3
Operation
12
Blue Seal Evolution Series GT45 / GT46 / GT60
©
Moffat Ltd, January 2007
Revision 1/
3.2
Explanation of Control
System - GT45/GT60
(Single tank fryers)
The gas control circuit in these fryers is operated
by three millivolt circuits.
The first two circuits are the pilot system which
consist of two thermocouples, the pilot burners,
the gas control and a second flame failure valve
separate from the gas control.
The thermocouple from the right pilot is
connected to the main gas control valve, while
the other thermocouple is connected to a
separate flame failure valve downstream from the
gas control pilot gas line. Heat on the
thermocouples from the pilot flames generates a
20-30 mV electrical potential between each
thermocouple and earth. These millivolt circuits
connected to the gas control valve and flame
failure valve are enough to hold the gas valve
magnets within the gas controls open, thereby
allowing the pilot burners to operate.
The third millivolt circuit consists of the
thermopile (a collection of
thermocouple
connections in series), and the gas control. Heat
on the thermopile from the pilot flame which is
constantly on as explained above, generates
approximately 500-700 millivolts which, when
connected to the main burner valve magnet
within the gas control, allows the magnet to pull
open the main burner valve therefore allowing
gas to pass through to the burners.
This main valve circuit is interrupted by the main
thermostat and as the thermostat cycles on/off, it
closes or opens this millivolt circuit, thereby
opening and closing the main burner valve to
cycle the main burners on/off.
The over-temperature thermostat is included in
the pilot millivolt circuit in this same way so that
when it open circuits it cuts the electrical supply
to the main gas valve magnet, thereby shutting
off the pilot burner. The fryer then becomes
inoperable until the oil cools to below 200°C, at
which point the over-temperature thermostat will
close again and allow the millivolt circuit to be
complete, thereby allowing the pilot burner to be
lit again.
The troubleshooting Guide section 5 should be
used to identify any incorrect fryer operation. On
correct identification of the fault, the Trouble-
shooting Guide will make reference to the
corrective action required, or refer to the Fault
Diagnosis section and/or Service section to assist
in correction of the fault.
The gas control circuit in these fryers is operated
by two millivolt circuits.
The first is the pilot system which consists of the
thermocouple, the pilot burner and the gas
control.
Heat on the thermocouple from the pilot flame
generates a 20-30 mV electrical
potential
between the thermocouple and earth. This
millivolt circuit connected to the gas control valve
is enough to hold the pilot valve magnet within
the gas control open, thereby allowing the pilot
burner to operate.
The second millivolt circuit consists of the
thermopile (a collection of
thermocouple
connections in series), and the gas control. Heat
on the thermopile from the pilot flame which is
constantly on as explained above, generates
approximately 500-700 millivolts which, when
connected to the main burner valve magnet
within the gas control, allows the magnet to pull
open the main burner valve therefore allowing
gas to pass through to the burners.
This main valve circuit is interrupted by the main
thermostat and as the thermostat cycles on/off, it
closes or opens this millivolt circuit, thereby
opening and closing the main burner valve to
cycle the main burners on/off.
The over-temperature thermostat is included in
the pilot valve millivolt circuit in this same way so
that when it open circuits it cuts the electrical
supply to the pilot valve magnet, thereby shutting
off the pilot burner. The fryer then becomes
inoperable until the oil cools to below 200°C, at
which point the over-temperature thermostat will
close again and allow the millivolt circuit to be
complete, thereby allowing the pilot burner to be
lit again.
The troubleshooting Guide section 5 should be
used to identify any incorrect fryer operation. On
correct identification of the fault, the Trouble-
shooting Guide will make reference to the
corrective action required, or refer to the Fault
Diagnosis section and/or Service section to assist
in correction of the fault.
3.3
Explanation of Control
System - GT46
(Twin tank fryers)
