In New York City, where Local Law 97 penalizes buildings for emissions over a cap, compliance tracking depends on knowing what equipment runs, and for how long. Current sensors for New York building automation confirm that equipment is drawing current, rather than simply being commanded on. Functional Devices, Inc. manufactures solid- and split-core RIB® (Relay-In-a-Box®) current sensors alongside its relay and power-supply product lines.
Why Status Feedback Matters Under Local Law 97
As of 2024, Local Law 97 now places emissions caps on New York City buildings over a certain size. Because anything emitted over this cap will result in fines from the city, many building owners are attempting to streamline their BAS. This streamlining often starts at the control layer.
In BAS, a relay is typically responsible for switching a load. However, relays do not have any inherent capability to confirm whether this switch was successful. A binary output can be commanded on while the equipment behind it fails to start; and without feedback, the BAS will log the command, not the result.
A current sensor provides additional information. Because it reads the actual current draw of the equipment itself, it can distinguish between a running motor and a motor that was commanded on but never actually started. Understanding and narrowing this gap between assumed performance and measured performance makes a significant difference for buildings working toward Local Law 97 emissions targets.
Split-Core Sensors for Retrofit Work
Many of New York City’s buildings are older, meaning that current sensors are often needed specifically for retrofit applications. Split-core models are built for this: the core opens and clamps around an existing conductor without disconnecting or re-terminating wiring, so a sensor can be added to running equipment without taking it offline.
- The RIBXGTA is a split-core adjustable current switch with a 0.75–150A sensing range, a terminal-strip connection, and a dry contact output that interfaces directly with BAS binary inputs. It covers standard motor and equipment loads in most monitoring applications.
- The RIBXGTA-ECM reads the low, variable current that electronically commutated motors (ECMs) and variable-speed pumps produce, with an adjustable trip point as low as 0.25A. It is self-powered with a solid-state output, uses a split-core clamp, and has a narrow hysteresis band to hold a clear on/off distinction without chatter as motor speed increases.
Wiring and Placing Current Sensors in a New York Retrofit
A current switch reports status to the BAS through a dry contact wired to a controller binary input. The RIBXGTA provides a terminal-strip connection that accepts #14–22 AWG wire, which lands directly on a controller input without an interposing device. The RIBXGTA-ECM is self-powered, so the sensing side needs no separate supply; it produces a solid-state contact closure when current exceeds the set threshold.
Placement affects reading quality. The sensor clamps around a single conductor of the monitored load, not the full cable bundle, since sensing the supply and return together cancels the reading. On a retrofit, that means it’s necessary to identify the correct conductor inside an existing raceway or panel before clamping. Keeping other current-carrying conductors out of the sensor’s window avoids stray coupling that can affect the apparent reading.
The environmental range also matters for equipment rooms and rooftop mechanical spaces. The RIBXGTA-ECM operates from –30°F to 140°F, which covers most indoor mechanical rooms and many semi-conditioned spaces where retrofit monitoring is needed.
A Worked Example: Fan Proving on an ECM
Consider a retrofit where a variable-speed fan on an ECM needs a proving signal for the BAS. A standard current switch can miss the distinction between the motor’s low standby draw and its running draw, because both fall at the low end of the switch’s range. With the RIBXGTA-ECM, the trip point can be set between the two. Measure the motor’s standby draw, then its running draw at the lowest speed it will operate, and set it above the highest standby current but below the lowest running current. The split-core clamp installs around the existing motor conductor without cutting wire, and the dry contact reports true run status to the BAS binary input.
Frequently Asked Questions
How do I size a current sensor for a retrofit?
Match the sensor’s range to the equipment’s running current, and confirm the trip point can be set above standby but below running draw. The RIBXGTA covers standard loads, 0.75–150A; for low, variable ECM and variable-speed loads, the RIBXGTA-ECM adjusts down to 0.25A.
Can a current sensor be installed without shutting equipment down?
Yes. A split-core sensor opens and clamps around an existing conductor without disconnecting wiring, so it can be safely installed on running equipment.
What is the difference between a current sensor and a current transformer?
A current transformer (CT) is the sensing element. A current sensor is the finished device built around a CT, adding the trip point, hysteresis, and output that let it report status to a BAS.
What is the difference between a current switch and a current transducer?
The difference is their output. A current switch gives a go/no-go result: its contact changes state when current crosses a set threshold. A current transducer outputs a proportional signal, such as 4–20mA, that tracks the actual current draw across a range. Functional Devices offers both current switches and transducers.
Should I use a split-core or solid-core current sensor?
Use a split-core sensor for retrofit work. Its core opens and clamps around an existing conductor without disconnecting wiring, so the equipment stays in service during installation. A solid-core sensor requires threading the conductor through a closed aperture, which means disconnecting the wire, so it best suits new installations or panel builds where the conductor is being run anyway.
Can current sensors help detect equipment faults?
Yes. Because a current sensor reads actual draw, a reading that drifts from a piece of equipment’s baseline can flag a developing problem before it becomes a failure. A motor that is pulling more current than its established baseline, for example, indicates that something has changed. When wired to a BAS input, a current sensor lets the system log draw over time, run-hours, and readings outside a set threshold.
Source Current Sensors for a New York Building Automation Project
Functional Devices’ split-core RIB® current sensors report actual equipment status to a retrofit BAS and can be installed without disconnecting wiring. The RIBXGTA covers standard loads; the RIBXGTA-ECM covers low, variable ECM draw. Browse the full current sensor lineup or find an authorized Functional Devices distributor in New York.