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Bzzzzzt
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# Posted: 7 Feb 2015 16:58
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I've had my solar set up running for about 2 years now. I have the 45W Harbor Freight panels and they charge 1 12V deep cycle battery. The original inverter that came with the solar cells crapped out almost immediately when I installed it. It might have worked 3 weeks or so, but not long. I had purchased a 750W inverter from Harbor Freight and it lasted until last June when it accidentally got wet and I had to replace it. The replacement worked from June until 3 weeks ago, the last time we were at the cabin. It worked fine then, but this time it just beeps at me and doesn't work.
So I decided enough with the cheap-o Harbor Freight inverter and I found one at Lowes that is 750W Shumaker. I plugged this one in and the first thing it did was blow the internal fuses. I obtained some new fuses and tried again. This time I put it on the battery and turned it on. Seemed to work, but my multi meter says 90VAC. I turned off the breaker on my panel and plugged in the cabin (I have a pig tail that I can either plug into the generator or the inverter. Kind of a poor man's transfer switch.) As soon I plug the pigtail in the inverter it smoked and sizzled. I'm not sure if I have a bad one, or if the Harbor Freight ones are so cheap they didn't care that I'm using a sub panel. Inside the panel the neutral and ground are bonded together but they have been the whole time and this has never been an issue before. I had to drive an hour and a half to get to Lowes but it's sort of on my way home. I plan to stop by and replace it on the way.
Anybody on here who has experience with inverters have any ideas? Just a bad one or maybe it didn't like my setup or something else?
Any help would be appreciated.
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MtnDon
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# Posted: 7 Feb 2015 17:39
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Quoting: Bzzzzzt Inside the panel the neutral and ground are bonded together....
That is the likely problem right there. Most inverters that have a receptacle built in have an internal N-G bond and will immediately release the magic smoke when DC is applied or the switch turned on. Remove the panel bond and everything should be okay. I toasted one that worked fine off my truck battery for small stuff while away from grid or generator power. Worked for years. Smoked the moment I connected it to the cabin with the service panel having a N-G bond.
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toyota_mdt_tech
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# Posted: 7 Feb 2015 18:12
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Do not bond the neutral and ground together, will smoke them every time.
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Bzzzzzt
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# Posted: 7 Feb 2015 18:50
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I suspected that might be the trouble but the other ones had worked just fine with the exact same setup. I'll replace it and remove the bonding jumper and try again.
Thanks for confirming my suspicions.
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Bzzzzzt
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# Posted: 12 Mar 2015 20:37
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I am just getting back to my cabin after the February winter weather and brought the replacement inverter. I did as you all suggested and UNbonded my neutral and ground with the new Shumaker inverter and it now works perfectly. Thanks MtnDon and Toyota for confirming my problem. I wonder why the Harbor Freight inverters worked just fine with the exact same setup but a better quality one is more persnickety?
See? Even a master electrician can learn something new. I have been thinking about branching off into some solar stuff in my business so it's good to know little things like this. Thanks guys!
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MtnDon
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# Posted: 12 Mar 2015 21:37 - Edited by: MtnDon
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Quoting: Bzzzzzt I wonder why the Harbor Freight inverters worked just fine with the exact same setup but a better quality one is more persnickety?
Want my opinion?
HF stuff is cheap junk. 
If the inverter has a plug in receptacle it is supposed to have an internal neutral-ground bond. The vast majority do, even some of the other cheap junk. I have a couple of Cobra's that do. The B&D I toasted also had an internal N-G bond. Guess how that one got toasted.
The rule is that portable inverters with receptacles, outlet,s built in are all supposed to incorporate the N-G bond.
Then there is a group on "mobile" inverters that are supposed to have an internal switching where the N-G is "made" or "broken". That would be for use in an RV or boat where some of the time the inverter supplies power from batteries and the rest of the time the RV or boat is plugged into campground/shore/grid power.
Then there are the "stationary", designed to be hard wired type of inverter that has no N-G bond as the bond will be be in the service panel the same as in a grid tied building.
So if we use a portable inverter to supply power to a electrical service panel, we need to break the service panel N-G rule. Using an inverter with a plug in receptacle to feed power to a service panel is already breaking a different NEC rule. The latest NEC version requires the AC wires from inverter to panel to be enclosed.
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Bzzzzzt
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# Posted: 12 Mar 2015 22:57
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I know that neutrals and grounds are supposed to be separate after leaving the panel but if you take a meter anywhere in the system they will show continuity. I find it interesting that to be connected together in what would be downstream of the first panel (in this case the inverter) would cause this much of an issue. I know from experience that there are a lot of older appliances that have those connected together internally. Just interesting how the theory has changed over the years.
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