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Crestron 

GLS-LCL

Crestron Green Light® Photocell, Closed-

L

oop 

Operations & Installation Guide

The GLS-LCL Closed-Loop Photocell responds to ambient light 
levels within an occupied space and provides an analog voltage 
proportionate to the ambient light level.

The ambient light measured is the light from any light source in the 
visible spectrum. The photocell does not distinguish between 
natural sunlight and artificial light. It contains a sensor which is 
color and spatially corrected to provide a true representation of 
changes in lighting levels that the human eye perceives.

The sensor measures the ambient light that actually falls upon it 
within a 60º cone extending downward from the sensor (refer to 

Field of View

 illustration below). This is the light that gets reflected 

to the ceiling from the walls, floor and furniture.

GLS-LCL Specifications

 

MOUNTING

NOTE:

 Care must be taken when choosing the mounting location.

It is recommended that the sensor be mounted directly above the 
work space, such as a desk, conference table or computer terminal.

Mounting location is important because the ambient light level will 
be different at different points in the room, depending on the 
location of the windows, lighting fixtures, wall colors, etc. The 
ambient light at the doorway can be much less than that at the 
windows, corners of the room, or especially on the ceiling. There-
fore, it is important to measure the ambient light level over the 
workplace.

INSTALLATION

The GLS-LCL can either be fastened onto the ceiling surface, flush 
mounted into the ceiling, or installed in a 4" (102 mm) round or 
octagonal box, depending on ceiling material and local codes.

 

1.  To fasten the photocell to the ceiling surface, attach the 

outer shell provided to the ceiling at the desired location 
using two #4 screws and appropriate anchor hardware, 
where necessary. For concealed wiring, access to the 
space above the ceiling is required, as well as a hole in the 
ceiling above the photocell to connect the wires from the 
optional GLS-SIM or other Crestron interface device.

DESCRIPTION

Crestron Electronics, Inc.

 

 

Operations & Installation Guide - DOC. 6773D

15 Volvo Drive   Rockleigh, NJ 07647 

(2023020)

Tel: 888.CRESTRON 

10.11

Fax: 201.767.7576  

Specifications subject to 

www.crestron.com change 

without 

notice.

SPECIFICATION

DETAILS

Power Consumption

Field of View Coverage

Output

1W (42mA @ 24VDC)

60° Cone

0 - 10VDC (0 - 70 footcandles)

Recommended Mounting Location

Directly above work space

60

°

Field of View

Further Inquiries

If you cannot locate specific information or have questions after reviewing this guide, please take advantage of 
Crestron's award winning customer service team by calling Crestron at 1-888-CRESTRON [1-888-273-7876]. For 
assistance in your region, please refer to the Crestron Web site (www.crestron.com) for a listing of Crestron 
worldwide offices.

You can also log onto the online help section of the Crestron Web site (www.crestron.com/onlinehelp) to ask 
questions about Crestron products. First-time users will need to establish a user account to fully benefit from all 
available features.

Future Updates

As Crestron improves functions, adds new features and extends the capabilities of the GLS-LOL units, additional 
information may be made available as manual updates. These updates are solely electronic and serve as 
intermediary supplements prior to the release of a complete technical documentation revision.

Check the Crestron Web site periodically for manual update availability and its relevance. Updates are identified as 
an “Addendum” in the Download column.

• 

To be installed and/or used in accordance with appropriate electrical codes and regulations.

• 

If you are unsure about any part of these instructions, consult a qualified electrician.

WARNING: 

To avoid fire, shock, or death; turn off power at circuit breaker or fuse and test that power is off before 

wiring!

CAUTION: 

Insufficient power can lead to unpredictable results or damage to the equipment. Please use the 

Crestron Power Calculator to help calculate how much power is needed for the system 
(www.crestron.com/calculators). 

 

NOTES: 

Observe the following:

FCC Compliance Statement

This device complies with Part 15 of the FCC Rules. Operation is subject to the following conditions:

1. This device may not cause harmful interference, and
2. This device must accept any interference received, including interference that may cause undesired operation.

When wiring the Cresnet

®

 network, consider the following:

• 

Use Crestron Certified Wire.

•  Use Crestron power supplies for Crestron equipment.

• 

Provide sufficient power to the system.

Network Wiring

Preparing and Connecting Wires

Strip the ends of the wires approximately 1/2 inch (13 mm). Use care to avoid nicking the 
conductors. Twist together the ends of the wires that share a connection and tin the 
twisted connection. Apply solder only to the ends of the twisted wires. Avoid tinning too 
far up the wires or the end becomes brittle. The label on the rear of the dimmer contains 
a gauge for wire stripping. 

Light Level Testing

Before installing the photocell, verify the daylight levels on a sunny day at the proposed 
location of the photocell. With the lights switched off, use a light meter to read the daylight 
level. Orient the light meter in the same direction the photocell will view. The light levels 
under sunny conditions must be at least 35 fc. If the light levels are less, you should select 
another location or reorient the photocell

.

SETUP

This product is Listed to applicable 
UL Standards and requirements by 
Underwriters Laboratories Inc.

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