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For the above example of a 10°F (5.5°C) temperature differential, this yields a tolerance of 10%. The test tolerance would allow for the chiller rated at an IPLV of 0.580 kW/ton (0.170 kW^/kWT) to operate at 0.638 kW/ton (0.187 kW£/kW). Correspondingly, recalculating the IPLV by substituting the maximum tolerance performance rating for each of the four load levels individually in Table 33-3 also yields an IPLV performance value of 0.638 kW/ton (0.187 kWe/kWr).

In addition to these allowable performance result tolerances, one must also consider the impact of tolerances on other test variables. For example, chilled and condenser water flow rates and temperatures may deviate by up to 5% and 0.5°F (0.3°C), respectively. Correspondingly, for air-cooled condensers, the average entering air dry-bulb temperature to the condenser may vary by up to 1°F (0.6°C). As discussed below, varying evaporator and condenser temperature will impact performance. If, for example, the leaving chilled water temperature is measured at an increased level of 0.5°F (0.3°C) and the entering condenser water temperature at the same level of decrease, the measured performance of the unit will be improved by 1% or more.

Allowances such as these can be added to the allowable performance tolerances listed above to describe the actual full deviation that could be experienced in the worst case scenario and still meet certification requirements. This means that performance at the target temperatures could actually deviate by more than the allowable performance tolerance in the test result. The actual total IPLV deviation then might be 11 or 12%, as opposed to the 10% tolerance. In this example, the actual normalized IPLV performance might be 0.650 kW/ton (0.190 kWe/ kWr), as opposed to the published rate of 0.58 kW/ton (0.170 kWe/kWr).

It is also important for the specifying engineer to consider the impact of these tolerances on auxiliary equipment for sizing and energy usage analysis. As another example, if the test flow rate is increased by the allowable 5%, the capacity of the unit will appear greater by this amount. However, in order to achieve that capacity, the water pressure drop and expected auxiliary pumping requirements will be elevated above the level that would be calculated based on the published performance rates. Other subtle differences may also be found. For example, if the performance rating does increase, so does the heat of compression and, in turn, the heat rejection duty imposed on the condenser. Hence, slightly more fan energy or cooling tower water usage requirement can be expected. While these all may be modest changes, if all of the deviations occur in the same direction, the additive impact can be significant.

All of these factors should be carefully considered when specifying equipment and performing life-cycle cost analyses. It may be prudent to confer with the manufacturer and request zero tolerance data on performance, indicating the worst case scenario that would still meet certification standards. It should be understood that the manufacturers will have their own actual fleet manufacturing tolerances, which may differ from the certification tolerances. Therefore, they may seek to ensure that the equipment they produce does not fall below the tolerances and will establish their published ratings accordingly. In summary, while certification tolerances may be fairly significant, the certification process allows for uniformity in the industry. The tolerance specifications also allow the specifying engineer to understand the deviations that may result and plan accordingly.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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