Munters HCUw, Эксплуатация и техническое обслуживание

Страница: 29 / 122

27
The HoneyCombe® wheel has been carefully designed. The honeycomb material is nonmetallic and
does not react to bacteria. The desiccant material is made of silica gel, and depends on the “adsorption”
principle. As moisture collects, each particle of the gel can bond with a large number of water molecules.
The process can be reversed by adding heat. As the desiccant is heated, it releases water to the air.
Several other parts must be added to make up a working machine. The HCU has two seals, mounted on
the wheel plates on each side of the HoneyCombe® wheel. These seals separate the two streams of air
– the damp air from the evaporator and the heated air from the condenser. Notice that the two air
streams move through the HCU in opposite directions (“counterflow”). The HoneyCombe® wheel is
turned by a drive motor and a belt. The belt tension adjusts automatically.
The supply air is pulled through the wheel by a fan. A filter is included to keep dirt from the evaporator air
from plugging the wheel. On the reactivation side of the system, the ambient air is pulled through the
wheel by a second fan. Just upstream of the wheel, this ambient air passes through the condenser coil.
The heat provides the energy needed to “reactivate” the desiccant.
The condensing portion of the unit has two separate circuits on the HCU 6000 and 8000, each with its
own compressor set. The heated air from the first circuit, Circuit A, is used to dry out the desiccant wheel.
The other circuit, Circuit B, is used to provide additional cooling and/or dehumidification when necessary.
Air is drawn through the circuit A condenser coil with the reactivation and condenser fans. These fan are
each controlled by a variable frequency drive (VFD) working in tandem to maintain a constant head
pressure and therefore constant condensing coil leaving air temperature. Not all of the air from the
condensing coil is needed for reactivation of the wheel, so a portion of the air is exhausted through the
condenser fan.
See
Appendix D: Sequence of Operation
for a detailed description of the operation of the HCU.
6.2 Troubleshooting
The HCU has a sophisticated control system that uses a microprocessor to control the internal functions
of the unit along with variable frequency drives (VFDs) on some or all fans. When the microprocessor or a
VFD detects a problem, it will go into an alarm mode. The first step in troubleshooting a unit is to look for
an alarm code on the microprocessor and each VFD.
If a VFD goes into a fault mode, it sends a signal to the microprocessor by closing the fault output
contacts on the VFD that go to digital input contacts on the microprocessor. The microprocessor will shut
down the unit for 2 minutes to allow all fans to come to a complete stop. The microprocessor will then
send a reset signal to all VFDs and start the unit. If a VFD trips again, the microprocessor will wait 30
minutes, reset the VFDs, and restart the unit. The microprocessor will retry 4 times (each try after a 30
minute delay) in case of repeated VFD trips. After the 4th try, the unit will lock out.
Do not shut power off until the microprocessor and VFDs are checked for alarms and the alarm codes
noted. If an alarm is present on the microprocessor, see “Using the Microprocessor” below. If an alarm is
present on a VFD, go to Appendix C: Variable Frequency Drives to the applicable VFD model and check
the “Maintenance Operations” section for the cause and solutions.
The next step is to refer to Appendix A: Troubleshooting.
Using the Microprocessor:
The HCU microprocessor is equipped with a keypad display. Whenever the
microprocessor detects a fault, the alarm button will illuminate red. See Section 4.4 for detailed
operating instructions and viewing faults via the microprocessor display.
Variable Frequency Drives (VFD):
VFDs are used to control fan motor speeds on reactivation and
condenser fans. They replace the motor contactors and overload relays. They provide a soft start for
the motor. If the VFD detects a problem such as high amperage, low voltage, etc, it shuts the motor
down to protect it and indicates a fault condition. The fault indications are shown in Appendix C.
Appendix C contains the trouble shooting portion of the VFD O&M Manuals that list all possible
faults and probable solutions. Note that there are two basic VFD drive types: 3G3JV and 3G3MV.