FireBird Enviromax Popular C20 Technical Manual page 11

2 HOUSEHOLDER
INTRODUCTION TO COMBI
OPERATIONS
FIREBIRD COMBI C
The Firebird Combi C is designed to give separate
control to both the domestic hot water and to the
central heating. The Combi C has three thermistors
connected to a PCB board that gives very accurate and
fast temperature control and one high limit
thermostats that help to achieve this.
Tank thermistor
The Tank Thermistor controls the temperature of the
heat store (or Slave Tank). The Tank Thermistor
sensor is located in stat pocket in the top of the tank at
the side of the boiler. When the thermistor senses that
the heat store is seeking heat it activates a relay on the
PCB. board in the control panel this in turn sends
power to the domestic circulating pump and burner.
The Flow sensor is the only other device that will
activates the relay in this way when it detects the flow
of water on opening a tap. This heat store is a tank
with a bank of water stored at a higher temperature
than that normally used on a central heating circuit,
and is used for domestic hot water production. The
temperature of this heat store has priority over central
heating. Central heating will not work until the heat
store reaches a temperature of 78˚C. + -3˚C
The Boiler Control thermistor
The boiler Control thermistor has a number of
functions.
1. It controlling the temperature of the water in the
boiler when in central heating mode (60˚C to 80˚C).
When the central heating is on it does not effect the
temperature in the heat store. The check valve on the
domestic flow circuit prevents any circulation to or
from the heat store. The sensor from this thermistor is
situated in stat pocket in the boiler.
2. The over heat function activates the domestic
circulating pump when due to residual heat rise in the
boiler, the temperature reaches 93˚C. The water is
circulated from the boiler into the heat store tank thus
preventing the boiler from activating the high limit
thermistor.
3. The early alert function controls the burner when
the Combi is operating in domestic hot water mode. If
the temperature in the boiler reaches 87˚C before the
tank thermostat cuts out, the early alert thermistor
cuts off the burner.
The High Limit Thermostat
The High limit thermostat cuts off power supply to the
burner should all thermostats fail. It is a manual re-set
thermostat, and will stay off until such time that it is re
set. If this thermostat is activated, the reason for
activating must be resolved before re setting. The sen-
sor from this thermostat is situated in stat pocket in
the boiler in the same Thermostat pocket as the boil-
er control thermistor. The re-set button is located at
the back of the control panel directly behind the
location for the optional DWH timer. See Control
Panel Diagram - on page 26.
Flow Switch thermistor
The flow switch thermistor is coloured red and is
positioned in a pocket on the cold feed pipe to the
plate heat exchanger. When the thermistor senses
detects the flow of water on opening a tap it activates
a relay on the PCB. board, this in turn sends power to
the domestic circulating pump and burner.
Important
Keep thermistor sensor wires separate from mains
power cables. i.e.: Mains feed cable to combi and
circulating pump cables.
9
Firebird Enviromax Condensing Range