Electric Shower in a Hotel Bathroom
A small hotel is refurbishing an ensuite bathroom. The existing 8.5 kW, 220 V instantaneous electric shower is to be retained. It is fed by a 6 mm² PVC twin-and-earth cable from a 40 A Type B MCB in the room's consumer unit. There is no RCD. The local pull-cord isolator is mounted inside the bathroom, 0.4 m from the shower head. The shower unit is in Zone 1. The bathroom has a metallic waste pipe from the shower tray and a metallic towel rail; neither is bonded, although the main equipotential bonding to the water and gas services is present at the flat's origin. The client wants to keep the existing cable and MCB and asks whether a 30 mA RCD is really necessary, because the shower has a plastic casing and the circuit has worked for years. The shower's rated current is 38.6 A. The cable is clipped to a plasterboard wall and is grouped with one lighting circuit for 3 m.
1. Identify the main non-compliances in this bathroom installation and explain the risk associated with each.
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The main non-compliances are: (1) No 30 mA RCD for the bathroom circuit. A fixed shower is a low-voltage circuit in a special location, and the Code requires 30 mA additional protection for bathroom circuits and socket outlets. The plastic casing does not remove the need because the risk is from the circuit and associated metallic parts, not only the shower casing. (2) The pull-cord isolator is inside the bathroom only 0.4 m from the shower head. It must be suitable for the zone and IP rating; ordinary switches are not permitted in Zone 1, and the pull cord must not be reachable from the shower. (3) Supplementary equipotential bonding is missing for the metallic waste pipe and towel rail. Bonding may be omitted only where the Code's conditions are met, typically with 30 mA RCD protection and main bonding; otherwise these parts must be bonded to the protective earth. (4) The 6 mm² cable and 40 A Type B MCB must be verified: Ib = 8500 / 220 = 38.6 A; 6 mm² PVC clipped direct has a tabulated capacity around 47 A, but grouping and any thermal insulation may reduce it below 40 A. If the derated Iz is below 40 A, the cable is not adequately protected.
2. The client argues that the plastic shower casing makes the RCD unnecessary. How would you respond, and what would you require before re-energising?
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The plastic casing does not make the RCD unnecessary. The 30 mA RCD is required as additional protection in the special location, not because the shower casing is faulty. The bathroom contains earthed metalwork, water and wet surfaces, and the circuit has a protective conductor; a fault or damaged cable could energise exposed conductive parts or the shower's internal metal parts. A 100 mA or no RCD would not provide the required additional protection. Before re-energising, I would require: a 30 mA RCD (Type A or Type AC as appropriate) protecting the shower circuit; the isolator relocated outside the zones or replaced with a suitable cord-operated switch arranged so the cord is not reachable from the shower; supplementary bonding of the metallic waste pipe and towel rail, or documented justification for omission under the Code's conditions; and verification that the 6 mm² cable's derated capacity is at least 40 A and that the earth-fault loop impedance is satisfactory. The RCD should be tested at 1× and 5×, and the circuit should be inspected and tested before being returned to service.