Preferred FlexFit 110 - Burner Management System

Description – Burner Management System 1-5
FlexFit – Linkageless Control – Revision 1.0
PREFERRED
UTILITIES MFG CORPORATION
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or parameter "P3.5.3 Low Fire Hold, Override Seconds" on page 4-75 times out. This cycle occurs only once per boiler start-up. The
cold start warm-up cycle option overrides the burner light-off low re hold.
Integrated Draft Control
The FlexFit can perform proportional oating draft control with a servo-actuated damper. By utilizing oating control, the FlexFit
will maintain draft at a setpoint as determined during boiler commissioning. If the draft error (measured draft minus setpoint) is inside
the deadband (see "P4.2.2 Deadband, Draft" on page 4-79), the draft damper output doesn't change. If the draft error is outside the
deadband, the draft damper position is adjusted proportionally to the draft error until draft has returned to within the deadband. For
more information, see section "Servo Setup" on page 3-47.
RS485 Modulating Lead/Lag Interface
This option allows communication via a Modbus network to an optional Chief Dispatcher modulating lead/lag controller or to a
building automation system, thereby eliminating the need for individual ring rate and CFH signal wiring.
Burner Management System
The Burner Management System (BMS) logic provides automatic burner sequencing, ame supervision, system status infor-
mation, system and self-diagnostics, and troubleshooting information.
Once power is applied, after booting, the BMS sequence is divided into 11 separate states. Two of these 11 states are optional
operations: Assured Low Fire Cutout (ALFCO) and Gas Valve Leak Test. The 11 states are shown in "Figure 1 – 2 FlexFit BMS States"
in standard sequential order. Typical timing diagrams follow.
Figure 1 – 2
Standby (or Off)
Safe Start Checks
Prestart
Pre-Purge Gas Leak
Test (Option)
Purge
PTFI (Pilot Trial
for Ignition)
MTFI (Main Trial
for Ignition)
Release to Modulate
(single fuel)
ALFCO (Assured Low
Fire Cutoff) (Option)
Post Purge
Post Purge Gas Leak
Test (Option)
(if limits made)
Lockout (with Post
Purge, if required)
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Lockout
Boot
CFH Open or time
for 24 Hr Recycle
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FlexFit BMS States