Case Studies - how data logging can trace a fault
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Energy Efficiency Comparison |
British American Tobacco, London |
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Fridgetek have recently completed an efficiency upgrade to 2 York Chillers located at British American Tobacco in London. By retrofitting a Danfoss Electronic Expansion Valve, Danfoss Superheat Controller and Danfoss Inverter to the Condenser Fan Motors, BAT were able to realise average running cost savings over the year of around 25%.
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By Data Logging the Chiller before and after the retrofit, we are able to plot changes in absorbed power to refrigeration duty. Interpolating this into the Compressor’s COP’s extracted from the Data Logging to monthly average temperature loadings we can determine Running Cost Savings. To date our predictions are in line with site Monitored Power Usage. Click HERE to review document.
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Data Manipulation & Interpolation |
Data Acquisition |
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Examples of how the RAW DATA acquired can be exported into Tab Delimitated Format for easy import into Excel for filtering.
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Problem No 4 |
Data Logging Solution |
Two newly installed Air-Cooled Screws were having problems attaining duty. The Screw Compressors were experiencing flood-back problems as well. (Click Graph for better resolution.)
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Data logging showed that the total system chilled water flow was down by over 18%. This quick and simple FOOT-PRINTING of chillers is an easy exercise to determine whether the Chiller is delivering its rated output with its documented input. This DATA LOGGING made up part of the quotation process.
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Problem No 3 |
Data Logging Solution |
A service exchange Semi-Hermetic Screw Compressor was fitted to a Chiller. At full load the motor would overheat and trip on Thermistor Protection. (Click Graph for better resolution.)
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Data logging showed at low loads the compressor would run all ok. When the Absorbed Power from the compressor motor reached approximately 87% of its rated nominal input, the thermistors showed the winding overheating to a trip condition. It was suspected that an undersized winding was fitted to the re-manufactured compressor. Further inspection confirmed this to be the case and the correct winding was fitted. The compressor re-manufacturer carried out the works on site that saved the manhandling costs of a total replacement of an otherwise suspect rebuild.
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Problem No 2 |
Data Logging Solution |
A refrigerant retrofit was carried out on an R12 Centrifugal Compressor. The new refrigerant used was R134a. On recommission, the compressor at low loads surged and caused excessive vibration. (Click Graph for better resolution.)
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Extensive Data Logging revealed the Compressor's Temperature Lift (Compression ratio) profile would just enter a surge region at low loads. The Manufacturer examined the data and recommended the fitting of a Hot Gas Dump Valve to overcome the low load surging.
These works were successfully carried out. The customer asked for documentation on the comparisons between the R12, R134a pre-Hot Gas Dump and R134a Post hot Gas Dump Efficiencies. All this raw data was already collected by the data logging. A COMPARISON DOCUMENT was compiled and submitted to the customer.
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Problem No 1 |
Data Logging Solution |
A Copeland DH6 Compressor on a Water Chiller was experiencing intermittent Thermistor trips on the Windings.
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The Data Logging showed that in low ambient with low Discharge Pressures, the Suction Pressure would fall to just above L.P Cut-out. The compressor would run continuously and the windings were not being cooled sufficiently by the lower mass flow of suction gas.
Further investigations showed that the TX Valve was icing up internally due to moisture in the charge. A new drier, retrofitting a sight glass with moisture indicator, evacuating to 3 Microns and it holding for 12 hours, replacing the charge and the problem was identified and solved.
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