Engineering Documentation

Table Of Contents
Chapter 3 Field Panels
PX Series Service Boxes
125
-3002
83 | 231
Low voltage is routed from the transformer and supplies 24 Vac power at either 192
VA or 384 VA maximum. The CTLR and PS connectors are rated Class 1 power
limited and connected equipment must reside in the enclosure with the service box.
The Class 2 connector is limited to 96 VA and may also be connected to equipment
outside of the enclosure. A MOV (30V) is installed on the transformer secondary. See
the following figure for a wiring diagram.
Fig. 50: Wiring Diagram for 230V Service Box (192 VA or 384 VA).
PX Series Service Box Grounding
System Neutral () must be continuous throughout the TX-I/O bus.
System Neutral is required to be earth-grounded at a single point only.
For a PXA Service Box: Connect the green wire to the earth ground stud under the
wire cover.
For migrating with an MEC Service Box: The earth ground is installed in the
primary field panel by a single external jumper between the service box E terminal
and N terminal.
For a Third-party Transformer connect the transformer secondary neutral to the
building-approved earth ground at the terminal block.
When a separate 24Vac source is installed in any secondary field panel isolate
power using a TXA1.IBE communication module in primary and each secondary
field panel.
See the following figures for wiring information.