By Jim Spencer and Roger R
The plumbing and wiring involved in installing
an electric shower requires sound basic skills in both areas of expertise.
Ensure that wiring and plumbing are properly installed. Connect the
wiring at the consumer unit requires a competent person under the Part
P building regulation. Always turn off the electricity when making connections
to the mains.
Electric showers are economical to run and provide hot water on demand.
Using an electric shower can save up to a third of the water used for
a bath and, because a shower heats the water instantaneously, it does
not waste energy heating stored water. Electric showers are rated in
kilowatts (kW) - the higher the wattage, the better the performance
of the shower. An electric shower is relatively easy to install, requiring
only a connection to mains electricity and a single cold-water pipe
running from the rising main.
Planning the work
If you plan to install a shower over an existing bath, your primary
consideration is where you can tap into the rising main. The most convenient
location is often an airing cupboard close to the bathroom. If that
is not possible, make the connection in the loft and run the branch
pipe through the bathroom ceiling to the shower.
If you are building a new shower cubicle, you will need to consider
drainage:
Plumbing
Step 1: Start by mounting the shower unit in the required position.
Mark the fixing points using the template supplied by the manufacturer
or use the backplate if there is no template.
Step 2: Using a power drill fitted with a masonry bit of the appropriate
size, drill holes to receive the wall plugs for the mounting screws.
When drilling holes in ceramic tiles, stick a piece of masking tape
on the glazed surface to prevent the masonry bit slipping.
Step 3: Before you finally mount the shower unit, cut a piece of 15mm
(1/2in) copper pipe long enough to pass through the ceiling or sideways
into the airing cupboard. Try to make neat clearance holes through the
wall or ceiling to minimise the amount of making good.
Connect the pipe to the shower inlet. Cut copper pipe with a hacksaw - wrap a piece of paper around the pipe as a guide to keep the cut square. Alternatively, use a pipe cutter. File the cut ends to remove burrs.
Ideally pipe runs should be concealed and, in
some instances, it may be possible to make the connection at the back
of the shower unit so that you can run the pipe into the walls.
If the wall is a stud partition, it should be possible to run the pipework (and electrical supply) between the studs.
In a solid masonry wall, you could cut a channel in order to bury the pipe under the plaster. This type of work should be carried out before you fit the shower unit and tile the wall. Use soldered joints in this situation, to minimise the possibility of a leak.
Step 4: Inside the airing cupboard or loft, take
the new branch pipe up to the rising main but stop just short of it.
Fit a stopcock (not a gate valve) to the end of the branch pipe, with
the flow arrow pointing away from the rising main.
Alternatively, fit a miniature isolating valve to the branch pipe, close
to the shower unit, so that you can turn off the water for servicing.
Step 5: Turn off the main stopcock and drain the water from the pipe
by opening the kitchen tap.
Step 6: Fit the T-joint onto the rising main and hand-tighten the cap
nuts. Measure and cut a short length of pipe to connect the T-joint
to the stopcock.
Step 7: Assemble the component parts and tighten the nuts to make watertight
joints. Test the plumbing.
Showers connected to the rising main must be protected with a double-check
non-return valve fitted to the branch pipe - this prevents dirty water
being siphoned from the bath or shower tray into the drinking supply.
This applies only if the handset can come into contact with used water.
Caution must be exercised when inserting double check valves in the
water supply. If unsure, contact a professional plumber.
Fitting the sprayhead
Step 1: Mount the sprayhead slider rail on the wall to one side of the
shower unit. Check that there is enough room for the sprayhead to be
adjusted up and down to suit all members of the family.
Step 2: Connect the flexible hose to the sprayhead
and to the shower unit.
Wiring the shower
An instantaneously heating electric shower requires a dedicated radial
circuit running from the consumer unit. We recommend that the circuit
should include a 30 milliamp Residual Current Device.
Use 10mm two-core-and-earth cable for the circuit, which must be protected
with a 40amp Miniature Circuit Breaker (MCB) or a 45amp fuse in the
consumer unit. If there is no room in your consumer unit for a new circuit,
have an electrician install a separate 45amp switch fuse unit for the
shower.
Electrical Wiring Regulations require all non-electrical metal components
such as pipes, baths and basins to be connected, one to another, with
earthing cable that then runs to the consumer unit where it is connected
to the earthing block. For supplementary bonding, as it is called, use
6mm single-core cable, insulated with green/yellow sheathing.
Connect bonding cable to pipework with purpose-made earth clamps and
attach it to the special earthing tags on metal baths and basins. Your
shower unit must also be bonded to the pipework, using the earth terminal
provided in the appliance. Please check the details of your product
carefully, as the earth terminals within some showers should not be
used for cross bonding.
Fitting a pull-switch
Although an electric shower has its own on/off switch, there must be
a separate 45amp double-pole switch to isolate the circuit. The isolating
switch must be out of reach from anyone using the shower.
The isolating switch for a shower must have a contact gap of at least
3mm and an indicator, such as a flag which is normally incorporated
in the switch to show it is on.
If the isolating switch is to be situated inside the bathroom, use a
pull-switch mounted on the ceiling:
Step 1: Make a hole in the ceiling where the pull-switch is to be fitted.
Screw a mounting board between the joists above the ceiling on which
to fasten the backplate of the switch.
Step 2: Run the circuit cable to the switch position and pass a loop
of cable through the hole in the ceiling and mounting board. Then run
the cable on to the shower unit.
You can run electrical cable inside plastic mini-trunking fixed to the
surfaces of walls and ceiling.
Alternatively, bury the cable behind the plaster.
One way is to pass the cable down between the studs of a hollow partition
wall.
For a solid wall, you would have to cut out a
channel in which to set the cable. In this case, it is safest to run
the cable inside plastic conduit and cover it with plaster ready for
tiling.
Step 3: At the switch point, cut the loop of cable and strip the ends
of the cable. Fix the backplate of the switch in position. Cover the
bare earth wires with green and yellow sleeving and connect them to
the 'E' terminal.
Step 4: Connect the wires of the cable from the consumer unit to the
'Mains' terminals of the switch. Connect the wires of the cable to the
shower unit of the 'Load' terminals - red to 'L' terminals and black
to 'N' terminals.
Step 5: Strip the sheathing from the cable at the shower unit and connect
the wires to the terminal block as shown on the instructions - Red 'L'
(live), Black 'N' (neutral) and bare 'E' (earth). Cover the bare wires
with PVC earth sleeving.
Strip about 100mm (4in) of sheathing from a cable - slit it lengthways,
then peel it back and cut off the waste.
Use a Part P competent person electrician to make the connection to
the consumer unit and test the circuit.
