gledhill GB10 Installation And Servicing Instructions page 12

3.5. CENTRAL HEATING AND WATER SYSTEM
The Gledhill boiler is suitable for use with both vented and unvented traditional heating systems and also for
use with the thermal storage systems e.g. Gledhill BoilerMate and Gledhill SysteMate.
Plastic Pipes
When plastic pipe is to be used for the heating system, this must be suitable for the maximum pressures and
temperatures for the intended application. The class 'S' pipes and fittings are defined in BS 7279-1.
Some plastics are permeable to the oxygen and to prevent corrosion of system components (e.g. heat
exchanger) due to build up of oxygen, a barrier type pipe must be used i.e. pipes incorporating a polymer
barrier layer.
When plastic pipe is used, the first 2m of pipe work from the boiler (both flow and return) must be in copper.
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 22mm (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 2879, 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 20mm 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
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