Siemens UL 489 Operating Instructions Manual page 234

12.8.2.5 Wiring the Contact Blocks
The contact blocks are designated (front of cradle to rear of cradle) S50, S51, S52, and S53. Each contact block contains one "a" and one
"b" contact, with the terminal designations as shown below. Each terminal accepts a maximum of one wire, 14 AWG (or smaller), and shall
be tightened to 7 lbin (0.8 Nm).
S53
1
b
2
12.8.2.6 Installing the Contact Blocks
MOC Reliability
May cause intermittent signaling.
All four contact blocks, whether wired or not, must be installed into the MOC assembly to ensure reliable operation.
The contact blocks must be firmly seated, with the feet of the contact block latched into the MOC assembly housing. If there is damage to
the contact block assembly, a replacement contact block must be used. Replacement contact blocks may be purchased per catalog number
WLMOCSWK (includes four replacement contact block assemblies).
Contact block damage.
May cause loss of signaling.
Do not over-extend the feet of the contact block when reinstalling into the MOC assembly.
12 – 12
S52
S51
3 1 3 1
a b a b
4 2 4 2
7 mm
1/4"
S50
Attention: Four contact
blocks must be installed
for proper operation
3 1 3
a b a
4 2 4
NOTICE
NOTICE
Attention: Four contact
blocks must be installed
for proper operation
3,0 x 0,6
1/8"
0,8 Nm
7 lb-in