A generator interlock is essential equipment when using a portable generator to power your home. The interlock allows you to backfeed power into your electrical panel through a dedicated breaker that can only be turned on if the incoming utility power is turned off. This prevents power from being applied to the grid which would present an electrocution hazard to power line workers.
The complete interlock setup consists of:
Many people install their generator power inlet box right next to their power meter. Doing so provides the fastest installation and lowest cost.
I opted to locate my generator inlet box about 65 feet away next to my grill on a covered patio. What does this accomplish?
So in my mind this was well worth the extra cost which all told was only an extra $150 in conduit & wire and a few extra supplies.
Here is a complete breakdown of expected costs.
|6 gague THHN Green, Black, Red, White wire 100 ft x 4||$ 249.98|
|Conduit, conduit hooks, screws, & solvent glue.||$ 150.00|
|SDS concrete drill bit||$ 42.99|
|Electrician Fish tape – (i ended up not needing)||$ 100.00|
|Mechanical Interlock||$ 69.95|
|Power inlet cord Generator > House||$ 100.00|
|Outdoor Power Inlet Box w/ 50 amp connector||$ 71.56|
|Electrical Permit||$ 120.00|
I did start in the same location though as most. I opted to start from the main outdoor breaker panel and work back to the patio location.
Step 1 – survey available spaces on bottom of panel making sure you find the most ideal space to add another conduit run. Mine already had 2 conduits sticking out the bottom.
Step 2 – Disconnect power and remove dead front. IF You have ANY doubts about what you are doing here STOP and get help from a LICENSED electrician or your power company. A “dead front” is the panel that covers the live component terminals to prevent you from getting shocked. Per code you can’t have any holes in it that are not “filled” so exercise caution when removing blank spots from your dead front.
Reminder…As a homeowner you still need to comply with all local and federal laws regarding your installation. In many locations this type of project requires an electrical permit by the “AHJ” or “Authority Having Jurisdiction.” This will help make sure you are doing everything right and safe.
If you ever have a major insurance claim or liability issue with your home please know that it is very likely that a forensic investigation will occur to determine if the root cause was due to negligence which is not covered in most situations.
Note that almost everything manufactured has date codes stamped on them including wire and conduits. In most cases with electrical work it is fairly easy to determine if work that required a permit was not permitted.
I spent some time under the house in the crawl space determining where my new hole would appear before starting to drill. You don’t want to accidentally drill into a wire, drain, water pipe, gas line, or some structural component holding your house up!
Step 3 – If your power will be in another location than next to the distribution panel, drill any holes needed for conduit travel from point “A” to point “B.”
I used a 1.5” core drill to cut through both brick and cinder block. Supposedly a 1-3/8” hole is big enough for 1” schedule 40 PVC conduit. I wanted a little “wiggle room” just in case. It turns out the smaller hole would have worked ok. A little caulk will seal any gaps.
Step 4 – run & connect conduit paths from point “A” to point “B.”
Dry fit pvc assemblies before gluing together.
Step 5 – install your manual interlock. align the dead front carefully to make sure it will actually work. If you are off slightly it can cause the unit to not work as intended defeating the purpose of your project.
The ground bus i added (small aluminum block) was complete overkill. But from an engineering standpoint i wanted this to be safe. In the event a wire came undone, in theory the wire could electrify the box and shock someone. Now everything metal is grounded to the same potential.
Use cable ties to strap the breakers together to make sure they stay in place and secure!
Last step – put the dead front back on and call the inspector then test!