9
Fig. 8. Typical Open Vent Gravity Primary System.
Feed and
Vent Cistern
Primary cold
feed (15mm min.)
Primary cold
feed (15mm min.)
Heating vent
(22mm min.)
Heating vent
(22mm min.)
Boiler
Pump
Radiator
S.H. – Minimum static head 1m (3ft)
measured from the top surface of the
appliance or highest point in the
heating system to the water level in
the feed and expansion tank
N.B.
A drain cock should be
installed at the lowest point
of the heating circuit
Domestic
hot water
cylinder
S.H.
S.H.
Fig. 9. Typical Open Vent Fully Pumped System (Honeywell ‘Y’ plan).
Feed and
Vent Cistern
Diverting
valve
Boiler
Pump
Radiator
S.H. – Minimum static head 1m (3ft)
measured from the top surface of the
appliance or highest point in the
heating system to the water level in
the feed and expansion tank
N.B.
A drain cock should be
installed at the lowest point
of the heating circuit
Domestic hot
water cylinder
S.H.
S.H.
Summary of Contents for 70/90
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