Boiler By-Pass Piping; Air Elimination; System Pump - Keston Qudos 28s User, Installation And Servicing Instructions

WD420/3/2007 Chapter 3 - Boiler Location
m The installation must be designed to work with flow temperatures of up to 110
All components of the system must be suitable for a working pressure of 3 bar
and a temperature of 110
the risk of leakage is minimised.
n The pipe from the safety discharge valve must not discharge above an entrance,
window or any type of public access area. The boiler safety discharge valve pipe
must be extended using not less than 15mm pipe to discharge, in a visible
position, outside the building, facing downwards, preferably over a
pipe must have a continuous fall and be routed to a position so that any discharge
of water, possibly boiling, or steam cannot create any danger to persons, damage
to property or external electrical components or wiring. To ease future servicing it
is advisable to use a compression type fitting to extend the safety discharge valve
pipe.
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
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

System Pump

Selection (if required)
The Qudos 28s features an
integral circulating pump which
has sufficient excess head to
drive most domestic systems.
The available head is shown in
the graph below. If the system
index circuit resistance is in
excess of the available head
from the integral
additional system pump will be
required.
The schematic below illustrates
a recommended approach to
using an
pump. The additional system
pump should
overcome
resistance only as the boilers
integral pump will overcome
boiler resistance.
Installation & Servicing Instructions
pump an
additional system
be sized to
the index circuit
The Keston Qudos 28s & Qudos 28sP Boilers
o C. Care should be taken in making all connections that
Q28s Available pum p head
7
6
5
4
3
2
1
0
0 5 10
drain.
o o
C to 20 C. To comply
15 20 25 30
Flow Rate (lpm )
Page : 16
o
C.
The
35 40