Carrier 50HQP072-120 Operating Limits, Start Up System, Unit Start-Up in Cooling Mode

MECHANICAL NIGHT SET BACK — When NSB input is connected to ground C, all thermostat inputs are ignored. A thermostat set back heating call will then be connected to the OVR input. If OVR input becomes active, then the Deluxe D control will enter Night Low Limit (NLL) staged heating mode. The NLL staged heating mode will then provide heating during the NSB period.

WATER VALVE (SLOW OPENING) — If relay is config- ured for Water Valve (slow opening), the relay will start 60 sec- onds prior to starting compressor relay.

OUTSIDE AIR DAMPER (OAD) — If relay is configured for OAD, the relay will normally be ON any time the Fan Enable relay is energized. The relay will not start for 30 min- utes following a return to normal mode from NSB, when NSB is no longer connected to ground C. After 30 minutes, the relay will start if the Fan Enable is set to ON.

START-UP

CAUTION

To avoid equipment damage, DO NOT leave system filled in a building without heat during the winter unless anti- freeze is added to system water. Condenser coils never fully drain by themselves and will freeze unless winterized with antifreeze.

Use the procedure outlined below to initiate proper unit start-up.

NOTE: This equipment is designed for indoor installation only.

WARNING

When the disconnect switch is closed, high voltage is pres- ent in some areas of the electrical panel. Exercise caution when working with the energized equipment.

Operating Limits

ENVIRONMENT — This equipment is designed for indoor installation ONLY. Extreme variations in temperature, humidi- ty and corrosive water or air will adversely affect the unit per- formance, reliability and service life.

POWER SUPPLY — A voltage variation of ± 10% of name- plate utilization voltage is acceptable.

UNIT STARTING CONDITIONS — All units can start and operate in an ambient of 7.2 C with entering-air at 10.0/7.2 C (db/wb), entering water at –1.1 C and with both air and water at the flow rates used. All other conditions are the same as shown in Table 10.

NOTE: These operating conditions are not normal or continu- ous operating conditions. It is assumed that such a start-up is for the purpose of bringing the building space up to occupancy temperature.

Air Coil Cleaning — To obtain maximum performance, the air coil should be cleaned before start-up. A 10% solution of dishwasher detergent and water is recommended for both sides of the coil. A thorough water rinse should follow. Ultra- violet based anti-bacterial systems may damage e-coated air coils.

Start Up System

1.Restore power to system.

2.Turn thermostat fan position to ON. Blower should start.

3.Balance airflow at registers.

4.Adjust all valves to the full open position and turn on the line power to all heat pump units.

5.Operate unit in the cooling cycle. Room temperature should be approximately 7.2 to 43.3 C dry bulb. Loop

water temperature entering the heat pumps should be between 10.0 and 43.3 C.

NOTE: Three factors determine the operating limits of a

unit: (1) entering-air temperature, (2) water temperature and

(3)ambient temperature. Whenever any of these factors are at a minimum or maximum level, the other two factors must be at a normal level to ensure proper unit operation. See Table 10. Extreme variations in temperature and humidity and/ or corrosive water or air will adversely affect unit perfor- mance, reliability, and service life.

Table 10 — Operating Limits

AIR LIMITS	COOLING (C)	HEATING (C)
Minimum Ambient Air db	7	4
Rated Ambient Air db	27	20
Maximum Ambient Air db	43	29
Minimum Entering Air db/wb	16/10	10
Rated Entering Air db/wb	27/19	20
Maximum Entering Air db/wb	35/24	27
WATER LIMITS
Minimum Entering Water	–1	–6.7
Normal Entering Water	10 to 43	–1 to 21
Maximum Entering Water	49	32
Normal Water Flow	1.6 to 3.2 L/m per kW

LEGEND

db — Dry Bulb wb — Wet Bulb

Scroll Compressor Rotation — It is important to be certain compressor is rotating in the proper direction. To determine whether or not compressor is rotating in the proper direction:

1.Connect service gages to suction and discharge pressure fittings.

2.Energize the compressor.

3.The suction pressure should drop and the discharge pressure should rise, as is normal on any start-up.

If the suction pressure does not drop and the discharge pressure does not rise to normal levels:

1.Turn off power to the unit. Install disconnect tag.

2.Reverse any two of the unit power leads.

3.Reapply power to the unit and verify pressures are correct.

The suction and discharge pressure levels should now move to their normal start-up levels.

When the compressor is rotating in the wrong direction, the unit makes an elevated level of noise and does not provide cooling.

After a few minutes of reverse operation, the scroll com- pressor internal overload protection will open, thus activating the unit lockout. This requires a manual reset. To reset, turn the thermostat on and then off.

NOTE: There is a 5-minute time delay before the compressor will start.

Unit Start-Up in Cooling Mode

1.Adjust the unit thermostat to the warmest position. Slowly reduce the thermostat position until the compres- sor activates.

2.Check for cool air delivery at unit grille a few minutes after the unit has begun to operate.

3.Verify that the compressor is on and that the water flow rate is correct by measuring pressure drop through the heat exchanger using pressure/temperature plugs. Check the elevation and cleanliness of the condensate lines; any dripping could be a sign of a blocked line. Be sure the condensate trap includes a water seal.

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