All Functional Devices' AC power supplies, stepdown transformers and isolation transformers have floating outputs. "Floating" because they are isolated from the input and have no internal connection to it. Since that is the case, when measuring the output voltage of any of those devices, ground cannot be used as the reference for that measurement; doing so in this situation will lead to erroneous readings. To accurately measure the voltage of a floating output, the meter probes should be connected directly to the output terminals.
Our AC power supply and transformer outputs provide galvanic isolation for connected equipment. Separating the input and output circuits prevents ground loops from forming. Ground loops can cause potentially damaging currents to flow in a system. It can also help to reduce noise on the line.
While the above listed devices do come from our factory with the outputs isolated, it is possible to connect the primary and secondary when it is required or desired. The diagram below shows how the primary and secondary can be connected. When connecting the primary to a source with a neutral, that neutral can be connected to the "Com" output of the transformer. It is important to make this connection properly, especially when dealing with phase-dependent applications. If the incorrect output is connected to the primary neutral, the output will be out-of-phase with the input. This can adversely affect operation. On Functional Devices Power Supplies and Transformers the primary "Neutral" or "Com" will be in phase with the secondary "Com" terminal or wire.
When installing any Functional Devices products, make sure to follow all national and local codes. If you have any questions about or interest in our products, give us a call or an email. Our support engineers are always around and happy to help. Alternatively you can contact us online by submitting the form here.
About Functional Devices, Inc.
Functional Devices, Inc., located in the United States of America, has been designing and manufacturing quality electronic devices since 1969. Our mission is to enhance lives in buildings and beyond. We do so by designing and manufacturing reliable, high-quality products for the building automation industry. Our suite of product offerings include RIB relays, current sensors, power controls, power supplies, transformers, lighting controls, and more.
We test 100% of our products, which leads to less than 1 out of every 16,000 products experiencing a failure in the field.
Simply put, we provide users of our various products confidence and peace of mind in every box.