Carrier EY024-048, 48EJ, EW, EK Ð Field-SuppliedSmoke Detector Wiring, Ð Smoke Control Modes

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 (®eld-supplied) is required. The re- set option does not require enabling.

POWER EXHAUST OPERATION Ð The optional power exhaust packages are factory- or ®eld-installed with vertical units and optionally installed in the return air ductwork for horizontal applications. The standard (offered with constant volume or variable air volume units) and the modulating power exhaust (offered on VAV units) are the two packages offered. The modulating power exhaust package is equipped with a ®eld-adjustable static pressure controller to stage up to 4 power exhaust stages which will maintain a building static pres- sure. The blue controller located in the control box below the control board can be adjusted, by removing the covers and adjusting the set point dial to the desired building pres- sure. The blue controller monitors the 4 individual sequenc- ers which activate the 4 individual power exhaust motors. The standard power exhaust package controls up to 2 stages of power exhaust to maintain building pressure. The power exhaust package can be con®gured to deliver positive or nega- tive building pressure. These power exhaust stages are staged according to a percentage of the economizer dampers position. Default values are 25% for Stage 1 and 75% for Stage 2. This package has set points that are adjustable through software (Service Tool, Building Supervisor, or ComfortWorks™).

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 24-v transformer, secondary ``B'' terminal to the control circuit breaker (CB4). See Fig. 44. The wire that con- nects these two points is white and labeled ``W78.''

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 45-second delay will occur.

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 ®eld-mounted and wired to the expansion board installed in the unit main control box. The IAQ sensor must be powered by a ®eld-supplied 24-v power supply (ungrounded). Do not use the unit 24-v power supply to power the sensor.

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 supply-air temperature is less than the supply-air tem- perature set point minus 8° F or when the supply-air temperature is greater than the supply air temperature set point plus 5° F for 4 minutes.

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
HIR Ð Heat Interlock Relay
VFD Ð Variable Frequency Drive

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