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City of New York Department of Education

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Project info:

Efficiency Measure:
Control of thru-wall A/C units
Type:
Energy Retrofit. Owner Direct
Client:
City of NY Dept. of Education
Engineering Design:
Building Energy & Sustainability Technologies / Cortland Research
Building:
44-32 Vernon Blvd Office Building / 20 AC units
Key Results:
Units automated for temperature control (no previous T-Stat), 51% reduction in kWh, System performance tracking

DESCRIPTION

The Point of Use Network Controlled Energy (POUNCE®) Lighting Controls & Energy Management System technology was installed on the 5th floor of the 44-32 Vernon Blvd office building. Building Energy & Sustainable Technologies, Inc. (BESt Energy) completed a Turn-key Project (Design, Build and Commission) in June 2015.

The pre-existing air conditioning system on the 5th Floor of 44-32 Vernon Blvd. consisted of a central forced air HVAC system which was supplemented by twenty (20) individual Through-Wall A/C Units (120V, 208V) installed through the perimeter curtain wall. The building Central HVAC System is thermostat controlled. However, control of the twenty (20) Through-Wall A/C Units (A/C Units) was accomplished through use of a local “On/Off” switch and using the “built in thermostat” to set a “control” temperature for each A/C Unit individually. Ambient temperature throughout the space was locally controlled by employee(s)/occupant(s) who had the ability to turn On/Off individual A/C Units. At the end of each work day, employee(s)/occupant(s) were tasked with turning off the switches for the twenty (20) A/C Units.

The A/C Units are installed at approximately 8’ above the floor level. Therefore, changing of Thermostat settings required use of a ladder to physically access and modify the A/C Unit set point temperature. The A/C Unit supply fan delivers cooled “Supply Air” directly into the area and the A/C Unit Thermostat utilizes the “Return Air” temperature (8’ above floor level) to control the individual A/C Unit. The measurement of “Return Air” temperature, at a height of 8’ above floor level, results in an “overestimate” of the actual ground level ambient “Room Temperature”; i.e. hot air rises. The overestimate of ground level ambient “Room Temperature” results in “overcooling” of the space which results in both wasted energy and occupant discomfort.

POUNCE® is an integrated energy management system which has the capacity to sense, measure and record occupancy, temperature and power consumption at Point of Use. The POUNCE® devices were installed to replace existing standard electrical receptacles and switches in pre-selected locations. The POUNCE® devices communicate wirelessly via radio frequencies with the POUNCE® System Control Units (SCU).

The POUNCE® SCU serves as a control module for lighting, plug loads & HVAC systems that can also be used to record, view and analyze the system performance data. The POUNCE® control parameters are fully programmable at a Zone Level, and can be monitored and changed remotely by an authorized System Administrator. The diagnostic capabilities offered by the POUNCE® System provide the ability to detect further energy conservation opportunities in most buildings that can represent significant potential opportunities for additional energy and cost savings.

Deployment and Commissioning of the POUNCE® system established three Cooling Control Zones (North, East, South), created a “Virtual” integrated centralized temperature based HVAC Control System, enabled intelligent management of the A/C Unit building electrical loads to occur seamlessly and minimized the construction impact to building occupants during the retrofit.

The POUNCE installation resulted in a 51% reduction in electric usage as compared t o the base period. This reduction accounts for savings related to more efficient operation of the AC units only. The installation did not include lighting or plug loads.

PROJECT case study

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