Due to rising power costs and the looming phaseout of R22, the owner of the 18-storey Citibank building in Perth decided to make the switch to hydrocarbons.
Previously, a Carrier 30L Series Chiller, comprising of eight compressors configured in two circuits of four compressors each, was used to cool the building. It had a nominal rated cooling capacity of 814 kilowatts.
The project was undertaken by Engas Australasia, which assists companies in reducing their refrigeration and air conditioning energy consumption costs by 15 to 54 per cent (depending on the application) by converting equipment to hydrocarbon refrigerants.
Engas Australasia managing director, Selwyn Wallace, said that despite the age of the chiller it was operating well and only had minor issues. However, the building owner had to plan for the future.
Wallace said the decision was made to keep the existing chiller and convert it to use Engas M50 Hydrocarbon Refrigerant.
He said the cost advantage of just replacing the refrigerant and not the chiller was enormous, even when taking into account the additional works required to make it suitable and safe for the new refrigerant.
Prior to HC’s being utilized in this system various modifications to the plant room and surroundings had to be made.
The original plant room layout encompassed the chiller, all the pumps, the controls and the main switchgear.
There was no suitable ventilation; the lighting was of the standard fluorescent type. The pressure release valves had never been piped to the exterior of the building. The electrical panel on the chiller was only just hanging on, with most of the retaining bolts missing.
To prepare for the conversion Engas separated the chiller from the rest of the mechanical and electrical equipment with an industry standard two hour rated partition wall. Two hour rated doors were fitted complete with fresh air intake vents.
The pressure release valves were piped to the outside of the building, with the piping correctly sized to ensure complete release with back pressure build up.
Four HC leak detectors were mounted in the new ‘Chiller only’ plant room and these were wired into a purpose built control system that in the event of a leak the Chiller and main power supply was completely isolated. A manual shut off push switch was also fitted.
This system also incorporated warning lights and audible signals plus it was also connected to a purpose built extract system using a spark proof motor. The ducting for the extract system was run through the roof and supported at suitable centres, to allow discharge of the plant room air away from buildings and people.
The lighting and switches were changed over to sealed type, as were the power outlets in the area. Advice and warning signs were fixed to suitable highly visible positions.
A Grant 24 channel data logger was placed in the plant room with sensors located at all relevant positions.
Wallace said logging of the chiller performance was undertaken for about six weeks at 15 minute intervals, after which the data was downloaded and exported direct to an Excel spreadsheet.
The control and electrical panels were repaired, with new bolts. New door sealing was added, and all cable entry glands were sealed with silicone. Electrical terminals were checked for tightness and corrosion and rectifications were made where necessary.
General checks of the integrity of all valves and fittings was also undertaken.
According to the on-site contractor the oil/lubricant was regularly tested (using an external lab) and was of good quality and did not require changing. We carried out on site, physical checks, on the oil/lubricant.
Wallace said the existing refrigerant was recovered into suitable cylinders and stored and the liquid line filters were replaced.
He said the chiller was then run on an extended vacuum, using the triple evacuation process and oil/lubricant levels were checked.
“The Chiller was then charged with Engas M50 to approximately 35 per cent of the original R22 charge; the circuit was then extensively leak tested,” Wallace said.
“The electrical control system was then switched on and small amounts of refrigerant were slowly added until optimal operating pressures were achieved, we monitored the chiller for 24 hours.”
Engas safety labels and stickers were attached to various locations on the Chiller indicating that Engas M50 was in use in the chiller.
Further adjustments were made over the next few weeks to further improve performance.
Wallace said the head pressures were 20 per cent lower than when operating on R22.
He said there has been a huge improvement in performance along with significant energy savings and of course zero impact on the environment. For more information call Engas Pty Ltd on 1300 463 642