Advanced Pedestal Testing
More info on using the Extech CT70 outlet tester on a campground outlets
Hi Mike,
At first glance, I thought this article was only relevant to folks using a 50 amp splitter.
But after watching the Extech CT70 YouTube video and reading your description, it became clear to me that:
1. The Extech CT70 is designed to test NEMA 5-15 and 5-20 amp "Edison" outlet, not "RV" 30 or 50 amp circuits.
Primary tests include: neutral to ground voltage; hot, neutral, and ground impedance; GFCI trip time/trip current; and open or reversed wiring.
2. The Extech CT70 can also test a/c circuit under working load conditions, but only up to 20 amps since it was only designed to test common "Edison" wall plugs.
Within this limitation, additional a/c load tests include: loads of 12, 15, and 20 Amps; loaded and unloaded AC line voltage measurements; voltage drop/line impedance calculations; and peak line voltage.
3. So to test a "RV 30 or 50 amp circuit" you will need to use (or purchase) an appropriate RV adapter, knowing that for the a/c load tests the Extech CT70 load is limited to 20 amps, still a very useful test. Is this correct?
Cheers, Michael (lots of Mike's and Michael's these days!)
Hey Michael N.
You are correct, which is why I showed a 50-amp to dual 20-amp splitter with an Extech CT-70 tester. You’ll also need a 30-amp to 15-amp adapter for the TT-30.
And yes, the empirical data you gather from a 20-amp voltage sag can be extrapolated to estimate voltage drops at 30 and 50-amps. Plus this tester measures the neutral/ground bond impedance under load. That’s highly important to the pedestal being able to supply enough fault current to quickly clear a circuit breaker in the event of a line-to-chassis short-circuit.
Full article on this procedure coming soon
I’m currently creating an SOP document for campground maintenance staff on testing pedestals for proper wiring. Once it’s been published for campgrounds I’ll post it here as well.
Read the previous article below ⬇️
Let’s play safe out there… Mike (Sokol)
