I am shopping for a 48v DC to AC inverter. Ideally, I'd like the plugs on the inverter to be GFCI protected, but not all inverters have this feature.

This inverter is on a boat, mounted in a difficult to reach location. Appliances will not be plugged in directly, but the inverter will feed a circuit that has all GFCI projected outlets.

I realize I won't get protection from the inverter to the outlet, but aside from that, is this the same as having GFCI on the inverter plugs?

  • 1
    Welcome to Home Improvement! Could you clarify what you mean by "having GFCI on the inverter plugs"? GFCI protects by cutting power to whatever is downstream to it if something downstream has a problem. Are you asking if the GFCI outlet will protect the inverter if something goes wrong with it? – IronEagle Jun 10 '19 at 21:30
  • What make/model is the inverter you're looking at? – ThreePhaseEel Jun 11 '19 at 0:19
  • There are two models, one has GFCI the other does not. The prices are very different. No GFCI: theinverterstore.com/product/… With GFCI: donrowe.com/samlex-pst-1500-48-pure-sine-inverter-p/… – MorningCloud Jun 12 '19 at 8:53

As I understand it, the boat has an existing cord with a male end -- a shore power cord, or similar -- which feeds the AC outlets throughout the boat. You'd like to plug that cord into an inverter in order to have mains voltage supplied by the battery and inverter. The question is whether the receptacle on the inverter should be the ordinary type or the GFCI type. Did I get that right?

In my opinion GFCI exists to protect personnel, not wiring. Because the boat system already provides GFCI protection for all outlets I suggest that having GFCI protection at the source too is unnecessary. (Assuming that the boat's existing GFCI work properly with your inverter, as noted in Ed Beal's answer.)

I'd even go so far as to say GFCI in the inverter would be undesirable: as noted, the inverter will be in an inconspicuous location. If a GFCI in that spot were to trip the consequences could be inconvenient (or worse?). It could be that the inverter's GFCI might be more sensitive than the others in the boat and would trip first. A person unfamiliar with this boat's system might spend a lot of time troubleshooting to discover the multi-level GFCI protection.

  • Agreed, putting a GFCI on a GFCI is a mistake. That said, electricity around boats is nothing to trifle with! Electrical drownings are some of the most tragic and avoidable accidents, and GFCIs are quite good at preventing them. – Harper - Reinstate Monica Jun 11 '19 at 5:43
  • You are mostly correct. There will be an A/B switch for the AC circuit to select between shore power for AC or the inverter. That is mostly the same as plugging the inverter into the receptacle for the purposes of the question. The downside to the GFCI on the inverter is access, especially because it will be mounted in an out-of-the-way location. The only upside I can see is redundancy if the GFCI outlets are faulty (won't trip), is that right? – MorningCloud Jun 12 '19 at 9:04
  • With inverters they isolate the input and output in almost all cases this is part of how they provide surge or spike protection. Even a dead short won’t trip most gfci’s on the input side because of the isolation. – Ed Beal Jun 12 '19 at 13:05
  • @MorningCloud You didn't ask about ground-neutral bonding, but it's important enough to mention anyway. While configuring the A/B switch take care with this. I suppose in marine it would be the same as it is in the RV world: when the system runs on power supplied by the inverter a ground-neutral bond is needed, but when the system runs on shore/mains power in a marina the ground-neutral bond in the boat should be opened. Some inverters have the bond built in. – Greg Hill Jun 12 '19 at 17:19
  • When running with the inverter, shouldn't the inverter take care of ground-neutral bonding? Egads, I don't don't want to mess with that. – MorningCloud Jun 13 '19 at 19:59

If your house inverter is a true sine inverter it will work to have the GFCI outlets after the inverter, any imbalance in the hot neutral and they are I’ll trip just like with normal residential wiring you are used to. If the output is a modified sine wave the harmonics generated have caused problems with GFCI’s I have installed on a PV system. I did have luck with a second system back in 05? That was modified sine it did work when we tested it but I am not sure if under a heavy load the GFCI may trip like the first system did. These were the only ones the owners wanted GFCI protection many times on emergency circuits folks don’t want them to trip, I can see using them on a boat would be a good idea. Check the specifications on your inverter out put, if the graph shows a sine wave with lots of steps it is a modified sine, some of the newer ones the steps may be small enough to not cause the bad harmonics, if your inverter is pure sine it should have no problems at all.

  • Both models claim to be pure sine wave. The only difference between the two are the GFCI and price. I'd like all outlets to have GFCI protection. I didn't know if it was needed between the outlet and the device (that is, on the plug on the inverter itself). – MorningCloud Jun 12 '19 at 8:56
  • The way inverters work having a GFCI on the output is the only way to have true protection. Inverters usually have isolated input from outputs if a true UPS or uninterruptible power supply they usually convert the line voltage to a battery voltage then convert the battery voltage back to 120v the electronics create isolation and protect from spikes, when the power drops out the system draws the voltage from the battery so there is no hiccup in the output until the battery(s) voltage is depleted. If the output has a GFCI it should be fine but the input being GFCI protected is not enough. – Ed Beal Jun 12 '19 at 13:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.