Overloading 13a rcd

[NGEddie]

I recently put in an outside socket for a hot tub. The hot tub is rated as 13a and hot tub company recommended this outside socket from Screwfix.
BRITISH GENERAL IP66 13A 2-GANG SP WEATHERPROOF OUTDOOR SWITCHED PASSIVE RCD SOCKET

But I thought I'd get "clever" and instead put in a separate RCD inside and then run cable to the socket location closer to where the hot tub is positioned. So I bought...

BRITISH GENERAL IP66 13A 2-GANG DP WEATHERPROOF OUTDOOR SWITCHED SOCKET
and
PRYSMIAN 6943X BLACK 3-CORE 2.5MM² ARMOURED CABLE 10M COIL
and
BRITISH GENERAL 900 SERIES 13A UNSWITCHED PASSIVE FUSED SPUR WHITE

It's all fitted, but... it's only when I considered plugging in a lawnmower into the second socket outside that it occurred to me that I'm then running more than 13a through the RCD.

Someone tell me please... should I be worried?
If I should... I'd like to solve it by replacing the RCD. What would you recommend I swap it for?

Thanks!

 

[EFLImpudence]

If the fuse hasn't blown then I don't think there is anything to worry about - but don't use the second socket when the hot tub is going.

Does the test button still trip the RCD?

There isn't really anything that can replace the RCD Fused Connector Unit apart from a small consumer unit.


Where does the supply come from?

 

[winston1]

It seems that the hot tub company have got their instructions wrong.

Why a double socket? RCD socket not required if circuit is already RCD protected.

Your idea of the RCD inside is OK unless if the circuit is already RCD protected, either way it does not need to be fused as the hot tub plug will have a fuse. (Many hot tubs also have an inline 10mA RCD as well, perhaps yours does not).

Regarding your lawn mower question, the hot tub won't take 13 amp continousy, only while heating up. If you are really worried I suggest not cutting the grass while in the hot tub.

 

[ericmark]

It seems that the hot tub company have got their instructions wrong.

Why a double socket? RCD socket not required if circuit is already RCD protected.

That is not correct, a RCD comes as different types, I see no reason why a hot tub should not use the basic AC type, however where a RCD is shared with other equipment then consideration must be given to other equipment desenserising the RCD, so the general statement is not true.

The problem is remote from any job mistakes can be made when relating a situation and as a result I can see why any company stipulates a particular RCD, I do not agree in this case what has been asked for, however it is down to person signing the minor works or installation certificate as to what is correct.

Personally I would not want to supply 13 amp for an extended time with a 13 amp plug due to cooling, I would want hard wired, however theroy says you can draw 13 amp from 13 amp plug.

 

[winston1]

That is not correct, a RCD comes as different types, I see no reason why a hot tub should not use the basic AC type, however where a RCD is shared with other equipment then consideration must be given to other equipment desenserising the RCD, so the general statement is not true.

Personally I would not want to supply 13 amp for an extended time with a 13 amp plug due to cooling, I would want hard wired, however theroy says you can draw 13 amp from 13 amp plug.

I accept what you say about different types of RCD, though this seems to be a recently debated problem mainly by yourself.

Why do they suggest a double socket however?

Regarding the 13 amp load, as I said it is not continuous but cycles on and off.

I have an inflatable hot tub plugged into an existing outside socket and there have been no overheating problems. As I mentioned earlier it also has a 10mA inline RCD on it’s flex.

 

[ericmark]

With an immersion heater there have been cooling problems with the fuse in a plug, and the method used even as far back as when dads house was built in 1954 was to have a feed from a dedicated 15 amp supply and use 15 amp plug and socket which did not have a fuse, so the plumber could change the immersion heater without needing an electrician but not over heating problems. It is time which causes the problem, with it drawing current for so long before a thermostat starts to work, increasing the physical size of the plug, and selecting a dark colour clearly helps, also being in free air. Having a socket inside a water resistance enclosure reducing free air could result in the plug over heating.

I would agree a 10 mA RCD would be better for out door supplies, and where there is a lot of water, however the one I had was active, and pressing the test button would also trip the 30 mA and 100 mA type S on the same supply, so it was never tested after finding this, and even the RCD tester did not have a 5 mA, 10 mA, and 50 mA test current so there was no way to know if it worked, OK reasonable make MK so likely would work, but never tested, as clearly would trip anyway once voltage removed, it clearly tested line to earth and over 50 mA since took the 100 mA trip out, so test but was potentially dangerous and useless. So never fitted in this house.

The RCD socket linked to

I would say not suitable for a hot tub, as the cover will stop plug cooling, great for a 3 amp battery charger or Christmas lights, not really any good for an electric car charger or hot tub.

The RCD FCU is a far better idea where the fuse is cooled by the wall and does not rely on free air, although you can get 15 amp sockets that would fit in the water resistance cover, personally see this as a problem as lawn mowers and the like use moulded 13 amp plugs, even electric car chargers will likely be 13 amp plug or a special for car charging, so in spite of all I have said, in real terms there is no option but use some thing like in the picture, but would not put the cover down when using to first heat hot tub, once hot then as you say mark/space switching will reduce the heat at the plug.

 

[NGEddie]

The RCD is placed next to a socket and daisy chains it's supply from the mains wiring into that socket. The socket is in the garage. Garage has it's own supply from the consumer unit.

Seems like the worst case scenario at the moment is the 13A fuse in the RCD may blow. No other risk, right?

Seems like my options are...

1. Don't worry about it unless the fuse does blow.
2. Replace the RCD with a blanking panel. I won't have a RCD, but also won't have a 13A fuse feeding 2 sockets, and the whole main is protected by the consumer unit anyway.

Other suggestions?

 

[ericmark]

Go for option 1. Don't worry about it unless the fuse does blow.

 

[JohnW2]

Seems like the worst case scenario at the moment is the 13A fuse in the RCD may blow. No other risk, right? .... Seems like my options are... 1. Don't worry about it unless the fuse does blow. ...

I reckon that's probably the option for you. In theory it takes at least about 22A to blow a 13A fuse, so it's probably never going to happen.

Kind Regards, John

 

[DetlefSchmitz]

No-one seems to have mentioned the possibility that the RCD itself is not rated at more than 13A.

 

[JohnW2]

No-one seems to have mentioned the possibility that the RCD itself is not rated at more than 13A.

Interesting point, and I suppose it's even conceivable that it might have "13A" specified as its 'rating.

However, (a) it would probably not be all that easy to design an RCD which couldn't safely cope with a lot more than 13A, even if one wanted to and (b) it is 'protected by' a 13A fuse, anyway.

Kind Regards, John

 

[NGEddie]

Thank you all - great information and peace of mind!