Carel MC, Руководство пользователя

Страница: 20 / 48

20
ENG
MC DUCT +03U400025 - rel. 4 - 20201201
Recommended Sequence of Operation for DDC Controls
1. There should be a control air humidity sensor located
either in the return air duct or in the room being humidified. There
should be a supply air humidity sensor located downstream of
the humidifier system, mist eliminators, or cooling coil (after the
fan is acceptable) to sense humidity from the system.
2. The control software should allow a set point for the
control air humidity, which will be set to the desired level of
relative humidity in the controlled space. The control software
should also allow a set point for the supply air humidity, which
will be set to a high limit setting of about 90%RH with a wide
band of about 10%.
3. On a fall in control air relative humidity and supply air
relative humidity below their controller set points, the control
logic should bring the system atomizing heads into operation
and modulate them from 0-100% of capacity according to the
lowest demand, either from the control air sensor or from the
supply air sensor.
4. On approaching either the control air humidity set
point or the supply air humidity set point, the control logic
should cause the system atomizing heads to decrease their
output proportionally from 100-0% again according to the
lowest demand, either from the control air sensor or from the
supply air sensor. In effect this is a low signal selector routine.
5. On reaching either set point, the atomizing heads
should be turned off by giving the MC system the lowest control
signal.
6. In addition to the humidity sensors, there should also
be temperature sensors located downstream of the preheat coil,
and downstream of the humidifier mist eliminators. The software
should permit a preheat temperature set point, and a cooling
coil set point.
7. A preheat set point should be set and will modulate
the preheat coil according to the preheat temperature sensor to
maintain the preheat set point. A cooling coil set point should
be set to maintain the supply air temperature by modulating the
cooling coil.
8. During operation of the atomizing humidifiers, the
supply air temperature will drop due to evaporative cooling.
As the supply air temperature drops, the cooling coil should be
modulated toward closed. When the cooling coil is closed and
the supply air temperature continues to drop below the supply
air temperature set point, the preheat coil should be modulated
toward open to maintain the supply air temperature set point
and compensate for the evaporative cooling of the humidifier.
This action supercedes the preheat control based on the preheat
sensor.
9. If reheat is used, then the supply air temperature set
point should reset to the point where it controls the coldest zone
without needing its reheat. It is pointless to overcool the supply
air and then force massive amounts of reheat. Do not activate
reheat unless preheat is at 100%.