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START-UP PROCEDURE
and 4-20 mA signal when all the dip switches are in the
"ON" position. The modulating valve is modulated open or
closed based on the voltage from the amplifier (less gas
flow required = higher voltage, more gas flow required =
lower voltage), which correlates to the control signal from
the BMS.
Note: For further information regarding the operation of
any of the electronic modulating system options above,
consult the literature provided with the unit.
6. If the unit was provided with a time delay relay, the blower
starts after 30 to 45 seconds.
7. The unit continues to operate until the thermostat is satisfied,
Once satisfied:
a. Single-Stage Units: Both the main and pilot valves close
100%.
b. Two-Stage Units: Once the high stage of the thermostat
is satisfied, the main valve closes to 50% fire. The unit
continues to operate until the low stage thermostat is
satisfied, at which time both the main and pilot valves close
100%.
c. Electronic Modulation Units: The unit continues to
operate in this manner until the thermostat is satisfied or
the BMS heat enable contact opens. Power is then cut to
both the main and pilot valves, closing them 100% and
stopping gas flow to the main and pilot burners.
8. If the unit was not provided with a time delay relay, the blower
stops immediately. If the unit was provided with a time delay
relay, the blower stops after 30 to 45 seconds.
Multiple Furnace Controls
Staged Control (Digit 12=1 or 2):
For control of multiple staged units, each furnace would be
individually controlled. Refer to the section for Single Furnace
Controls, Staged Control (Digit 12=1 or 2).
Electronic Modulating Control (Digit 12=4):
Electronic modulation control of multiple furnaces with model
nomenclature Digit 12=4 is not available. Refer to the section
below for Electronic Modulating Control (Digit 12 = 5 and 6).
Electronic Modulating Control (Digit 12=7, or 8):
For control of multiple electronic modulation units for BMS
control, each furnace would be individually controlled. Refer to
the section for Single Furnace Controls, Electronic Modulation
Control (Digit 12=7 or 8).
Electronic Modulating Control (Digit 12=5 and 6):
These units are the same as Electronic Modulating Gas Controls
– Single Furnace (Digit 12=4) except the Master unit (Digit
12=5) features a modulating amplifier capable of driving multiple
modulating gas valves for systems with a Master and up to three
Slave units (Digit 12=6). Slave units do not have a modulating
amplifier. The units would be controlled by one of the following:
• Modulating room thermostat
• Modulating duct thermostat with remote temperature set point
adjuster
The sequence of operation for Electronic Modulating Gas
Controls - Master/Slave is the same as Electronic Modulating
Gas Controls - Single Furnace. The modulating amplifier sends
an equal voltage signal to all of the modulating gas valves so
that they modulate at the same percentage, between 40% and
100% full fire.
Variable Air Movement Applications
When the air mover supplied by others can provide variable air
movement (i.e. variable frequency drive units), the allowable
minimum CFM of the duct furnace can be reduced below
standard minimum airflow based on whether the factory installed
air distribution baffle remains on the unit or is removed (refer to
"Air Distribution Baffle Removal" on page 4). Refer to Table 13.1
for a summary of the reduced minimum airflows, indicated in the
column "Extended Range". To allow the reduced airflows, the
unit must be applied as follows:
1.
The unit has 2-stage or modulating gas controls.
2.
The unit is provided with a discharge air thermostat.
3.
The system does not include a room thermostat.
The discharge air thermostat will prevent the unit from firing
above the allowable 100°F rise when the unit is at or above the
minimum CFM by monitoring the discharge air and going to low
fire. A room thermostat, because it is located remote from the
unit, could cause the unit to over-fire.
Table 13.1 - Extended Range VAV Minimum Airflow
Factory Installed Air
Distribution Baffle
Input Rating
(Digit 4-6)
Standard
75
563
100
750
125
938
150
1,125
175
1,313
200
1,500
225
1,688
250
1,875
300
2,250
350
2,625
400
3,000
j Extended range minimum can be 75% of standard minimum.
k Extended range minimum can be 66% of standard minimum.
5-564.4
Minimum Airflow (CFM)
WITH
WITHOUT
Factory Installed Air
Distribution Baffle
Extended
Range j
Standard
422
938
563
1,250
703
1,563
844
1,875
984
2,188
1,125
2,500
1,266
2,813
1,406
3,125
1,688
3,750
1,969
4,375
2,250
5,000
Extended
Range k
619
825
1,031
1,238
1,444
1,650
1,856
2,063
2,475
2,888
3,300
13
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