Assume all units you work on are dangerous
When you inspect hundreds of units and most are safe, it is easy to assume the equipment you will be working on is safe. Don’t assume units are safe, assume the opposite. When approaching a unit, particularly one that you don’t know anything about, assume it is dangerous.
Test BEFORE you Touch
Carry a non-contact voltage detector with you at all times. Test all disconnects and units with the non-contact voltage detector BEFORE touching ANYTHING. While you may go your entire career without ever seeing an energized case or disconnect, they do occur and it only takes a few seconds to test.
All Units and Power tools SHOULD BE GROUNDED
Everything that operates on electricity should have a ground wire. The purpose of the safety ground is to provide a good path for power should electricity contact the exterior metal parts. The idea is for the ground wire to be a better path then you are. The only exceptions are double insulated tools with non-conductive cases.
You should NOT be grounded
Try to avoid grounding yourself. If at all possible, don’t lean on grounded equipment and don’t sit or stand on wet ground or pavement. The idea is to make yourself a poor path. Wearing shoes with thick rubber soles helps.
If possible, turn the power off before working on a unit
Don’t do any more live work than necessary. If you can perform the service or maintenance with the power turned off to the unit, turn the power off. Obviously this is not always possible. For example, the power must be on and operating to check the system charge.
Use only Category III or IV electric meters on HVAC Systems
That “free” meter from El Cheapo Freight is not safe to use on an air conditioning system. You have no assurance that it can withstand voltage surges. Remember, when using an electrical meter the meter quality is what separates you from the electricity you are testing – that includes the leads. They should also be rated as Category III or IV.
Always Use a Fuse Puller to Change Cartridge Fuses
Channellocks, Vise grips, and pliers are NOT fuse pullers. That bit of rubber on the grip is NOT a very good electrical insulator.
NEVER change a fuse with the circuit still energized
Removing or inserting a fuse with the circuit energized can create an arc flash. An arc flash is an electrical fireball which can hurt you even if you are not touching any energized surface.