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GENERAL REQUIREMENTS AND SPECIFICATIONS (CONT’D)
*FACTORY SETTINGS.
SUBJECT TO CHANGE WITHOUT NOTICE.
240 VOLTS – SINGLE PHASE TEMP. RISE @ 0.20 IN. W.C.
MODEL NO. KW BTUH AMPS INCL. MOTOR HP BLOWER °C °F *SPEED RPM
21D10 10 34120 46 1/3
10” x 8”
(254 mm x 203 mm)
21 70 MED-LOW 814
21D15 15 51180 67 1/3 24 25 MED-LOW 814
21D18 18 61420 77 1/3 27 81 MED-LOW 814
21D20 20 68240 86 1/3 33 91 MED-LOW 814
21D23 22.5 76842 94 1/3 36 97 MED-LOW 814
21D25 25 85003 107 1/3 37 99 MED-LOW 814
21D27 27 92130 116 3/4
12” x 8”
(304 mm x 203 mm)
36 97 MED-HI 707
OPERATING OPTIONS
The furnace is shipped from the factory in a “Standard Heating
Mode” (all switches in the Down position). When the thermostat
calls for heat, the automatic controls will be activated and the
furnace turns “ON”.
The blower will run at low speed or higher speed (as selected by
S
PEED SELECTOR switch).
As the furnace heats up, it automatically switches to a medium
speed when additional elements are activated by the electronic
control, if it was initially set to run at low speed. The timing of this
blower speed change will depend on whether C
OLD or MILD is
selected on the SEASON SELECT switch.
You may, however, change from the Standard Heating Mode by
using the controls built into your furnace.
SPEED SELECTOR SEASON SELECT
HIGH
MILD
COLD
The SPEED SELECTOR switch is used to control the fan speed
(ventilation). Even if there is no call for heat, the ventilation can be
controlled by the thermostat; the fan speed is determined by this
switch.
LOW – The blower motor will operate at low speed.
H
IGH – The blower motor will operate at a higher speed.
During spring or fall, you may require less rapid response when
the thermostat calls for heat.
When M
ILD is selected, it takes more time to bring all the elements online.
When C
OLD is selected, the heating elements come online faster.
10” x 8” (254 mm x 203 mm) BLOWER
SPEED
FLOW
RATE
STATIC PRESSURE
(INCHES OF WATER COLUMN)
0.2 0.3 0.4 0.5 0.6
LOW**
CFM
L/s
756
357
749
353
740
349
729
344
713
337
MED-LOW
CFM
L/s
1035
488
1018
480
997
470
971
458
935
441
MED-HIGH
CFM
L/s
1177
556
1157
546
1132
534
1102
520
1063
502
HIGH
CFM
L/s
1301
614
1276
602
1247
588
1207
569
1145
540
WARNING:
**These speeds can only be run with heater off, for cooling/ventilation purposes only.
3
LOW
12” x 8” (304 x 203 mm) BLOWER
SPEED
FLOW
RATE
STATIC PRESSURE
(INCHES OF WATER COLUMN)
0.2 0.3 0.4 0.5 0.6
LOW**
CFM
L/s
727
343
699
330
667
315
636
300
606
286
MED-LOW**
CFM
L/s
912
431
897
423
878
414
853
402
823
388
MED-HIGH
CFM
L/s
1216
574
1200
566
1181
557
1157
546
1129
533
HIGH
CFM
L/s
1640
774
1601
755
1558
735
1513
714
1466
692
MILD SEASON (First Stage)
Slow Response Sequence
COLD SEASON (Second Stage)
Rapid Response Sequence
Element 1 - Heat on instantly Element 1 - Heat on instantly
Blower on after 3 seconds delay Blower on after a 3 seconds delay
Elements 3 and 5 after 1 minute delayElements 3 and 5 after 10 seconds delay
Element 2 after 2 minutes delay Element 2 after 20 seconds delay
Elements 4 and 6 after 3-minute delayElements 4 and 6 after 30 seconds delay
NOTE: Elements 4, 5 and 6 only where applicable.