Carel pCO1 series Application Program

Standard air-conditioning units
Carel Cod. +030221421 – Rel. 1.2 – April, 11, 2003
35
17.0 MODULATING VALVES
17.1 THREE-POSITION VALVES
Valves with three electrical contacts (besides supply): shared, opening and closing. The two relays of pCO1-pCO2 boards (opening – closing
relays) must be connected to these contacts.
Based on the relays enabling time, the valves opening range varies from 0% to 100% taking an opening/closing time defined as “running time”
(time taken to open or close completely; it is a valves rating). The relays must never be enabled simultaneously, thus the valve open, close or
keep still.
The valves opening range is calculated based on the proportion between temperature differential and running time. When ambient temperature
corresponds to the set point, the valves keep closed; the more temperature is offset compared to the set point the more the valves are opened,
until they open completely when temperature is equal or higher than set point + / - differential.
During operation, the valves are frequently subject to partial opening and closing; the program can recognise the valves opening range at any
time by adding up and subtracting all partial times executed from board start-up.
17.1.1 REALIGNMENT
As there is no feedback to define precisely the valves opening range, the program cannot easily manage the three-position valves. A slight
difference between the time calculated by the program and the relays enabling time or a mechanical friction preventing the valves from moving
freely may originate discrepancy between the valves actual opening range and the range calculated by the program. To obviate this problem, the
following precautions are provided for:
• whenever temperature control requires a valve complete opening or closing, the program increases the opening or closing relay
enabling time by 25% to ensure complete opening/closing.
• whenever the board is started, the valves are completely closed during the running time; only after time has elapsed, the valves start
modulating their opening range based on the control request.
17.2 0-10Volt VALVES
These valves use a 0-10Volt modulating signal coming from the pCO1-pCO2 to modify their opening range from 0% to 100%.
The 0-10Volt electric signal is directly proportional to the temperature proportional band. Unlike the three-position valves, these valves do not
require adjustment since their opening range is directly proportional to the analogue output value.
18.0 OUTLET FAN
With unit enabled, the outlet fan keeps switched on. It can be managed with On–Off or modulating output. The fan is provided with a thermal
alarm and an air flow controller alarm, which lock the unit setting it to OFF state; thermal alarm requires manual rearm, whereas air flow
controller alarm is rearmed automatically. Description of modulating management:
During dehumidification, speed is automatically decreased to 5.0V (50%) default value, modifiable if required. The minimum and maximum
speeds default values correspond to 5.0V and 10.0V, modifiable if required.
19.0 MANUAL DEVICE MANAGEMENT
The devices connected to outputs can be enabled manually without using timing, compressors rotation and independently from control and
probes values. In manual mode, the only available support is the management of the alarms safeguarding devices safety and soundness. The
analogue outputs enabling allows forcing a value between 0V and 10V.
The manual procedure can be enabled by button only if the unit is in OFF mode and is automatically stopped within 30 minutes after enabling
the last device or disabling all devices manually.
During devices manual management, the air-conditioning unit cannot be turned on. This operative mode is identified by message “MANUAL
PROCEDURE” shown on the last display row, on the Menu main screen. The enabling parameters are displayed in the Maintenance screens
branch under Password.
mb
COOLING
HEATING
0%
100%
100%
0%
Cold proportional band
Warm proportional band
Temperature set
19.5 22.5 23.0 23.5 26.5
100%
3°C 0.5°C 0.5°C 3°C
Min. speed (5.0V)
Max. speed (10.0V)
Fan speed
100%
50%

Carel pCO1 series Specifications

General

Brand	Carel
Model	pCO1 series
Category	Controller
Language	English