Loading refers to the size and length of tubing in a particular neon circuit operated by a given transformer. Both overloading and underloading a transformer can cause failure. Overloaded transformers provide inadequate current for the length of tubing operated. This frequently causes the GTO insulation to break down and the wiring to short-out. It can also burn out the transformer.
Underloaded transformers create excessive heat throughout the system.
Turn on the power and observe the milliammeter reading. For a typical 30mA transformer, a low reading of 15mA indicates overloading, while a high reading of 29mA indicates underloading. If the transformer is overloaded or underloaded, you have the options of either installing a different transformer or altering the tube-loading arrangement. It's a mistake to assume that the original installer necessarily observed proper loading requirements. In cases of chronic transformer failure, always consider transformer loading as a potential cause.