Best inverter for the buck

[prroots]

I'm satisfied with the concept developed so far as exhibited above in my crude sketch and appreciative of the mostly positive contributions. I've received recommendations for everything from galvanic isolators to switches to inverters. I've learned a lot and hopefully, others have as well. At the outset I wasn't even aware that galvanic isolators existed I will definitely use the recommended switch and galvanic isolator. I'm still actively evaluating standalone pure sine wave inverters and this will be my primary focus going forward. These inverters are not marine grade and in most cases are not even designed for integration into existing AC systems. I justify this, in part, on the fact that the inverter is to be use in a non-critical application as opposed to electronics that provide navigation or communications. With this in mind, I will focus on finding reputable companies that stand behind their products and warranties. My favorite of the moment is Samlex America.
Pete

 

[Bill Roosa]

The only problem with this is when both shore power and inverter are on at the same time. The water heater and bat charger neutrals will have to have duel breakers as otherwise the neutrals will connect the two sources.
This can work but you have about 8 extra CBs over the just use a 4 pole switch solution. I think if you do the cost analysis you will find the bill of materials for your solution is more expensive. Perhaps you are reusing CBs that we don't know about. You can't beat free.

 

[mitiempo]

Bill

When the switch is on the inverter side there is no connection to the shorepower system except the common ground, the hot and neutral switched to inverter.

 

[prroots]

Bill

When the switch is on the inverter side there is no connection to the shorepower system except the common ground, the hot and neutral switched to inverter.

Very true; only the ground is tied between shore and inverter when the switch is in the inverter position and ground is isolated by that very nice galvanic isolator. Also not sure why Bill calls it a 4 pole switch. The one I intend to use by Sterling Power (as referenced above) is a DP3T (ie, double pole, 3 throw) although I only plan to use two of the throws. This one would allow for one extra source which in my case will remain unused.
Pete

 

[prroots]

I came across something interesting in the manual for the Samlex ST1500-112. This is a 1500 watt pure sine wave inverter with hardwired AC connections and transfer switch rated at 30A. Here is the quote:

When the unit is feeding the internally inverted voltage (Power Status LED is green, power from the AC input source is not available), the current carrying conductors connected to the “L” and “N” terminals of the AC output will be isolated from the metal chassis of the inverter. Hence, during this condition, when the metal chassis of the inverter is connected to the earth ground, the “N” terminal of the AC output will not be grounded (bonded) to the earth ground. Under this condition, the “N” terminal of the AC output will not be a Neutral in the true sense. Do not touch this terminal as it will be at an elevated voltage(almost half the value the AC output voltage) with respect to the metal chassis / earth ground and may produce an electrical shock when touched!

When the unit is transferring power from the AC input source (Power Source LED is orange), the grounding condition of the “N” terminal of the AC output will be the same as the condition of the “N” terminal of the AC input source. If the AC input source is the power supplied from the utility, the “N” terminal would be a Neutral in the true sense, will normally be bonded to the earth ground and will read almost 0 V with respect to the earth ground. In this case, touching this terminal will not be a shock hazard.

The second paragraph makes sense, but what about the first one? The inverter intentionally isolates neutral from ground. I understood that neutral should be connected to ground at source? BTW, the manual states that this inverter is suitable for marine use although no mention of ABYC.
Pete

 

[Maine Sail]

I came across something interesting in the manual for the Samlex ST1500-112. This is a 1500 watt pure sine wave inverter with hardwired AC connections and transfer switch rated at 30A. Here is the quote:
The second paragraph makes sense, but what about the first one? The inverter intentionally isolates neutral from ground. I understood that neutral should be connected to ground at source? BTW, the manual states that this inverter is suitable for marine use although no mention of ABYC.
Pete

This is why a "marine" type inverter should be used that meets the applicable safety standards. A marine inverter is a new "source" and therefore White & Green are tied together inside the unit.

"A1-25.5.3 All marine power inverters shall meet the applicable requirements of UL 458, Power Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles and Marine Crafts, and Supplement SA, Marine Power Converters/Inverters and Power Converter/Inverter Systems."

 

[prroots]

This is why a "marine" inverter should be used that meets the applicable safety standards. A marine inverter is a new "source" and therefore White & Green are tied together inside the unit.

Thanks. True, but I can arrange that as shown in my crude sketch on the inverter side of the switch, right? Actually, I showed the connection internal to inverter, but if the inverter doesn't take care I can add it externally. I just found it interesting that the manual specifically stated that it was suitable for marine applications.
Pete

 

[Bill Roosa]

In your diagram you do not show the return neutrals for the HW heater and battery charger, just shows the hots. So where do you attach those neutrals and not create a connection across shore power and inverter power? It can be done but my point is it will take 2 more CBs. When you add up all the CBs and switches to accomplish the task this way verses the "normal" way you will see that you have 8 more CBs. At $25 a pop where is the economy?
I recommend a 4 pole transfer switch so you can put the switch on the sources side of the AC panel and not after it. The shore power comes in and energizes 2 sets (hot and neutral) of contacts (4 poles) the first is for the AC outlets and the second is for the "shore power only" appliances. The inverter power comes in on the other side and only feeds the AC outlets contacts. The two outputs from the switch feed the AC panel. The hot and neutral busses on that row of CBs are broken into two bars, shore power only and everything else.
So all you need to do is hacksaw your AC hot and neutral busses and rearrange the CBs so all "shore power only appliances" are grouped on one end and buy a 4 pole transfer switch.

Sometimes it takes genius to see the blindingly obvious

 

[Bill Roosa]

If you use a non-marine rated inverter you MAY or MAY NOT be able to ground the neutral. While in concept it would just require taking things apart (and voiding the warranty no doubt) and connecting the neutral to the ground at the output it does not always work that way. If the inverter is designed to operate as a floating neutral (see above post on the ST-1500) then grounding it will blow a fuse. But they are cheaper. I'd recommend placing it in a well ventilated enclosure that has some sort of lock on it so little fingers can't accidentally touch it.
I would hazard that no matter how you set up one of these type of inverters if it connects to the ships ground you will have some sort of 120 volt electrolysis problem. Make sure no one is in the water the first time you turn it on and then start looking for dead fish.

I would re-state again. The codes are there for your (and others) safety not to lower the cost.

 

[Maine Sail]

Sometimes it takes genius to see the blindingly obvious

Yet you can't see the isolation of the neutrals..? The switch breaks the shore neutral from inverter when wired in that fashion because it isolates the outlet circuits black & white from the vessels AC system..

So long as the boat is NOT improperly wired, so the AC white and AC green ground are tied together on-board, the wiring diagram can work and there is isolation of the neutral. Is it a "preferred" way to wire it, no.

FWIW perhaps 98% of the boats I work on are wired so the inverter could power the entire AC panel. I have yet to have a customer who has complained of killing a bank by leaving the battery charger or water heater on when turning on the inverter. If you leave the water heater on your fist indication will be the inverter fan and pretty soon after the low voltage alarm on the inverter will sound. This does not mean the bank is dead just that you hit the low voltage threshold as you can with any high amp draw. It's pretty simple to get into the habit of killing all AC circuits before disconnecting shore power, and this is how it should be disconnected..

I find it interesting that Bill routinely argues the 1/2/BOTH is "so simple" it does not need an ACR or Echo charger to make it easier, but he then insists that leaving the H20 heater on, or the battery charger on, is so common that you need to cut buss bars apart and use a 4 pole AC transfer switch. Nothing wrong with that, but it is very similar to simplifying the 1/2/BOTH with an automatic charge distribution device, simplification on the user end but more installation and labor on the installation end..

Proots' diagram is not far off an ABYC accepted external source selection wiring diagram except that is "source" is the "outlet circuit" not the entire panel. He will need to wire carefully, and make sure the white/neutral he cuts into is actually for the outlets, and not something else, to ensure complete isolation, but it can quite easily be done.

Seems to me that if you PROPERLY disconnect from shore power, which should always include shutting off ALL AC loads before unplugging, then you turn the inverter on and then flip the OUTLET breaker to on, it is pretty simple. Most marine inverters designed for permanent installation use a remote panel to turn on. So before pressing "INVERTER ON" a quick glance at the breakers is about as simple as it gets. No more difficult than a 1/2/BOTH that "does not need an Echo or ACR for charging simplification"....

Because the rest of us are apparently not as "genius" as Bill, perhaps he could draw where the shore neutral and inverter neutral are tied together in Proots' system..?

 

[Bill Roosa]

Wiring a transfer switch

A picture is worth a thousand words

 

[Maine Sail]

A picture is worth a thousand words

But not relative to Proots' drawing which you claim will leave the neutrals somehow connected....

In your diagram you do not show the return neutrals for the HW heater and battery charger, just shows the hots. So where do you attach those neutrals and not create a connection across shore power and inverter power? It can be done but my point is it will take 2 more CBs. When you add up all the CBs and switches to accomplish the task this way verses the "normal" way you will see that you have 8 more CBs. At $25 a pop where is the economy?

His diagram breaks into the outlet circuit and:

Breaks Outlet Hot From AC Shore Side
Breaks Outlet Neutral From AC Shore Side

With the outlets isolated via the AC source selection switch there is no connection between the AC shore side and inverter side, hot or neutral, unless a wiring mistake has been made.

Please show us where what you claim is happening, is actually happening because as I see the schematic he does not need additional equipment or breakers for shore inverter isolation.....

 

[Bill Roosa]

an alternate to the 4 pole transfer switch is to use 4 CBs. Gang two (hot/neutral) together for each source. Course this does not allow you to remove power from the HWH while on inverter power.....
http://bluesea.com/category/106/88/productline/339

 

[Maine Sail]

Thanks. True, but I can arrange that as shown in my crude sketch on the inverter side of the switch, right? Actually, I showed the connection internal to inverter, but if the inverter doesn't take care I can add it externally. I just found it interesting that the manual specifically stated that it was suitable for marine applications.
Pete

There are lots of products that make false claims but it does not make them any more true. A disreputable water heater maker claims they are "marine" but they are sooooo far off NFPA & ABYC standards that it is laughable. They still claim "marine" just as many inverter and battery charger makers do when they do not meet acceptable "marine" standards..

The inverter I mentioned earlier, the Xantrex ProWatt SW series is UL458 and is true sine wave. They are quite reasonably priced. I use one on our boat and have not had any issues but it is Xantrex. I bought it because it met UL458 and was the most reasonably priced sine wave inverter that did so. Yes sometimes even I will take a gamble on the "X" brand... Ours powers dedicated outlets only...

ProWatt SW Data Sheet

ProWatt SW $342.06

 

[Bill Roosa]

Where to put the transfer switch??

Hey MS. I never said that his configuration could not work. His diagram does not show the neutrals for the HWH and battery charger. Depending on where you attached these you may or may not isolate the two sources. My comment was that it is kinda dumb to say you are saving money buying 6 (my bad I said 8 before) CB and a 2 pole transfer switch verses just buying a 4 pole switch. In fact if you are comfortable with the risk of powering your water heater with you inverter you would only need a 2 pole TS and no new CBs.
Given Pete's innovative proviclivities I figured I'd better state the solution explicitly.

 

[Bill Roosa]

oops

Dang it! After all that the switch is shown wired wrong. A thousand pardens please.
The hots are crossed
This one is correct

 

[Bill Roosa]

Most of my genius was stolen from the manual that came with the transfer switch. Course you have to know to order a 4 pole......
You guys must really think I take myself seriously. My primary concern is Pete's safety and those of his crew.

 

[mitiempo]

I don't understand the need for a 4 pole switch when all that is being switched are 2 wires from each source to one output.

And 6 circuit breakers? Why?

In Pete's situation all the inverter will power are the outlets, which are already protected by a single breaker on the current AC panel. Since the inverter/shore switch will be after the main breaker only a single pole 15 amp breaker is needed after the switch in the hot line.

The transfer switch need only be a simple 2 pole 2 source switch like the Blue Seas 9009 shown below. Pete has sourced a 3 source 2 pole switch and will ignore 1 source input. His only additional cost vs installing the transfer switch before the main panel is one 15 amp breaker.

 

[joker460]

@mitiempo

The small difference in your diagram would be that the inverter would replace the Genset. The bigger difference is that they want to make sure that if the hot water heater breaker is left on, the inverter will not be connected to it when the transfer switch is activated.

I assume that when the inverter is connected to the receptacles it has internal fusing, just in case the device plugged in shorts out.

On mine I just make sure to turn off the AC breakers that I don't want the inverter to run before throwing the transfer switch. That's the way Beneteau installed it.

 

[mitiempo]

joker

You are a bit late to this lengthy thread and that has been covered.

Pete plans to install the 2 pole transfer switch after the existing AC breaker that only goes to the outlets. He is also planning for a 15 amp breaker in the hot line.

The diagram is representative of 2 AC sources - inverter, shore, or gen - it is from Blue Seas.