– Roy’s Blog –
A Multimeter’s Purpose
Commercial door operator and gate operator techs must have a multimeter and know how to use it. A multimeter is essential to successfully troubleshoot an operator. The tester should be digital with an LCD and have measurements for volts-AC, volts-DC, and OHMs with a 20,000-ohm maximum. It should also maintain continuity with a beeper and may employ a clip-on amp meter. I do not recommend spending over $50 on a multimeter.
Operator manufacturers usually strive to source good, reliable electrical components. Like everything else, however, these components can occasionally wear out, fail, or go bad.
Common User Errors
Sometimes you can see a component has gone bad because it looks or smells burned. A burned-out component, such as a transformer, is easy to replace, but the proper course of action is to figure out why it burned out. I state this during every training seminar: “Transformers don’t burn out, they’re burned out”. This means that there is a reason why the transformer burned up, and it is up to you to figure out why.
Door operator transformers typically step down the main voltage to a lower voltage, making it less harmful to touch. The pushbuttons, safety devices, and other exterior controls may operate off this lower voltage. Most of the time, the stepped-down voltage is 24 volts AC or DC, which makes it safer to handle. The main power is known as the high voltage (or primary voltage) and will be supplied from the building main. The lower voltage is known as the secondary voltage.
Let’s keep using the common transformer as an example. If you don’t do a little detective work and find the reason why the first unit burned out, you won’t get a chance to remedy the fault, leading to a possibility of the new component burning out very quickly.
During my experience in the industry, I fielded a tech call where the tech said he had to replace the transformer 5 times within the last 5 days. He asked me, “Why did I receive so many defective transformers?” To help him out, I agreed to meet at the job site to figure out the source of the problem. It turned out that the electrician needed 24 volts to power up a set of traffic lights, and instead of installing another 24-volt power supply, he found and decided to use 24 volts on the operator transformer. The operator transformer provided an output voltage of 24 volts, but there’s a limit to the amperage a transformer can provide. The common 40VA transformer is gauged exactly to power the contactor coils, relay coils, radio receiver, and a set of photo-sensors, but not much more. This transformer was a finite generator of 24 volts. If excessive lower power is required, you can use a larger transformer (say a 50-100VA) or install a second transformer, which can power more devices without interfering with the operator circuit and the functions.
What is a Transformer?
At this point, you may be wondering what the purpose of a transformer is. A transformer is an electrical device that transfers energy from one circuit to another by using magnetic coupling with no moving parts. A transformer comprises 2 or more coupled windings and a magnetic core to concentrate magnetic flux. A changing current in one winding creates a time-varying magnetic flux in the core, which in turn induces a voltage in the other winding.
NOW IN ENGLISH
A transformer has 2 separate windings. The primary is where the high voltage enters the transformer, and the secondary produces a lower voltage (typically 24 volts AC). Let’s say that a transformer has a primary of 120 volts, and 230 volts are applied to the primary winding. That winding will burn out very quickly, become useless, and will not provide a lower voltage, which in turn kills all the inputs from outside controls.
Additional Best Practices
Your meter must have a volts-AC setting so that you can test and verify the incoming voltage. Operators will only operate on a single voltage. If your operator is not rated for the building voltage, you may be able to modify it to do so, but it would be foolish to attempt this before calling customer support for directions. For example, A 120-volt/1-phase operator can be made to work on 230 volts/1-phase if you swap out all the 120-volt components for 230-volt components. Most motors will work on 2 voltages once you configure the interior motor wires, so you do not have to change the motor. If you do not configure the wires correctly, however, the motor windings will burn out. Other electrical components, such as the motor relay, transformers, and brake solenoids, work only at one fixed voltage, so you have no choice but to swap those out.
The voltage of an operator can be found on the operator cover only. Electricians have been known to ignore the operator label and look at the motor sticker, which may say a certain voltage, and they goof up big time by ignoring the operator sticker, which displays a different voltage. Then the electrician thinks he can bring the wrong number of volts to the operator. This has happened before and leads to added costs from purchasing new components.
Finally, your meter must have an OHMS setting so that you can verify inductive fields that can be found in relay coils, transformers, solenoids, and contactor coils.
