Honeywell W7761A Owner's Manual page 22

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
AT20A
AT40A
AT72D
AT87A
AK3310 Assembly
Attach earth ground to W7761 Device terminal 1. See Fig. 12, 13 and 14, 16 through 20.
TRANSFORMER
W7761A
CONNECT POWER TO
TERMINALS 24 AND 25
1
EARTH
GROUND
VA Rating
20
40
40
50
100
27
26
25
24
23
22
21
20
19
18
17
16
15
14
0
Fig. 11. NEMA class 2 transformer voltage output limits.
TRIAC
COMMON
TRIAC LINES
TO ACTUATORS
AND CONTACTORS
25 24 22 20
M10089
Fig. 12. Power wiring details for one Excel 10 per transformer.
EXCEL 10 W7761A INPUT/OUTPUT DEVICE
50 100 150
% OF LOAD
22
200
M993
74-2699