Description of functioning
t e c h n i c a l
13
92º C Security (without DHW demand)
If
flow
thermistor value arrives to 92º C, the pump
will run
making cycles of 10 se-
cond
starting
and stop
p
ing. If the temperature remains high the pump will continue
cycling until
a lower temperature is detected.
180 minutes security:
When the burner is working continuously for 180 minutes, the burner
will shut down
for a
period
and if it is necessary, the
burner will relight.
Control and safety components:
Main PCB
:
This circuit governs the correct functioning of all the boiler
functions
.
High limit
thermostat:
(Part number MCB2250)
This is in direct contact with th
e
the
primary
heat exchanger (
dry pocket)
It controls the temperature of the outlet circuit, protecting the boiler against overhea-
ting. It
goes to open circuit
at 102º C.
The contacts of this thermostat are normally closed. When the thermostat is activa-
ted, the boiler will
lock out
(F4 block). The thermostat resets automatically,
although the F4
fault will need resetting from the control panel.
Thermistors:
(MCB2245)
There are two thermistors incorporated
in
to the boiler.
The
flow
thermi
stor is located top
left on the primary heat exchanger
, and is
responsible for most of all boiler functions along
with the return thermistor which is located on the return pipe from the pump body.
Th
e flow & return
thermistor
s
control the temperature of
the primary circuit
within the boiler.
The
flow
thermistor is also responsible for first stage over heat protection
any overheating within the boiler is detected and controlled by the pump
cycling in 10 second intervals until a lower value is reached.
The
flow
thermistor also reads the temperature for the built in frost
protection.Faulty or out of range thermistors will cause the boiler to
lock out
. Both thermistors are the same
(Part number MCB2245)
.
Flow thermistor fault code: F13
Return thermistor fault code:F12
MCB2250
12
MCB2245
