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5. Outdoor Fan Operations
5.1.
High Ambient Conditions
5.1.1.
Energence Ultra-High Efficiency (7-1/2- to 20-ton)
Under high ambient conditions (outdoor air temperature greater than 105°F), if one or both compressors are running,
then all the fans corresponding to that circuit, run at speed set in parameter 96 - FAN HI AMBIENT SPD. When the
outdoor air temperature drops below 100F, the fans will switch to normal ambient condition speed.
5.2.
Normal Ambient Conditions
5.2.1.
Energence Ultra-High Efficiency (3- to 6-ton)
During normal ambient operation, the fan speed is based on the compressor speed.
5.2.2.
Energence Ultra-High Efficiency (7-1/2- to 12-1/2 ton)
Under normal ambient conditions the fan speed for part load and full load are as follows:
•
12.5 ton: Full load speed is 70% and part load is 50%
•
10 ton: Full load speed is 70% and part load is 50%
•
7.5 ton: Full load speed is 70% and part load is 40%
5.2.3.
Energence Ultra-High Efficiency (15- and 20-ton)
Under normal ambient conditions the fan speed for part load and full load are as follows:
•
on f
15 t
ull load speed is 70% and part load speed is 40%
•
20 ton full load speed is 75% and part load speed is 45%
5.3.
Low Ambient Conditions (S11, S84, S85 and S94)
See table 16 for fan layouts and tables 17 through 19 for low ambient fan operations.
5.3.1.
Energence Standard Efficiency (3- to 5-Ton) and High Efficiency (6-Ton)
During low ambient conditions, the outdoor fan is cycled by liquid line pressure switch S11. The M3 unit controller will also
de-energize fan due to low outdoor temperature. See unit installation instruction or service manual for specific
operational details. Low ambient temperature lockout for the compressor can be set using parameter 85.
5.3.2.
Energence High Efficiency (3- to 5-Ton)
The outdoor fan in Energence High Efficiency (3 - 5 Ton) unit operates at three distinct speeds; High, Low and Extra-low.
At higher outdoor temperatures, (above 65°F), the fan operates at high speed for a high cooling demand and at low speed
for a low cooling or de-humidification demand. At low outdoor temperatures, the fan is off until the liquid pressure switch,
(S11) closes. Then the fan runs at extra-low speed. See unit installation instruction or service manual for specific
operational details. Low ambient temperature lockout for the compressor can be set using parameter 85.
5.3.3.
Energence Ultra-High Efficiency (3- to 6-ton)
Low ambient operation is activated when the outdoor temperature drops below 62°F. At low outdoor temperatures, the
fan is off until the liquid pressure switch (S11) closes. Then the fan runs at 25% of full speed.
5.3.4.
Energence Ultra-High Efficiency (7-1/2- to 20-ton)
The following is the sequence of operations for the outdoor fans during low ambient conditions:
•
Low ambient operations will be activated based on the parameter 84 (Low Ambient Outdoor Air Limit Temperature
2 Set Point). Factory default setting is 55°F. Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 84 (LAC
SP TEMP 2)
•
Low ambient is deactivated when outdoor air temperature exceeds parameter 84 + 3°F.
•
During normal operation all fans are energized. During low ambient operation, two fans are de-energized on the
Energence Ultra-High Efficiency 7-1/2 to 12-1/2 ton) units leaving a single fan energized and four fans are
de-energized on the Energence Ultra-High Efficiency 15 and 20-ton units leaving two fans energized. During low
ambient operation the fan speeds are determined by the number of compressors running per refrigeration circuit.
If one compressor is running the corresponding fan will run at part load low ambient speed, if two compressors are
running the corresponding fan will run at full load low ambient speed.
•
During low ambient operation, the fan speed is based on the outdoor air temperature and the number of running
compressors in the corresponding refrigeration circuit.
•
When switching back from low ambient to normal operation, the energized fan for each circuit will be de-energized,
then all fans will be re-energized simultaneously after a user configurable delay. The delay is set using parameter
82 - COND FAN RESTRT DLY.
25
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