Space Temperature Reset Example Ð The occupied cooling set point is set to 73 F. The Reset Ratio is set to 5. The Reset Limit is set to 20° F. The Reset Ratio determines how many degrees F the temperature is reset. At 72 F, the supply tem- perature will be reset 5 degrees higher. At 71 F, the supply temperature will be reset 10 degrees higher. At 70 F, the sup- ply temperature will be reset 15 degrees higher. At 69 F, the supply temperature will be reset 20 degrees higher and the Reset Limit will have been reached.
SUPPLY AIR TEMPERATURE RESET Ð Supply air tem- perature reset is used to reset the supply air temperature util- ity. A 4 to 20 mA signal
POWER EXHAUST OPERATION Ð The optional power exhaust packages are factory- or
SMOKE CONTROL MODES Ð The 48EJ,EK,EW,EY units with an optional expansion board perform ®re and smoke control modes. The expansion board provides 4 modes which can be used to control smoke within the conditioned area. The modes of operation are ®re shutdown, pressurization, evacuation, and smoke purge. See Table 19.
SMOKE DETECTOR Ð A smoke detector can be used to initiate ®re shutdown. This can be accomplished by a set of normally closed pilot relay contacts which will interrupt power from the
NOTE: On standard gas models, the indoor fan will con- tinue to run 45 seconds after the call for heat has been ter- minated. If ®re shutdown is initiated the fan will stop im- mediately. No
The smoke detector may be mounted in the return air duct or the supply duct. Carrier does not make recommendations
Fig. 44 Ð Field-Supplied Smoke Detector Wiring
as to speci®c smoke detector location due to liability considerations.
INDOOR AIR QUALITY CONTROL Ð The accessory ex- pansion board and accessory IAQ sensor are required for IAQ control. The Carrier sensors operate with a 4 to 20 mA sig- nal. The 4 to 20 mA signal is connected to T11 (+) and T12
(−)on the expansion board for the IAQ sensor, and T13 (+) and T14 (−) on the expansion board for the OAQ (Outdoor Air Quality) sensor. The sensor is
Once installed, the sensor must be enabled. The sensor is con®gured with default values which may be changed through network access software. To work properly, the IAQ sensor high and low reference points for the sensor that is used must match the con®gured values. The expansion board reacts to a 4 to 20 mA signal from the IAQ sensor. The low reference (4 mA output) must be con®gured to the minimum IAQ sen- sor reading. The high reference (20 mA output) must be con- ®gured to the maximum IAQ sensor reading.
The IAQ sensor can be con®gured to either low or high priority. The priority value can be changed by the user. The default is low.
Low priority Ð When the priority is set to low, the initial control is to the IAQ set point, but the outside air damper position will change to its minimum position when the fol- lowing conditions occur:
·CV units with sensor Ð when the space temperature is greater than the occupied cooling set point plus 2° F or when the space temperature is less than the occupied heating set point minus 2° F.
·VAV units and CV units with thermostat Ð when the
Table 19 Ð Smoke Control Modes
DEVICE | PRESSURIZATION | SMOKE PURGE | EVACUATION | FIRE SHUTDOWN |
Economizer | 100% | 100% | 100% | 0% |
Indoor Fan/VFD | ON | ON | OFF | OFF |
Power Exhaust (all outputs) | OFF | ON | ON | OFF |
Heat Stages | OFF | OFF | OFF | OFF |
HIR | ON | ON | OFF | OFF |
LEGEND |
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HIR Ð Heat Interlock Relay |
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VFD Ð Variable Frequency Drive |
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43