Introduction—ASC and N2 Bus Networking and Troubleshooting Guide 7
3.
Before connecting the transformer to the ASC, connect the input
power to the primary leads of the 24 VAC transformer.
a.
Measure the voltage of each secondary transformer lead to earth
ground with the DMM in parallel with a 100K ohm 1/4-watt
resistor (Figure 3; if using double banana plug, insert plug into
DMM).
If you read 5 VDC/VAC or greater, the transformer is earth
grounded. If this is a VAV or UNT100/101, you’ll need an
isolation transformer in order to isolate the connections from earth
ground and protect system components. Wire a separate 24 VAC
to 24 VAC isolation transformer (such as the Y65) to the ASC. If
this is any other ASC, make sure the ground is on the common side
of the transformer, not on the 24 VAC side.
If you read less than 5 VDC/VAC, the circuit is properly isolated.
Usually a value less than 0.10 VDC/VAC indicates a completely
isolated circuit.
Line
Voltage
24 VAC
TRANSFM1
100K ohm
1/4-watt
DMM
100K ohm
1/4-watt
DMM
Figure 3: Testing the Transformer
b. Determine the polarity of the transformer’s leads by using a DMM
referenced to earth ground without the 100K ohm resistor.
Connect the transformer’s secondary lead with the higher voltage
potential to the 24 VAC terminal on the ASC. Connect the
transformer’s secondary lead with the lower potential to the
24 VAC Common terminal on the ASC.
4.
If the field wires are not yet connected (because you skipped Step 2),
disconnect one 24 VAC wire (or turn off AC power) and terminate the
field wires. Reconnect power.
Summary of Contents for METASYS ASC
Page 4: ...4 Introduction ASC and N2 Bus Networking and Troubleshooting Guide ...
Page 10: ...10 Introduction ASC and N2 Bus Networking and Troubleshooting Guide ...
Page 30: ...30 Introduction ASC and N2 Bus Networking and Troubleshooting Guide ...
Page 32: ...32 Introduction ASC and N2 Bus Networking and Troubleshooting Guide ...
Page 42: ...42 Introduction ASC and N2 Bus Networking and Troubleshooting Guide ...
