Small inverter & crossover switch

[Mistroma]

I usually run small 230V items from a little inverter and that works well enough. As always, the number of appliances grows each year (tv, laptops, hair tongs and misc. bits & pieces). Not enough to merit a serious inverter but it is messy running wires around the saloon from inverter to each device.

I'm considering fitting a small inverter 300W should be plenty & not too inefficient at low loads. The first thing I thought of was:

1) Mount the inverter close to the house batteries (probably near the mains charger) and take a fused feed from the battery switch panel and fit an On/Off switch nearby.
2) Feed the Inverer output back up near the shore power socket in aft. locker.
3) Fit a 3-way (can't find a 2-way model) crossover switch beside the shore power socket to switch between shore & inverter.

That sounds OK but I'd need to be careful to avoid turning the small inverter on with a large load (charger, water heater etc.). I'm pretty careful, think that most inverters have overload protection and would probably also fit a trip to limit 12V side to 30A. I rarely use more than 200W so could probably live with that . But I can fine tune the trip size depending on typical use and startup surges.

Questions:
1) Any problems I've not considered (likely as I've not given it much thought)?
2) Does anyone have a wiring diagram for a 2009 42DS? Mine is on the boat 1000miles away and I opened my electronic copy to find that it doesn't include the wiring diagrams.
3) Do you know where the shunt is fitted? My Webasto heater power draw doesn't show on the panel (so Jeanneau didn't wire it as expected). I'd like to wire the inverter so that the drain would show on the panel.

Having thought about the shunt a little more, I suspect it may be fitted behind the panel at the chart table. The Scheiber meter often display quite a low voltage when drawing 8-10A when my SmartGuage says battery Voltage is fine. That tells me that the shunt is probalby remote from the batteries and that Jeanneau wiring is undersized (surprise). I will be interesting to see if anyone agrees. The drop can be around 0.6V and the Scheiber unit alarms when batteries are fine.

[Don Reaves]

I would recommend connecting the inverter between the electrical panel and the electrical outlets only. This would prevent the inverter from trying to supply current to the high-power items like the water heater.

You may be very careful and not need this type of protection. But remember, someday you'll want to sell the boat, and the new owners might not be as careful as you are. And of course, there are always guests...

Just an opinion, of course.

Don

[Mistroma]

Good point, I think I see what you mean.

1) Put Inverter in aft cabin next to batteries (low V drop on 12V side)
2) Run 230V forward to panel in saloon
3) Move 230V panel feed for sockets to 3-Way Input 1
on saloon bulkhead
4) Connect feed from inverter to 3-Way Input 2
5) Connect 3-Way Output back to original supply connection for sockets

That would leave the 3-Way switch in the saloon somewhere next to the panel. Makes sense.

I'll keep my original safety measures as well in case anyone plugs a kettle in (a lot less likely than flipping the water heater on but possible).

Inverter will cutout on overload if sustained draw of around 360-390W. It also has an internal 40A fuse on 12V supply and I was going to fit a trip set slightly lower than that (35A).

Sounding better now. I'm still trying to get a simpler crossover switch as I don't really need a 3-Way.

[Mistroma]

Just thought about the suggested change. I'd see 230V on the panel gauge with the original plan and 3-way would be visible when connecting shore power. The modification would probably make it easier to leave the inverter feeding the sockets. I think that would make it more likely that I'd plug in a kettle when on shore power but sockets left on inverter.

I can imagine seeing 203V suddenly come up on meter as power connected to shore and forgetting to switch over the sockets.

I might still go with plan "A" as I'd notice power on panel prior to connecting to shore and also see the position of the changeover ever time I took the cable out to connect to shore.

Thanks again for the suggestion, I've plenty of time to weigh up the pros & cons. before installing the kit.

[Xantia]

On our 2011 SO42DS the 1500W inverter is factory fitted but I think the changeover switch was fitted by the dealer because it's a bit out of character, ie. almost normal and logical. It switches after the 230V section of the panel and is wired to only go to the outlets, not to the water heater or battery charger. My suggestion is to add your own shore/inverter switch at the inlet side of the outlets breaker on the panel.

I also added a main switch to the inverter to disconnect it completely when not needed. On the left hand battery switch panel at the foot of the aft berth is an unused position for a shunt switch between the house and engine batteries. I had to order the switch from Jeanneau (45 euros), paint and relabel it. Extending the cables from the 150A breaker was pretty straightforward.

It's neat and not too inconvenient. You could put your inverter under the bed and don't forget the breaker too.

Cheers, Ian

[rxc]

One other thought. I fried my Cristec battery charger this year because I left it powered on when I turned on my Prosine inverter, and they both ran together for quite a while. I had this happen before, but caught it in a few seconds. This time I didn't realize what had happened, and the Cristec died. I already have a switch and a relay that physically disconnect the inverter from both the AC and DC connections when the red key is removed, but I am going to install another relay to disconnect the input to the battery charger whenever the inverter is powered up.

I already have a 2-way switch to control whether shore power or the generator supply the boat. But my AC system is pretty complicated, having both 110v and 220v feeds, and an isolation transformer, so a 3-way switch that included the inverter would not have been the best solution for me.

Sometimes I think about going back to sailing dinghies....

[Mistroma]

Nov 26, 2012 20:20:23 GMT Xantia said:

On our 2011 SO42DS the 1500W inverter is factory fitted but I think the changeover switch was fitted by the dealer because it's a bit out of character, ie. almost normal and logical. It switches after the 230V section of the panel and is wired to only go to the outlets, not to the water heater or battery charger. My suggestion is to add your own shore/inverter switch at the inlet side of the outlets breaker on the panel.

I also added a main switch to the inverter to disconnect it completely when not needed. On the left hand battery switch panel at the foot of the aft berth is an unused position for a shunt switch between the house and engine batteries. I had to order the switch from Jeanneau (45 euros), paint and relabel it. Extending the cables from the 150A breaker was pretty straightforward.

It's neat and not too inconvenient. You could put your inverter under the bed and don't forget the breaker too.

Cheers, Ian

Thanks, as I didn't get hold of a wiring diagram I started from scratch thinking it through from memory. I went back to the earlier suggestion about a changover switch.

I now have a 300W inverter and tested it at home with several items. It works as promised and delivers 300W, cuts out immediately on overload, has a built in 40A fuse, high/low Voltage cutouts on 12V side.

My plan ended up exactly as you suggest (great minds think alike).
1) Fit inverter it on a plinth close to charger (aft cabin as you suggest)
2) Put a 25 or 30A trip (Carling) with switch exactly where you suggest
3) Fit RCD to Inverter output (Earth connects to Shore power earth & back to Galvanic Isolator)
4) Run 230V cable to saloon behind chart table
5) Fit 3 way change over (Inv. - Off - Shore)
6) Divert original socket feed to above switch, same with feed from inverter
7) Connect switch output back to socket connection point
Trip will warn if I'm overloading the inverter (it will shutdown anyway)
Inverter internal fuse protects wiring anyway
RCD covers sockets via inverter when shore power RCD not used

Only negative seems to be that I won't see 230V on meter in panel. That means I'm less likely to spot crossover in wrong position when connecting shore power. If I've left the inverter on then I might plug in a kettle without noticing.

I don't think that this will be a big issue as the inverter will cutout or the trip will go. I'm trying to get one with a very short delay, less than the time it takes the inverter to respond. I tend to mostly use a max. of 150W but could go to 220W so accidental tripping shouldn't be a problem.

[Mistroma]

Nov 29, 2012 14:04:11 GMT rxc said:

One other thought. I fried my Cristec battery charger this year because I left it powered on when I turned on my Prosine inverter, and they both ran together for quite a while. I had this happen before, but caught it in a few seconds. This time I didn't realize what had happened, and the Cristec died. I already have a switch and a relay that physically disconnect the inverter from both the AC and DC connections when the red key is removed, but I am going to install another relay to disconnect the input to the battery charger whenever the inverter is powered up.

I already have a 2-way switch to control whether shore power or the generator supply the boat. But my AC system is pretty complicated, having both 110v and 220v feeds, and an isolation transformer, so a 3-way switch that included the inverter would not have been the best solution for me.

Sometimes I think about going back to sailing dinghies....

I started from scratch and tried to draw out the circuit from memory (just main items and approx. location). Once this was in place it became obvious that the inverter would be feeding the charger and I suspected that wouldn't be a good idea. However, I thought it would just shutdown. But now you mention it I have a vague memory of reading about someone ruining some kit in this way (might just be imagining it).

Thanks for the warning, now I know that it is a really bad idea. The more I thought about the design the more paranoid I became and that's why I went for an On-Off-On design for the switch. On-Off would be fine (break before make) but I wondered about the possibility of something eventually breaking inside the switch.

It would be nice to get hold of a wiring diagram and print a modified version before I start work. Haven't found one yet but will keep searching.

Thanks again to everyone for all the useful advice.

[rxc]

Really the best solution is to install a combination charger/inverter, like the Xantrex Freedom units. I had one on my last boat and it was wonderful, because it does the transfer automatically. Unfortunately, when you want to add an isolation transformer, a genset, and have both 110 and 220 power on the boat, it gets a bit complicated.

[Mistroma]

Dec 4, 2012 16:45:59 GMT rxc said:

Really the best solution is to install a combination charger/inverter, like the Xantrex Freedom units. I had one on my last boat and it was wonderful, because it does the transfer automatically. Unfortunately, when you want to add an isolation transformer, a genset, and have both 110 and 220 power on the boat, it gets a bit complicated.

Thanks, but I don't think it would be best for my needs. I'd be scrapping my existing 40A charger and end up with a charger with a 1-2kW inverter. It would be a very expensive way of getting a couple of hundred Watts of AC. I think I'll stick with the cheap inverter and a changeover switch.

However, I'm sure it's a good bit of kit for someone starting out to buy a charger and large capacity inverter.