Engineering Documentation

Appendix A – Discontinued Products
Multi-Point Unit/Digital Point Unit (MPU/DPU)
125
-3002 195 | 231
MPU Grounding
MPUs connected to a power trunk with the optional ground wire should have the
ground wire connected to the field panel ground lug in each field panel.
Fig. 155: AC Earth Ground for MPU Connected to a Power Trunk.
Metal Oxide Varistors (MOVs)
Metal Oxide Varistors (MOVs) must be used across the DO terminals when connected
to loads. MOVs are factory-installed in all FLN products.
When installing MOVs across the DO relay contacts on termination boards, keeping
the MOV leads as short as possible makes the MOV more effective at reducing spikes
from field wiring or controlled devices. Remove and reinstall any MOVs with leads
longer than 1 in. (2.5 cm). See the section Controlling Transients [➙ 23] for MOV part
numbers.
Line Voltage Receptacle
MOVs are factory-installed in the line voltage receptacle of Rev. 6 and later MPU
enclosures and Rev. 8 and later DPU enclosures.
Fig. 156: MPU/DPU Receptacle with MOVs.