: but it has been suggested this is illegal 
 Forgetting BS 7671 for a moment, if any safety incident occurs, which could range from burns to damage to electrical equipment causing a fire or shock, if this is in a workplace, it could be considered as a potential breach of legislation ... i.e. 'illegal'. Worth having a look at, in particular the Electricity at Work Regulations: 
 Regulation 5 : Strength and capability of electrical equipment 
 Regulation 11 : Means of protecting from excess current 
 In terms of BS 7671, in my opinion, it's not conformant if you are using 13 A accessories, or a 13 A overcurrent protective device, to supply the equipment. Regulation 132.2.2 in particular: 
 133.2.2 Current Electrical equipment shall be selected with respect to the maximum steady current (rms value for AC) which it has to carry in normal service and with respect to the current likely to be carried in abnormal conditions and the period (e.g. operating time of protective devices, if any) during which it may be expected to flow. 
 If you are supplying through a BS 1363 series plug and socket-outlet combination, or any type of connection unit to BS 1363-4, it's worth remembering that the likelihood of damage from overheating, particularly around the fuse, increases as you go above 13 A load current. BS 1362 fuses are required to have a maximum power dissipation of 1 W at their rated current. A 'calibrated test link', that is designed to dissipate 1 W, is used in temperature rise tests, during type testing in the relevant parts of the BS 1363 series of standards.In addition, the conditions of use in BS 1363-series should be considered. 
 For example, it is common to see BS 1363 plugs overheating around the fuse, and externally the line pin of the plug (which is close to the fuse) if used with welding equipment with peak input current of 14-15 A, even if this is short-term. 
 
 So, what to do? 
 If there is no evidence of overheating at the moment, recommend any 13 A equipment is checked regularly (if possible, by users) for signs of overheating. 
 Recommend, if possible, connection by an appropriate-rated isolator, connection unit, or socket-outlet ... if a workplace, for example, BS EN 60309-2 or BS EN 60309-4 socket-outlet ('commando socket') could be used. Even if this requires a new circuit, it's probably still going to be in the ballpark of 'reasonably practicable' ?

gkenyon · Answer

Chris Pearson said: Not "illegal", 
 Are we sure about that? It does depend on whether the machinery actually takes that much power, but if it does and something happens ... see above, Electricity at Work Regulations.

mapj1 · Answer

Agree - its not illegal in the sense the police will break down your door. 
 Nor is it against the wiring regs. 
 But it may be the sort of thing that insurance companies might decide to point to if there is a fire, to justify not paying in full. In a place of work it may be seen as endangering the workforce. Things like ovens and hot plates are a classic for this - where the sum of all the heaters greatly exceeds the supply rating, but so long the situation can be avoided where it is all switched on at once for a cold start, in practice it runs without issues. 
 note that 13A *230V is 2.99kW and 13A * 240V is 3.12kW. Look hard at that plate - what is the voltage is has been tested at ? 3.2kW is not really a full fat 16A - that is much closer to 3.7 (230V) or 3.8kW (240V). You may be overloading things, but not by an amount likely to be any more dangerous than full load. And I say it like that because there are plenty of designs of 13A plugs, and even more 13A extension leads, that actually run very warm at 13A and don't take much in the way of restricted ventilation or a warmer than normal environment, to tip them over the edge at currents below the nominal 13A anyway. 
 This example of a 13A plug and socket were on a ~ 3kW heated catering service counter - the fuse did not blow, but as you can see, it ran 'really quite warm'. My warning is that there really is not a lot of slack in some examples of nominally '13A' rated hardware. Mike.

13A supply to 16A (3.2kW) machine. It works fine, but is it illegal?

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