The Challenge
Bryn Martin undertook another project, a strategic study into the future heating needs of the RNZAF base at Woodboune, near Blenheim.
During the course of that investigation, it was realised that the Ground Training Wing (GTW),
a two-story training establishment which was built in the mid 1990's was so different in its needs and equipment that it did not fit within the sorts of heating solution which applied to the rest of the base. It was also fully air conditioned, which the rest of the base, with a few exceptions, is not.
The strategic study had recognised that the correct long-term solution for air conditioning the Ground Training Wing might well be a 4-pipe heat pump.
Shortly after the strategic study was finished, the chiller failed, providing an opportunity to make the change to a 4 pipe system. Bryn Martin provided the investigation and design works for this project.
Consequent upon that change, it became apparent that there were a number of long standing heating and cooling problems within the GTW systems, which required a solution.
Main Features
The Ground training wing air conditioning design is relatively simple. A dedicated chiller provides all of the cooling through local fan-coil units. (Now a 4-pipe heat pump.)
Heating is all electric resistance; being wall hung, overhead and some ducted. (In the process of being changed to low temperature hot water from the heat pump.)
Fresh air is provided by a set of eight air handling units, seven of which provide warmed air only, the eight being a full heating and cooling device for the theaterete.
Bryn Martin were asked to take the results of a set of recently completed air and water flow measurements taken across the GTW, to see if any conclusions could be drawn as to the cause of the various air conditioning problems.
The Response
Bryn Martin took the air and chilled water flow measurements, and related them back to the original commissioned data and as-built drawings.
We then spent a day on site, talking to the operations and maintenance personnel, and to the building users to gain an appreciation of the perceived problems. A considerable part of that day was spent looking and listening. It was listening that gave the first clues. A number of chilled water control valves appeared to be excessively noisy.
The Works
On return to the office, the chilled water measurements were related back to the control valve manufacturer's selection data, which told us that almost all appeared to be working at the far extreme of their range, a place where no-one would normally have selected them to operate.
Further investigation suggested that to overcome a problem of some sort in one or perhaps two small legs of the chilled water distribution system, the main child water pump had been changed for a very much larger, higher pressure unit during commissioning.
It was the excessive pressure generated by the oversized main circulating pump which was driving many of the cooling control issues.
A comparison the airflows associated with fan coil air conditioning units between those recently measured and the original commissioning results, indicated that some fan coils appeared to have deteriorated markedly in their performance.
Others, it could clearly be seen in the original commissioning data, were under-performing from the beginning.
The report has provided site maintenance staff with an insight into what is driving their problems of heating and cooling. They now know where to look and what to look for.
It also has highlighted that the main chilled water circulating pumps can be changed for a unit of less than half of the size, with considerable electrical savings.
When the maintenance and rectification works are complete, the GTW should be more comfortable, more controllable, and less costly to operate.
For more Information on this or any other project or service please contact Brian Anderson or Tim Allan.