DRAWING FOUR PREFERRED PERFORMANCE CHART Drawing four is the same as drawing three with the exception of the performance chart at the upper right corner. The chart on drawing three illustrates the actual performance as we found the system and Drawing Four illustrates the performance chart of the desired sequence of operation. Two other points worthy of note are the locations of the return air temperature transmitter (TT1) and the electric high limit (HL1). The electric high limit replaced PE1 and its associated sprinkler heads (SPH) in the original design. The original design was well arranged regarding sensing for high temperatures. The location of HL1 could hinder the device from sensing a high temperature if the building were on fire. If the outside air temperature were between 55°F and 70°F, the dampers would drive to full fresh air as the fire warmed the return air. HL1 would be sheltered from sensing the fire while the system fed the fire with oxygen. TT1 senses the heat gain from the return fan. Up stream of the return fan is a better location for sensing the return air temperature. 8.74
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