Trane OABE OADE OAKE OANE (Water Source Heat Pump) Katalog
OAU-PRC003A-EN
19
Application Considerations
The Trane OAU utilizes recovered energy from the cooling process to reheat the air leaving the
evaporator coil as required to meet the discharge air setpoint. The reheat refrigeration circuit is
adequate to deliver enough reheat to supply neutral-temperature air (e.g., 75°F dry-bulb) under
most operating conditions. On very low load days, the reheat circuit may not contain enough
energy to meet the desired reheat setpoint.
evaporator coil as required to meet the discharge air setpoint. The reheat refrigeration circuit is
adequate to deliver enough reheat to supply neutral-temperature air (e.g., 75°F dry-bulb) under
most operating conditions. On very low load days, the reheat circuit may not contain enough
energy to meet the desired reheat setpoint.
Heating
The OAU has electric, heat pump, or gas heat options. The electric heat option is available in 0°F–
80°F temperature rise offerings with SCR modulation. This means that the lowest temperature rise
provided depends only on heater size and unit airflow. Calculate the temperature rise to confirm
that it provides acceptable control. The electric heat will modulate to maintain heating setpoint.
80°F temperature rise offerings with SCR modulation. This means that the lowest temperature rise
provided depends only on heater size and unit airflow. Calculate the temperature rise to confirm
that it provides acceptable control. The electric heat will modulate to maintain heating setpoint.
When using hot water heat, the unit controller will modulate a field-provided coil control valve.
Provide an ethylene glycol and water mixture or other means of freeze protection for the hot water
coil if the OAU will be subject to sub-freezing temperatures.
Provide an ethylene glycol and water mixture or other means of freeze protection for the hot water
coil if the OAU will be subject to sub-freezing temperatures.
Capacity Control
The capacity control system on the Horizon™ Outdoor Air Unit is flexible enough to accommodate
a variety of system applications. These applications include:
a variety of system applications. These applications include:
•
treating outdoor air to supply a single space or multiple spaces or
•
simultaneously meet building make-up air needs while controlling the temperature and relative
humidity of a single space.
humidity of a single space.
Each of these applications requires careful consideration to achieve the desired results.
Discharge Air Control
For many multiple space, dedicated outdoor air systems, the OAU will continuously supply outdoor
air at a dry-bulb setpoint and a dew point that does not exceed its dew point setpoint. This control
approach is simple because it allows the OAU to function independent of local terminal unit
operation or actual space conditions. If the unit selection criteria is determined using the method
suggested in
air at a dry-bulb setpoint and a dew point that does not exceed its dew point setpoint. This control
approach is simple because it allows the OAU to function independent of local terminal unit
operation or actual space conditions. If the unit selection criteria is determined using the method
suggested in
, the Outdoor Air Unit will limit the space
relative humidity to the target level.
Table 3.
Supply air dew point temperature, 75°F at 50 percent RH space limit
Latent Load
Btu/h per Person
cfm per person
10
15
20
25
30
35
40
45
50
55
60
100
48.4
50.8
51.9
52.6
53
53.3
53.6
53.8
53.9
54
54.1
120
46.8
49.8
51.3
52.1
52.6
53
53.3
53.5
53.6
53.8
53.9
140
45.2
48.9
50.6
51.5
52.2
52.6
52.9
53.2
53.4
53.5
53.7
160
—
47.9
49.8
51
51.7
52.2
52.6
52.9
53.1
53.3
53.5
180
—
46.8
49.1
50.4
51.3
51.8
52.3
52.6
52.9
53.1
53.3
200
—
45.7
48.4
49.8
50.8
51.5
51.9
52.3
52.6
52.8
53.0
220
—
—
47.6
49.3
50.3
51.1
51.6
52
52.3
52.6
52.8
240
—
—
46.8
48.7
49.8
50.7
51.3
51.7
52.1
52.4
52.6
260
—
—
46
48.1
49.4
50.3
50.9
51.4
51.8
52.1
52.4
280
—
—
45.2
47.4
48.9
49.8
50.6
51.1
51.5
51.9
52.2
300
—
—
—
46.8
48.4
49.4
50.2
50.8
51.3
51.6
51.9
320
—
—
—
46.2
47.9
49
49.8
50.5
51
51.4
51.7
340
—
—
—
45.5
47.3
48.6
49.5
50.2
50.7
51.1
51.5
360
—
—
—
—
46.8
48.2
49.1
49.8
50.4
50.9
51.3
380
—
—
—
—
46.3
47.7
48.7
49.5
50.1
50.6
51
400
—
—
—
—
45.7
47.3
48.4
49.2
49.8
50.4
50.8
420
—
—
—
—
45.2
46.8
48
48.9
49.6
50.1
50.6
440
—
—
—
—
—
46.3
47.6
48.5
49.3
49.8
50.3
460
—
—
—
—
—
45.9
47.2
48.2
49
49.6
50.1
480
—
—
—
—
—
45.4
46.8
47.9
48.7
49.3
49.8
500
—
—
—
—
—
—
46.4
47.5
48.4
49.1
49.6
Note:
Minimum dew point selectable is 45°F.