Benchmark GB10 Design, Installation And Servicing Instructions page 12

INSTALLATION DESIGN AND PLANNING INFOrMATION
3.5.1. Open vented heating system
(a) The open i.e. vented heating system is shown schematically in diagram 3.3.
It is important that the relative positions of the pump, cold feed and the open
vent are as shown in diagram 3.3 to minimise the chances of air ingress and
pump over conditions arising.
(b) The cold feed must be 15mm minimum size. The mm (minimum) open
vent must rise continuously and be unrestricted.
(c) The boiler must be supplied from an unrestricted water supply taken from
feed and expansion cistern situated at a maximum height of 30 meters above
the boiler.
(d) A safety valve need not be fitted to an open vented heating system.
(e) A draining tap conforming to the current issue of BS 879, must be provided
at the lowest point of the system, which will allow the entire central heating
and hot water system to be drained.
(f ) The overflow/warning pipe should be in 0mm internal diameter pipe of
suitable material for use in heating systems in accordance with BS 5449 (such as
copper). It should have continuous fall and discharge in a conspicuous external
position. It should not have any other pipework directly branched into it.
(g) The water level in the F & E cistern should be at least 50mm above the
highest point on the system including the radiators
3.5.2. Sealed heating system
(a) Design Standards
The sealed heating system is shown schematically
in diagram 3.4. The sealed system installation must
comply with the appropriate requirements of current
issues of BS5449, BS6759, BS6798 and BS7074.
(b) Safety valve
A non-adjustable safety valve must be fitted to a sealed
system. It shall be pre-set with a lift pressure of 3 bar
and incorporate a seating of resilient material, a test
device and a connection to the drain
(c) Safety valve Drain
The drain from a safety valve must be routed outside
the building and positioned so that any discharge can
be seen. It must not discharge above an entrance or
window or any type of public area and be clear of any
electrical fittings.
(d) Pressure Gauge
A pressure gauge with a set pointer and covering at
least 0 – 4 bar shall be fitted permanently to the sealed
system. It should be positioned where it can be seen
when filling the system.
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