We move around a lot and I confess - I don't always check the polarity of the outlet at the pedestal before I plug in. Maybe 50% of the time I remember to check it but I'm thinking after today, at least for a little while, I'll be more diligent.
We arrived at 16 West on the NW side of Saskatoon late this afternoon. It's a long story how we got here and its not really relevant. What is relevant is what happened when I plugged the rig in. They put us behind the office because they're pretty well full and we plugged into a 30 amp outlet on the back of the office building. Like I said I didn't bother checking the polarity on the outlet. When I plugged in the smoke came out. Of course when I checked the outlet the polarity was reversed.
As near as I can figure the reason I got smoke was because my pass through inverter bonds the neutral and ground when we're not on a shore pedestal. That means that when I plugged into the reversed outlet I was grounding out the hot lead with predictable results. The girl in the office wasn't a whole lot of help but she did call Richard, the relatively recent proprietor of this fine establishment. Richard is a pretty sharp dude and he was more interested in figuring out what the problem was than in blaming me for causing it --- don't laugh, I've been in RV parks where management would rather blame the camper than admit they've got a problem.
So I ended up with a ground pin that's a little charred on the end of my 30 amp cord and a much better attitude about checking the polarity before I plug in. And Richard ended up with a repaired pedestal and a plan to check the rest of the park for reversed plugs. I expect his electrician is going to get tuned in too because the (reversed) outlet we plugged into was installed relatively recently.
My understanding is that an inverter should only connect ground and neutral when it is inverting. When connected to shore power neutral and ground should be bonded at the panel supplying the shore power already. When using your generator ground and neutral should be bonded inside the generator.
This doesn't fix the issue that polarity was wrong on this outlet.
Yep. Always good practice. We went to a campground this weekend. I pulled out the meter and tested the 50 amp plug. It was showing 178 volts on each leg which seemed
a little high. I got a different meter which had fresh batteries and tested again at 118 volts.
You cannot always trust that the person who last worked on it knew what they were doing.
I once bought an electric dryer from Sears. It was delivered while I was at work. The kind delivery man offered to connect the 240v cord for us. When I got home, I noticed
the dryer was still sitting partially in the walkway so I pushed it back into place. When it contacted the metal vent tube, sparks flew! Yep, they had crossed a hot wire and
the safety ground wire in the connection, which was really hard to do, but they managed. So the metal case was wired to 120 volts! After several calls up the management
chain at Sears, I think 2 or 3 people lost their jobs simply due to the improper way they handled the situation. Basically they called me a liar. Said it was not possible because
their delivery people don't hook up cords to dryers. In the end, I had them bring me a new dryer and take that one away as I didn't know if it might have been damaged.
You're right Brian but at the moment when you plug into the outlet the inverter is still inverting and therefore the ground bond is still in place. A millisecond later its all different but it only takes a millisecond to let the smoke out.
Now you guys bring this up I had a PowerPal for years and never used I just gave it to Doyle last week but I do have a reverse polarity breaker and light on the RV
Quote from: bobofthenorth on August 11, 2013, 07:13:53 PM
You're right Brian but at the moment when you plug into the outlet the inverter is still inverting and therefore the ground bond is still in place. A millisecond later its all different but it only takes a millisecond to let the smoke out.
Ah. I misread and thought you meant the neutral and ground are always connected when connected to shore power.
I have one digital meter that reads a high voltage on AC when connected one way and the correct voltage if I reverse the leads. I thought a low battery was causing issues, but new battery didn't help so I quit using that meter for now.
http://www.myrv.us/electric/index.htm (http://www.myrv.us/electric/index.htm)
Good info on RV electric. Includes testing outlets.
I bought a circuit tester at a hardware store years ago that i use every time we plug in someplace new. It was about 5-6 bucks and is still about the same price, just saw one the other day somewhere. We have 30 amp so i keep it plugged into a 30 amp adapter. It has 3 lites that show you what is going on. It will show if you have an open ground, open neutral, open hot, hot/grd. reverse, hot/neu. reverse, and if everything is correct. It has a schematic on it that shows what each reading looks like if lit up. Really simple to use, even someone as electrically challanged as me can use it. ;D So far over the years it has saved me from plugging into an outlet that has one problem or another, about 6 times.
Hi All, it's not just pluging in that is risky, in some parks, brownouts or spikes can occur after your initial hookup, one parks voltage dropped below 100 volts in summer afternoon heat, not good for your air conditioner or refridgerator, in another a spike happened at sunset that melted the 30amp plug, I got a hi lo voltage protector, to buy some peace of mind, lvmci...
Quote from: Ed Hackenbruch on August 11, 2013, 09:28:53 PM
I bought a circuit tester at a hardware store years ago that i use every time we plug in someplace new. It was about 5-6 bucks and is still about the same price, just saw one the other day somewhere. We have 30 amp so i keep it plugged into a 30 amp adapter. It has 3 lites that show you what is going on. It will show if you have an open ground, open neutral, open hot, hot/grd. reverse, hot/neu. reverse, and if everything is correct. It has a schematic on it that shows what each reading looks like if lit up. Really simple to use, even someone as electrically challanged as me can use it. ;D So far over the years it has saved me from plugging into an outlet that has one problem or another, about 6 times.
Those are great for 120v hookups. Don't do much good for 220v.
Those testers don't tell you anything about the voltage, either, only the wiring configuration. You still need a meter to check for proper voltage.
I've been considering putting in a box with a double outlet connected to the shore line and having two of those testers plugged into it. Each outlet would be connected to one leg of the 220v shore line. The testers would be connected prior to my master shore line disconnect switch. Then, when I plug in, I could easily check the tester lights before switching on the master disconnect. Again, still need a meter to check for acceptable voltage range.
As soon as i plug in i go inside to turn on my fridge, and as i go by my control panel for my inverter i check to see what the voltage coming in is at.
We always turn the breaker in the pedestal off before we plug in the shore cord. Then if the out let is miswired the breaker will trip when it is turned on, instead of having the potential of burning your hand where the arcing is happening. Best practice, of course is to check the outlet for polarity and voltage BEFORE plugging in. But, we all get in a hurry at times.
Good luck and be safe, Sam
I know a few people that have autoformers to protect against low voltage. In the park that we are in right now they do not allow the use of them......they will kick you out if you do. Don't know why, haven't asked them yet about it.
I'm pretty good about tripping the breaker at the pedestal before plugging in WHEN THERE'S A BREAKER TO TRIP. Yesterday we were the last ones into the campground and the amenities were less than ideal. At a lot of the parks we stay at the breakers are "somewhere". When you trip one it usually involves at a minimum a long walk to look for the box and sometimes a trip to the office to get the key.
On the voltage front I took a couple of those cheapo RV voltage meters that are designed to plug into a 15 amp outlet and mounted them in a project box. They are wired into each leg of the 50 amp service and mounted by my Trimetric so we have a pretty easy way to monitor the incoming voltage.
Quote from: Ed Hackenbruch on August 12, 2013, 07:34:08 AM
I know a few people that have autoformers to protect against low voltage. In the park that we are in right now they do not allow the use of them......they will kick you out if you do. Don't know why, haven't asked them yet about it.
Not sure I know what an autoformer is, but I'd be curious to know why the park considers it bad to protect your expensive electronics from their potentially hazardous setup.
Craig, an autoformer just has a primary winding; the output is taken off of that winding at a point that will give the desired voltage. There is no isolation between the input and output.
The main trouble that I know of is that with low voltage from an overloaded system, the autoformer draws more amps to make up for the missing voltage.
HTH
Tom Caffrey
We are leaving early this morning before the office opens up and i never got around to asking them about it yesterday. Tom's answer makes sense to me, which is kind of scary since i am not that good at electrical theory/comprehension. :)
Quote from: pvcces on August 12, 2013, 10:59:24 PM
Craig, an autoformer just has a primary winding; the output is taken off of that winding at a point that will give the desired voltage. There is no isolation between the input and output.
The main trouble that I know of is that with low voltage from an overloaded system, the autoformer draws more amps to make up for the missing voltage.
HTH
Tom Caffrey
Thanks Tom,
I guess I could see them not wanting to allow them if they draw more current to make up for low voltage. Potentially overloading already questionable campground circuits.