Frequently Asked Questions


What is a digital scroll compressor?

A digital scroll compressor is one that modulates capacity by sequencing compression cycles on and off during a 10 second period through the use of a solenoid valve and diaphram.  This allows modulation from 10-100% capacity which increases system efficiencies and improves temperature and humidity control.


What is a variable speed scroll compressor?

A variable speed scroll compressor utilizes a variable speed drive connected to the compressor to vary the speed of the compressor and it’s output.  This allows modulation from 35-75Hz, increasing system efficiency and improving temperature and humidity control.


When should I use a digital scroll compressor versus a variable speed compressor?

This is typically dictated by the system manufacturer, however digital scroll compressors are available in smaller tonnages and variable speed scroll compressors are more readily available in the larger tonnages.  Most often the system size will automatically dictate the compressor type.


What is Single Zone VAV?

A Single Zone VAV system is one in which a variable speed fan controls the amount of airflow provided to the space by modulating the fan motor speed based on the difference between the actual space temperature and the temperature setpoint.  The modulating compressor uses the temperature of the supply air leaving the unit to determine how much refrigerant flow is needed to maintain the supply air temperature setpoint.


Is Single Zone VAV A Design Requirement?

Single Zone VAV is defined as required per ASHRAE Standard 90.1-2010.  Chilled water systems with over 5 hp fan motor requirements, and DX systems over 110,00o btuh must be single zone vav.  This standard became effective January 1, 2012.  On October 19, 2011 the Department of Energy stated that by October 18, 2013 that all 50 states must meet or exceed ASHRAE Standard 90.1-2010.


What Is An Active Chilled Beam?

An Active Chilled Beam has ventilation air introduced directly into a sheet metal casing that contains hot water and/or chilled water coils.  The air passes through nozzles that creates a 4:1 induction ratio of supply air to venitlation air.  This system does not require a fan and motor in the zone and greatly reduces energy consumption and sound levels.

What is BACnet?

BACnet stands for Building Automation Controls Network.  It was developed by ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) as a means to get various networks from various manufacturers to communicate freely to give building owners the freedom to choose manufacturers.