Carrier 48MA/50ME016-040 Installation, Start-up And Service Instructions Manual

Contents

Carrier 48MA/50ME016-040 Installation, Start-up And Service Instructions Manual Manual pdf 39 page image

HEATING (48MA) — On call for heating from a zone, theforced draft blower will start and the pilot will light. Thezone burner will ignite after the pilot has been proven. (Ap-proximately 60 seconds.)NOTE: A time-delay relay will shut unit down in 180 sec-onds if the unit main gas valve is not open.HEATING (50ME WITH ELECTRIC HEAT) — On a callfor heating from a zone, the first-stage heating relay, con-tactor, and heating element are energized. Upon additionalcalls for heating from that zone, stage 2 is energized in asimilar manner. However, second element on 2-element heaterassemblies and second and third heating elements on 3-elementheater assemblies are energized as described in Outdoor AirThermostat Adjustment section on page 36.Heating Lockout (50ME with Electric Heat) — If any zonemodule is operating on mechanical cooling (Compressor[s]is operating), one heating element in each zone module islocked out and zone module cannot be energized. Operationof lockout circuit is independent of outdoor-air thermostatoperation.HEATING (50ME WITH GLYCOL HEATING COILS) —On a call for heating from a zone, the heating relay and heat-ing coil solenoid valve for that zone are energized. If 2 ormore unit zone modules are joined to serve a common zone,stage 2 of heating thermostat operates remaining heatingrelays and solenoid valves depending on connectionarrangement.OUTDOOR-AIR DAMPER — This control regulates theamount of outdoor air that passes through the outdoor airevaporator coil and enters the return air-stream (Fig. 34 and35). A knob in the zone control and thermostat panel acti-vates the damper control motor (damper operator). Dampermay be fully closed, fully open, or set at any intermediateposition by setting the knob as desired. In the fully open po-sition, the damper will permit 25% outdoor air and 75% re-turn air into the unit.SERVICECabinet Panels and GrillesSIDE PANELS — To remove a panel, remove lower screwon T-fastener. Loosen T-fastener pivot screw. Swing asideT-fastener. Pull bottom of panel out and down.TOP PANELS — Remove end caps from each end of raincovers. Remove panel screws and lift off panels as required.Save end caps and screws for reinstallation.HEATER ACCESS PANELS — See Side Panels section above.Cleaning — Inspect unit interior at the beginning of eachheating and cooling season and during each season as op-erating conditions require. Remove unit side panels and toppanels to expose unit interior as required.EVAPORATOR COILS (ZONE COOLING COILS) ANDGLYCOL HEATING COILS — Clean with a stiff brush,vacuum cleaner, or compressed air.CONDENSER AND OUTDOOR-AIR COOLING COILS— Clean with a stiff brush or vacuum cleaner. If cleaningwith compressed air or low-pressure water or steam, guardagainst damaging compressor, wiring, and nearby controls.CONDENSATE DRAINS — Check and clean annually atstart of cooling season.INDOOR-AIR FILTERS — Clean or replace filters at startof each heating and cooling season and as often as necessaryduring each season, depending on operating conditions. Re-fer to Table 1 for type and size of filters used. Filter sectionis shown in Fig. 34 and 35. Indoor-air filter tracks will ac-cept 2 layers of one-in. thick filters.OUTDOOR-AIR INLET SCREENS — Clean with steam orhot water and mild detergent.GAS HEATING SECTION — Inspect burners and heat ex-changers before each heating season. Remove exhaust grillesto inspect heat exchangers. Clean with wire brush if there isany accumulation of debris. The main burners should alsobe cleaned if there is any accumulation of debris. Fire eachzone to be assured of proper operation. Correct pilot heightis 1 to 11⁄ 2 inches.COMBUSTION AIR FAN — Inspect blower wheel for dirt,and remove and clean if necessary.Airflow SwitchesINDOOR AIRFLOW SWITCH (AFS1) — This switch islocated in evaporator fan inlet venturi. This switch will shutdown unit if airflow through zone modules is insufficient.COMBUSTION AIRFLOW SWITCH (AFS2) — This switch(48MA only) is located in combustion air plenum. This switchwill shut down unit heating mode if combustion air is in-sufficient. See Forced-Draft Blower (48MA) section onpage 42 for details on combustion air shutter adjustment.Service Switch — A control circuit service switch islocated in the power and condensing control box (Fig. 34and 35). Shut down unit (compressors, fans, and control cir-cuits) at this switch.Do not use compressor circuit breakers to start and stopcompressors except in emergency.Time GuardT Control Circuit — Each compressorcircuit has a 5-minute delay before restarting compressor af-ter shutdown for any reason. On starting, Time Guard devicetimer causes a delay of 15 seconds after thermostat closesbefore compressor starts. On compressor shutdown, timer re-cycles for 4 minutes, 45 seconds. During this time, compres-sor cannot restart.On 2-compressor units, no. 2 compressor will not start forat least 2 1⁄ 2 minutes after no. 1 compressor starts. SeeCapacity Control Pressure Switches section below.Capacity Control Pressure Switches (CCP)(2-Compressor Units Only) — These switches areconnected to the suction side of the system on compressorno. 2. Approximately 21⁄2 minutes after compressor no. 2 starts,the timer makes the circuit to CCP1 and CCP2 to operatecompressor no. 2 as follows:1. CCP1 is open (opens at 63 psig; closes at 83 psig). Thisprevents cycling of compressor no. 2 at start-up.2. CCP2 is closed (opens at 54 psig; closes at 78 psig).3. Holding relay no. 2 (HR2) is deenergized.When the suction pressure reaches 83 psig, CCP1 closesto energize HR2 and compressor no. 2. Compressor no. 2will then be operated by CCP2.Compressor Oil — Compressors have their own oil sup-ply. Compressor crankcases on 2-compressor units are in-terconnected. Loss of oil due to a leak in the system shouldbe the only reason for adding oil after unit has been in op-eration. A sight glass is provided in the crankcase intercon-nection line or on the compressor crankcase. Remove endpanels to gain access to compressors. Sight glass on 06Dcompressor should be about 1 ⁄3 to 2 ⁄3 full of oil. Sight glasson 06E compressor should be about 1⁄8 to 1⁄2 full of oil.Compressor data is shown in Table 1 and on dataplate at-tached to compressor body. Refer to 06D or 06E Compres-sor Service Manual for additional compressor serviceinformation.39