AIR CONDI T IONING
Getting commissioning right
Martyn Ives, Technical Manager of FG Eurofred/ Fujitsu air conditioning looks at some of the key points on commissioning a VRF system.
T
here are several key areas that need detailed attention in order to commission a newly installed VRF system
efficiently and successfully. These are pre-commissioning checks, additional charge calculation, addressing, system operation, controller settings and maintenance – all of which need to be carried out in the correct manner to enjoy a trouble free operation.
Pre-commissioning checks
Pipe work: It is extremely important to make sure that the installation is correct to the design schematics supplied by the manufacturer. Visual checks need to be made on all pipe work and fittings, ensuring the pipe work is supported correctly and well insulated and separation tubes and refrigerant Branch Boxes are installed at the correct angle as shown in the installation manual. Cabling: Before turning on
any power check the wiring. Ensure the cables have been terminated correctly and the correct specification of cable has been installed. Miss-wiring and wrongly specified cables can be very costly to rectify. The installer: Get to know the
installer and, if possible, go to site during the installation stages. Confirm with the installer that OFN (oxygen free nitrogen) was used while brazing. Ensure the system passed the leak/strength test in accordance with F-Gas regulations. Confirmation is also needed that the pipe work has been in a holding vacuum for at least 12 hours at a minimum of 2 torr, as this will prove to the commissioning engineer that there are no signs of moisture or leaks in the system.
Additional refrigerant charge
Calculating the additional charge correctly is very important as both overcharging and undercharging will cause the system to run inefficiently and in some cases cause the system to malfunction. Working with the schematics together with the installer, calculations need to be made for the total length of each size of liquid pipe. Calculate the amount of refrigerant
required by
multiplying the liquid pipe length as detailed on the condenser then charge the system with virgin refrigerant until the desired quantity has been reached. For future reference always remember to note the additional charge details on the condenser.
Addressing
There are several different methods to address a VRF system: • Manually, via rotary switches on the indoor and outdoor units PCB’s.
• Manually, via infa-red/wired controllers.
• Automatically, by pushing one button at the outdoor unit. Whichever way you choose
to address your VRF system it is very important it is done correctly. Incorrect addressing can result in the end user operating indoor units in completely different parts of the building to where they are situated.
Manual Rotary Switch Addressing
As a manufacturer Fujitsu always tries to address manually via the PCB rotary switches where possible. By doing it this way it makes future addressing work relatively foolproof. For instance, if a PCB has to be replaced or an indoor unit needs to be relocated it
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enables the engineer to read the rotary dial.
Manual Controller Addressing
This is an easy address method for the commissioning engineer to use if the building is occupied and accessing the indoor unit is restricted.
Automatic Addressing
This method is used when the commissioning engineer cannot gain access to the building, or when some indoor units are not accessible. The commissioning engineer can give one push on the condenser’s PCB and this will address the system.
System operation
Fujitsu offers a very powerful piece of software – Service Tool – which allows the commissioning engineer (or service engineer) to firstly check that all address settings are correct. It is then possible to view all temperature and
pressure readings from the condensers, monitoring running currents, valve control, compressor frequencies and amps, and fan speeds. On the indoor units it is possible to monitor all temperatures, fan speeds, valve control and operation mode. Service Tool connects on to
Fujitsu’s VRF 2-core communication cable, making access very easy because this can be done at the indoor unit, outdoor unit, and various system controllers and interfaces. I especially like this as you no longer have to stand outside in the rain and cold while you connect your laptop to the condenser. Once the system is ready to run Service Tool allows you to select Commissioning Mode. The Commissioning Mode monitors and logs all the data allowing it to be printed or transferred to an official FGE commissioning report.
Controller settings
Now the system is operational it is important to configure all controllers to the customer’s requirements. Local controllers can have daily/weekly timers set, including night set-back timers to allow the space to be conditioned at a higher/lower temperature compared to normal working hours. System and touch panel
controllers allow schedules to be set, allowing timed mode changes, fixed and/or restricted set temperatures, and reduced operation control for holidays and nights. The system controller also features remote monitoring and control, enabling a number of buildings to be controlled from one site. On larger VRF projects and
on an increasing number of high-end domestic properties BMS interfacing is the preferred choice of control. The FGE engineer can assist the BMS
engineer in configuring the Fujitsu VRF system onto the site’s BMS system; the BMS can then control not only the air conditioning, but additional heating, ventilation, lights, and much more.
Maintenance
The contractor will have a maintenance contract with the end user ensuring the system runs efficiently and complies with F-Gas regulations. Fujitsu can augment this by offering a remote Service Tool software package – Web Monitoring Tool. The Web Monitoring Tool is similar to the Service Tool, but can send emails if an error occurs, and allows the service engineer to remotely monitor and view operation history. A VRF system that is
designed well, installed well, commissioned well, and maintained well is an efficient and trouble free VRF system.
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