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10.C Shutting Down the Unit
Thisstepmustbeperformedbyaqualifiedservice
person.
1.
Turn off the main electrical disconnect switch.
2.
Close all manual gas valves.
3.
If freezing is anticipated, drain the unit and be sure
to also protect the building piping from freezing. All
water must be removed from the heat exchanger or
damage from freezing may occur.
10.D Restarting the Unit
If the system has been drained, see 10.A for instructions
on proper filling and purging.
1.
Turn off the main electrical disconnect switch.
2.
Close all manual gas valves.
3.
Wait five minutes.
4.
Set the aquastat or thermostat to its lowest setting.
5.
Open all manual gas valves.
6.
Reset all safety switches (pressure switch, manual
reset high limit, etc.).
7.
Set the temperature controller to the desired
temperature setting and switch on the electrical
power.
8.
The unit will go through a prepurge period and
ignitor warm-up period, followed by ignition.
10.E Controllers
This unit utilizes three (3) separate controllers to
manage system functions, burner management and air/
fuel ratio control:
- Burner Integrated Control (BIC)
- Linkageless Modulating Valve (LMV)
- Oxygen Controller (O2C)
These controllers communicate with each other
via voltage and current signals, and serial digital
communication using Modbus protocol. The BIC also
communicates with the touch screen display and all
user inputs.
When there is a call for heat the BIC will provide an
enable signal to the LMV which tells the LMV to initiate
burner operation. For this signal to be sent and acted
upon, the safety circuit must be satisfied and both
controllers must be in standby mode.
The system pressure sensors, which measure the
overall system pressure drop must also read zero in
order for the Safety Status to be verified.
The Safety Circuit status can be verified on the
Services/Digital I/O screen. Once the LMV is enabled it
will proceed through the startup states listed in Table 26
until it gets to Run. Once in Run, the LMV will receive
a firing rate demand from the BIC and position the fuel
and air dampers and blower speed accordingly.
BIC Status
Phase
Standy
Call For Heat
LMV Enable
Pressure Transmitter Verification
Read (via Modbus) ACC State
and Display at
Touchscreen
Fan Speed Governed by
Controller Demand Signal
End Call for Heat
LMV Disable
Standby
Table 26. BIC Status and LMV Status
Page 113
LMV States
Phase
12
Standby
22
Blower On
Component Calibration
24
30
Prepurge
Move to Ignition Position
36
38
Igniter On
40
Pilot On
42
Verify Pilot
50
Main Fuel On
Pilot Off/Verify Main Burn
52
60
Run
70
Post Purge
74
Shutdown
Standby
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