FIGURE 27
F
ACTORY SET BLOWER SPEEDS
35
MODEL
PSC MOTOR
COOL HEAT COOL HEAT
X-13 MOTOR
2.0 TON W/40K HEAT HIGH LOW HIGH (Tap 3) DEDICATED (Tap 1)
2.0 TON W/60K HEAT HIGH HEAT HIGH (Tap 3) DEDICATED (Tap 1)
2.0 TON W/80K HEAT HIGH HEAT HIGH (Tap 3) DEDICATED (Tap 1)
2.5 TON ALL HEAT INPUTS LOW LOW HIGH (Tap 3) DEDICATED (Tap 1)
3.0 TON ALL HEAT INPUTS MED LOW HIGH (Tap 3) DEDICATED (Tap 1)
3.5 TON ALL HEAT INPUTS HIGH LOW HIGH (Tap 3) DEDICATED (Tap 1)
4.0 TON ALL HEAT INPUTS HIGH LOW HIGH (Tap 3) DEDICATED (Tap 1)
1st Stage - DEDICATED (Tap 2)
DEDICATED (Tap 1)5.0 TON ALL HEAT INPUTS N/A N/A
2nd Stage - HIGH (Tap 4)
*460 volt units: Do not adjust from factory speed.
3. Cooling speeds can be adjusted as noted in Figure 26 by moving appropriate wire
between taps at the blower (Do not connect wires to unspecified speed taps).
Note: Heat speed is dedicated and should not be changed. The first stage cooling
speed on 5-ton models is dedicated and should not be changed.
4. Replace blower access panel.
XI. UNITS WITH ECM BLOWER MOTORS
XI. (RRRL-B MODELS ONLY)
The ECM (Brushless permanent magnet) motor used on the blower in this product is pro-
grammed to operate over a wide range of external static pressures (0.0” - 1.0” W.C.) with
essentially constant air flow (CFM). Motor efficiency on ECM type motors is higher than that
of P.S.C. type motors normally used on this type product. See air flow performance data
tables.
The ECM motor is programmed to provide a “soft” start and stop. On a call for heat or cool,
the motor will gradually ramp up to the field selected CFM speed. This eliminates the sudden
rush of air and noise normally associated with a P.S.C. type motor. Once the thermostat and
blower delay are satisfied, the motor will gradually ramp down as well.
IMPORTANT: Units equipped with ECM motors cannot be used in by-pass zoning applica-
tions.
IMPORTANT: The A.C. power plug to the blower motor has locking tabs. It has been shown
that by applying excessive force to the A.C. cable half of the connector it is possible to force
the connector in backwards. It will not seat and “click” properly but will make connection. If
A.C. power is applied with the connector reversed the motor will be immediately destroyed. Do
not force power plug into motor connector backwards.
NOTE: Because of the harmonic content of the A.C. Line current to the ECM motor a conven-
tional ammeter will not read correct motor amps. Only a true RMS meter will give accurate
AMP readings.
IMPORTANT: The flexibility of ECM motors and the fact that this flexibility is contained in pro-
grammed memory, not hardware, emphasizes the need for exact motor numbers for replace-
ment motors. Because they all look the same, ECM MOTORS FROM DIFFERENT PROD-
UCTS OR DIFFERENT MODELS OF THE SAME PRODUCT MUST NOT
BE INTER-
CHANGED.
IMPORTANT: If an ECM motor is replaced, it is important that the motor be mounted as the
original, as far into the blower wheel as practical for proper motor cooling.
IMPORTANT: The ECM motor is controlled directly from the room thermostat (in all modes
except heating). In cooling, the motor is controlled from the thermostat “Y” terminal. When the
“Y” or “R” thermostat circuit is opened a 30 second delay will occur before the blower motor
will cycle. In the heating mode the furnace control board controls the ECM through the blower
relay. When the “W” thermostat circuit is opened, a 90 second delay will occur before the
blower will cycle off. When the “G” to “R” thermostat circuit is opened for low speed blower,
there is no “off” delay. All thermostat sub-base combinations as recommended and provided
through the Parts Department have been tested and are compatible with the ECM motor used
in this equipment. Some thermostats may not be compatible with the ECM motor provided in
this unit. With thermostat in off state, the voltage on control lines “G”, “Y”, or W with respect to
24 vac common should be less than 3.5 VAC. If the measured voltage is too high, thermostat
is incompatible with the ECM motor and will cause the motor to run when it should be off.
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