| Adjusting Airflow (Variable Speed Motor Equipped Units Only) |
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Model | Motor | ADJUST | HEAT | COOL | CFM | CFM | CFM | CFM | ADJUST, HEAT, and | |||
Nominal | Heating | COOL Taps | ||||||||||
Cooling | Size | HP | Setting | Setting | Setting | A | B | C | D | and Dehumidify | ||
kBTU | kW |
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| Resistor on | ||
24 | 1/3 | NORM | B | B | 1000 | 800 | 600 | 900 | Interface Board | |||
30 | 1/3 | NORM | A | A | 1000 | 800 | 600 | 900 | ADJUST | HEAT | COOL | |
36 | 1/2 | NORM | A | A | 1200 | 1000 | 800 | 1100 | NORM | A | A | |
(+) | B | B | ||||||||||
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| C | C | |
42 | 3/4 | NORM | C | C | 1800 | 1600 | 1400 | 1200 | TEST | D | D | |
| D1 |
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48 | 3/4 | NORM | B | B | 1800 | 1600 | 1400 | 1200 |
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| DEHUMIDIFY | |||||||||||
60 | 3/4 | NORM | A | A | 1800 | 1600 | 1400 | 1200 |
| CUT TO ENABLE |
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Table 4
There is no blower “on” delay after a call for heating or cooling. Blower “off” delay is 90 seconds after the thermostat is satisfied.
Variable Speed Motor
Units equipped with a variable speed circulation air blower motor will deliver a constant airflow within a wide range of external static pressures. Other features of this variable speed motor include:
Soft Start/Stop – The variable speed motor will slowly ramp up to normal operating speed. This minimizes noise and increases comfort by eliminating the initial blasts of air encountered with standard motors. At the end of a cooling or heating cycle, the motor will slowly ramp down.
Circulation Airflow Adjustments – The controls include a variable speed motor interface board. The ADJUST tap can be used to raise (+) or lower
Heating and Cooling Airflows – The units are factory set for the correct heating and cooling airflows. However, airflow changes can be made by moving the position of the HEAT and COOL taps (see Table 4).
Continuous Blower – The comfort level of the living space can be enhanced when using this feature by allowing continuous circulation of air between calls for cooling or heating. The continuous circulation of air occurs at half the full cooling airflow rate. To use this feature, place the thermostat fan switch into the ON position.
Cooling Airflow Ramp Up – At the beginning of a call for cooling, the blower will run at 80% of full airflow for 7.5 minutes. This improves the system’s moisture removal and saves blower power during cooling start.
Reduced Airflow Operation (Dehumidification) – For situations where humidity control is an issue, the variable speed motor can be connected to operate at a 25% reduction in the normal airflow rate. The variable speed motor interface board provides for connection of a humidistat on the HUM terminal. When a humidistat is connected, the dehumidifier resistor on the interface must be cut. The humidistat should be wired to open during high humidity, which will reduce blower airflow.
Cooling System Performance
For maximum performance of the cooling system, operating temperatures and pressure should be checked. Subcooling should be determined at Standard ARI test conditions of 82°F outdoor and 80°F indoor dry bulb/67°F wet bulb. If subcooling measured deviates from values found in Table 5, refrigerant charge should be adjusted accordingly for maximum performance.
Liquid Subcooling
| Liquid Subcooling | |
Size | @ARI Conditions | |
82° OD - 80° IDDB/67° IDWB | ||
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| R22 | 410A |
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24 | 10° | 9° |
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30 | 8° | 11° |
36 | 10° | 11° |
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42, 48 | 5° | 7° |
60 | 10° | 10° |
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Table 5
Issue 0902 | Page 9 of 14 |
