Standard air-conditioning units
Carel Cod. +030221421 – Rel. 1.2 – April, 11, 2003
42
22.2.3 FIXED-HOUR ROTATION
A system consisting of both running and stand-by
units is subject to unbalance in the working hours, causing running units to age faster than
stand-by ones. To obviate this problem, pLAN network can provide for units rotation, favouring balancing in the working hours. In practice,
rotation sets a running unit to stand-by mode and starts a stand-by unit.
The fixed-hour rotation is based on a parameter establishing the rotations time interval. The programmable minimum time is 0h; in this case,
automatic rotation enables every 5 minutes as a test. The maximum time is 240h (10 days). Time is counted from start-up of the unit with pLAN
address 1 that manages rotation. Rotation can be executed following the pLAN addresses logic or the units working hours.
Selecting the addresses logic, the unit with highest address (among the running ones) switches from on to stand-by mode, whereas the unit with
lowest address switches from stand-by mode to on.
Selecting the working hours logic, the unit with highest working hours (among the running ones) switches from on to stand-by mode, whereas
the unit with lowest working hours switches from stand-by mode to on.
22.2.4 FIXED-DAY ROTATION
The clock card (optional on pCO1, integrated on pCO2) allows setting the hour and the days interval (max. 7) for units rotation. Logic is the
same as the fixed-hour rotation, but in this case the rotation interval can be programmed for a determined day and hour.
22.2.5 ROTATION BASED ON WORKING HOURS
This type of rotation involves the units with highest and lowest working hours, switching the former to stand-by mode and the latter to On
mode. The reference working hours for this type of rotation are the same as the outlet fan ones; due to practical reasons, they can be modified in
screens E6 and E7 of branch Maintenance.
23.0 MASTER CONTROL
The units connected with pLAN network and in Present/… mode follow the working logic of the unit with pLAN address 1, functioning as a
“driver” unit so that the system can work with the same logic. This precaution prevents units from having opposite logic, something that may
occur in wide environments with different temperatures or humidity areas. In such environments, each unit could follow the indications of the
relevant probe, causing the uncontrolled start of humidification, dehumidification, heating or cooling. This would nullify their effect and cause
energy waste.
WARNING: the “driver” unit temperature and humidity probes must be located in an “intermediate” position inside the controlled
environment.
The “driver” unit sends the information concerning the logic to be adopted to the pLAN network. Therefore, the network units found devices
enabling on both reading of the relevant probes and “driver” unit order, so that devices can turn on in case the two factors coincide.
The “driver” unit modifies the working logic in case the measured temperature or humidity exceed the set point, even by few decimal points.
In case of black-out or “driver” unit disconnection from pLAN network, the network units start functioning independently again based on the
relevant probes only.
24.0 GLOSSARY OF TERMS
• Step: term identifying a (temperature or humidity) proportional band area within which the device is turned on; it also defines the
device start and stop values. Refer to diagram 7.2.
• Set point: term identifying a temperature (or humidity) value to be met; the system enables the warm or cooling devices until the
temperature or humidity set points are reached.
• Default: term identifying some values, i.e. temperature set point and proportional band, automatically used by the system in case the
user does not intervene; the entire list is given in table 24.1.
• Proportional band: term identifying a temperature zone consisting of few degrees from the set point, within which the system
manages the control devices. Refer to control diagrams from 7.1 to 7.11.
• Dead zone – neutral zone: terms identifying a small temperature zone between set point and proportional band, within which the
devices do not turn on.
• Branch – loop: series of screens relating to the same subject, thus easily accessed by pushing the arrow buttons only. The branch can
be accessed by pushing any of the terminal buttons; after pushing, the first loop screen is displayed.
• Screen: term identifying the displayed window; the program consists of the screens listed in paragraph 27.0.
• Ramp: term identifying the modulating valve opening/closing time from 0% to 100%.
• Three-position valve – modulating valve: the three-position valve, commonly used, is enabled by two relays providing for time
opening and closing. The modulating valve is controlled by a 0-10V voltage signal and ensures higher precision.
• Master: term identifying the pCO2 board intended for controlling the pLAN local network and, consequently, all the connected pCO2
boards; generally, it corresponds to the board with address 1, unless it is shut down or disconnected.
• Sleep mode: term identifying the Off state of a pCO2 unit when required by the Master unit, in automatic rotation mode.
• Built-in: term identifying the display located on the pCO2 board back.
• Range: term identifying the range of a parameter available values; refer to table 24.1.
• Outlet: term identifying air introduced by the unit into an environment.
• Intake: term identifying the controlled environment air, sucked by the air-conditioning unit.
• Free cooling: term identifying the introduction of external air into an environment by opening a damper, to refresh air saving energy
• Manual: term identifying the start and stop of all devices connected with the pCO2 board outputs by appropriate screens and with unit off.
• Buffer (memory): term identifying the pCO2 memory in which the default values (selected by Carel) of all parameters are stored.
Memory is permanent even if voltage is cut off.
• Buzzer: term identifying a warning buzzer assembled on the external terminals. In case of alarm, its sound is prolonged; in case limits
are exceeded when setting the parameters, its sound is shorter. The built-in terminals are not equipped with buzzers.
• Upload: term identifying the operation for uploading the application program to the Flash memory of pCO1 – pCO2 board by a
computer or programming key.
Carel SpA reserves the right to make modifications or changes to its products without prior notice
To Next Page
Loading...
Need help?
General
