Inverter problem

[Gunna Do]

Had 1000watt quasi sine inverter fitted linked through a Sterling manual changeover switch. Everything worked fine but inverter was just too small for our microwave so have swapped it for a 1500watt pure sine jobby. Now when I switch over to the inverter my Shoreline galvonic isolator pulses the 2 red LED's indicating an AC fault! If I turn off the cross over switch and run the appliance directly there appears to be no problem so my immediate thought of 'duff inverter' doesn't ring true. Checked through the AC wiring with Avo and cannot find any earth leakage. Refitting the original inverter, everything works as it should. Has anybody had this problem or can suggest a solution?

[Nickhlx]

Had 1000watt quasi sine inverter fitted linked through a Sterling manual changeover switch. Everything worked fine but inverter was just too small for our microwave so have swapped it for a 1500watt pure sine jobby. Now when I switch over to the inverter my Shoreline galvonic isolator pulses the 2 red LED's indicating an AC fault! If I turn off the cross over switch and run the appliance directly there appears to be no problem so my immediate thought of 'duff inverter' doesn't ring true. Checked through the AC wiring with Avo and cannot find any earth leakage. Refitting the original inverter, everything works as it should. Has anybody had this problem or can suggest a solution?

 

Maybe the start-up surge of the microwave is still overloading the inverter ? A 750 watt microwave will take about nearly double this as running power and the start-up surge will be higher.

 

Nick

Edited October 6, 2011 by Nickhlx

[WotEver]

Is the new inverter Neutral-Earth bonded?

 

Tony

[Iain_S]

This may be relevant.

Iain

[NB Willawaw]

Let me get this clear in my head.

 

Your old inverter works through the switch with no GI lights

Your new inverter works directly into the same load with no GI lights (are you just by-passing the switch on this ?)

your new inverter when working through the switch, lights up both lights on the GI ??

 

Doesn't make a lot of sense if the boat is wired right.

 

Tell me more about the function of the switch and what else it's connected to ?

 

Are the tests above all conducted with the shoreline and the same AC consumers connected - is there any possibility that different items are plugged in to the sockets while you are trying these different configurations ?

 

Is the neutral-earth link made on the new inverter ?

 

Had 1000watt quasi sine inverter fitted linked through a Sterling manual changeover switch. Everything worked fine but inverter was just too small for our microwave so have swapped it for a 1500watt pure sine jobby. Now when I switch over to the inverter my Shoreline galvonic isolator pulses the 2 red LED's indicating an AC fault! If I turn off the cross over switch and run the appliance directly there appears to be no problem so my immediate thought of 'duff inverter' doesn't ring true. Checked through the AC wiring with Avo and cannot find any earth leakage. Refitting the original inverter, everything works as it should. Has anybody had this problem or can suggest a solution?

Edited October 6, 2011 by NB Willawaw

[Gunna Do]

Let me get this clear in my head.

 

Your old inverter works through the switch with no GI lights

Your new inverter works directly into the same load with no GI lights (are you just by-passing the switch on this ?)

your new inverter when working through the switch, lights up both lights on the GI ??

 

Doesn't make a lot of sense if the boat is wired right.

 

Tell me more about the function of the switch and what else it's connected to ?

 

Are the tests above all conducted with the shoreline and the same AC consumers connected - is there any possibility that different items are plugged in to the sockets while you are trying these different configurations ?

 

Is the neutral-earth link made on the new inverter ?

 

Thanks for reply and yes you have it correct. The crossover switch is a standard manual unit with an off position, shoreline position or inverter. The prime reason for the inverter is the microwave which has a stated start up of 1200 watts running at 800watts. I went right around the boat checking that nothing else was switched on while testing and also tried with the shoreline connected and disconnected. Yes the earth link is connected to the inverter, which ever one I was using.

Ian's link looks interesting (to the smart gauge site) as when I tried the new inverter at home before fitting, I noticed it gave off a lot of RF to a nearby radio. I hadn't of course connected the earth link at this point so it MAY be something to try. I could also try disconnecting the GI temporarily. When operating the inverter directly to microwave or kettle there is no link to the AC earth by the appliance so no problem.

[NB Willawaw]

Are you saying that the GI LEDs lit up when the shoreline wasn't even plugged in ??

 

I went right around the boat checking that nothing else was switched on while testing and also tried with the shoreline connected and disconnected. Yes the earth link is connected to the inverter, which ever one I was using.

[WotEver]

Where is your GI wired? Is it on the incoming shore power prior to the changeover switch?

 

Tony

[by'eck]

Where is your GI wired? Is it on the incoming shore power prior to the changeover switch?

 

Tony

 

As it should be!

[WotEver]

As it should be!

Indeed - but is it?

[smileypete]

Had 1000watt quasi sine inverter fitted linked through a Sterling manual changeover switch. Everything worked fine but inverter was just too small for our microwave so have swapped it for a 1500watt pure sine jobby. Now when I switch over to the inverter my Shoreline galvonic isolator pulses the 2 red LED's indicating an AC fault! If I turn off the cross over switch and run the appliance directly there appears to be no problem so my immediate thought of 'duff inverter' doesn't ring true. Checked through the AC wiring with Avo and cannot find any earth leakage. Refitting the original inverter, everything works as it should. Has anybody had this problem or can suggest a solution?

First of all I take it that your boat is in the water and not on hard standing.

 

Having said that I suspect your new inverter has a 'floating earth'. I'd test this by safely connecting a mains filament lamp between live and earth (then trying between neutral and earth just in case) on the inverter's output socket. If the lamp doesn't light then there's no internal connection to the earth contact on the output socket.

 

Also I suspect there may be no electrical bond between mains earth and the hull. This should be on the 'boat' side of the galvanic isolator that connects to the earth of the boat's mains wiring. The shore side of the galvanic isolator should be connected to the shoreline earth, and nothing else!

 

If you're a little unsure what the above means then it's best to get an electrician that's familiar with boats, or someone with the same competence and knowledge.

 

It's possible the old inverter had a some sort of internal earth bond to it's output and case, and it's mounting bolts also made a connection between earth and hull (tho not a very suitable one!).

 

cheers,

Pete.

[WotEver]

... I suspect your new inverter has a 'floating earth'...

I asked the quesion in post #3 and never got a response.

 

Tony

[Gunna Do]

Sorry for delay but been elsewhere today. Thanks for the responses.

Yes the GI lights up with the new inverter even when the shoreline isn't plugged in which clearly means that the GI is not correctly connected. I'm not at the boat till next week but will make it a priority to check this. Sometimes one can look at a problem and just not see what is obvious.

[Tony Ross]

Where is your GI wired? Is it on the incoming shore power prior to the changeover switch?

 

Tony

 

Tony,

 

As someone who has a similar setup and has just wired a GI after the changeover switch but before the distribution panel as access was simpler, what is the problem you alude to? I haven't stuck my nose in the changeover switch but is there a common earth to both sides that I have overlooked which regardless of switch position allows the earth to use the the negative earth on the inverter case as a short cut bypassing the GI or have I missed something?

 

regards,

 

Tony

[WotEver]

Hi Tony,

 

Ideally, the GI breaks the earth wire as soon as it enters the boat. The alternative means that, depending on how the consumer unit is wired, the inverter might be going through the GI. I'd be immensely surprised if a changeover switch switched the earth, but regardless of that, the whole idea of a GI is that it isolates (kind of) the incoming earth from the rest of the boat and by wiring it straight at the back of the shore power socket you ensure that any subsequent wiring won't defeat it.

 

I suspect that OP's GI is wired downstream of the consumer unit and that hence the inverter also feeds through it, and that said inverter doesn't have N-E bonding. However as I've had no feedback to my questions about this I could be completely wrong.

 

Tony

[Gunna Do]

Just an update:

The GI is correctly wired and have proved the problem is not connected with it by removing temporarily. The boats 12v and 230v are bonded to earth and so is the inverter. I had 1 slightly dodgy battery (out of 4) so have replaced that with a known good un. The changeover switch just switches live and neutral, the earth is completely separate. I am fairly sure that the problem is with RFI being dumped to earth in the new inverter. I also have an alarm sounding (assume low voltage warning) even though I have 13.2 volts at the input terminals and 24v truck battery to inverter cables so have contacted the supplier for advice. No response so far, meanwhile the old unit is back in place with no perceived probs!

[WotEver]

But is the new inverter N-E bonded?

 

Tony

[Gunna Do]

But is the new inverter N-E bonded?

 

Tony

 

Hi Tony,

I have been a mechanic and auto electrician for some 30 years or so but my knowledge of mains is limited to the basic stuff. I have checked that the inverter case is earthed and also the output sockets. Beyond that would be up to a proper electrician. I tried to get one to check the boats wiring last time I was down there but he was busy so it will have to wait until next visit. I would have thought that if there was a problem with the basic wiring it would have caused me problems in the 3 years that I have owned the boat but as I have said, I'm no expert here. Perhaps you would like to explain N-E Bonding and how to test?

[WotEver]

I would have thought that if there was a problem with the basic wiring it would have caused me problems in the 3 years that I have owned the boat but as I have said, I'm no expert here. Perhaps you would like to explain N-E Bonding and how to test?

Hi,

 

I'm not accusing your wiring of being faulty (can you accuse wiring?) just suspecting that your (new) inverter output doesn't have Neurtal and Earth bonded together.

 

See this post from Gibbo about how to test and, if necessary, correct it.

 

Tony

[Gunna Do]

Hi,

 

I'm not accusing your wiring of being faulty (can you accuse wiring?) just suspecting that your (new) inverter output doesn't have Neurtal and Earth bonded together.

 

See this post from Gibbo about how to test and, if necessary, correct it.

 

Tony

Thanks Tony (and Gibbo), I now understand the bonding issue a little better. Off to boat again next week with my trusty Avo to check this out.

ps still haven't heard from the seller, suspect He has had this problem before and is keeping his head down!

[aread2]

Just an update:

The GI is correctly wired and have proved the problem is not connected with it by removing temporarily. The boats 12v and 230v are bonded to earth and so is the inverter. I had 1 slightly dodgy battery (out of 4) so have replaced that with a known good un. The changeover switch just switches live and neutral, the earth is completely separate. I am fairly sure that the problem is with RFI being dumped to earth in the new inverter. I also have an alarm sounding (assume low voltage warning) even though I have 13.2 volts at the input terminals and 24v truck battery to inverter cables so have contacted the supplier for advice. No response so far, meanwhile the old unit is back in place with no perceived probs!

Did you say cables designed for 24v from the batteries to the inverter? These would be half the cross section of those designed for 12v operation and more likely to cause volt drop between the battery and inverter. Or is this a red herring?

[Bob18]

Is that 13.2v with the inverter running at full power, or just sitting there twiddling its thumbs?

If its under full load its a little on hte low side, but nothing to worry about, but if its in thumb twiddle mode then repeat the test at full load.

Don't forget that a 1500W output inverter will be drawing something between 1650W and 1800W from the battery, which equate to between 137.5A and 150A so the cable should be sized for that current. (Its only a little one, so probably nearer 1800W/150A)

Further the length of the cable is the total length of both the positive and negative cables from the battery terminals.

[Justme]

which equate to between 137.5A and 150A so the cable should be sized for that current.

 

 

In almost all cases it is better to size the cable for voltage drop & not max amp carrying capacity. Doing it that way the max amp capacity is almost always more than is needed.

 

(so yes you do need to check the max capacity of the chosen cable but dont choose the cable for its max capacity, if that makes sense)

 

Our local expert electrical shop owner cant see why I always want a much higher amp rating than he suggests.

[WotEver]

CWDF Post containing Voltage Drop cable calculator.

 

Tony

[Nickhlx]

.....Our local expert electrical shop owner can't see why I always want a much higher amp rating than he suggests....

So I guess he's not such an "expert" after all

 

Nick