Johnson Controls METASYS ASC, Networking And Troubleshooting Manual

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20 Introduction—ASC and N2 Bus Networking and Troubleshooting Guide
This procedure allows you to test for proper voltage and polarity of the
following components:
●
RS232-to-N2 Bus converter (MM-CVT101) [Steps 1 and 2]
●
Companion Panel/LTD’s RS-485 N2 Bus converter [Steps 1 and 2]
●
ASC N2 Bus [Step 3]
●
N2 Bus wiring [Step 4]
Follow the steps specific to your installation.
1. If you have a Companion PC Version, remove the 25-pin RS-232
connection from the MM-CVT101 converter. This removes the
fluctuating voltage due to communications and allows you to read the
DC bias voltage. Disconnect the N2 Bus wires. Wire the transformer
to the MM-CVT101 and plug into a 120 VAC source.
If you have a Companion Panel/LTD Version, disconnect the N2 Bus
wires from the Panel/LTD. Wire 24 VAC to the Panel/LTD.
2. Connect the DMM (without a 100K ohm resistor installed) across the
N2+ and REF inputs on the N2 terminal block (Figure 10). Write
down the DC voltage reading. Repeat for N2– and REF, then for
N2+ and N2–. Compare the voltages you read on the DMM to the
following values:
N2+ to REF = +2.45 to 2.98 VDC
N2– to REF = +2.06 to 2.54 VDC
N2+ to N2– = +0.36 to 0.92 VDC
If your readings are not approximately within the ranges listed above,
the N2 EOL device jumpers are probably set incorrectly. For the
PC Version, ensure that pins 1 and 2 on both W1 and W2 of the
MM-CVT101 are jumpered (EOL=In). For the Panel/LTD Version,
pins 1 and 2 on both W2 and W4 of the Panel/LTD circuit board must
be jumpered (EOL=In). If not, jumper them and repeat the DMM
readings. If the voltages read are still not close to those above, and,
after connecting the ASCs to the N2 Bus, the ASCs are still not
communicating, replace the MM-CVT101 or Companion Panel/LTD.
If your readings are approximately within the ranges listed above, the
N2 EOL device jumpers are set correctly. Go on to Step 3.
N2 Bus
Installation
Steps