My builders have installed two unvented hot water cylinders each with a 3kW immersion heater. Each heater has a normal 13A fused plug and they are both plugged into the same double socket. I wasn't sure whether the double socket is rated for 13A or whether 26A is acceptable. Can anyone advise? Also, I assume that even if this is on a dedicated circuit it needs a 30A fuse at the consumer unit... is this correct?
26A on double socket?
- Thread starter DanAir
- Start date
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1) A double socket is not safe for 26A. It is offically designed for 13A total but will overheat and start to degrade at about 20A if a top-quality brand (MK, Crabtree, MEM). A cheap brand will probably overheat sooner. It is not unusual for double sockets to char and melt if e.g. a washing machine and a tumble drier are both plugged into it.
2) A Fixed water heater should not be on a plug and socket. it should be on a dedicated radial circuit with its own MCB. Usually a single immersion heater is provided with a 16A circuit. If that have two that can be used at the sme time, then (depending on rating) you might use a 20A or 32A circuit (32A needs thicker and more expensive cable) with a13A FCU for each element.
2) A Fixed water heater should not be on a plug and socket. it should be on a dedicated radial circuit with its own MCB. Usually a single immersion heater is provided with a 16A circuit. If that have two that can be used at the sme time, then (depending on rating) you might use a 20A or 32A circuit (32A needs thicker and more expensive cable) with a13A FCU for each element.
Do you mean those small 15 litre under-sink type heaters or cylinders over 15 litres? The installation of unvented water cylinders >15 litres is notifiable work unless done by a registered installer qualified in the field of unvented systems.
The rest is as JohnD has said. It's a very very poor job electrically speaking, and I'd also be concerned with the safety of the cylinders unless your builders happen to be qualified, which I doubt they are...
The rest is as JohnD has said. It's a very very poor job electrically speaking, and I'd also be concerned with the safety of the cylinders unless your builders happen to be qualified, which I doubt they are...
Thanks guys for your replies. From what I can tell from a quickish look there is a dedicated radial circuit but I can't be sure - I'll investigate when I get home. If is is dedicated radial, is it not the same effect to use two fused plugs rather than FCUs (ignoring the fact that at present the socket is overloaded)? Either way I think I'm going to have to get the installation checked properly. Has anyone got any experience with retrospective notifications to building control. Do they take a harsher view?
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DanAir said:
The FCU has a far more reliable connection that a plug in a socket. In an FCU with screw connections there is (almost ) zero chance of a bad joint developing.
With a 13 amp plug and socket a corroded pin and socket or weakened socket spring causes a resistive connnection and it is these that get hot and burn the plug / socket and melt insulation of the cables
In most cases if you are honest with them and do not try to be clever or pull a fst one they will do all they can to help you. And they will be fair to you as well.
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