I'm learning a lot here. To clear one thing up, I have no intention of trying to use the inverter and shore power at the same time. So not to worry. I found the bluesea.com website and plan to study it.
The boat currently has one cranking battery and one house battery. I can't help but think more batteries may be in our future. The good news is that our power requirements are normally low. We're talking small fans and phone chargers. (I won't mention the coffee maker since y'all will certainly remind me how much current they draw.)
To recap what I've learned and now know... What I want to do is possible and I have lots more research to do on how to make it happen. Refer to my original post if you can't understand why I don't feel any more knowledgeable than you think I should at this point.
I'll ask more questions as I get into the project. Thanks!
These types of inverters, I call them "
automotive type" are not intended to be hard wired to your vessels AC system. Any inverter used on a vessel should also meet Marine UL standards, specifically UL458, plus the marine supplement testing, which is referred to as
SA or UL458-SA. Most inverter only options DO NOT have marine UL rating. Also most stand alone inverters, & I currently know of none, have a built in marine wired auto-transfer switch which would make them suitable for connection to the vessels existing AC system.
The easiest and least expensive way to add a stand alone "
automotive-type" inverter to your vessel is to simply add an inverter, and fuse within 7" of house bank positive terminal, and preferably an ON/OFF battery switch as well, and just use the inverters
built in outlet or add one or more sub outlets that are tied
only to the inverter.
This keeps the inverter
isolated or installed as a
stand-alone unit from the ships AC system and becomes easier and significantly less costly to install.
If you want to wire an inverter, one that not intended for feeding the vessels AC system, it into the ships AC system, it gets more complicated, more expensive. It requires an expensive transfer switch (Kraus & Naimer style) and a very, very solid understanding of marine grounding and neutral/ground isolation & bonding in regards to shore position and inverter position.
The correct method for installing a marine inverter is to install one that is specifically designed to feed the vessels AC system adn one that has been specifically built for this type of marine use. These are almost always a marine "inverter/charger" not a
stand alone or
isolated inverter only device.. Marine I/C's break neutral/ground when it should and bonds neutral/ground when it should and they do so automatically. These I/C's are more expensive because they are specifically designed and tested to meet Marine UL 458SA safety standards. Installation of any inverter should always follow ABYC standards. AC is deadly and the vast majority of inverter installations I see out there are
NOT SAFE INSTALLATIONS..
Inverters not designed for marine use, that lack auto-transfer switches, must use a shore/inverter switch that transfers the AC connections properly.
On a small boat an
isolated or
stand alone inverter installation works best and is a
keep it simple approach. Currently I know of only one stand alone inverter that meets marine UL standards, and that is the Xantrex ProWatt series. It would still require a transfer switch if you were to wire it to the ships AC system which I strongly advise against with an "
automotive type" inverter...
If you are looking at just phone chargers, computers, small fans etc. then I would urge you to stick with 12V devices as they will be significantly more efficient charging on 12V than rather that converting from DC to AC than back to DC.. Efficiency gains can be as much as 40% improvement sticking with 12V..
12V sockets and USB insert chargers for your phones are dirt cheap these days. We charge everything aboard with the 12V system such as phones, iPads, iPods, iPhones, laptop, hand held VHF, GPS etc. etc....
Also keep in mind that inverters are energy hogs and your battery bank and charging system need to be able to support what ever inverter you choose.
Wiring & over-current protection must also be sized for the SURGE loads not just the maximum running watts. For example a 2000W inverter can pull over 4000W for a short duration when starting motors or other loads that have in-rush. Thus the wire is much larger than folks often assume it is.
A typical calculation looks like this for a
small 800W microwave when accounting for battery voltage sag and an inverter inefficiency of about 20%:
1350W / 11.8V = 114.4A X 1.20 =
137.3A
Bump that to a 2000W load and..
2000W / 11.6V = 172.4A X 1.20 =
207A
