Hi all I am building an ensuite bathroom and have almost finished.The bathroom contains bidet wc handbasin and power shower.All the plumbing is in plastic including the central heating radiator. Do I need to earth bond the metal taps and the metal radiator. Tom
No, but if the power shower unit is the type with a built-in electric pump and you have mains-voltage lights, a fan or shaver point within the defined zones you will need to bond together the earths of the circuit which feeds the shower pump, and the lighting circuit.
Zone 1 contains a fan-but-Ive fitted a 12 volt fan with the transformer installed in the loft space above the en-suite. The shower is a Mira event xs thermostatic with a built in pump-it has its own earth connected via the lighting circuit earth. The light is a sealed type for bathrooms again connected to the lighting circuit earth. There is no other electric point or appliance within the en-suite. Tom
In that case it sounds as if no supplementary bonding is required. I'm not sure that feeding the power shower unit from the lighting circuit is a good idea though - it's more usual to feed these from a ring circuit via an FCU. I looked at the Mira instructions: the loading is only 150 watts, which is unlikely to worry your lighting circuit too much, but you might find that the starting current of the pump motor causes a noticeable dip or blink in the lights. I presume you've provided an isolator, 3 A fuse and RCD, as recommended in the instructions.
">> Zone 1 contains a fan-but-Ive fitted a 12 volt fan with the transformer
The fan transformer and the pump both have independant 3 amp fused supplies off the lighting circuit. I take your point about the lights dipping - if its a problem I can take power from the ring main. RCD is a problem since the main board is 1974 fuse wire type set up.Im very reluctant to have RCDs anywhere-my experience of them is that they are oversensitive-a pain in the posterior-.
Your experience is either of a poorly designed system, or a poorly maintained one.
The only times my RCDs have ever tripped is when I've stuck my RCD tester on them and hit "Test". (Actually, the earth loop tester can have a similar effect...)
Christian.
I agree entirely, however BS 7671 does allow a shower pump in Zone 1 without RCD protection [Reg. 601-09-02], so omission of the RCD here won't violate the wiring regs, only the manufacturer's instructions.
Back in 1999/2000, I fitted an RCD protected CU to my parents' 1955 (PVC) installation, and they've not had a single false trip. There's no reason a 1974 install should be leaking.
I've just tested my system. The "old" circuits, which look to be about 1970s to early 1980s vintage had no insulation reading below 800 Mohms. Most tests were > 999 Mohms.
Christian.
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