Carrier 39LA Installation, Start-up And Service Instructions Manual

Also see for 39L Series: Installation, Operation, and Start-Up Instructions

Contents

Carrier 39LA Installation, Start-up And Service Instructions Manual Manual pdf 36 page image

36STEAM INNER DISTRIBUTING TUBE COILS — Rotatein horizontal plane and reinstall. See Fig. 42.PIPING — Direct expansion, chilled water, and hot watercoils should always be piped for counterflow. (Fluid shouldenter the coil at the leaving-air side.) Steam coils must have thecondensate connection at bottom of coil.To determine intervals for cleaning coils in contaminated airoperations, pressure taps should be installed across the coilsand checked periodically. Abnormal air pressure drop will indi-cate a need for cleaning the coils.Annual maintenance should include:1. Clean the line strainers.2. Blow down the dirt leg.3. Clean and check operation of steam traps.4. Check operation of control valves.5. Check the operation of check valves to prevent conden-sate flowback.6. Check operation of thermostatic air vents, if used. A floatand thermostatic trap will contain a thermostatic air vent.When the bellows is ruptured, it will fail closed.7. Check operation of vacuum breakers.8. Check operation of the thermal protection devices usedfor freeze-up protection.9. Steam or condensate should not be allowed to remain inthe coil during the off season.This will prevent the forma-tion and build up of acids.There are additional precautions and control strategies, asfound in various catalogues and in the ASHRAE FundamentalsHandbook and in the Carrier System Design Guide — PipingSection, when the entering-air temperature to the coil falls be-low 35 F. These conditions occur when IDT coils are used forpre-heat and/or face and bypass applications.Freeze up protection:1. Use a strainer in the supply line and the dirt leg ahead ofthe trap.2. Use a vacuum breaker in the return.3. Do not use overhead returns from the coil. A floodbackcan occur.4. An immersion thermostat to control outdoor-air dampersand the fan motor is recommended. This control is acti-vated when the steam supply fails or the condensatetemperature drops below a predetermined temperature,usually 120 F.5. On low pressure and vacuum systems, the immersionthermostat may be replaced by a condensate drain with athermal element. This element opens and drains the coilwhen the condensate temperature drops below 165 F.Note the thermal condensate drain is limited to 5 psigpressure. At greater coil pressures they will not open.In spite of the precautions listed above, a coil may stillfreeze up. An oversize capacity coil, at partial load, with amodulating steam control valve will occasionally freeze.Freezing occurs in the 20 F to 35 F range of entering-airtemperatures. A better installation would be an undersize coil,with an on/off control valve with thermostatic control in theoutside air, set at 35 F air temperature, installed downstream ofthe first coil; or setting the minimum steam pressure at 5 psig.FiltersFILTER SECTIONS — See Table 12 for filter data. Filtersare field supplied.On the size 03 angle filter, a spacer is required on each sideof the filters.Flat filter section can use 2-in. or 4-in. thick filters. (Size 03accepts 2-in. filters only.) The flat filter section as shipped ac-cepts 2-in. filters. Remove angle spacer in each filter track toprovide the 4-in. space required to accommodate 4-in. filters.On all filter sections except size 03, filters are pushed intothe track until they touch the opposite side of the unit. Any re-maining space is taken up by the adjustable 2-piece sheet metalspacer. See Fig. 43 for filter arrangements.Fan Shaft Bearing Removal1. Lock open and tag electrical disconnect.2. Enter through fan section access door or remove panels asrequired.3. Place plywood or other rigid covering on floor to protectinsulation from damage.4. Block wheel so that it will not pinwheel due to naturaldraft through the unit.5. Loosen motor base to frame bolts. Adjust motor to re-lease belt tension so removal of belts is done withoutstretching. Do not stretch belts over sheaves. Damage tobelt can result.6. Remove bolts on bushing of fan shaft sheave, insert boltsin jacking hole provided on bushing and slowly jackbushing from sheave. Then remove bushing on sheave.7. Loosen bearing setscrews and locking collar.8. Remove bearing holddown bolts.9. Remove bearing while observing the followingprecautions:a. Make certain fan shaft surface is not rough orscored. If so, clean up surface with fine emerycloth.b. Add a few drops of oil after cleanup of shaft end.Chilled and hot water coils must not be rotated horizon-tally. If coils are rotated horizontally, severe water blow-offwill result.It should not be necessary to drive a new bearing ontoshaft. If light tapping is needed, do not tap against outerrace.DX AND ALLWATER COILSSTEAM COILSONLYFig. 42 — Coil Rotation