11 ©ESP Ltd. Sept 2008
4.6 DRAIN TAP
A draining tap should be installed in the cold water supply to the unit be-
tween the Cold Water Combination Valve (or Expansion Core Unit if being
used) and the heater at as low a level as possible It is recommended that the
outlet point of the drain pipe work be at least 1 metre below the level of the
heater (this can be achieved by attaching a hose pipe to the drain tap outlet
spigot).
4.7 OUTLET PIPEWORK
Ideally the pipework from the unit to the outlet fittings should be in 22mm
pipe with short runs of 15mm pipe to showers and basin taps. Small bore pipe
can also be used to suit some taps, but runs should be of minimum length.
Pipe sizes may vary due to system
4.8 SECONDARY CIRCULATION
If a secondary circulation system is required it should be installed as per Fig-
ure 6. The secondary return pipe should be in 15mm pipe and incorporate a
check valve to prevent backflow. A suitable WRAS approved bronze circula-
tion pump will be required with appropriate unions. On large systems, due to
the increase in system water content, it may be necessary to fit additional ex-
pansion volume to the system by fitting an external expansion vessel to the
secondary circuit. This should be done if the capacity of the secondary circuit
exceeds 10 litres.
Pipe capacities (copper)
15mm o/d = 0.13 litres per metre run (10 litres = 77m)
22mm o/d = 0.38 litres per metre run (10 litres = 26m)
28mm o/d = 0.55 litres per metre run (10 litres = 18m)
Secondary circulation is NOT recommended for units being used on “Off
Peak” electricity tariffs.
4 . Installation
4 . Installation
Hot water air source heat pump
Hot water air source heat pump
