h
Jointing should be either with capillary, threaded or compression fittings. Pipes
should have a gradient to ensure air is passed easily to vent points and water
flows readily to drain points.
i
Draining taps must be located in accessible positions which permit the draining of
the boiler. Draining taps should be at least 22 mm in nominal size and be in
accordance with BS 2879.
AIR VENT POINTS
j
These must be fitted at all high points where air will naturally collect and must be
sited to allow complete draining of the system.
k
A filling point must be fitted, in accordance with local water authority
requirements.
m
The installation must be designed to work with flow temperatures of up to 110
o
C.
lll components of the system must be suitable for a working pressure of 3 bar and
a temperature of 110
o
C. Care should be taken in making all connections that the
risk of leakage is minimised.
3.7.1
Boiler By-pass Piping
Boiler water flows are critical to the operation of the boiler. If flow cannot be maintained
through the system piping to meet the minimums required by the boiler, insufficient water
flows through the boiler will cause the boiler to "kettle" or even produce steam which can
damage the heat exchanger and will invalidate the heat exchanger warranty. In addition,
an open circuit is required after boiler shutdown to permit circulation during the boilers 2
minute pump overrun sequence.
It is advisable to incorporate a boiler by-pass in the system, especially if thermostatic
radiator valves are used. The flow/return differential should be 10
o
C to 20
o
C.
To comply
with the Building Regulations Part L1 the bypass must of the automatic type.
3.7.2
Air Elimination
In the initial charge of water to the boiler system and in all subsequent additions of water
to the system some air will be dissolved in the water. As the water is heated the air is
driven out of the solution and will collect in high spots in the system.
These air bubbles
can interfere with pumping and heat transfer and must be eliminated.
Installation of air bleed valves at the high
spot(s) in the system will allow for air
elimination when filling the system and
will allow re-venting in a day or so after
all air has been driven out of solution.
3.7.3
Pump Selection
The Keston Qudos 28h and Qudos 28hP
boilers have low water content heat
exchangers with a high resistance to
flow, when compared with cast iron heat
exchanger boilers. As a result selection
of the correct pump is essential in order
to avoid localised boiling within the heat
exchanger. The selected pump must be
capable of maintaining the required flow
rate for the boiler against the pressure
losses contributed by the boiler.
The Keston Qudos 28h condensing
boiler offers a hydraulic resistance of
2.9m (9ft) water at the required flow
rate of 36 l/m (7.9 gpm).
See graph opposite
If a single pump is to be used for the entire installation the boiler resistance must be
added to the pressure loss caused by the rest of the system and a pump selected that is
WD440/3/2007 Chapter 3 - Boiler Location
The Keston Qudos 28h & Qudos 28hP Boilers
Installation & Servicing Instructions
Page : 16
1
2
3
4
5
6
7
20
30
40
50
60
lit/min
m
w
c
10
0
0
Q28h hidraulic resistance
