How to Protect a Power Transformer

Most transformers for household use are protected by their covers.

Household power transformers that change one level of AC voltage to another need two types of protection: physical and electrical. Housings protect the transformer from environmental and physical damage, while fuses or circuit breakers protect it from electrical damage. These protection needs vary with size, location and application of your transformer. But transformer protection also applies to keeping a safe environment for people. Consult an electrician for all transformer protection projects because federal, state or local codes may apply.

Instructions

1. 

   Inaccessible location protects commercial transformers from unauthorized access.

   Purchase an approved housing for your outdoor transformer to protect it from weather and dampness.

2. 

   Household circuit breakers or GFCIs protect transformers in appliances and electronic equipment.

   Install your transformer and housing in a safe location, away from personal or mechanical traffic such as children, neighbors, pets and lawnmowers. Install it at least 10 feet away from spas, ponds, fountains, pools or any other apparatus that uses water.

3. Keep a lock on your transformer housing to prevent access by children, pets and unauthorized users, and also to protect it from theft.

4. Protect your transformer with an appropriate fuse, circuit breaker or ground fault circuit interrupter (GFCI). This depends entirely on the type, size and location of your transformer. Consult the installation instructions for any purchased system--such as low-voltage lighting for indoor use or for pools or spas--or consult an electrician for any do-it-yourself project that requires a transformer. You must comply with codes that apply to your specific situation to protect against equipment damage, fire and personal shock.

Tips & Warnings

• You can order some transformers for outdoor use in prefabricated protective housing. Be sure to specify "outdoor" use when shopping.

• Some manufacturers add equipment, such as timers, inside a power transformer housing and then call it a power pack or a power supply. Power transformers for household use appear in appliances and electronic equipment with safety devices built in. Other than installing them in safe locations, you need not worry about protecting the transformer.

• Make sure power to a transformer is shut off before trying to install a fuse or circuit breaker.

• Never use a transformer rated as "indoor" or "outdoor" in a location for which it is not rated.

• In some arid locations, a transformer housing may require a ventilation system to prevent heat damage.

• Never attempt to modify the transformer in a manufactured appliance or electronic equipment unless you are a qualified technician.

References

• John DeDad: The Basics of Transformers; Part 1
• Malibu Lights: Transformer FAQ's
• Malibu Lights: 900 Watt Power Pack Instructions