| Author | Message | ||
| Randy Davidson (Rdavidson)
Registered Member Username: Rdavidson Post Number: 23 Registered: 7-2006 Posted From: 166.217.216.186 Rating: N/A |
This is less a question but a -- warning and need for confirmation. I stopped at RISCO in NJ to have my Aqua-Hot serviced and heating elements looked at. Since I arrived the night before I was allowed to "hook up" to their power overnight. I plugged into the 50amp socket and 'flipped her on'. My "awesome" inverters were blinking AC1 in good but would NOT sync and flip to shore power. I checked the voltage at the socket and got 122v on one leg and 124v on the other. Ok. I checked the voltage coming from my Iso Transformer and got 106v and 104v. That's why the inverters would not accept the power. My lower limit default is 108v. Um... Back to the socket and verified the 122/124v on the two legs, then checked across the two looking for 244v. It was 210v!!! What?? That explained the 106v+104v=210v. The next morning I spoke with Mark Berry (owner I think) about this surprise. "No problem. Never had a problem in 18 years." I said, "But, this won't work!" I figured you can't check the heating elements unless the inverters allow the juice to come in. We went around a few times, then "We'll handle it, no problem." (deer in headlights star). It was my opinion he did not understand my issue. As customers go, I had choices. I left right then. Afterward I had thoughts about my first time encounter with weird power. How can it happen? I figure the building was wired with 3-phase power and whomever wired the outside plug used the BLACK from one phase and the RED from another phase. Therefore, instead of being out of phase by 180 degrees the poles were out of phase by ? 120 degrees? Does this sound like it to you? And, in hindsight, I wonder now if Mark really did know about this issue and didn't want to address it. In either case, it's the 1st time I've come across strange power in 10 months of traveling. FWIW, Randy | ||
| ED Hackenbruch (Shadowman)
Registered Member Username: Shadowman Post Number: 128 Registered: 11-2003 Posted From: 70.193.199.120 Rating: N/A |
i have run into strange power situations 4 times in the last 5 1/2 years of busing. Old park, new park, friends place that he wired up for us. I just always test before i plug in. The manager at the old park told me nobody had ever had a problem with it.....but my inverter would not allow it. Said they would tell the owner about it but i would bet my bus that they never did. I won't risk thousands of dollars of electrical items on miswired outlets. It it ain't right i don't plug in. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 917 Registered: 1-2003 Posted From: 74.214.234.173  Rating: |
Three-phase "wye" power, very common in commercial buildings, is 120v phase-to-neutral, and 208v phase-to-phase. Almost every "220" or "240" volt appliance is designed to work on 208, for exactly this reason. If you have a 240-volt isolation transformer, and you are center-tapping the output to generate your 120, then, yes, if you have 208 coming in, you will see two "legs" of roughly 104 each on the transformer output. You are correct, the isolation transformer will put out "split phase" which is indistinguishable from two phases 180° apart, whereas commercial 120-volt wye power will have, on a 4-wire 120/208 connection, the two hots 120° apart. I do not understand your "red and black" comment -- this is normal for three-phase wye. It does not matter which two phases (of red, black, and blue) you choose. -Sean http://OurOdyssey.BlogSpot.com | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 872 Registered: 10-2006 Posted From: 76.216.70.120  Rating: N/A |
Sometimes its simply an area hassle. Different power co chose to deliver different voltage , there is no specific standard. Look in a Grangers catalog and you will find motors , bulbs and water heating or stove/range units for a variety of voltages. Just part of cruising. FF | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 919 Registered: 1-2003 Posted From: 74.214.234.173 Rating: |
Randy, It was late and after a long drive when I posted last night, and I left a couple of things out: I should have said that the business would have had no choice about the sort of power they made available to you. If they have 120/208 three-phase, they would have no way to turn that into 120/240 split phase. The converse is also true. 120/240 is mostly a residential voltage. There are some commercial exceptions, with campgrounds notably being among them. So there was nothing "wrong" with the outlet you used -- we plug into such outlets all the time, and even carry a variety of three-phase plugs to adapt to different three-phase outlets as needed. You will even find this 120/208 power at some campgrounds -- we've seen it at state parks as well as commercial ones. I'm quite certain that the proprietor was right when he said he had never experienced a problem, and, unless he was himself an electrician familiar with the technical differences between split phase and three-phase, he would most likely not even have understood your complaint. The vast majority of RVs and bus conversions would have had no problem with the outlet. What made it not work was something specific to your rig, which is the (extremely uncommon) 240-volt isolation transformer. It was an unusual choice to use one of these anyway -- it more or less precludes you from connecting to 120-volt sources, and it provides no real benefit. Such transformers are commonly used in boats, where they address two specific issues -- galvanic corrosion, and mating boats built for the North American grid to European and other grids or vice versa. If it was the type made for connecting to different grid voltages, it would have an adjustment to compensate for the lower voltage. Hope that makes things just a tad clearer. -Sean http://OurOdyssey.BlogSpot.com | ||
| Randy Davidson (Rdavidson)
Registered Member Username: Rdavidson Post Number: 24 Registered: 7-2006 Posted From: 209.183.32.50 Rating: |
Sean, Thanks much for the insights. I was/am clearly amazed that there are 120/208 systems out there. I thought "210" went away many moons ago. Contrary to your assumption that I am "precluded" from plugging into 120-volt systems -- for the general reader's sake -- I plug into 120-volt systems (30am, 20amp, 15am) all the time. I use a DPDT toggle switch to tell the transformer exactly what is coming in and the transformer is wired to always produce two 120 legs of 120vac power. It works perfectly and I plug into places most RV/rigs could never draw power. Combining the SW2512's with the IsoTransformer provides more flexiblity in places to plug in than any rig I've seen. Plus, I eliminate all the need for external transfer switches (much discussed on this board). You are also correct that these transformers are commonly built for boats... I got mine from Charles Marine. I thank you for making me check my electric dryer and verify that, yup, indeed it is labeled to accept 120/240 and 120/208 as input! The proprietor was still wrong to say "no problem" since he did not know I was using a transformer. He would have come to me later and said, "we have a problem". I've learned a bunch on this thread. Once again, BNO pays off. Thanks. |
