Back Feeding Supplying power in the opposite direction from its usual flow Electrical circuit gets energized normally Used for emergency power or testing purposes Listed as an exception in the NEC
Reasons for Systems Testing Often required to give a simple assessment of the operation of appliances or parts of the electrical systems. Testing process will only give information as to whether certain parts of the system seem to operate correctly. Only a licensed HVAC technician or electrician can determine actual status.
Knowledge & Training You must completely understand what you are doing before you attempt to back feed electrical power. If you do not understand exactly the process involved DO NOT ATTEMPT to do an electrical systems test!
Portable Generator The alternative power source that is used to do the electrical systems testing Needs to be fused to appropriate amperage for the system you are testing Needs to provide both 120V and 240V Must typically be 5,000W-10,000W in order to deal with the surge involved in powering up a standard heat pump or AC system.
Cables & Attachments Extension Cables Heavy duty extension cable Long enough to reach the appliances to be tested Stock several different lengths Adapter/Extension Cables Used to interconnect the portable generator with the housing power circuit 240V electrical receptacle “block” Typically the stove/oven, or dryer
240V plugs are distinct from normal 120V receptacles. This is a Standard 120V Receptacle
System Testing Types Individual Appliances/Systems Plugged into the electrical system through a receptacle: refrigerators, stoves/ovens, some microwaves, washers, dryers, free standing light fixtures, etc. Different plug configurations according to the voltage they require Extension cord from the generator directly to the component
Wired Systems Appliances or system components that are not “plugged” into the circuit Permanently connected to the wiring system: dishwashers, garbage disposals, electrical HVAC components, light fixtures, ceiling fans, some smoke detectors, etc. Tested by back feeding power to the isolated power circuit, and individually testing each component
… Answer These Questions 1. Are you sure that the main power is disconnected from the power grid? 2.Has the main switch been duct-taped into the off position? 4. Have all breaker switches in the main and all subpanels been turned to off? 5. Has the “In-Progress” warning sheet been posted on the main and all subpanels?
6. Have all of your on-site personnel been grouped together and told to remain in the front yard until testing is complete? 7. Is the portable generator outside of the building in a well-ventilated area? 8. Is the generator off? 9. Are all switches in the house off and all appliances unplugged? 10. Are any external switches for the HVAC system off?
11. Is the thermostat (or other heating switches) off? 12. Is the thermostat (or other heating switches) off? 13. Can you identify which switch is for the water heater? 14. Is there any standing water in the house? 15. Are there any smells of sulfur or natural gas anywhere around the building?
16. Do you have all of your supplies (cables, adapters, etc.) ready and by the generator? 17. Is the main power disconnected and locked out? 18. IS THE MAIN POWER DISCONNECTED AND LOCKED OUT? 19. And finally...IS THE MAIN POWER DISCONNECTED AND LOCKED OUT?
Once Your Checklist Is Complete Complete your testing Consult the HUD Subcontractor Reference Manual for recommended steps Provide proper photo documentation Warning Sheet Posted Main in OFF position & duct taped All breaker switches in OFF position Generator outside Back feed plugs in receptacle and attached to generator
Your safety is paramount. If you are not comfortable with back feeding DO NOT CONTINUE. Return with someone who is comfortable OR a licensed electrician.
Keys to Remember: Follow all steps to ensure every safety measure is taken Provide photo documentation to support your results Consult the HUD Subcontractor Reference Manual for recommended Back Feeding steps If you are unsure, walk away