Many 24v control voltage issues on BOTH commercial and residential systems are caused by not correctly setting up the transformer. Problems can be immediate or may surface may years later. Symptoms may include: low control voltage (24v), unit won’t do anything, contactor not pulling in, not being able to program thermostat, and erratic cooling, heating, or fan operation. When installing any system, one must check primary voltage at the transformer. If voltage is 228v or above, leave primary voltage tap on 240v. If voltage is lower then 228v, move primary voltage tap to 208v.
FIELD POWER SUPPLY — All units except 208/230v units are factory wired for the voltage shown on the nameplate. If the 208/230v unit is to be connected to a 208v power supply, the control transformer must be rewired by removing the wire from the 230v connection and moving it to the 208v connection on the primary side of the transformer.