I recently purchased a 3-light tester like you talk about in your newsletter, but I wonder what the lights actually mean. Can I use a 30-amp to 15-amp adapter for measuring my pedestal outlet? And how do I know if an outlet is safe to plug into? I’m a newbie so I have lots of questions. —Befuddled in Brooklyn
Well, I sometimes forget just how confusing this all can be, so thanks for reminding me to write about this topic. I won’t get into ALL the troubleshooting variables here, but let’s cover the basics as they relate to electrical safety.
First of all, yes, you can use a 30-amp to 15-amp adapter for this test. That’s because the RV pedestal TT-30 outlet is virtually identical to the home outlet except that it’s rated for 30 amps of current rather than the 15 or 20 amperes of a home outlet. However, a dedicated surge protector for a 30-amp TT-30 outlet would be a better unit for this test. But the light patterns are generally the same as the 15-amp versions. More on that in a future article.
To proceed you’ll need to get yourself a standard 3-light outlet tester that you can use in any home outlet. Here are a couple from Southwire. You really don’t need the GFCI version unless you want it for additional 20-amp outlet testing since 30-amp pedestals don’t require a GFCI by code. But it won’t hurt anything so go ahead and spend the extra $5 or so on a GFCI version.
You’ll see that there are three lights on the end of the outlet tester: two amber and one red. The pattern of the lights is key to understanding if the outlet is safe, but you really don’t have to know everything that’s going on inside to make a judgment. You just look for a pattern of two amber lights and no red light. When you see that you can assume that the Hot, Neutral and Ground wires are hooked up in the right places.
But if you’re curious, here’s what the other patterns mean:
Open Neutral: This means that you have no operational appliances, however, they’re actually energized with 120 volts and can be dangerous if you open up an access panel and poke around inside while the appliance is plugged in. Never assume anything is electrically safe to work on unless it’s unplugged.
Correct Wiring: This means the outlet is safe unless you have a rare miswiring condition I’ve named an RPBG (Reverse Polarity Bootleg Ground), in which case everything will operate normally but there will also be a hot-skin voltage. That’s why I suggest you also use a Non Contact Voltage Tester to confirm there’s no hot-skin voltage after plugging in.
If you want to know more about RPBG wiring and troubleshooting, I wrote an in-depth article where I introduce the concept to the electrical contracting industry. Read it here – but this is a really long and technical article, so don’t go wading in unless you’re ready for Deep Thought. Yes, the answer is 42.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.