Question 219General Subjects - 1st Asst/Chief70% to pass
In the illustrated single zone HVAC system, what prevents the simultaneous flow of steam through the preheat coil and flow of chilled water through the cooling coil? Illustration GS-RA-09
AI Explanation
The correct answer is A) The supply air duct thermostat controlling the steam flow is set several degrees lower than the design off-coil temperature associated with the cooling coil.
This is the correct answer because the supply air duct thermostat controlling the steam flow is set to a lower temperature than the design off-coil temperature of the cooling coil. This prevents the simultaneous flow of steam through the preheat coil and chilled water through the cooling coil, as the system is designed to only use one source of heating or cooling at a time to maintain the desired temperature in the space.
The other options are incorrect because B) setting the thermostat equal to the cooling coil's design temperature would allow simultaneous heating and cooling, C) simultaneous heating and cooling is not typically permitted for humidity control, and D) setting the thermostat higher than the cooling coil's design temperature would result in continuous heating, not the desired sequential heating and cooling.
Related Questions
#216 Referring to the illustrated dual duct multiple zone HVAC system, how is the space temperature directly controlled? Illustration GS-RA-43 #217 Referring to the illustrated single zone HVAC system diagram, what statement is true concerning the damper controls? Illustration GS-RA-09#220 Referring to the illustrated psychrometric chart, under what conditions are the dry bulb, wet bulb, and dew point temperatures for air all equal in value? Illustration GS-RA-22 #221 Referring to the illustrated psychrometric chart, suppose during the cooling season that air passes over a cooling coil with a mean surface temperature above the dew point temperature, and this results in sensible heat loss with no change in moisture content. What statement represents the direction of the air conditioning process line? Illustration GS-RA-22 #222 Referring to the illustrated psychrometric chart, if the dry bulb temperature is 70oF and the relative humidity is 40%, what is the absolute humidity? Illustration GS-RA-22