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Old 09-04-2016, 11:58 PM   #161
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I remember that the conversation about two inverters happened, but I don't recall the exact details.. For the most part it looks pretty good. But note that with two independent switches it's possible that a person could accidentally connect shore power and one of the inverters both to the ac panel at the same time. If shore power wasn't connected then instead the male shore power plug would be sitting somewhere with an energized blade exposed.

If the two switches are connected on the schematic with a dashed line it would indicate they're mechanically operated together -- a dual-pole dual-throw (DPDT) switch rather than two independent single-pole double-throw switches. Use of a DPDT switch prevents the accidental shore power connection problems above.

Also of course the two inverters will have to support parallel operation. Though there's a faint memory in my head that maybe you were considering a two-pole ac panel with one inverter wired to each pole, and sometimes shore power feeding both poles? In that case the schematic should be modified so the red and yellow lines aren't joined just to the left of the "AC Panel" label. The DPDT switch would still be good practice.
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Old 09-05-2016, 09:49 AM   #162
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Originally Posted by family wagon View Post

Though there's a faint memory in my head that maybe you were considering a two-pole ac panel with one inverter wired to each pole, and sometimes shore power feeding both poles? In that case the schematic should be modified so the red and yellow lines aren't joined just to the left of the "AC Panel" label.
A minor correction: sometimes shore power OR 110VAC from the Gen Set feeding both poles ...

Yes, This was my intent.

One inverter circuit and circuit breaker feeds the left side of the bus, the other inverter circuit and circuit breaker feeds the right.

It seems simpler and safer somehow.

I'll correct my diagram to reflect that.

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The DPDT switch would still be good practice.
Agreed. DPDT switch on a nice CLEARLY LABELED panel (or relays) with the rest of the switches is the hot setup.
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Old 09-05-2016, 11:43 AM   #163
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Agreed. DPDT switch on a nice CLEARLY LABELED panel (or relays) with the rest of the switches is the hot setup.

Just to clarify ... I should only need ONE SPDT switch selecting between Shore Power and the GenSet and ONE DPDT switch between the inverters and the Breaker Panel.

I checked my 6500 watt genset ... the neutral and the ground are NOT bonded together in it, therefore I need no spdt switch to ground. I will re-check this before I "fire it up".


On a separate, but related matter, I am trying to come up with a DC-DC Charger (or other and posted this thread the other day:
http://www.skoolie.net/forums/f13/dc...one-14916.html

Thinking about my needs, could you suggest units that might work for me? Remember that I am on a bit of a budget.

Thanks for your help FW, I really appreciate it.
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Old 09-05-2016, 01:57 PM   #164
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I am not a sparky by trade but have had many experiences in a commercial style? I went with the KISS method?
I ran one extension cord to power all 120 whether it be Generator or shore power (100' to get the generator away from the bus for the one I have now)?
I know this don't help much but I am going out of my way to keep my starting/running bus system completely seperate from my house stuff because in my mind if I have a house power problem I can't figure out on site? then I can always crank up and go home to work on it and if I have a starting problem I can always stay/live where I am at while I work on the bus to get it on the road.
For me ?
I will keep the house anything seperate from the bus anything? That way if I have a problem with one or the other I will know it is specific to that system and the other will not impede me from using the other while I work on the issue?
My thoughts? Good luck.
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Old 09-05-2016, 04:22 PM   #165
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...
I know this don't help much but I am going out of my way to keep my starting/running bus system completely separate from my house stuff because in my mind if I have a house power problem I can't figure out on site? then I can always crank up and go home to work on it and if I have a starting problem I can always stay/live where I am at while I work on the bus to get it on the road.
And THAT is exactly what the switches are for. To separate the circuits and isolate various components. I don't see that diagnosis of a fault should be hard at all, either the genset circuit is working or it isn't; either the shore power circuit is working or it's not, etc.

Can a mechanical switch fail? Sure it can, but that shouldn't be hard to figure out either.

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For me ?
I will keep the house anything separate from the bus anything? That way if I have a problem with one or the other I will know it is specific to that system and the other will not impede me from using the other while I work on the issue?
My thoughts? Good luck.
That will work and is exactly what Family Wagon has been doing, as mentioned in the beginning of the thread. Will extension cords work? Sure they will and they are cheap too. And if its easy for you ... go right ahead, It's fine with me.

Is it "by the book" I don't think so, but then, some would argue that bringing 2 sources of power into a Breaker Panel is not exactly kosher.

BUT ... my system will be clean and neat AND a clearly labelled panel will make it easy for anybody else (like my wife) to operate if I'm not there. 2 switches. That's it. Add in a clearly marked wire diagram and it should be easy for a pro to diagnose a fault.

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My thoughts? Good luck.
And the same to you ... all the luck and blessings in the world.
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Old 09-06-2016, 12:12 PM   #166
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Just to clarify ... I should only need ONE SPDT switch selecting between Shore Power and the GenSet and ONE DPDT switch between the inverters and the Breaker Panel.
Yes, that sounds good to me.

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I checked my 6500 watt genset ... the neutral and the ground are NOT bonded together in it, therefore I need no spdt switch to ground. I will re-check this before I "fire it up".
I would disagree with this view. The ground terminal on the genset's receptacles is likely wired to the generator chassis, while the neutral terminal is probably isolated from the chassis. I suggest that the neutral and ground should be bonded together when running from generator power so that (for example) a fault inside the generator which results in line or neutral becoming connected to generator (and bus) chassis will result in prompt tripping of a breaker or GFCI. If the shore/genset SPDT switch were replaced with DPDT, the second pole could be used for switching the ground-neutral bond. The trouble is, the ground-neutral bond is also appropriate when running on inverter power..

I was going to propose swapping the order of the switches, but then realized that for your dual-inverter application it would also require one 3PDT instead of a DPDT. Here it is anyway, in case it's of use to others. Maybe the thing to do is to change the ordering of the switches. First could be the DPDT genset/inverter selector. Second could be the DPDT (3PDT) for selecting shore/local power while at the same time connecting/disconnecting the ground-neutral bond when on local power.

Quote:
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On a separate, but related matter, I am trying to come up with a DC-DC Charger (or other and posted this thread the other day:
http://www.skoolie.net/forums/f13/dc...one-14916.html
The only one I have experience with is 12V input lead acid battery charger for 12V batteries; fully isolated taper-style DC Input 12V Battery Chargers useful for charging electric golf trolley in cars from PowerStream. I used it for maintaining the deep-cycle battery on a dump trailer. Electrically it did a wonderful job. I always liked the feeling of getting to the landfill, pull the tarp off, open the doors, and start dumping while everybody else is rolling out two sets of jumper cables to run the dump trailer's pump off their truck's starting battery... Its output is limited at 8 amps, but that was perfect for the single ~80AH deep cycle battery on that trailer. This device can be paralleled.

I'll be totally honest about this product, though: its achilles' heel is vibration. It has several TO-220 package components mounted to the aluminum housing while the circuit board is slightly loose retained in some slots. It isn't much, but the vibration of the circuit board eventually fatigues the leads on the TO-220 parts and breaks them. You can imagine what the road vibration might be on a tandem-axle trailer with 12k GVW when riding empty at 4k pounds. I still mention this product though because I think vibration would not be so severe mounted in a bus as it was when mounted in a trailer. Also if one goes in aware of the vulnerability, it's literally just a few dollars to buy spare parts to keep on hand and they're easy to change. A spot of caulk or something to help hold the circuit board inside the housing also goes a long way toward extending the failure interval, as would thoughtful mounting in a vehicle that doesn't vibrate so much.

Powerstream offers a number of other models also. When I spoke with the VP of engineering there several months ago he had an in-house design that was nearly ready.. I'll check in with him on its status and post again if there's anything useful to report. (disclosure: I don't have any relationship with anybody at Powerstream; I just ended up getting connected to this guy when I called asking tough questions about the product mentioned above the last time mine vibrated to death.)

An alternative that isn't the gold-star model of efficiency, but is easy to understand and to source parts for, is to configure things so that an inverter runs off the bus engine alternator, then a normal mains-powered battery charger runs off that inverter.
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Old 09-06-2016, 01:24 PM   #167
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I would disagree with this view. The ground terminal on the genset's receptacles is likely wired to the generator chassis, while the neutral terminal is probably isolated from the chassis. I suggest that the neutral and ground should be bonded together when running from generator power so that (for example) a fault inside the generator which results in line or neutral becoming connected to generator (and bus) chassis will result in prompt tripping of a breaker or GFCI. If the shore/genset SPDT switch were replaced with DPDT, the second pole could be used for switching the ground-neutral bond. The trouble is, the ground-neutral bond is also appropriate when running on inverter power..

I was going to propose swapping the order of the switches, but then realized that for your dual-inverter application it would also require one 3PDT instead of a DPDT. Here it is anyway, in case it's of use to others. Maybe the thing to do is to change the ordering of the switches. First could be the DPDT genset/inverter selector. Second could be the DPDT (3PDT) for selecting shore/local power while at the same time connecting/disconnecting the ground-neutral bond when on local power.
Given all of this ... I guess it's simpler just to use a SPDT switch for the Neutral-Ground bond that you suggest. But I'm not sure is needed given the Genset I'm using.

BUT ... I have to admit that now I'm a bit confused. Remember, I AM NO ELECTRICIAN, but my reading seems to indicate that mixing grounds with neutrals on these mixed 110VAC 12VDC RV systems can cause problems and that they should ALWAYS be separate. That was the reason for making certain that the Neutral buss bar and the Ground in the panel should be separated.

I've read that older, larger (5000 watt+) gensets were better for use in RV's than the newer, smaller gensets (with floating neutrals) just for this ground/neutral reason. I have an old school Coleman 6250 with ZERO hours that I'm converting to dual fuel (gasoline and propane). The reason I didn't buy a new genset, other than the watt output, was the grounding/bonding difficulties. Please note that this old Powermate has its own circuit breaker.

Maybe I'm misunderstanding or have mis-tested something.

My source for this information is Sokol's Book (RV Electrical Safety) Chapter 14, Generator Bonding.

I have it on my desk and am re-reading it to try to figure this out.
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Old 09-06-2016, 03:59 PM   #168
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A solution. I think.

I re-checked my Coleman 6250. It is definitely NOT internally grounded. When I put one of my fluke leads onto (or into) the grounds and touch the other to common ... I get an OPEN.

Sokol suggests making a G-N jumper plug, using a 15 or 20 amp Edison plug in which the ground and neutral lead are bonded together with a piece of 12 or 14 gauge wire.

Put the jumper plug in when I'm using the inverters or Genset, pull it out when I'm using shore power. Make a cautionary note on the switch panel ... and label the the plug VERY clearly so it doesn’t get misused ... and attach it to the genset with a cable so it doesn’t get lost.

This all could be accomplished with a simple switch on the Genset Panel that bonds the neutral and ground wires from one of the receptacles, but the plug seems a simple enough and very positive solution.
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Old 09-06-2016, 04:07 PM   #169
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If you squint your eyes just right, his plug-in bonding jumper looks almost like a toggle switch. Mike Sokol's work is a great reference. You've probably seen this or another page like it where he proposes and explains the idea. Much of what I've learned on the topic began with his work.

For my specific case on the bus the plug-in jumper isn't so great because I'll eventually have the genset sitting in a compartment with remote start and wouldn't have any reason to be getting into there when switching to shore power. If a person were going to keep the generator portable and plug the shore power cord into the generator then the plug-in jumper is a great solution. I haven't built one yet but I intend to do so and to tie it to the generator with a short string. It'll be right there as a reminder when I plug something in to think about whether or not the jumper should also be plugged in.
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Old 09-06-2016, 04:25 PM   #170
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If you squint your eyes just right, his plug-in bonding jumper looks almost like a toggle switch.
Thank you for your patience.

My head is spinning just now, trying to keep all this straight, but you're right, that bonding plug DOES look a lot like a simple old SPST switch.

All I know about this stuff is what I've read in Sokol's book ... his posts here, RV Electrical Systems (Moeller) and YOUR diagram. I don't understand all of it just yet, but I've only been reading the books about two months.

I'll get their eventually ... but I ain't TOUCHING a wire until I have it nailed ... and can explain it to somebody else.

I's a-feared of electrickery. It WILL bite you.
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