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PLUMBING CONNECTION Summer 2017
NOTE:
The water heater should not be
placed in direct contact with a concrete
surface less than two months old and
not fully cured as this may attack the
metal coating. A moisture barrier should
be used between the two surfaces in
this instance.
HOT WATER DELIVERY
The water heater can deliver water at
temperatures which can cause scalding.
It may be required by regulations
(and where recommended) that a
temperature limiting device be fitted
before the hot water outlets in any
ablution area such as a bathroom or
ensuite to reduce the risk of scalding.
Where a temperature limiting device
is installed adjacent to the water heater,
the cold water line to the temperature
limiting device can be branched off the
cold water line either before or after
the isolation valve, pressure limiting
valve and non-return valve to the water
heater. If an expansion control valve is
required, it must always be installed
after the non-return valve and be the
last valve prior to the water heater.
If a pressure limiting valve is installed
on the cold water line to the water
heater and the cold water line to a
temperature limiting device branches
off before this valve or from another
cold water line in the premises, then
a pressure limiting valve of an equal
pressure setting may be required prior
to the temperature limiting device.
HEAT TRAPS
If the hot water outlet is located on
top of the water heater an external heat
trap may need to be installed to ensure
against convection and heat losses.
It must be within 1m of the hot water
outlet, before the first hot water branch
and have a vertical drop of 250 mm
from the outlet.
Therefore if the outlet connection is
located at the top of the unit and the
direction of supply to fixtures is vertical,
a heat trap extending 250mm must be
plumbed.
PIPE SIZES
To achieve true mains pressure
operation, the cold water line to the
water heater should be the same size or
bigger than the hot water line from the
water heater.
Pipe sizing should be carried
out by persons competent to do
so, with reference to the technical
specifications of the water heater and
local regulatory authority requirements.
RECOVERY RATING
When hot water is released from
a water heater, cold water comes in
to replace it. The amount of cold
water that can be brought up to
temperature per hour is the heater’s
recovery rating.
The recovery rating
is calculated based on the known
properties of water and assumes no
heat loss during recovery – that it is
100% efficient.
COMMISSIONING
Once installed, the power supply must
not be switched on until the water heat
is filled with water and a satisfactory
megger reading is available.
To do that,
∫ ensure all the hot water taps in the
house are open;
∫ Open the cold water isolation valve
fully on the cold water line to the
water heater. Air will be forced out of
the taps.
∫ Close each tap as water flows freely
from it
∫ Check the pipe work for leaks
∫ Switch on the electrical supply at the
isolating switch to the water heater.
Explain to the householder the
functions and operation of the water
heater. Upon completion of the
installation and commissioning, leave
the installation instructions/owners
guide with the householder.
MAJOR SERVICE EVERY FIVE YEARS
It is recommended a major service
be conducted on an electric water
heater every five years. Only genuine
replacement parts should be used on
the water heater.
The major service includes the
following actions:
∫ Replace the temperature pressure
relief valve.
∫ Inspect and flush the expansion
control valve (if fitted). If required,
replace the valve.
∫ Check the element for excessive
calcium build up or corrosion and
replace if necessary.
∫ Visually check the unit for any
potential problems.
∫ Inspect all connections.
∫ Check the drain line from the safe tray
(if one is installed) is not blocked.
TABLE 1: CALCULATING THE RECOVERY RATING
ELEMENT RATING (W)
40°C RISE
50°C RISE
60°C RISE
70°C RISE
1200
26
21
17
15
1500
32
26
22
18
1800
39
31
26
22
2000
43
34
29
25
2400
52
41
34
29
3000
65
52
43
37
3600
77
62
52
44
4800
103
83
69
59
6000
129
103
86
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IN HOT WATER -
JON PALFREY