Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting

Also see for /50HC 04-28: Manual

Contents

Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting Manual pdf 93 page image

93ENTHALPY WHEELThe enthalpy wheel is the “heat exchangers” of the ERV. Itconsists of several wheel segments aligned in a cassette assem-bly. These are not “filters” but made of a desiccant material.The wheel is rotated by a motor and belt, no adjustments re-quired. When the wheel rotates it uses the building exhaust airto pre-conditions the outside air as it passes through the wheel.MODULATING FANThe modulating ERV is equipped with direct drive variablespeed plenum fans for outside air intake and exhaust air. Themotors have built in VFDs that accept a 2 to 10vdc signal fromthe EXCB. This 2 to 10vdc signal is used by the VFD to deter-mine the speed to run the motor at (0 to 100%). Some ERVmodels are equipped with multiple outside air and/or exhaustair fans. The additional motor’s signal is parallel off the firstmotor through the coupling signal plug. Motor status switchesare also paralleled for additional motors.Each motor is capable of diagnosing problems within the mo-tor to provide fan status. The fan status switches are built intoeach motor and provide a feedback to the EXCB if a problem isdetected. The feedback signal is a discrete input that is normal-ly open, when closed the EXCB will initiate the motor statusalarm.MODULATING OUTSIDE AIR DAMPERERV units include a factory-installed modulating outside airdamper. This damper is controlled in parallel with the modulat-ing intake fan(s). This damper adds static to the outside air andwill be open to the same percentage as the outside air fan(s) isrunning. The modulating outside air damper will also close inthe unoccupied mode to prevent unwanted air from being intro-duced to the rooftop unit.EnergyX Options and AccessoriesThe modulating ERV has several optional factory-installed op-tions and field-installed accessories: Frost Protection, Econo-mizer, Wheel Motor Status, Filter Maintenance, horizontaladaptor curb, building pressure sensor, and Outside Air Tem-pering Kit. Refer to Table 35 for where these options wire intothe EXCB.ECONOMIZER DAMPER (FACTORY-INSTALLED ONLY)The economizer damper is a factory-installed option that pro-vides a wheel bypass damper. This damper is controlled by thebase unit rooftop as an economizer for the purpose of free cool-ing. The damper is installed adjacent to the ERV wheel to al-low outside air to flow through it when opened instead of thewheel. The ERV’s outside air fan(s) will run as this damper isopened to allow proper airflow.FROST PROTECTION (FACTORY-INSTALLED ONLY)Frost protection is a factory-installed pressure sensor devicewhich senses a differential pressure across the wheel. This oc-curs if frost builds up on the wheel. The sensor closes its con-tact when the pressure differential is greater than the setpoint.When the EXCB reads the contact closer it will activate defrostmode. The setpoint is a dial on the sensor, is adjustable from0.2 to 2.0 in.wg, and is factory preset to 2.0 in.wg. Changingthis setting may cause false signal causing defrost mode whennot needed.WHEEL MOTOR STATUS (FIELD-INSTALLED ONLY)The wheel motor status accessory can be installed in the fieldand consists of a wheel motion proxy sensor and a relay. Thewheel motion sensor is aimed at the wheel to detect rotation. Ifthe wheel does not rotate at the appropriate speed the sensorwill open causing the rotation monitor relay to close a contactto initiate the wheel status alarm. The motion sensor is factoryset at the highest speed (clockwise until stop) and should not bechanged. Refer to the troubleshooting section for details on thealarms.FILTER MAINTENANCE (FIELD-INSTALLED ONLY)Filter maintenance consists of two field-installed pressure sen-sor devices which sense differential pressure across the ERVfilters. This occurs if dirt builds up on the filters. There is aseparate pressure sensor for each filter (outside air and exhaustair). The sensor closes its contact when the pressure differentialis greater than the setpoint. The sensors are wired in parallel, sowhen the EXCB reads a contact closer from either sensor itwill activate the filter alarm. The setpoint is a dial on the sen-sor, is adjustable from 0.2 to 2.0 in.wg, and is factory preset to2.0 in.wg. Changing this setting may cause false signal causingfalse dirty filter alarms.HORIZONTAL TRANSITION CURB (FIELD-INSTALLEDONLY)EnergyX units must receive vertical return. If the applicationrequires horizontal return then a horizontal transition curb mustbe used. Units cannot be field converted to horizontal supply.To accomplish horizontal supply a horizontal transition curbmust be used.SERVICE AND MAINTENANCEEnergyX System CleaningWHEEL AND SEGMENT CLEANINGWheel cleaning periodicity is application dependent. Field ex-perience shows that offices, schools and other “clean” environ-ments will often go 10 years before any build up of dust anddirt is noticed. Other applications such as restaurants, casinosand factory environments may experience fairly rapid build-upof contaminants and may require multiple cleanings per year tomaintain airflow and recovery efficiencies.All air-to-air energy recovery devices will become dirty overtime, even with well-maintained filtration. Proper filtration us-age and changes will improve the life of the wheel transfer seg-ments. Once the wheel is exposed to oils, tars or greases in ei-ther the supply or exhaust air streams, these pollutants depositon the rotary surface which then become “sticky” and begin toattract and hold the dust particles that previously passed thruthe wheel. Over time this particle build up can lead to blockedairflow passages, loss of recovery, excessive pressure dropthrough the wheel and loss of energy savings.1. Follow steps for wheel and segment removal to removethe affected energy transfer matrix segments. (For one-piece wheels 25 inches in diameter and smaller, removethe entire wheel from the cassette.)2. Gently brush the wheel face to remove loose accumulateddirt.3. Wash the segments with a non-acid based (evaporator) coilcleaner or alkaline detergent solution. Non-acid based coilcleaner such as KMP Acti-Clean AK-1 concentrate in a5% solution has been demonstrated to provide excellentresults. DO NOT use acid based cleaners, aromatic sol-vents, temperatures in excess of 170°F or steam. Damageto the wheel will result.4. Soak the wheel and/or segments in the cleaning solutionuntil all grease and tar deposits are loosened. An overnightsoak may be required to adequately loosen heavy depositsof tar and oil based contaminants.5. Internal heat exchange surfaces may be examined by separat-ing the polymer strips by hand. (Note: some staining of thedesiccant may remain and is not harmful to performance.)6. After soaking, rinse the dirty solution from the wheel seg-ments until the water runs clear.