ACCX Air Conditioning Run / Stand-by changeover

ACCX Air Conditioning Run / Stand-by changeover
CMR Electrical Ltd
Bolton House
Five Chimneys Lane
Hadlow Down
East Sussex
TN22 4DX
Tel: 01825 733600
ACCX
Air Conditioning
Run / Stand-by changeover
Controller
Installation and operation
Manual
1
Two Air conditioning Changeover Unit
The unit consists of two volt free contacts (Start/Stop AHU1 & 2) and will control both AHUS. Both
contacts are normally closed, this allows a failsafe for when the unit is powered down or becomes faulty
as both AHUS will start. In normal operation the Run AHU volt free contact will be closed (relay deenergized) and the standby AHU volt free contact will be open (relay energized). Both AHUS will need
to supply an individual control interlock through the units control relays.
Three fault inputs are provided, “AHU1”, “AHU2” and Room over temperature “TEMP”. A four way
selector switch has been provided within the unit to allow the individual fault signals to be set at
normally open or normally closed. Any combination of normally open/closed can be set by this switch,
i.e. AHU1 normally open (close in fault), AHU2 the same and Room over temperature normally closed
(open in fault) . This switch is located on the left hand side of the main PCB just above the terminals
marked RS485. Identification numbers on the switch relate to, “1”= AHU1 is a normally open input when
the switch is pushed to the far left or normally closed when pushed to the far right, “2”= the same but for
AHU2 and “4”= the same but for Room over Temperature (switch “3” is unused). The control unit will
provide a 12vdc signal to all the remote fault contacts which should be volt free.
A “common” alarm relay is provided which again will be energized in normal operation, de-energize in
alarm. Again, this allows a failsafe for when the unit is powered down or becomes faulty as it will start a
remote alarm if fitted or signal a fault to the BMS due to power failure.
The unit has been designed to control two air handling units and allows one unit to provide heating /
cooling with the second unit being off and in standby. After a time delay which is user selected between 1
and 999 hours, the run unit will stop and the standby unit will start up. This feature allows even ware of
both AHUS.
In the event of a fault developing with the run unit, the system would automatically shut down the run
unit, start the standby unit, give an audible warning (requiring a Mute to stop) and operate the common
alarm relay. The system would remain in this configuration until the faulty AHU had been rectified and
the “Reset” push button operated. Having changed as described above to the standby unit, if a fault
developed with the standby unit i.e. both AHU1 and 2 faulty, both AHUS would start. This has been done
in an endeavour to obtain some heating / cooling from both units whilst waiting for repair.
If a fault developed with the standby unit, the system would inhibit automatic transfer after the preset
time delay, start the audible warning and operate the common alarm relay. Again, if during this
configuration the run unit became faulty, both units would be started as described above.
On over temperature fault signal has been provided which would be connected to a standard thermostat
within the room. If the thermostat detected an over temperature within the room, the system would start
both AHUS to give the maximum cooling to the room. Again, the system would remain in this
configuration until the “Reset” push button was operated.
A non volatile memory store has been used within the unit to hold the “Time between automatic
changeovers” and the time until the next changeover. In the event of power failure both time periods
would remain held within the unit so that on re-powering the time delay to the next changeover continues
from where it stopped i.e. on power down it was 63 hours to the next changeover, on re-powering up of
the system it will still be 63 hours to the next changeover.
Three push buttons are provided “Mute” to stop the audible warning device, “Reset” to revert the system
back to normal operation after a fault and “Set” used to manually select which unit is to be run unit or
change the time period between automatic changeovers. A timer is activated when entering the “Set”
mode which will automatically revert the system back to normal operation if a push button has not been
operated within 10 seconds.
All events are displayed in a back lit 16 character 2 line alpha numeric display.
2
In Normal Operation
With the system up and running without any faults and AHU1 selected as the run unit the display will
show the following.
AHU1 is Running
Time run 030 hrs
The display shows that AHU1 has been selected as the run unit and has been running for 30 hours. Relay
Start/Stop AHU1 will be de-energized (contact closed) and relay Start/Stop AHU2 will be energized
(contact open). A few seconds later the display will change to the following.
AHU2 in Standby
C/Over in 136hrs
This shows that AHU2 is the standby unit and will become the run unit in 136 hours. Again after a few
seconds the display will go back to displaying AHU1 status and continue to cycle through both screens.
Once AHU2 becomes the run unit the same display format is used but showing “AHU1 in Standby” and
“AHU2 is Running”. The Start/Stop relays would change to AHU1 energized ( contact open) and AHU2
de-energized ( contact closed).
AHU1 or 2 is selected as the run unit but becomes fault.
The display would change from normal operation to the following.
STANDBY AHU HAS
BEEN ACTIVATED
The run unit would stop, the standby unit would start up, the audible warning device would sound and the
common alarm relay would operate. This would remain until the “Mute” push button were operated when
the display would show the following.
AHU1 is Faulty
Standby Running
A few seconds later a new screen would display the following.
AHU2 is Running
C/O Cancelled
Again after a few seconds the display would change back to the first screen and continue to cycle through
both screens. This would remain until the faulty AHU had been rectified when the screens would change
to the following.
AHU1 is Faulty
Reset Required
Followed by.
AHU2 is Running
C/O Cancelled
3
Even though the faulty unit has been repaired, the system will not allow a transfer back to it until the
“Reset” button had been operated. Whilst in this configuration, the automatic transfer due to time would
be inhibited. However once the fault had be rectified and reset, the timer would start from where it had
been stopped i.e. fault happened with 63 hours until next changeover, fault lasted 5 hours after reset time
to next changeover would be 63 hours.
AHU1 or 2 is running but the standby unit becomes faulty
The display would change from normal operation to the following.
The Standby Unit
Is Faulty
The run unit would continue to run, the standby unit would be locked out, the audible warning device
would sound and the common alarm relay would operate. This would remain until the “Mute” push
button were operated when the display would show the following.
AHU1 is Faulty
C/O Cancelled
Followed after a few seconds by.
AHU2 is Running
C/O Cancelled
Again after a few seconds the display would change back to the first screen and continue to cycle through
both screens. This would remain until the faulty AHU had been rectified when the screens would change
to the following.
AHU1 is Faulty
Reset Required
Followed by.
AHU2 is Running
C/O Cancelled
Again even though the faulty unit has been repaired, the system will not allow a transfer back to it until
the “Reset” button had been operated. Whilst in this configuration, the automatic transfer due to time
would be inhibited as above.
Both AHUS become faulty
In the unlikely event that at some time both AHUS be come faulty. The display would change to the
following.
STANDBY AHU HAS
BEEN ACTIVATED
4
The run and standby units would both run, the audible warning device would sound and the common
alarm relay would operate if not already done so. This would remain until the “Mute” push button were
operated when the display would show the following.
AHU1 is Faulty
All AHUS Faulty
A few seconds later a new screen would display the following.
AHU2 is Faulty
All AHUS Faulty
After a few seconds the display would change back to the first screen and continue to cycle through both
screens. This would remain until one or both faulty AHUs had been rectified. when the screens would
change to the following.
Only AHU1 rectified.
AHU1 is Faulty
Reset Required
Followed by.
AHU2 is Running
C/O Cancelled
Or both AHUS rectified
AHU1 is Faulty
Reset Required
Followed by.
AHU2 is Running
Reset Required
Again, even though both faulty unit had been repaired, the system will not allow a transfer back to it until
the “Reset” button had been operated. Whilst in this configuration, the automatic transfer due to time
would be inhibited as above. If only one of the AHUS had been rectified and depending upon weather it
was a run or standby unit, the system would display one of the fault screens shown above. This would
required a second “Reset” after the remaining faulty unit were rectified.
Room Over Temperature
If the room becomes to hot, the system will start both AHUS, start the audible warning device and operate
the common fault relay. The display will show the following.
5
C/O ACTIVATED
BY HIGH TEMP
This would remain until the “Mute” push button were operated when the display would show the
following.
AHU1 is Running
Room over Temp
Followed after a few seconds by.
AHU2 is Running
Room over temp
Again after a few seconds the display would change back to the first screen and continue to cycle through
both screens. This would remain until the room temperature fell back to normal when the screens would
change to the following.
AHU1 is Running
Room over Temp
Followed after a few seconds by.
AHU2 is Running
Reset Required
If again the room became to hot before a manual “reset” occurred, the display would revert back to both
AHUS running and Room Over Temp. The audible warning device would not start again nor would the
relays change.
Once the room reached the normal temperature, the system will not allow a transfer back to normal
running until the “Reset” button had been operated. Whilst in this configuration, the automatic transfer
due to time would be inhibited as above.
Manually select which AHU is to be the run unit
This feature can only be used when the system is in normal running with no current faults. It allows at any
time to manually select which unit is to be the run unit i.e. AHU2 is now the run unit with 100 hours
before it becomes the standby. After manual selection AHU2 becomes the run unit with AHU1 as
standby. After using this feature the time clock will reset back to the maximum hours before the next
changeover. A timer is activated when entering the “Set” mode which will automatically revert back to
normal operation if a push button has not been operated after 10 seconds.
First press the “Set” push button, the display changes to the following.
Mute = C/O Time
Reset= AHU Duty
Press the “Reset” push button, the display changes to the following.
6
S=Save, M=Change
Run Unit AHU 2
The display is showing that the current run AHU is number 2. “S” = the “Set” push button and “M” = the
“Mute” push button. Press the “M” (Mute) push button changes the 2 i.e. AHU2 into 1 i.e. AHU1. More
presses of the “M” (Mute) button will toggle between AHU1 and 2. When satisfied with the selection
press the “S” (Set) push button. The system will change the run / standby configuration, restart the time
delay to next changeover and display the normal running screens.
Change the time delay between automatic change between run and standby configurations.
This feature allows a user to determine the period between changing the run unit into a standby unit. By
using this feature twice, an automatic changeover can occur at a specific time on a specific day i.e.
Monday at 5pm. However attendance may be required to carry this out. To do this first workout the hours
between now and Monday 5pm and set the system up for this time, next on Monday at 5pm use this
feature again to set the next changeover to 168 hours. The system will then carry out a changeover every
Monday at 5pm. Any time period between 1 and 999 hours can be set i.e. 1 hour to 41 day 15 hours. A
timer is activated when entering the “Set” mode which will automatically revert back to normal operation
if a push button has not been operated after 10 seconds.
First press the “Set” push button, the display changes to the following.
Mute = C/O Time
Reset= AHU Duty
Press the “Mute” push button, the display changes to the following.
S=Save, R=Next
M= Change 999hrs
The display is showing the current time delay between changeovers (999 hrs) “S” = the Set push button,
“R” = the Reset button and “M” = the Mute button. The cursor will be flashing over the hundreds number
to indicate that this is the number being worked on. Pressing the “M” (Mute) button will increment the
number as shown by the flashing cursor. If no change is required to the hundreds, or you are satisfied with
your selection, press the “R” (Reset) push button to move the cursor to the tens number. Again using the
“M” (Mute) button will increment the number as previously described. pressing the “R” (Reset) push
button once again to move the cursor to the units number which can be change as described above. One
more press of the “R” (Reset) push button will take the system back to the hundreds number. Once you
have selected your required time delay press the “S” (Set) push button. This will save the new time , reset
the time until next changeover back to the new time and reset the system back to normal operation. The
“S” (Set) push button can be used at any time.
7

The unit providers a 240VAC 8amp normaly closed
contacts to start and stop the AHUS
How to change AHU1and or AHU2 and or Thermostat
from normaly open to closed contact arrangment.
A small 4 way switch can be found on the far LEFT
of the PCB located about 30mm from the bottom of
the PCB. For normally Open contacts the relivant switch
should be pushed to the LEFT, normaly closed the switch
should be pushed to the right.
Normaly Open Contact
1 2 3 4
Notes
Both AHU 1 & 2 must have a volt free contact
normaly open or closed to indicate
to the unit of a fault within the AHU.
Normaly Closed Contact
AHU1 Fault
AHU2 Fault
NOT USED
Thermostat

An over temperature thermostat can be used to
start both AHUS. The contact can be normaly
open or closed
AHU 1
AHU Fault
Circuit N/O
or N/C Volt
Free contact
AHU 2
AHU Fault
Circuit N/O
or N/C Volt
Free contact
Stop/Start
Circuit
Stop/Start
Circuit
Thermostat if
required
Volt Free Common
Alarm Contacts
8
230VAC Mains Input "L"
= Live, "N" = Neurtal,
"E" =Earth
N/O
COM
OUTPUT ALARM
CONTACTS
NOT USED
AHU 2 START/STOP
AHU 1 START/STOP
REMOTE THERMOSTAT
IF REQUIRED
NOT USED
AHU 2 FAULT CONTACT
AHU 1 FAULT CONTACT
NOT USED
N/C
L E N
9
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement