Low Fire Hold With An Rwf55; Introduction; Steam Boiler With An Rwf55 With Analog Output; Hot Water Boiler With An Rwf55 With Analog Output - Siemens LMV5 Series Technical Instructions

Technical Instructions
Document No. LV5-8000

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
ExtLC X5-03
IntLC
IntLC Bus
IntLC X62
ExtLC X62
ExtLC Bus
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.
Appendix A
Description
External load control,
firing rate from
3-position input
Internal load control,
setpoint set locally on
LMV5
Internal load control,
setpoint from Modbus
command
Internal load control,
setpoint from analog
signal on terminal X62
External load control,
firing rate from analog
signal on terminal X62
External load control,
firing rate from Modbus
command
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Upon X62.1 – X62.2
Setpoint
Contact Closure
Change to "IntLC",
N/A
setpoint W1
Remain in "IntLC",
W1
setpoint W2
W3
Remote
setpoint
Change to "IntLC",
setpoint W1
N/A
N/A
LMV Series
SCC Inc.