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Old 21-01-2012, 14:55   #31
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Re: Best Inverter for the Buck

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Please review my previous post. A DPDT switch is not adequate as that implies a permanent connection of the shore safety ground to the boat ground, which is a bad idea. Use a 3 gang selector switch, or 3PDT. If this doesn't make sense to you I can elaborate.
Thanks. I do understand what you are saying. What I don't understand is how my boat is setup now with respect to ship's ground vs shore ground. The 30 Amp cord goes to an AC panel and contains hot, neutral, and ground. I'm guessing that the ground must go to the AC outlets, but not to ship's ground. Is that correct? If so, I can see where we'd have a problem. In fact, if shore power wasn't connected, the outlets would not be grounded. Are 3PDT switches readily available?

Edit: I googled and see plenty of them. Thanks again
Pete
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Old 21-01-2012, 15:20   #32
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Re: Best Inverter for the Buck

Assuming that the boat was not wired originally for an inverter, then it is likely that the safety ground coming from ashore is connected to the AC system but not to the boat's ground. But this is not a certainty - best to check. The problem is that the inverter output is referenced to the ship's ground (where else when out on the water?) so the safety ground is connected to the ship's ground, and the neutral is either connected or otherwise referenced to that ground. That means that the AC outlets' safety ground will be attached through the inverter to ship's ground, and if not disconnected when using shore power will tie the shore ground to the ship's ground. Makes sense?
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Old 21-01-2012, 15:25   #33
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Re: Best Inverter for the Buck

I wouldn't say that 30A 3PDT switches are "readily available", for instance at the local chandler or home improvement store, but they can be found. Usually they will be rotary style switches, and hence "3 gang" rather than "3PDT". The best approach is to look on the internet.
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Old 21-01-2012, 15:35   #34
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Re: Best Inverter for the Buck

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I wouldn't say that 30A 3PDT switches are "readily available", for instance at the local chandler or home improvement store, but they can be found. Usually they will be rotary style switches, and hence "3 gang" rather than "3PDT". The best approach is to look on the internet.
Thanks. I was going to wire one side of the 3PDT switch to the AC Outlet breaker of AC panel which is just 15 Amps. I noticed 3PDT switches rated at 15 and 20 Amps. In other words the switch will be selecting either shore power via the 15 Amp breaker or inverter.
Pete
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Old 21-01-2012, 15:57   #35
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Re: Best Inverter for the Buck

That sounds reasonable. However, you might consider installing an isolation transformer. If you do that then you are back to a DPDT switch because all of the AC on board (downstream of the transformer) would share the same boat ground. This is the absolute best prevention for stray current electrolysis and other safety issues resulting from wiring errors in marinas or aboard nearby boats.
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Old 21-01-2012, 16:40   #36
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Re: Best Inverter for the Buck

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That sounds reasonable. However, you might consider installing an isolation transformer. If you do that then you are back to a DPDT switch because all of the AC on board (downstream of the transformer) would share the same boat ground. This is the absolute best prevention for stray current electrolysis and other safety issues resulting from wiring errors in marinas or aboard nearby boats.
Thanks. Sounds like a winner in several respects. Electrolysis problems can be expensive to repair and a safety issue besides.
Pete
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Old 21-01-2012, 16:57   #37
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Re: Best Inverter for the Buck

Consider getting the Charles IsoG2 3.8 kVA transformer. It is very high quality, and can take either 30A 110V or 16A 220V input (also can select for output). That solves the voltage issue in much of the world. (well, really all of the world...)
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Old 21-01-2012, 17:28   #38
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Re: Best Inverter for the Buck

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Consider getting the Charles IsoG2 3.8 kVA transformer. It is very high quality, and can take either 30A 110V or 16A 220V input (also can select for output). That solves the voltage issue in much of the world. (well, really all of the world...)
Thanks. Wow, those things are expensive with prices starting at $551.
Pete
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Old 21-01-2012, 19:52   #39
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Re: Best Inverter for the Buck

I'd strongly recommend the AIMS brand of inverters and have used an AIMS1000 bought from Power Inverters and Solar Inverters for Home and Businesses The Inverter Store . I live off the grid using wind and solar for power and though my boat is essentially 12 volt however I do have AC.

The way mine is set up, I flip on the switch (using one of the red Guest switches) and that powers up my inverter. The inverter is direct wired to the AC panel so when I turn on the switch it's just as if I was at a dock plugged into 120. All my panel breakers are turned on except the battery charger one so the boat is good to go.

Since it's just the Skipper and I aboard there's no much likelihood of exceeding the specs for the AIMS1000 (peak 3000, continuous 1000 watts) .... in over a year of real world usage I've had zero problems. It runs everything that's electric (lights, powers the computer, charges cell phone, runs the lights and a small Haier AC reefer, my sewing machine) ... I've not noticed radio interference but then again I generally don't have the inverter on 24/7.

It works and the company (see link above) has good information on the website; in addition (this may come as a shock so sit down) they answer the phone. Yes, someone who knows the products actually answers the phones. What a concept!

The "problem" with the 1000 unit is the fan always runs. That costs a tiny bit of power and there is a bit of a whirls sound too. The AIMS800's fan only comes on when power is being used.
I wouldn't be concerned about having an inverter large enough to run EVERYTHING, only the one or three things you'd be running at the same time... but that's just me.

Happy shopping.
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Old 21-01-2012, 20:08   #40
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Re: Best Inverter for the Buck

Any boat built to ABYC standards should have the shorepower ground connected to the 12 volt negative bus.

A marine inverter with a transfer switch will not connect the neutral and ground internally unless the inverter is producing power. It connects when power is transferred to the inverter from shorepower. I believe a non marine inverter will have neutral and ground connected continuously.

Below is the proper way to wire an inverter (with an external transfer switch) from ABYC A-31. The grounds you will notice are connected to the vessel's negative bus. This gives a safe path for a fault. When using the inverter you will not be connected to shorepower and its safety ground.
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Old 22-01-2012, 03:26   #41
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Re: Best Inverter for the Buck

If wired as shown I would not consider the galvanic isolator as "optional". Either a galvanic isolator or isolation transformer would be required IMHO to protect the boat from the inevitable stray current (cruise long enough and you will have the problem).

As for ABYC, although I review their recommendations before doing a job I do not slavishly follow them. They have had bad recommendations in the electrical field in the past, which were clear to me at the time and which were later changed. In this case we both agree that an iso transformer is the best way to go, but also the most expensive (and heavy). Otherwise a galvanic isolator can be used. It was my impression that the ABYC has changed to require one of these two so I would be interested to know if this is the most current recommendation. I would never recommend connecting the shore ground to the boat ground without isolation, and until someone explains to me why that is not an invitation for stray current corrosion I'll stick with it. As for safety, I see no reason to not believe the shore ground to be adequate.
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Old 22-01-2012, 03:27   #42
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Re: Best Inverter for the Buck

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Originally Posted by janice142 View Post
I'd strongly recommend the AIMS brand of inverters and have used an AIMS1000 bought from Power Inverters and Solar Inverters for Home and Businesses The Inverter Store . I live off the grid using wind and solar for power and though my boat is essentially 12 volt however I do have AC.

The way mine is set up, I flip on the switch (using one of the red Guest switches) and that powers up my inverter. The inverter is direct wired to the AC panel so when I turn on the switch it's just as if I was at a dock plugged into 120. All my panel breakers are turned on except the battery charger one so the boat is good to go.

Since it's just the Skipper and I aboard there's no much likelihood of exceeding the specs for the AIMS1000 (peak 3000, continuous 1000 watts) .... in over a year of real world usage I've had zero problems. It runs everything that's electric (lights, powers the computer, charges cell phone, runs the lights and a small Haier AC reefer, my sewing machine) ... I've not noticed radio interference but then again I generally don't have the inverter on 24/7.

It works and the company (see link above) has good information on the website; in addition (this may come as a shock so sit down) they answer the phone. Yes, someone who knows the products actually answers the phones. What a concept!

The "problem" with the 1000 unit is the fan always runs. That costs a tiny bit of power and there is a bit of a whirls sound too. The AIMS800's fan only comes on when power is being used.
I wouldn't be concerned about having an inverter large enough to run EVERYTHING, only the one or three things you'd be running at the same time... but that's just me.

Happy shopping.
Thanks. I have been looking at the AIMS line of inverters especially the model PWRI150012S 1500 watt pure sine wave inverter. Is yours modified sine or pure sine? Do you happen to have the model number of the Guest switch? I'd like to see if it functions as a DPDT switch?
Pete
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Old 22-01-2012, 05:46   #43
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Re: Best Inverter for the Buck

After reviewing all the great feedback, I have concluded the following:
  • Select a standalone (without transfer switch) inverter with pure sine wave output
  • Use a 3 gang or 3PDT switch to isolate hot, neutral, and ground lines when switching between shore power and inverter. This ensures that shore ground is isolated from ship's ground whenever inverter selected. It also ensures that there is only one connection between neutral and ground in either shore or inverter position. The switch will be located such that AC outlets are connected to the common with position 1 being AC outlet breaker at AC panel and position 2 being inverter output. This ensures that inverter will never inadvertently power water heater or battery charger. It also allows switch to be sized to 15 or 20 Amps as opposed to the full 30 Amps of shore power connection.
  • Ensure neutral and ground are tied together at inverter
  • Isolate shore ground from ship's ground with isolation transformer or galvanic isolator. Given cost considerations it will likely be the latter
I would very much like to receive recommendations for standalone pure sine wave inverters, 3 gang switches and galvanic isolators.
Pete
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Old 22-01-2012, 07:02   #44
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Re: Best Inverter for the Buck

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Originally Posted by prroots View Post
Thanks. I have been looking at the AIMS line of inverters especially the model PWRI150012S 1500 watt pure sine wave inverter. Is yours modified sine or pure sine? Do you happen to have the model number of the Guest switch? I'd like to see if it functions as a DPDT switch?
Pete
Good morning Peter. The AIMS1000 is a modified sine wave unit. Specifically she
is the AIMS PWRB1000W at a delivered cost of $74 in August of 2010, and the same in September of 2011. Why two?
Okay, I messed up. The side of the unit has three plugs. From my AC panel I've got hard wired on heavy gauge wire a plug that plugs into the unit. It makes the power get to the AC panel and from there, through the boat. HOWEVER, after a year of being out there I pulled into a dock and had the "opportunity" to plug in to real power. I forgot to unplug the inverter and that's what fried it. Dumb on my part and totally my fault. I "knew better" (we hadn't put in a switch -- recommended above) to insure idiot moments wouldn't happen. THAT is still in my things to do list but I'm way smarter now, you know?

The PERKO switch I used was one of your standard battery ones... you know, the Bank 1, Bank 2, All or Off things, except this was one that simply has On and Off. It makes the inverter turn on or off. It's not a Guest.

Anyway, though pure would be right nice to have, my power usage doesn't merit the higher cost. Oh, one more thing (aside note) -- I'd heard that the AC powered electric blankets do not work on modified sine wave inverters, so I bought a 12 volt version and am delighted. I'm on Amazon (isn't everyone?) and have written a full review over there for the Comfy Cruise.
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Old 22-01-2012, 08:48   #45
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Re: Best Inverter for the Buck

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Please review my previous post. A DPDT switch is not adequate as that implies a permanent connection of the shore safety ground to the boat ground, which is a bad idea. Use a 3 gang selector switch, or 3PDT. If this doesn't make sense to you I can elaborate.
Thanks. I've located 3PDT switches rated at the required 15 Amps without problems. Note: I'm switching only the circuit feeding my AC outlets. Can you provide an example of a suitable 3 gang selector switch? I have a mental image of what you are describing, but can't seem to locate any.

Also, as a point of clarification, could one get away with a DPDT switch if one installed a galvanic isolator into the ground wire upstream of AC panel? I need to study exactly how they work.
Pete
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