© 2023 Carrier 52
Notes on operation:
Terminal 16 is used for selection of fuel type between OIL or GAS, providing full burner operation even
if two fuels are fired simultaneously. Fuel selection (terminal 16) is active HIGH for GAS fuel type and
active LOW for OIL fuel type. The fuel selection between OIL or GAS shall be made only before the
start of burner cycle i.e., in STANDBY state only. Once the burner cycling starts, change in fuel
selection input shall be ignored and shall be considered only in the next cycle during STANDBY
state only. YP148/YP184 programmers support valve proving (terminal 23) and low gas pressure
check (terminal 21) feature only if the fuel type is of GAS (terminal 16 is active HIGH).
Terminal 21 is used to monitor the low gas pressure in the gas fuel train where the burner cannot operate
properly, when the main fuel valves are energized in the MTFI state. This input must be proven by the
end of the first five seconds of MTFI/MFEP and remain on during the run cycle.
Note: When both main fuel valves (MV1 and MV2) are energized, the LGP switch (Low Gas Pressure
Switch) is expected to close (active high for YP148 and active low for YP184) between terminals L1 and
21. If the L1-21 circuit does not close within the first five seconds of MTFI/MFEP
,
the
control
will move
to safety
shut
down
and
display:
" LOCKOUT
MTFI,
LGP CHECK FAIL
". This input shall remain
active during the entire run state, else the control will move to safety shutdown and display
:
" LOCKOUT
AUTO,
LGP CHECK FAIL
".
Terminal 23 is used to check the effective closure of automatic shut-off valves by measuring the pressure
differential between two fuel shutoff valves (MV1 and MV2) during the valve proving test sequence. This
input must be proven during the evacuation test time 1 and pressurization test time 2.
Note: During the evacuation time, the main valve 2 (7) is energized and the valve prove switch (terminal
23) is monitored for active low during the evacuation test time 1. If the valve prove switch (terminal 23)
is active during the period of test time 1, then the control will move to safety shutdown and display
:
“LOCKO UT V ALV EPROVE, EVAC T E ST F AIL". During the pressurization time, the main
valve 1 (6) is energized and the valve prove switch (terminal 23) is monitored for active high during the
pressurization test time 2. If the valve prove switch (terminal 23) is not active during the period of test
time 2, then the control will move to safety shutdown and display
:
“LOCKO U T V ALVEPRO V E,
PRES TEST FAIL".
Note: In case of power failure or lockout or interruption during execution of valve proving at post-
purge, the system will start with the valve proving at pre-purge upon power-on followed by the valve
proving at post-purge.
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