Best inverter for the buck
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Be careful! When you are using shore power, neutral and ground are not connected to each other. When using an inverter, they must be connected for safety. Marine inverter systems take care of this automatically. If you plan to use a non-marine inverter, make sure it is installed properly. See http://www.google.com/url?sa=t&rct=...sg=AFQjCNEq84QR4KlS0lAjpMsxLL_IPDA0uA&cad=rja
Inverter wiring & Safety
Every time we discuss these kinds of issues with folks, especially if they come up with "...I've learned on another forum..." comments, I personally begin to care very much about the SAFETY of that person.
I think you're trying to cut corners, and would do well to do some more homework before you buy and start wiring.
Your safety is our primary concern.
Good luck.
Pete, what has occurred to me is that you may need a lot more understanding of boating system electrical info that you seem to have at hand. In addition to learning about that, you could also download some of the inverter installation manuals and start looking at the wiring diagrams.
Every time we discuss these kinds of issues with folks, especially if they come up with "...I've learned on another forum..." comments, I personally begin to care very much about the SAFETY of that person.
I think you're trying to cut corners, and would do well to do some more homework before you buy and start wiring.
Your safety is our primary concern.
Good luck.
Thanks. Actually, I've already read several user/installation manuals. I'm now very familiar with their recommendations. Actually, another thread introduced me to the issue of shore vs ship's ground when switching back and forth between shore and inverter. That was new to me and not mentioned here or in the aforementioned manuals. I'm glad to receive multiple sources of information and sort through them. It's a process which is not complete, but I'm certainly gaining on it. As mentioned, I now believe a 3PDT switch is the way to go to ensure that we always have a proper safety ground and never permit the shore ground to be tied to ship's ground which can lead to electrolysis. As an aside, also from another forum, an isolation transformer inserted into the shore power connection, will allow one to revert back to the DPDT switch and use ship's ground as the AC safety ground whether connected to shore or inverter. That's a far superior solution especially with respect to electrolysis, but again those isolation transformers are not cheap. While these forums are great, one does need to sort through all the sometimes conflicting inputs. That of course does require a technical background and a willingness to learn. Rest assured that I will not order anything until I am fully confident of what I'm doing. In the meantime, I continue to learn and hopefully will be in a position to share my results, whether good or bad, with others.
Pete
You WANT the ships ground and the AC shore power ground to be connected. This is an important safety connection.There is a device called galvanic isolator that connects to the shore power ground right after it enters the boat shore power plug. It allows current to pass but only if it is over 2-3 volts. Since the corrosion voltages are less than that --> no corrosion.
As Stu said, we value you safety and it is what you do not know that can result in unfortunate events.
West marine has a great primer on grounding in boats, AC, DC, radio, corrosion and lightning... yes Martha it can be done but you have to see the big picture.
http://www.westmarine.com/webapp/wc...catalogId=10001&page=Marine-Grounding-Systems
and some pitfalls to avoid
http://www.westmarine.com/webapp/wc...51&catalogId=10001&page=Ten-Deadly-Conditions
As Stu said, we value you safety and it is what you do not know that can result in unfortunate events.
West marine has a great primer on grounding in boats, AC, DC, radio, corrosion and lightning... yes Martha it can be done but you have to see the big picture.
http://www.westmarine.com/webapp/wc...catalogId=10001&page=Marine-Grounding-Systems
and some pitfalls to avoid
http://www.westmarine.com/webapp/wc...51&catalogId=10001&page=Ten-Deadly-Conditions
Thanks. The first West Marine link confirms what I have learned on another forum. To summarize it's best to isolate the shore ground from ship's ground to prevent electrolysis. The best (and most expensive) way is via an isolation transformer and the second best way is via a relatively inexpensive galvanic isolator. Here is a quote from that link that explains it better than I can:
I have already priced out a recommended isolation transformer, the Charles IsoG2 3.8 kVA. Here is a link to one:
http://www.marine.com/charles-isog2-transformer-38kva-3016amp-120240vac-p-76656.html
Pete
Thanks. That article does an excellent job of explaining the neutral ground connection issue. And, yes it would seem that a 3PDT switch is preferred so that when in the shore position, neutral and ground are connected on shore and when in the inverter position neutral and ground are connected at the inverter. As noted, they should be tied together at the source. If the ground were not switched (along with hot and neutral), one could have the situation where neutral was tied to ground both on shore and at inverter. Fortunately 3PDT switches are readily available at reasonable cost.
Pete
You NEVER switch the ground wire.
Check the diagram again. You only switch the hots and neutrals. The ground wire connects everything all the time no matter what position the transfer switch may be in.
Also, I'm thinking you are getting a little target locked on the electrolysis issue. most of us do not have galvanic isolators or transformers and we manage to survive. I'd only add one if I had a problem.
Check the diagram again. You only switch the hots and neutrals. The ground wire connects everything all the time no matter what position the transfer switch may be in.
Also, I'm thinking you are getting a little target locked on the electrolysis issue. most of us do not have galvanic isolators or transformers and we manage to survive. I'd only add one if I had a problem.
After reviewing all the great feedback here and elsewhere, I have concluded the following:
Pete
- 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 at 15 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
Pete
Thanks. Based upon my study to date, we should use a 3 gang switch which will switch hot, neutral, and ground to ensure that shore ground is isolated from ship's ground when not using shore power. Also, when using shore power, shore ground should not be connected directly to ship's ground; rather it should be isolated with either an isolation transformer or galvanic isolator. You are right, if safety was the only concern, however, we intend to be safe and eliminate electrolysis. When you think about it, electrolysis is also a safety concern since the ultimate result, if unchecked, is the loss of a thru-hull fitting. My philosopy is that if I'm going to all this work, might as well do the job right
Pete
Doing the Job Right is always a good idea.
1. What's a common?
2. Switches are rarely rated for 30A or 15A. Breakers are.
3. Unless you wire it specifically to do so, the issue of the inverter feeding the hw heater is moot. You have to simply say that your inverter is NOT wired to the hw heater or the charger. But then you can't wire the inverter into your entire ship-side A.C. wiring system.
4. There are BIG differences between galvanic isolators and isolation transformers. It's not an either or issue.
5. Inverters - look around, I believe you've been given that information.
6. 3 gang switches - you keep talking about it. Does someone make one? We've already told you about the "proper" transfer switch to use.
Pete, I go back to my earlier posts, and those from others. Your lack of specificity ("common"?), and trying to reinvent the wheel for inverter installations has us concerned for your safety.
Keep asking, but you may find that sooner or later, we'll start asking for a wiring diagram from you to help you out some more, since words don't seem to have gotten through to you yet.
- 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 at 15 Amps as opposed to the full 30 Amps of shore power connection.
- Isolate shore ground from ship's ground with isolation transformer or galvanic isolator. Given cost considerations it will likely be the latter
1. What's a common?
2. Switches are rarely rated for 30A or 15A. Breakers are.
3. Unless you wire it specifically to do so, the issue of the inverter feeding the hw heater is moot. You have to simply say that your inverter is NOT wired to the hw heater or the charger. But then you can't wire the inverter into your entire ship-side A.C. wiring system.
4. There are BIG differences between galvanic isolators and isolation transformers. It's not an either or issue.
5. Inverters - look around, I believe you've been given that information.
6. 3 gang switches - you keep talking about it. Does someone make one? We've already told you about the "proper" transfer switch to use.
Pete, I go back to my earlier posts, and those from others. Your lack of specificity ("common"?), and trying to reinvent the wheel for inverter installations has us concerned for your safety.
Keep asking, but you may find that sooner or later, we'll start asking for a wiring diagram from you to help you out some more, since words don't seem to have gotten through to you yet.
I too am concerned when he insist on switching the ground. this is a major safety no-no. The grounds NEVER have a switch in them.
A common is the neutral wire not a ground.
The transfer switch is a specialty item. It can also be done with 4 CBs one each for the two hots and neutrals (and the grounds is not switched) Esure you get the lock out slider that prevents both shore and inverter CBs to be on at the same time.
A common is the neutral wire not a ground.
The transfer switch is a specialty item. It can also be done with 4 CBs one each for the two hots and neutrals (and the grounds is not switched) Esure you get the lock out slider that prevents both shore and inverter CBs to be on at the same time.
Additionally, you can wire the AC panel and transfer switch so that when on shore power the WH and charger receive power and when on inverter they do not but everything else does. Course you would need a 4 pole transfer switch to accomplish this.
Lets try this tack
The reason you never want to switch the grounds is if the switch breaks you will not have safety circuit and could electrocute yourself or others.
Having the inverter and shore power grounds connected will not effect the electrolysis issues in any way what so ever. The problem with shore power is not it's ground connection to the inverter. It is with being connected to all the other boats in the marina via the ground. Having the inverter ground tied into that circuit will not matter in the lease as far as electrolysis is concerned.
Course if you do switch the grounds and forget and leave the inverter on then switch the transfer switch to shore power you wil have a floating ground on the inverter side which will allow the hot and neutral to have some voltage not associated with 120 volts AC referenced to a common ground. ie you could have 480-500 volts ac (net 120 volts AC) on the inverter which will no doubt cause some interesting effects. Now ask yourself, is the transfer switch rated for that kind of voltage or will it blow/arc and release $200 worth of the magic blue smoke?
If you don't get this you really should not be messing with AC.
The reason you never want to switch the grounds is if the switch breaks you will not have safety circuit and could electrocute yourself or others.
Having the inverter and shore power grounds connected will not effect the electrolysis issues in any way what so ever. The problem with shore power is not it's ground connection to the inverter. It is with being connected to all the other boats in the marina via the ground. Having the inverter ground tied into that circuit will not matter in the lease as far as electrolysis is concerned.
Course if you do switch the grounds and forget and leave the inverter on then switch the transfer switch to shore power you wil have a floating ground on the inverter side which will allow the hot and neutral to have some voltage not associated with 120 volts AC referenced to a common ground. ie you could have 480-500 volts ac (net 120 volts AC) on the inverter which will no doubt cause some interesting effects. Now ask yourself, is the transfer switch rated for that kind of voltage or will it blow/arc and release $200 worth of the magic blue smoke?
If you don't get this you really should not be messing with AC.
Thanks for the warnings. Unfortunately, you address the pitfalls without presenting solutions that provide for both safety and freedom from electrolysis. I am now looking into the use of a DPDT switch in combination with galvanic isolator installed in the shore ground wire. This may be a cost effective solution that avoids the possibility of switch failing. By the way, I consider electrolysis a safety issue. Please be aware that I'm not messing with AC; rather I'm climbing the learning curve; there is a difference. Sometimes experts forget that at some point in the perhaps distant past they weren't experts
Since others read these forums, I hope to be able to describe, in the not too distant future, a solution that satisfies both requirements. Pete
Pete,Thanks for the warnings. Unfortunately, you address the pitfalls without presenting solutions that provide for both safety and freedom from electrolysis. I am now looking into the use of a DPDT switch in combination with galvanic isolator installed in the shore ground wire. This may be a cost effective solution that avoids the possibility of switch failing. By the way, I consider electrolysis a safety issue. Please be aware that I'm not messing with AC; rather I'm climbing the learning curve; there is a difference. Sometimes experts forget that at some point in the perhaps distant past they weren't experts
Pete
Please don't try to cut corners on shore/inverter isolation. Sterling sells a VERY REASONABLY priced transfer switch. They do the same as the Newmar or Blue Sea switches only for a lot less money.
Sterling AC Transfer Switch $29.00
Blue Sea 9009 AC Transfer Switch
AC Transfer Switch Schematic Courtesy Blue Sea Systems
For they type of inverter you want to buy it is often easier to simply wire it to two or three dedicated "inverter outlets" and be done with it. This is what I've done on our boat. I only ever use it for running tools and charging tool & camera batteries (pure sine as I ruined a number of power tool batteries running of a modified sine inverter). Wiring in two outlets was less money than wiring in a transfer switch and re-wiring my system so the inverter was isolated from battery charger and hot water heater etc..
I generally do not recommend Xantrex but their ProWatt SW sine wave inverters are very reasonably priced. I've installed a few and not YET had an issue. If I do have an issue I consider them almost disposable at the price so no big loss.
The text book solution is:
use a 4 pole transfer switch
break the AC panel buss into WH-charger and all the other loads
use an un-switched ground wire for ALL circuits
us a galvanic isolator/isolation transformer if you think you need one between the shore power plug on the boat and the rest of the ground wire circuit.
tie the inverter ground to the inverter neutral at the inverter (should be the way it comes from the factory)
Comply with all wire sizing recommendations
Use a CGFI outlet on each AC outlet circuit. Should be the first outlet in each daisy chain.
use a 4 pole transfer switch
break the AC panel buss into WH-charger and all the other loads
use an un-switched ground wire for ALL circuits
us a galvanic isolator/isolation transformer if you think you need one between the shore power plug on the boat and the rest of the ground wire circuit.
tie the inverter ground to the inverter neutral at the inverter (should be the way it comes from the factory)
Comply with all wire sizing recommendations
Use a CGFI outlet on each AC outlet circuit. Should be the first outlet in each daisy chain.
Pete, #1 simply isn't true. You have three choices: do nothing and don't stay plugged in, get a galvanic isolator or get an isolation transformer.
#2 I look forward to seeing something new, BUT, and a big but, the answers have already been explained to you. The answer, again, is that an inverter - like an onboard generator - is a second SOURCE of A.C. power on your boat. You either wire it into your A.C. system and REQUIRE a transfer switch, or you do a standalone version. The inverter is not an electrolysis issue.
I fail to understand how you are going to come up with alternate designs for something so simple.
But, have at it, I'd love to see it. Could be fascinating.
Stay safe.
Thanks. That Sterling is a great find. On our boat it's difficult to route wires around, so I still think it will be easier to switch inverter to the existing AC outlets. Also, given the location of microwave plug it will be difficult to switch it back and forth, but I'll keep that in mind as we progress.
Pete
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