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WD53/0/1999
2.6.1
Open Vented Systems
A typical system is shown in Figure 2.6.1 which includes a combined feed and
vent. Note the valve between the boiler flow and the open vent is a three way
blowdown type valve. Note that the minimum static head required is 3m at the top
of the system pipework. If the cold feed/vent is not brought to the low loss header
as shown, then the pressure loss across the heat exchanger may have to be
taken into account when estimating the static pressure. Cold feed/vent size must
comply with BS6644.
Although suitable for open vented systems with combined feed and vent
arrangements, the Keston is a low water content boiler. 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.
Boiler
2.6.2
Sealed Systems
Sealed systems must be designed in accordance with BS 6644 and BS 7074 Pt1.
A typical sealed system is shown in Figure 2.6.2. It must include :
(i)
(ii)
(iii)
(iv)
(v)
Installation & Servicing Instructions
Chapter 2 - Boiler Connections The Keston 260 & 340 Condensing Boilers
Safety Valve
AV
IV
Low loss
header
Keston
IV
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.
An expansion vessel complying with BS 4814 and sized on the basis of
the total system volume and initial charge pressure. The vessel must be
positioned as shown in figure 2.6.2.
A filling point, in accordance with local water authority requirements.
A method of system make-up (automatic or manual), in accordance with
local water authority requirements.
The installation must be designed to work with flow temperatures of up to
110
o
C.
Pump
IV
IV
Strainer
IV
IV
Fill Point
Expansion
Vessel
DOC
System flow(s)
System return(s)
Figure 2.6.2
Sealed System
Page : 7
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