Square D is the brand name for an electrical supply company that makes circuit breakers and transformers. Square D transformers use the principle of magnetic induction to transfer one level of voltage from a circuit down to another level of voltage. Electricians install square D transformers to make it so that a lower electrical voltage is then achieved to an electrical device, even though the power is coming at a higher voltage. One simple example would be an electric doorbell. When Square D transformers are installed in electrical door bells the transformer will take the incoming 100 VAC and convert it down to 12 VAC.
Electricians use Square d transformers in heating and air conditioning equipment. When replacing transformers the electricians install used transformers and other used electrical parts that they get from an electrical surplus store or a store that sells industrial electrical equipment. Installing used electrical equipment is a way to save money. The first thing to check in an air conditioning unit when it is not working right is the transformer. Electricians know how to test the voltage and then replace the transformer if it is too large or too small for the system. Some homeowners are able to make these kinds repairs on their own. However, you should always hire an electrician if you have no experience in installing Square D transformers.
The electrical rating describes the capability of Square D transformers. The maximum load rating on a Square D low voltage transformer is 1000 VA and secondary rating is a maximum of 30 volts. When installing a transformer it is important to follow the instructions from the manufacturer. There are also instructions online that tell how to install square d transformers and some website include videos showing exactly how the installation process is done. The best way to have a transformer replaced however, is to hire an experienced electrician today.