In RMK-002, the AC/DC adapter converts 24V AC from the RTU control transformer to 12V DC to power the modem. • In RMK+ Long Range, the AC/DC adapter converts 24V AC from 24VAC Xfmr Multi-Tap Primary Transformer to 12V DC to power the modem
Power IN and Power OUT:
- 24VAC at the AC IN of the adapter
- 12V DC at the DC OUT of the adapter (polarity sensitive)
Step 1: Verify power from the AC/DC adapter
In RMK-002, power from RTU transformer (common in rooftop HVAC units
In RMK+ Long Range, power from the 24VAC Xfmr MultiTap Primary Transformer
Check that the transformer is tapped correctly because the RMK’s voltage range is 21.6 to 26.4 VAC. An incorrectly tapped transformer can exceed that maximum or not reach the minimum required voltage. Using an example transformer: This transformer can accommodate 120V, 208, or 240V. (See Primary side values outlined in red on the transformer in this screenshot:
The Primary side of the transformer has 10 times as much copper as the Secondary side. (The Secondary side voltage is noted on the transformer as SEC:24V GRN-RED.)
When 240V is wired to the Primary side and divided by 10, the resulting Secondary voltage is 24V. That is correct for the RMK.
Example where maximum is exceeded:
When 240V is incorrectly tapped to 208V. Primary side has 8.6 times as much copper as the Secondary. 240V divided by 8.6 = 28V, which is too much for the RMK!
Note: Moving the (R) red connection to (O) orange on the primary would decrease the secondary to 24V.