Emerson 2 user manual Unit Controls, Remote Control Interface, High Pressure Standard

Operation

5.4Unit Controls

5.4.1	Remote Control Interface
	Control connections to the InteleCool2 unit use customary HVAC terminal designations R, G, W & Y.
	Contact closures between the 24 VAC (R) and different control connections supply control voltage to
	the electric panel components responsible for the desired function. Operating modes are controlled by
	contact closures as follows:
	Table 2	Operating modes/contact closures
	Connection		Operating Mode
	R		24 VAC
	G		Evaporator Fan
	W		Heating
	Y		Cooling (compressorized or Economizer)
	Wall-mounted thermostats are to be low voltage, snap action or mercury type. Un-manned sites should
	use a HEAT/COOL/AUTO type subbase to provide automatic switchover during climate changes.
5.4.2	High Pressure (Standard)
	The high pressure switch is mounted in the liquid line. Electrically, it is connected in series with the
	compressor start circuit, which will shut down the compressor and condenser fan if the liquid pres-
	sure exceeds 400 PSIG (2758 kPa). This protects the InteleCool2 in the event of condenser motor fail-
	ure or condenser coil blockage.
	The pressure switch is an auto reset device. When the system pressure drops below 300 PSIG
	(2069 kPa), the switch will reset. (An optional lockout relay is available which allows the switch to be
	used as a manual reset safety.) If the call for cooling is present, the compressor start circuit will be
	energized and the compressor will start after the 3 minute anti-short cycle time.
5.4.3	Refrigeration Control Options
	Please review the following table for the recommended control options based on the site ambient and
	your need for year-round operation.
	Table 3	Recommended applications for control options
	Application			Unit	Options	Min ambient	Max ambient
		General		Standard	None	50°F (10°C)	115°F (46.1°C)
		General		Standard	Low pressure with low pressure bypass	50°F (10°C)	115°F (46.1°C)
					timer
		General		Standard	T-pack1 or T-pack2	-20°F (-28.9°C)	115°F (46.1°C)
	Telecom/365-day operation			Standard	T-pack1 or T-pack2	-20°F (-28.9°C)	115°F (46.1°C)
		General		Standard	High ambient	50°F (10°C)	125°F (51.7°C)
		General		Standard	High ambient, low pressure with low	50°F (10°C)	125°F (51.7°C)
					pressure bypass timer
	Telecom/365-day operation			Standard	High ambient with T-pack1 or T-pack2	-20°F (-28.9°C)	125°F (51.7°C)

Low Pressure Switch and Low Pressure Bypass Timer (Winter Start)

Low Pressure Switch—The low pressure switch is mounted in the compressor suction line. Electri- cally, it is connected in series with the compressor start circuit, which will shut down the compressor and condenser fan if the suction pressure drops below 35 PSIG (241 kPa). The switch will automati- cally reset once the system pressure rises above its cut-in setting (60 psig, ±5 psig [414 kPa, ±34 kPa]). This protects the InteleCool2 in the event the evaporator fan fails, the filter becomes clogged or there is a loss of refrigerant. If the call for cooling is present, the compressor will start after the 3 minute anti-short cycle time.

Low Pressure Bypass Timer—A low ambient temperature start relay is included with the low pressure option. This relay locks out (ignores) the low pressure switch on start-up until the system pressure stabilizes. This bypass relay is adjustable and should be set for 3 minutes greater than the anti-short cycle timer setting. This option can be used for applications down to 50°F (10°C). For con- trol down to -20°F (-28.9°C), use the T-pack1 and T-pack2 options, which include fan cycle control.

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