Keston Qudos 28s User, Installation And Servicing Instructions page 64

Qudos 28sP and Qudos 28hP
NG CONVERSION INSTRUCTIONS
FOR KESTON QUDOS 28sP and Qudos 28hP MODELS
The Keston Qudos 28sP and Qudos 28hP condensing boilers are supplied fabricated for LPG
combustion at a supply pressure of 37 mbar.
These conversion instructions must be read in conjunction with the Keston Qudos 28s or Qudos 28h
Installation & Servicing Instructions - WD420 and WD440.
To convert to NG (natural gas) you must carry out the following sequence:
i) Isolate the appliance
(Section 8.1)
ii) Gain access (Section 8.2)
iii) Replace the LPG main
PCB (part number
Q.10S.4.15.00.0) with the
NG main PCB (part
number Q.10S.4.01.00.0)
according to section 8.4.6
iv) Replace the LPG gas
valve/venturi assembly
(part number
Q.10S.3.05.00.0) with the
NG gas valve/venturi
assembly (part number
Q.10S.3.04.00.0)
according to section 8.4.8
v) Check the gas rate and
combustion –
MANDATORY
Although the gas pressure is
preset at the factory it is required to
assure proper combustion
measuring gas input and the level
of carbon dioxide, or oxygen and
carbon monoxide, in the flue outlet from the boiler. Overfiring or underfiring the burner will reduce the
longevity of the appliance and may result in excessive carbon monoxide levels
Carbon dioxide and carbon monoxide are colorless, odorless gases produced by all combustion
processes. When the Keston condensing boiler is operating properly, carbon dioxide (CO
be between 8.4 to 8.8% (low rate) and 8.9 to 9.3% (high rate) and the carbon monoxide will be
between 5 to 20 ppm (low rate) and 50 to150 ppm.
In any event, the CO
by
level at low rate must ALWAYS be less than CO
2
WD480/0/2008
) levels will
2
levels at high rate.
2
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