Calling all 'crats, techno, electro, intellectual, regarding inverters

As you also have a generator...

Didn't realise you also had a generator. In that case, you might look at getting a multiway changeover switch which allows you to select either shorepower, generator or inverter as the source of your AC. Index Marine list one (ref C3302) on here.
 
Re: One solution...

To be honest, we had decided to fit the inverter with a switch in the live 12v feed cable and another switch to connect it to the 240v circuit on board. We already have the ''shore-off-generator switch'', which failed this summer, and I got Richard to strip and repair it, so I didn't want to have to go and buy another.

You have confirmed our plan, so thank you for all the help. /forums/images/graemlins/grin.gif
 
Re: One solution...

Becky

To answer your original question........ /forums/images/graemlins/smile.gif

If you wire the output of the inverter into the ships 220/240 volt circuit permanently you will produce at least one loud, short, sharp bang. It may or may not be followed by smoke ( highly probable ) and fire ( very likely )

The posters that have suggested a changeover switch are right.

PS Be sure to specify or purchase a 'contact break before make' switch ( most are but its worth checking ) otherwise above result will be duplicated!

I have rigged a relay ( sealed unit ) so that if shore power is connected then all else is automatically disconnected.
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inver

Right, that's sorted then. Two switches and a fuse (big).

Oh! and not forgetting the warning light(s). /forums/images/graemlins/wink.gif
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inver

As regards the mains voltage circuitry it is vital that the inverter and the shore power are not on line together. I am surprised that the inverter instructions are not clear on this issue. If you want to be completely safe do not even connect the inverter to the mains wiring in the boat. Use an entirely separate set of wiring with sockets clearly marked "Inverter" and plug your appliances in to them or in to the regular sockets as required. If you must connect the inverter to the existing mains wiring then you need a two way isolator switch which disconnects either the shore power or the inverter, and cannot physically allow both to be connected.
A simple and safe alternative is to wire the output from the inverter to a connector which can only be plugged in to the shore power input connector when the shore power cable is removed.
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inverters

I'm qualified as an Incorporated Engineer and one of my careers was as "Machine-Load-Control-And-Automation-Systems Technician" at British Leyland Longbridge. I was accepted by the EETPU as a Skilled Electrician but now this crazy government tells me I can't do a bit of wiring in my own house!!!! (The infamous Part P building regs, courtesy of the ODPM. Its still OK for me to wire up a factory though!)
Your inverter will go bang if you try to run it in parallel with shore power. You need a change-over switch but these are usually big and clumsy ironclad things. For the very modest amount of power that you are using a 15amp double pole double throw toggle switch will do. These have six pins. The output to the yacht wiring goes from the middle two pins and the inputs are the end pairs of pins. Using relays (they are called contactors when switching mains) is another method but they are liable to produce an annoying hum.
As to these inverters guzzling power. I have a 1000 watt model and have successfully run a 1000 watt electric fire from a car battery (briefly). The inverter makes a lot of beeping (low battery alarm) but with the engine running it is OK. Big cars now have big alternators and 70 amps is now entry-level. The polyvee belts can transmit a lot of power so driving 100 amp or 120 amp alternators is not a problem. During prolonged power cuts when trees brought down the power lines I used my car and inverter to power a 650 watt microwave oven - it worked a treat!
One other point, these inverters will not run in parallel with one another as they cannot synchronise their outputs. There are some very expensive American inverters that will do this but unless you've won the lottery they are just too dear.
My 1000 watt inverter has driven a 1050 watt circular saw OK and a 950 watt Kango hammer (not at the same time). IT WILL NOT WORK POWER TOOLS WITHH VARIABLE SPEED DRIVES. To do this you must have a sine wave and this is where the rotary converters are still king.
By the way when using a variable speed drill you really need proper mains. If a portable generator is used nasty voltage spikes will occur as the "chopper" (thyristor switch) takes gulps of current. These spikes will destroy the speed controller. To prevent this happening run an ORDINARY light bulb from the generator (100 watts is good, 60 will do). Now when the chopper chops, the spikes will be absorbed by the bulb. Not rocket science but it could save you a few shillings. Good luck with your projects.
ELECTRICITY IS DANGEROUS. PORTABLE GENERATORS, INVERTERS, AND ROTARY CONVERTERS CAN ALL KILL JUST LIKE THE MAINS AT HOME. Be careful and if you are not sure how to do it get someone who is an expert. I cannot be held liable if you make mistakes. Best regards from David
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inverters

I've read it, but many won't


Chuck in a few return keys once in a while to break up the text? It would make it much easier to read
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inverters

Failing switch problems: - It could be the damp salty air but it could be inductive loads. If you have any items with large coils in them (motors) then they will usually produce an incredible voltage spike on switch-off. This doesn't do the switch or motor any good at all. It is possible to buy Voltage Dependent Resistors from firms such as Maplin Electronics or Farnell. Choose a 275 volt AC device. With mains spiking prevented it is amazing how long things last (Sony TV bought in 1987 has never nedded any repairs!)
 
Re: One other solution...

... is the one we use - which is the invertor is mounted near the batteries and you can connect them up through a switch...

The 240v end runs to a 16amp female connector that just plugs into the same place as the shore power (or generator if I had one - but I have a gas toaster as well ... unlike some!)

No switches - and if it fails it is quick and easy to isolate and sort out!
 
Re: One other solution...

Hi becky. It is quite amusing to look at all the posts when I get up in the morning to check the forum. Regarding your problem I can see why you would buy a big inverter cos they are relatively cheap and yes it will handle overloads.
I am not absolutely sure the mains fed into the inverter would melt it but I wouldn't risk it either.
Now the bad news. As I understand it square wave inverters are not so good at driving induction motors. As in refrigerators and proably your water maker. Motors with brushes are fine. You may find that the motor on the water amker gets hot on the inverter due to ineficiencies from the high frequyency components of the square wave. i would be pleased to hear any comment on this. The best trick would be to compare the DC input to the inverter driving the water maker in watts to the rating of the water maker and allow another 20% for inverter inefficiency. I suspect you may find something closer to 100% difference. good luck...... olewill
 
Re: One other solution...

Hi OleWill

Depends on how squarewave the inverter is, they are not naturally bad.

The good "quasi" square wave ones I have not had a problem with driving anything common with (which has been most things including power tools, tv's, radio transcievers, computers, laser printers, recharging things such as PDA's, notebooks, cameras, etc, etc) and are efficient.

The only thing I have discovered that does not like our own "quasi" square wave inverter is a 600 watt solid state high frequency linear amplifier for radio transmitting but I think that is related to internal protection mechanisms in the amplifier (as you likely know the protection in largish solid state rf amps can be quite touchy and a special case unlikely to ever be in the experience of more than a very few).

I can imagine though that el cheapo really square, square wave inverters may be unkind but not in my line of experience or my recommendation.

John
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inverters

Wow! Lots of ideas posted so I'll add another one.

I have an 1800W continuous rated (3.6kw max) pure sine wave inverter/charger so it is always hooked into the batteries. The output goes to a separate ring circuit "inverter only" however if on shore power (or Genny power) the inverter cuts out and feeds 240v to the "inverter only" ring from the Genny mains and automatically starts charging the batteries. I do not have the Genny hard wired in - I use the shore-power socket and plug the Genny in there so no chance of having Genny and mains on at the same time. There is also no chance of back feeding the inverter. The problem is getting the two different supplies in phase. If the inverter and Genny/mains were connected to the same circuit and were out of phase you would bølløx the inverter and/or what ever else was connected.
Keep it simple, fail safe and most important of all "idiot-proof".

BTW, the square wave inverters are OK for lights etc but NFG for induction motors, laptops, TVs, Microwaves, any tool with electronic speed control etc. (I have knackered several batteries on my mobile phone before I realised the little inverter I was using was square wave. New battery (again) and then used the big inverter and no more problems)
--------------------
hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inverters

IT WILL NOT WORK POWER TOOLS WITHH VARIABLE SPEED DRIVES.

That is contrary to my own experience with modified square wave inverters (aka quasi sine wave). Maybe I was born lucky /forums/images/graemlins/smile.gif but I dare say it is true for the el cheapo ones, but there again cheap means problems and tears in the case of most things.

John
 
Re: One solution...

[ QUOTE ]
Yeh
Like a degree that would burn your brain out. Plus forty years experience of serious electricity and RF. I suggest you look up a thing called Ohms Law. It is common knowledge among intelligent 12 year olds.

[/ QUOTE ]I am trying to decide what amuses me most about this post. Perhaps that fact that ohms law isn't generally used in power calculations...?
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inver

On the 12V supply side you would want to use pretty heavy cables capable of carrying 150 A min. Keep the run as short as possible and fit a 150 A fuse in between the battery and the inverter. On the 240 side you need a cross over switch. Off - Shore - Inverter.
Never have shore and Inverter connected at the same time. YOU WILL FRY THE INVERTER INSTANTLY and perhaps your boat along with it.
I had an Inverter fire once (for a different reason /forums/images/graemlins/blush.gif) not pretty believe me.

Joerg
/forums/images/graemlins/blush.gif
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inverters

Forgot - don't worry about any comments about burning out cables - just size then according to your needs, in your case 1800w equates to around 150A so go for a couple of 300A cables and keep them as short as possible. (Arc welding cable works just fine and comparatively cheap).
--------------------
hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>
 
Re: Calling all \'crats, techno, electro, intellectual, regarding inver

Simple question, simple answer.

Yes!!! The inverter will be harmed if it's hard wired into the mains circuit, without an inverter/off/shorepower/generator switch. It must be isolated when the shorepower/generator is on.

My brothers burnt out for just this reason.
 
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