Technical Instructions LMV Series
Document No. LV5-800
0
Appendix A Page 14 SCC Inc.
Low Fire Hold with an RWF55
Introduction
Low fire hold assists in
preventing boiler damage from thermal shock. If an RWF55 is the
external load controller with the LMV5, a low fire hold can be easily incorporated. With an
RWF55, a low fire hold is accomplished by breaking the increase load signal to the LMV5. The
wiring and setup for four cases will be described:
• Steam boiler with an RWF55 with analog output
• Hot water boiler with an RWF55 with analog output
• Steam boiler with an RWF55 with 3-position output
• Hot water boiler with an RWF55 with 3-position output
Table 4 describes the six different load controller operating modes in the LMV5.
Table 4: Description of LMV5 Load Controller Operating Modes
Label Description Setpoint
Upon X62.1 – X62.2
Contact Closure
ExtLC X5-03
External load control,
firing rate from
3-position input
N/A
Change to “IntLC”,
setpoint W1
IntLC
Internal load control,
setpoint set locally o
n
LMV5
W1
Remain in “IntLC”,
setpoint W2
IntLC Bus
Internal load control,
setpoint from
Modbus
command
W3
Change to “IntLC”,
setpoint W1
IntLC X62
Internal load control,
setpoint from a
nalog
signal on terminal X62
Remote
setpoint
ExtLC X62
External load control,
firing rate from a
nalog
signal on terminal X62
N/A
ExtLC Bus
External load control,
firing rate from
Modbus
command
N/A
When executing a low fire hold with
the RWF55, either “ExtLC X5-03” or “ExtLC X62” may be
chosen for the LMV5’s operating mode. The wiring and setup of the RWF55 differs slightly
depending on the mode selected as shown on the following pages.
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