Simultaneous Heating & Cooling

The Air Handling Unit (AHU) preheat coil valve was leaking when signaled closed (0% valve signal), resulting in a preheat discharge temperature that was over 40 degrees warmer than the required temperature. As a result, the cooling coil valve opened simultaneously to maintain the final supply air temperature at its setpoint of 55°F. The simultaneous heating and cooling resulted in excess heating and cooling costs. Continue reading “Simultaneous Heating & Cooling”

Life Science Building: Sample AHU Operating Conditions

The building is 275,000 sq. ft.  It has over 7,500 Siemens BAS points monitored, 725,000 samples per day, 4 chillers, 4 cooling towers, 12 pumps, 9 air handling units, and over 1,000 terminal units.

Sample AHU Operating Conditions

Figure below shows the base and post operation of the 3 main AHUs in the building.  Prior to the modifications, all 3 AHU supply fans were pegged at 100% speed, the air change per hour (ACH) rates were over 15 in many labs and the building initially had an energy intensity of 366 kBTU/sq. ft./yr. Continue reading “Life Science Building: Sample AHU Operating Conditions”

Example of Fault Detection and Diagnostics: Pneumatic actuator leak and Filters in Alarm

Pneumatic actuator leak

The building HVAC systems are controlled via a DDC front end connected to pneumatic actuators out in the field.  The heating and cooling valves for a large 100% outdoor air-handling unit (AHU) were operating off of a common pneumatic air feed to the valve actuators.  The pneumatic line developed an air leak that caused the actuators to not open and close correctly.

Continue reading “Example of Fault Detection and Diagnostics: Pneumatic actuator leak and Filters in Alarm”

Simultaneous heating and cooling issue

In this example we will show you how Analytika service helped to solve simultaneous heating and cooling issue.

The Air handler (AHU) discharge air temperature (DAT) setpoint was overridden from the sequence of operation and reduced from 55˚F to 51˚F. As a result, the cooling coil valve was opening to maintain the lower DAT and consequently requiring additional heating downstream. This resulted in additional heating and cooling costs. Continue reading “Simultaneous heating and cooling issue”