Control
Basic Operating Principles
Standard Control Options
Two Speed
Variable Speed
Control of Multiple Units
External Inputs: Timer, Thermostat and
Humidistats
Bleed Off
Detailed Description of Control System
EcoCooling evaporative coolers
are provided with their own external control panels. They are
designed, however, to be incorporated into other control systems
such as Building Management Systems and Ventilation systems. All
inputs are driven by a 24V source taken from the controller and
switched to the relevant input.
Basic Operating Principles
The purpose of the control system
in EcoCooling evaporative coolers is to control the following
functions which are accessible by the operator:
- On/Off
- Turns the cooler on - starts
the fan and operates in cool or vent as selected
- Turns the cooler off stops
all functions and cooler drains automatically
- Fan Speed
- Variable speed
- 5 point control electronic
control
- Two speed
- Controls two relays to
provide 240Vac to a double winding fan motor or to a two
motor fan system.
- Single Speed
- Uses a single relay to
operate a 240Vac fan motor
- Cool or Vent mode
- Vent mode
- Water circuit is disabled
- Sump drains automatically
- Cool mode
- Water circuit is enable
- Fill cycle enabled
- Bleed control enabled
- Pre-cool cycle enabled
(Optional)
Standard
Control Options
Two Speed
|
 |
This is the simplest of all controls. The Off/On completely
stops the machine in a safe mode, i.e. fully drained and ready
to start.
Switching to Cool enables the
water circulation and hence cooling. In vent mode the unit
simply acts as a fan.
The alarm light is common to
all systems and performs both as an alarm and as a
communicator of very simple faults;
Single flash Slow fill,
probable water switched off
Double flash Slow drain,
probable drainage blockage
Triple flash External alarm
Continuous Other fault, refer
to display on main controller |
This system is designed to
operate either double wound fan motors or a double fan system such
as the contra-rotating fan where each motor is independently
controlled.
A two speed unit is controlled
using only three switches. A 12V DC source is taken from the
controller which then provides the three control signals back to
the controller. The default position is OFF/LOW SPEED/VENT.
Variable Speed
This system is designed to
operate 5 increments of speed control. This is achieved by the use
of a double wound fan motor in conjunction with voltage
regulation.
Control of
Multiple Units
Simple Controls allow an
unlimited number of coolers to be controlled either as a group or
individually
External Inputs
The standard cooler controls
allow for an internal thermostat and an alarm function to be used.
An optional control panel can accommodate all of the following:
- External alarm shut-down
- Shuts down the cooler
completely
- Use of an internal humidistat
- Enables and disables the
water circuit according to the relative humidity within the
building
- Use of an external humidistat
- Enables and disables the
water circuit according to the relative humidity outside of
the building
- Use of an thermostat
- Enables and disables the
water circuit together with adjusting the fan speed according
to the temperature within the building
- Use of a timer
- Switches the cooler on and
off according to an external timer.
Note that the response time when
using a humidistat and thermostat can be up to 30 minutes when
switching the water circulation off. This is because the pads have
to dry out.
Control of Water Level
Water is at the heart of any
evaporative cooler. Its control is vital in maintaining an
efficient and hygienic cooler. The EcoCooling range of coolers has
the most sophisticated process controls available based on very
simple engineering. Central to this control are four level probes:
These probes provide the inputs
which are used to control the water level, the salinity level of
the water and identify alarm conditions.
The four probes have the
following basic functions:
Very High Level Alarm function
only. Shuts down both water inlet valves together with the machine
and initiates alarm. This prevents a continuous overflow situation
with its associated cost in lost water.
High Level The normal working
level. If this level is not reached within a set time during a
fill cycle, then a Slow Fill alarm is initiated
Low Level The normal refill
point during the evaporation cycle. When the water is reaching the
set point for salinity control this probe initiates a complete
drain. The set point can be adjusted using the dip switches in the
main control panel. This probe also protects the circulation pump
from dry running.
Very Low Level This probe
signals the end of drain and starts the fill cycle. If this probe
does not become uncovered within a set time during a drain cycle
then a Slow Drain alarm is initiated
The controller continuously monitors
the probes and should any probe go out of sequence (e.g. High
Level covered but Low Level un-covered which is impossible) an
alarm condition is raised and the cooler will shut down in a safe
and controlled way.
Why Bleed-Off?
If an evaporative cooler does not
have any water bled off then the water in the system becomes both
scale-forming and increasingly dirty.
How does an EcoCooling Cooler
bleed off?
At the heart of the control
system are four level probes. As the water rises the water inlet
valves are turned on and off to maintain the working level. The
process control system counts the number of tim es the sump is
replenished. From this it calculates, according to a point which
is set with regard to the water quality, when to drain the sump as
the water approaches the scaling point.
Advantages of a four probe system
The alternatives to a four probe
system are:
Continuous bleed: In this system
a set flow rate of water is bled off the cooler all of the tim e.
An evaporative cooler uses a variable amount of water according to
the air conditions and the fan speed. With a continuous bleed the
system is either over draining water or under draining water. It
is a difficult system to set up and control and inevitably a large
amount of guess work is involved during commissioning. Over
draining of the water is expensive and can also lead to a
softening of the pads. Under draining of water leads to scaling
and increased contamination. These systems are normally found to
be over-draining the water.
Timed drain : In this system the
sump is drained at set tim ed intervals. This suffers from the
same problems as the continuous bleed system.
Conductivity Probe: In this
system a conductivity probe monitors the water quality and drains
the sump accordingly. This requires a water analysis to be
performed on commissioning which few engineers can perform.
Conductivity probes require regular maintenance as their accuracy
is impaired as deposits form easily on the contact surfaces
The advantages of a four probe
system are:
- The most precise way of
controlling the salinity level of the water
- A high level probe which
prevents overflow and consequent water wastage
- A very low level probe which
verifies the sump is completely empty thus preventing the
possibility of stagnant water remaining in the sump.
- Simple maintenance with no
calibration required
- The most comprehensive alarm
facility available on any evaporative cooler
Description of Operation
1 - Fan Speed
All machines are supplied with
a 4 pole/8 pole 1.5KW 1380/810 rpm double winding motor as
standard (@220v). The fan starts in 8 pole for 10 seconds and
then moves to set speed to provide a soft start. The starting
current is 12A with a normal maximum running load of 8A at speed
5.
For five speed machine the
controls then use the electronic control to slow down the first
winding by two stages and then use the second winding. This is
then electronically controlled down to its minimum on speed 1
| 5
(A) |
Motor 1 (1240) |
1390 |
| 4
|
Motor 1 (1240) |
1220 |
| 3
|
Motor 1 (1240) |
1050 |
| 2
(B) |
Motor 2 (700) |
870 |
| 1
|
Motor 2 (700) |
600 (minimum possible) |
2 - Start Up
Firstly the low level probe is
checked if it is covered then the cooler drains fully prior to
starting the water cycle. Follow the pre-cool cycle, if enabled
on the dip switch, for five minutes from the tim e the second
probe and the circulation pump starting..
3 Water cycle
Fill cycles follow the dip
switch settings. On the cycle drain pulse the water to flush the
sump when the very low level probe is uncovered. When the low
level probe is wait 2 minutes and then run the water for 6
seconds. The drain then stays open for a further 20 seconds and
the recommence the fill cycle.
4 Draining
The drain will stay open and
the optional scavenge pump will run for 2 minutes after the low
level probe is cleared.
5 Stop/Vent
Machine drains down completely
when stop or vent are selected. If low level probe is covered
during this then the drain valve opens and scavenge pump runs as
(4)
6 Alarms
When the cooler enters an alarm
condition the LED on the wall controller flashes to give an
indication of the problem.
1 flash Slow fill Auto Reset
If the high level probe is not
covered within 20 minutes this means there is a water supply
problem. Either the water has not been switched on or there is a
problem with the inlet valves.
2 flashes Overflow Manual
Reset
This is activated when the Very
High Level probe is covered.
3 flashes Probes out of
sequence Manual Reset
If any probe is covered out of
sequence this alarm is activated. This is either a fault with
the probe or the float sticking on its support.
4 flashes Abnormal
evaporation Manual Reset
In COOL operation if a fill
cycle is not activated in a 6 hour period this alarm is
activated. This is typical of a circulation pump failure.
5 flashes Slow Drain Auto
Reset
In a drain operation if the
Very Low Level probe is not uncovered in 10 minutes this alarm
is activated
6 flashes - External Alarm Auto
Reset
In the control panel there are
a set of contacts which can be connected to an external alarm
switch. If this is activated this alarm is operated.
In Auto Reset the alarm will
automatically clear when the fault clears. A manual reset alarm
requires the cooler to be turned off at the wall box after the
fault has been cleared.
The LED in the main control box
also gives a readable value to the alarm condition. This value
will be kept after the alarm has been re-set so that the last
alarm condition can always be identified. If another alarm
condition occurs then this is lost. If the power is interrupted
the alarm condition is lost and the LED shows the salinity
control cycle for seconds
7 Maximum Speed Control
Maximum speed can be changed
using dip switches
Dip Switch Settings
|
|
|
D6
off
D7 off |
D6
on
D7 off |
D6
off
D7 on |
| 5
(A) |
Motor 1 (1240) |
1390 |
1220 |
1050 |
| 4
|
Motor 1 (1240) |
1220 |
1100 |
990 |
| 3
|
Motor 1 (1240) |
1050 |
980 |
930 |
| 2
(B) |
Motor 2 (700) |
870 |
870 |
870 |
| 1
|
Motor 2 (700) |
600 |
600 |
600 |
|
