valves are closed, then the safety valve may be omitted. Note that the minimum
static head required is 9 ft at the top of the boiler.
Although suitable for open vented systems with combined feed and vent
arrangements, the C45, C40P and C55(P) are low water content boilers. As such,
any air entrainment within the system water will produce boiler “kettling”. It is
therefore recommended, if in any doubt, to consider the use of sealed systems
where possible.
2.7.2
Sealed Systems
Sealed systems must be designed in accordance with BS 5449 and BS 7074 Pt1.
A typical sealed system is shown in Figure 2.7.2. It must include :
(i)
A safety valve fitted on the flow, adjacent to the boiler. It must be non
adjustable and preset to 3 bar. A drain pipe must be attached, at least as
big as the valve connection, and routed to drain in any area not
hazardous nor where it may be subject to freezing.
(ii)
An expansion vessel complying with BS 4814 and sized in accordance
with the requirements of BS 5449 and BS 7074 Pt 1. The vessel must
be positioned on the primary return to the boiler. Table 2.7.2
Expansion Vessel Selection provides guidance for the correct expansion
vessel size to use.
(iii)
A filling point, in accordance with local water authority requirements.
(iv)
A method of system make-up (automatic or manual), in accordance with
local water authority requirements.
(v)
There must be no permanent connection of mains water to the boiler
system.
(vi)
The installation must be designed to work with flow temperatures of up to
110
o
C.
WD536
Chapter 2 - Boiler Location
The Keston C45, C40P, C55 & C55P
Installation & Servicing Instructions
Page : 11
C45
Rad. 2
Rad. 1
Minimum
9ft Height
Cylinder
Figure2.7.1 : Open Vented System Diagram
Valve
Valve
Expansion
Pipe
Expansion
Tank
28mm
Minimum
L/S
Valve
By-pass
FLOW
RETURN
Safety
Valve
or
C55
(See note 2.7.1)