Our Solution:

It was observed that the hot water pumps were cycling excessively, thereby reducing the pump lifetimes. This also resulted in excess fluctuation in the discharge air temperature (DAT) within the building’s airside systems. Another issue that was observed was with the control valves, which were found closed during the operation of circulation pumps, resulting in undesirable pressure build up in the valves. CopperTree recommended the client check the controls sequence and ensure that any manual override was changed back to follow the intended controls. An increase in the deadband of the pump operation was recommended to reduce excess pump cycling.  

CopperTree also recommended that the control valve operation and circulation pump operation have matching/interlocked control sequences. This will prevent the pressure build up and ensure that the valves will continue to operate for their expected lifetime.

Below are some of the project’s most impactful findings: 

– A circulation pump had been experiencing an average of 23 daily ON-OFF cycles. It was found that the Supply Air Temperature (SAT) was controlling poorly to the SAT setpoint as a result. A suggestion was made to increase the temperature deadband before heating is required to reduce cycles and the associated overshooting of the SAT.

–  Control valves that are responsible to allow flow back to the main line after the water passes through the heating/cooling coils remained closed during pump operation. This can lead to a buildup of pressure in the valves. This behavior was observed in 4 different valves.

– It was observed that temperature sensors for 7 of the building’s room zones were stuck reading 0°C. This caused the hot water valves to excessively attempt to heat up the rooms unnecessarily to achieve their setpoint, driven by the faulty room temperature sensor values.