I'm trying to investigate a shore power isolation transformer installation requirements. We only have problems tripping the new power posts at one marina/port we tyically visit. I've checked isolation between the ground and the neutrals and have over 200,000 Ohms, which is 25 times what the new pedistals "should" trip at. Since we so far only have problems at one port it isn't on my urgent need list, but would like to find out what would be required. The hardware costs seem all over, but I can't see anywhere in the engine room that one could be located that would not be a major PITA for engine/transmission/exhaust access. If anyone has an isolation transformer in their 42/43/46, can you tell me which one you have and where it is located? Any photo would also be helpful. Thanks
Why not try to fix the problem instead ? You must have an appliance or pump or charger or inverter which bonds G to N.
I found and fixed issues before where there was a continuity between ground and neutral. The DVM says there is no continuity between ground and either neutral. ??
Unless my math is wrong: The new shore power pedestal trip limit is 30 mili amps, .030Amp. At 240V that is a resistance of 8000 ohms. Any resistance above that should not allow sufficient current for the pedestal to trip. 200,000 ohms is 25 times higher isolation/lower current than the pedestal can detect.
This doesn’t directly answer your question, but if you want an excuse to get another tool you could grab an earth leakage clamp meter. These measure current at lower levels than typical clamp meters. Looks like the fluke is around $1k but there’s several “lesser” brands for around $300, such as a megger dcm305e. That way you can measure any current leakage directly and determine if that one pedestal is tripping erroneously or if it’s actually seeing 30 mA
Do you mean that all other pedestals do NOT have an RCD that trips as soon as it detects a 30mA leakage? In Europe that is mandatory - in fact, any decent boat has that also in the electrical panel, protecting the whole AC onboard circuit not only on shore power, but also when running on genset. If you have AC leakage in the circuit, it's definitely better to fix that, as Pascal suggested. And the only way is looking for the culprit, armed with the clamp meter that Incoming mentioned. Measuring resistance with a plain vanilla multimeter doesn't help.
Greg, not to answer your question but I am also dealing with the same issue on the new shore power pedestals at certain marinas around the Bay. I've been trying to find an electrical contractor around the Kent Island area but to no avail.
Years ago when all this GFI stuff started on new/rebuilt docks, GFI service breakers and their specifications were rather thin in details and precision. Batches of breakers were too sensitive. Are there other slips at this marina? Another close by marina? Convincing a marina to change out a breaker, that seems to work well, is a tall request.
Thru the years troubleshoot boats with GFI issues, we discovered a few things. Here are just some examples of where my hair and blood has disappeared on. If, IF you have a problem on your ship, here are some eye-openers where your problems could be. Household 240Vac appliances still use 120Vac timers. When the old 3 pin plug is used, green is used for the timers return. On one customers fancy clothes dryer, a new 4 pin plug was installed but the white to green strap was not removed. Found a corroded neutral strip inside of a grounded breaker box. Neutral leaking to the green bonded box thru this corrosion. White & green strapping on a gen-set. Leaking connects in a wet Glendinning cord tub. Rusting Caps in A/C stations. My Fave; A bad GFI outlet. I would encourage fixing your boat vs covering it up. A properly isolated and properly grounded boat is safer than a patched boat.
Capt Ralph wins the Cupi Doll (typically he does). Doing a bunch more isolation testing it turns out that when the air freshener, which does not have a ground pin, is plugged into the galley GFCI the isolation drops to 8000 Ohm +/- 200 Ohm, right where a new pedestal will trip. I expect it is actually that it is a bad GCFI and the air freshener only part of the issue as when the galley GCFI outlet is turned on the isolation for that 120V bank drops from about 200,000 Ohm to about 80,000 Ohm. I'm sure the existing GFCI is a normal household one. Is there a special GCFI that should go in it's place that "expects" the pedestal pehavior and would not be affected by a non-grounded plug (although we are going to throw away the electric air fresheners anyway).
C team - I've been told by my boatyard the isolation transformer route is less than the labor to try to locate, and then fix/replace wiring in older boats. I did find a ground to neutral in several wire runs in our boat that are not used. I don't know where their open end is but expect the electrical tape used to cap them 30+ years ago has died. I removed them from the neutral bus, checked that nothing on the boat stopped working, capped them at the panel end and moved on.
My clamp meter claims to read below 1mA but the only place I could use it to capture a line and neutral is the split behind the show power receptecle. I can see it through the access door under the cockpit refrigerator but the only way I could reach it is removing the refrigerator unit. The connections at the panel breakers use right angle lugs so the wires run tight to the breaker body, then across the panel underneath most of the other wiring. No place there is enough room to get a clamp over just the desired cables. Would be nice if I could wire in a "problem" indicator mounted on the breaker panel as issues I have found/fixed have self generated over winter layup.
Greg, I also heard the same thing about the transformer route. Those can be very heavy, big and expensive.
Possibly what I need is to make a short chord I can plug inline at my dock with the separate wires accessible so I can check with a mA loop meter. Would just taking the ground external and L1, L2, N bundled together be a correct configuration for the loop tester? Or would testing one L-N pair at a time (with the other breaker open) be a better approach? I only have 120V at the dock, normally power just the bank to run the battery chargers and cabin lights. Could switch which bank is powered.
I have only had that problem at Chestertown Marina. And not all their pedestals trip for us. I have tied up in much newer marinas with no problem. Its the marina, not your boat.
I had my issues twice at Chesapeake Yacht Club on the West River. Chestertown Marina has had shore power issues with some of my friends' boats.
