Regency 4720 - Mounting and Transformer Installation Procedures

26
Regency
®
Model 4720 Control/Communicator Installation Manual (P/N 150476, Rev. A) Revised 10/98
6.3.2 Installing the Transformer
The main wiring diagram and Figure 6.3.2a show the connection of shielded 2-conductor cable and
the Model 7890 Transient-Surge Protector to the Model 9220 UL Listed Class II Power Transformer
(16.5 V
AC
, 40 VA). Both models are included with the Model 4720. The transformer should be
plugged into a 120-V
AC
, 60-Hz continuous duty (unswitched) grounded outlet.
The Model 7890 Transient-Surge Protector will protectively clamp the AC output of the transformer,
reducing transient voltages caused by lightning and other sources. The AC power lines are the most
common source of transient/lightning damage in alarm systems. The Model 7890 consists of two (2)
bipolar transient suppressors with lugs at its connecting points.
WARNING:
The Model 9220 contains an internally fused secondary
winding.
DO NOT SHORT the secondary terminals together
when power is applied or the internal fuse will blow. Be sure
the shield conductor cannot come in contact with the AC
output screws.
CAUTION:
Make sure that the AC outlet you intend to use for the Model
9220 has a “good” connection to earth ground. This can be
done at the outlet, by using a digital voltmeter to measure the
AC voltage between the “hot” side of the outlet and neutral,
then comparing that voltage to the voltage reading made
between the “hot” side and the ground connection. The
difference between these two voltage readings should not
exceed 1 V
AC
. If these voltages are not within 1 V
AC
, the outlet
does not have an earth ground and must be grounded by
running a 14-gauge wire from the outlet to a good source of
earth ground such as a water pipe.
Note: A licensed electrician may be required to perform this
procedure.
CAUTION:
To reduce the risk of electrical shock or fire, connect directly to
a grounded (3-prong) receptacle.