There is a well-known saying in the army that “no plan survives contact with the enemy.” This is a familiar fact of life for refrigeration and air conditioning field engineers, whose work plans can change at a moment’s notice.
Any combination of weather, unexpected breakdown, changed office priorities or manpower shortage can wreak havoc with the best laid plans for a day in the field.
“You have to be flexible and be prepared to rejig,” says Cool-Therm’s Alistair Michie, who works out of the company’s Bristol office. “It’s one of the reasons I love the job. No two days are ever the same - it is constantly interesting and challenging.
”The day RAC Engineer magazine joined Alistair proved to be no exception. The planned job was a visit to a high-tech plastics company just outside Bristol, for scheduled servicing and maintenance on three large McQuay chillers.
However, Alistair had received a call early that morning from hq asking for back-up at another site, and it was pressing. It involved final commissioning work on one of the company’s award-winning Turbomiser chillers at a multi-tenanted office building in the centre of Bristol.
The team were a man down, and – as he was the most experienced engineer within range – could he get over there and assist? Arriving on site, it became clear that the task was part sophisticated flight check, involving optimisation of flows and controls, and part metal-bashing, involving straightening a bent condenser fan cowling.
“This one requires the application of brains and brawn in perfect harmony!” commented Alistair, as he and colleagues bolted in place a now correctly aligned fan-motor unit on the upper deck of the roof-top mounted chiller.
The new 600kW Turbomiser, equipped with the Adiabatic Advantage technology, was a replacement for an aging RC R407C reciprocating unit, and being run in parallel during commissioning.
One of the commissioning tasks was to balance the inlet and outlet pressures on the chiller, as the plant kept tripping out due to too much water-flow.
It was time to get out the manometer and check transducers were reading correctly. That done, it was a matter of tweaking water flow rates across the evaporator to optimise performance.
“When you get it right, these Turbomiser machines sound like a silky turboprop aircraft on a glide path. It’s now running very sweetly, you can just hear the compressors and fans humming. The contrast with a conventional chiller is unbelievable.”
Ken Strong, Cool-Therm’s managing director, had a plan to use harvested rainwater with the Adiabatic system – which he estimated would cut energy consumption by around 10 per cent. That project was for another day, however, as it was time now to head off to the original planned job. Alistair packed up his tools and headed off in the van to the outskirts of Bristol.
After starting work as an electrician in the NHS, he worked for an FM company before joining Cool-Therm nine years ago. “Before I get a job in the industry, I had put myself through an evening course in refrigeration as I really liked the subject, and just felt drawn to it. I met a Cool-Therm engineer attending one of our FM sites, and the rest is history,” he says.
“I like the fact that in refrigeration I can get to use all of my skill sets, including electrics and control systems. Anyone can be a chiller engineer, but it takes a lot to be a really good one.”
On his beat, he gets to deal with all kinds of technology, including splits, VRF systems and large centrifugal chillers – “the kind of beasts that scare holy moly out of engineers on first meeting.”
He concedes that handling this kind of plant is still something of a black art. “There’s no doubt though that the future belongs to the new Turbomiser-type chiller. They are streets ahead in terms of efficiency and reliability. I have been working with them for six years, and I have never had a breakdown.” He points to the sophisticated onboard control and monitoring system on the Turbomiser as something of a revolution for field engineers. Data for alarms and performance is stored, giving engineers access to past history and enabling them to spot performance trends.
“I can connect up my PC in the field and there it all is, in beautiful graph form that can be used for analysis and reports. There is no comparison with working on conventional systems, which in their own way demand different skills and instincts.”
It is this contrast that he finds endlessly stimulating. “One day you are working on a roof-top overlooking a city centre such as Bristol or Dublin or Glasgow; the next you are hundreds of metres below the ground in a top security MoD installation. What other job could provide this kind of variety?”
On that note, we arrive at a large, smart industrial site that manufactures medical quality plastics. Hygiene is paramount, and we don hairnets and coveralls for the trip across the production floor, up the access point to the roof-space plant room – where three very large and stately McQuay chillers are at work on process cooling duties.
The three 1.5MW centrifugal units are 15 years old, and due for a quarterly service and maintenance checks - a mandatory requirement given their large refrigerant charge.
Alistair begins a long series of detailed checks, filling in the plant’s operating log as he goes. The work is more time-consuming because of the centrifugal technology, which requires checks on inlet guide vanes, separate oil pumps, water/oil cooler and so on. “It’s not so bad once you know the machine and any issues. It’s the first time you carry it out that is the challenge, as you have to quickly pin down and get to the bottom of any problems that come to light.”
Everything seems to be in order. There is a known problem with an oil pump on one of the machines, which has broken. Quotes to repair it have come in very expensive, as it would require a partial rebuild of the machine, and there is a debate as to whether it is worth doing or whether the time has come to replace the aging chiller itself.
“What they really need is a Turbomiser. That is something we will be talking to them about in the near future,” he says.