GeneralAire GA51 Current Sensing Relay - Manual

Designed to interface with humidifiers and most heating and cooling systems.
It senses current rather than measuring voltage, making it more reliable. It is less expensive than using traditional flow switches,
pressure switches or other types of relays. The relay installs around the blower motor’s common lead and interface easily into the
circuitry.
The current sensing relay case is constructed from high-impact plastic. The lead wire bracket is protected by a soft sponge insert, in
order to prevent damage to the motor/blower wire and/or accidental contact with any metal.
General Filters, Inc. 43800 Grand River Ave., Novi, Michigan 48375 • Phone: (248) 476-5100
Fax (248) 349-2366 • www.generalaire.com
24-volt and 120-volt Current Sensing Relays
Installation Instructions
Common
Blower Lead
5 Amp. Min.
24 or 120 VAC.
L
O
A
D
GA50 24-volt and GA51120-volt Current Sensing Relay
General Installation Procedures
Important:
The wire lead bracket needs to carry a minimum of 5.0 amps for proper operation. If the current draw is less than 5.0 amps,
wrap the lead wire around the bracket so that it passes between the bracket and relay housing two or more times.
Caution:
Turn off all power to the furnace motor circuit and cabinet.
1. Follow the step-by-step instructions for
mounting the General Filters humidifier,
found in the humidifier installation
manual. DO NOT connect the electrical,
water supply or drain at this time.
2. Please follow these wiring instructions:
A. Turn off electrical power to the
furnace. Attach the current sensing
relay around the common lead of
the furnace blower motor. The relay
must be located at least 3” from any
transformer. Make sure, the relay’s
metal bracket does not touch any
other metal. (See detail A)
B. Use a wire nut to connect one lead
wire. Use a wire nut to connect one
lead wire from the current sensing
relay to one of the 24V wires from
the humidifier. (X) (Additional wire
length may be needed.)
C. Use a second wire nut to connect
the remaining lead wire from
the current sensing relay to the
humidistat (Y).
D. To complete the circuit, use a third
wire nut to connect the humidistat’s
second lead wire to the 24V lead
from the humidifier (Z).
3. Follow the instructions supplied with the
humidifier to complete the installation.
Model X Wiring Diagrams
120 V
GeneralAire Fan Powered Humidifier
CURRENT SENSING
RELAY
120 V 24 V
GeneralAire Bypass with Temperature
Compensating Auto Control
FURNACE BLOWER
MOTOR
COMMON LEAD
CURRENT SENSING
RELAY
METAL BRACKET
COMMON LEAD
DETAIL A
120 V 24 V
GeneralAire Bypass with manual control
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