Wiring The Touchpads; Daisy-Chaining Touchpads; Wiring The Touchpads To The Model 4720 - Regency 4720 Installation Manual

Regency ® Model 4720 Control/Communicator Installation Manual (P/N 150476, Rev. A)

Wiring the Touchpads

7.2
All touchpads require four (4) wires to operate. The 4-conductor cable can be up to 1,000 feet long. The
minimum wire gauge is 22 AWG for runs under 500 feet and 18 AWG for runs between 500 and 1,000 feet.
Wire the touchpads as shown in Table 7.2a.
Touchpad
Terminal #
1
2
3
4

Daisy-Chaining Touchpads

7.3
Homerun wiring from each touchpad back to the panel is recommended. However, daisy-chaining the
touchpad wiring is permitted within the following limitations.
When touchpads are daisy-chained, the wiring leg between the panel and the first station must conduct
extra current to supply multiple touchpads. Since the wire has some resistance, there will be a voltage drop
at the end of the wire run and this drop must be within the tolerance of the touchpad requirement. To reduce
the drop, you should use lower resistance wire; 18 AWG is recommended. For example, suppose you want
to run a common leg for 300 feet, and then branch to two (2) touchpads, the farthest of which will be an
additional 200 feet. You plan to use 18 AWG for the common leg and 22 AWG for the two (2) branches.
Here is how you would decide if this is acceptable:
Model 4660B/C/R: Active current draw: 120 mA
For the common leg:
Maximum current = 120 mA × 2 = 240 mA (× 2 touchpads)
Resistance = .0064 ohms/foot × 600 feet = 3.84 ohms (18 AWG, 300 feet × 2)
(Note that the wire length is doubled since the current must flow out and back.)
For the longest sub-branch:
Maximum current = 120 mA
Resistance = .0161 ohms/foot × 400 feet = 6.44 ohms (22 AWG, 200 feet × 2)
Voltage drop = 120 mA × 6.44 ohms = 0.77 V
Total voltage drop at farthest touchpad: 0.92 V + 0.77 V = 1.69 V
Since this is less than the 2 V maximum allowed drop, the wiring is acceptable.

Wiring the Touchpads to the Model 4720

Table 7.2a:
Description
Touchpad Ground
Touchpad Power
Data In (from 4720)
Data out (to 4720)
AWG Ohms/foot
22 .0161
18 .0064
Maximum allowed voltage drop: 2 V
4720 Terminal
19 (GND)
20 (PWR)
21 (OUT) Panel Data Output to Touchpad
22 (IN) Panel Data Input to Touchpad
Ohms/1,000 feet
16.1
6.4
29
Revised 10/98