84
High Exhaust Gas Temperature Cutout - HEGTC
(Direct Fire Only)
The High Exhaust Gas Temperature Cutout (HEGTC)
provides machine shutdown when an unusual operating
condition causes excessive flue gas temperature.
The exhaust gas temperature limit and high temperature
cutout are two active sensors located in the stack that
continually monitor flue gas temperature during normal
operation. The exhaust gas temperature limit attempts to
reduce the stack temperature to safe operational levels. The
high temperature cutout shuts the burner off if the flue gas
temperature reaches 425°F.
The HTC control module (Figure 34) is located in a small
enclosure along side of the burner control panel. The
sensor is located in the exhaust gas temperature probe
along with the limit temperature sensor. The HTC trips if the
sensed stack temperature exceeds 425°F for more that 6
continuous seconds. The HTC device normally closed
contacts (NC) open, removing the burner flame safeguard
start command, and the normally open contacts (NO) close,
to provide a trip signal input to the circuit module optical
input. An MMR diagnostic message is displayed on the
CLD.
Figure 34. HTC control module
MMR Input
Burner Control
HPC
Device
Stack Probe
T-Couple
UCP2 reset
Reset
120Vac
NO
NC
TC+
TC-
L1
L2
C
The HTC device latches in the tripped position until the unit
control panel is manually reset from within the diagnostics
menu group.