Issue 1 06/02/20
21
Installation
6
Fig. 11
6.2.3 Secondary circulation
If secondary circulation is required it is recommended that it be
connected to the cylinder as shown.
• The secondary return pipe should be in 28mm pipe and
incorporate a check valve to prevent backflow.
• A suitable WRAS approved bronze circulation pump will be
required.
• On large systems, due to the increase in system water
content, it may be necessary to fit an additional expansion
vessel to the secondary circuit. This should be done if the
capacity of the secondary circuit exceeds 10 litres.
Pipe capacity (copper):
15mm O.D. = 0.13 l/m (10 litres = 77m)
22mm O.D. = 0.38 l/m (10 litres = 26m)
28mm O.D. = 0.55 l/m (10 litres = 18m)
See
See fig. 12
Note
Plastic pipe capacities may be reduced due to thicker wall
sections.
6.2.2 Primary circuit control
• The 2 port motorised valve supplied with the unvented
system kit MUST be fitted on the primary flow to the cylinder
heat exchanger and wired such that in the event of the
cylinder overheating it will close the primary circuit.
• Primary circulation to the cylinder heat exchanger must be
pumped; gravity circulation WILL NOT WORK.
• It is recommended that an air bleed or automatic air vent is
incorporated in the primary flow pipe work close to the unit.
Fig. 12
Pressure
relief valve
Take note of flow
direction
Pressure reducing valve
Take note of flow
direction
Mains water in
Pressure gauge
connection
Pressure
relief
discharge
To cylinder
To hot
outlets
Secondary
return
Cold water
inlet
WRAS approved
pump
