5
Concord CXS -
Installation & Servicing
Boiler Size
Cold Feed
Open Vent
CXS 40 - 50
3/4
"
1"
CXS 60-120
1"
1
1/4
"
Sealed system filling point - refer to Frame 8
Flow and return connections are 2" BSP.
A 1" BSP tapping is provided in the redundant return flange for the
cold feed or expansion vessel connection.
Safety Valve
A safety valve must be sized and fitted in accordance with BS.6644
for every type of system. The valve should be set at 0.7 bar (10 lb/
in.
2
) above the operating pressure in the boiler. The maximum
safety valve setting is 0.7 bar (10 lb/in.
2
) above the maximum
design operating pressure of 6.0 bar (87 lb/in.
2
).
Cold Feed/Open Vent
The independent cold feed and the open vent must comply with
BS. 6644 and be of the following minimum size:
Table 3
GENERAL
1
WATER CONNECTIONS
GAS CONTROLS
The boiler lights at Low rate (approximately 60% of Full rate) by
direct burner ignition. After about 3 minutes the boiler goes to
High rate and will continue at High rate until the thermostat
sensor set point is reached. The boiler will then drop to the Low
rate; if the temperature continues to rise the boiler will go Off, if
the temperature falls the boiler will revert to High rate.
ELECTRICAL CONTROLS
The boiler is supplied with 2 printed circuit boards; Board
S4561B1047 is the ignition board containing the flame-proving
logic; Board W4115A1020 contains the electronic thermostat and
pump overrun timer. A preset overheat thermostat is also provided.
The mains voltage supply is via a terminal plug in connection at
the control box. The control box displays neons indicating boiler
status as follows:
- Boiler on
- Lockout
- Overheat
A 4 minute anti-cycle delay is built in to the controls to prevent
rapid cycling.
FROST PROTECTION
Frost protection is incorporated in the boiler as long as there is a
permanent Live supply wired to Terminal L1 on the terminal plug-
in connection at the control box and the boiler thermostat knob is
not switched to Off.
If the temperature sensed by the boiler thermostat falls to about
5
0
C the boiler will fire until the temperature reaches 18
0
C.
Note that this is designed to protect the boiler and may not
necessarily protect remote parts of the system.
The mains voltage supply is via a terminal plug-in connection at
the control box.
OPTION KITS
Remote Indication Kit
This kit gives the facility of remote indication of boiler status.
Pressure Gauge Kit
A pressure gauge kit is available.
Downdraught Thermostat Kit
This kit is optional when used on a single CXS installation, but
mandatory when used on a multiple boiler installation.
DUTY
The range of boilers is suitable for: Combined indirect pumped
domestic hot water
and
central heating systems; Independent
indirect pumped domestic hot water
or
central heating systems.
Fully pumped systems may be open vented or sealed.
The range of boilers is NOT suitable for:
1.
Gravity DHW systems.
2.
Gravity heating systems.
3.
Direct domestic hot water supply.
WATER CIRCULATION SYSTEM
Due to the compact nature of the boiler the heat stored within the
castings at the point of shutdown of the burner must be dissipated
into the water circuit in order to avoid the overheat thermostat
tripping. In order to allow pump operation after burner shutdown
the boiler control box incorporates a pump overrun facility which
operates for approximately 6 minutes after the burner shuts down
and, in order to make use of this, the pump must be wired to the
appropriate terminal L2 (pump) in the boiler control box.
1.
The minimum flow rate as given in Table 5 must be maintained
whenever the boiler is firing and during the pump overrun
period.
2.
During the period of pump overrun there must be an open circuit
of adequate water volume and/or load. The minimum size of
this circuit is given by the use of Graph 1.
Examples shown on Graph 1
a.
For the
CXS 90
and
CXS 100
the minimum circuit during
pump overrun could be a load of 6 kW with a volume of 31
litres or any other combination given by the relevant line.
b.
For the
CXS 70
and
CXS 80
the minimum circuit during
pump overrun could be a load of 2 kW with a volume of 45
litres or any other combination given by the relevant line.
The above circuit capacity during pump overrun may be
achieved either by provision of an adequate bypass circuit or
by ensuring that a zone of suitable size is open for circulation
during this period by relevant control of zone valves or pumps.
The wiring diagrams in Frames 16,17 &18 illustrate the control
methods for achieving the above.
3.
Pump selection should take account of the hydraulic resistance
given in Graph 2.
