Honeywell W7761A User Manual
Page 22
EXCEL 10 W7761A INPUT/OUTPUT DEVICE
22
74-2699
No installation should be designed where the line loss is greater than two volts to allow for nominal operation if the
primary voltage drops to 102 Vac (120 Vac minus 15 percent).
To meet the National Electrical Manufacturers Association (NEMA) standards, a transformer must stay within the NEMA limits.
The chart in Fig. 11 shows the required limits at various loads.
With 100 percent load, the transformer secondary must supply between 23 and 25 volts to meet the NEMA standard. When a
purchased transformer meets the NEMA standard DC20-1986, the transformer voltage-regulating ability can be considered
reliable. Compliance with the NEMA standard is voluntary.
The following Honeywell transformers meet this NEMA standard:
Transformer Type
VA Rating
AT20A
20
AT40A
40
AT72D
40
AT87A
50
AK3310 Assembly
100
27
26
25
24
23
22
21
20
19
18
17
16
15
14
0
50
100
150
% OF LOAD
SECONDARY VOLTAGE
200
M993
Fig. 11. NEMA class 2 transformer voltage output limits.
Attach earth ground to W7761 Device terminal 1. See Fig. 12, 13 and 14, 16 through 20.
M10089
CONNECT POWER TO `
TERMINALS 24 AND 25
TRIAC LINES`
TO ACTUATORS`
AND CONTACTORS
TRANSFORMER
W7761A
EARTH`
GROUND
20
22
24
25
1
TRIAC`
COMMON
Fig. 12. Power wiring details for one Excel 10 per transformer.