N-E Bonding

[Biggles]

I did as was suggested and bonded my N-E on my inverter. This seems to have solved the problem of my RCD jumping out.

 

Later when I powered up the microwave the inverter stopped giving out 240v, but was still showing volts in.

 

I decided to open it up to see if there was any thing obvious inside causing the problem. Sure enough a small fuse had blow. Can't see the rating cos not got my glasses with me.

 

Interestingly there is a tiny resistor between the N&E inside the inverter. What's that for?

 

Finally my inverter Watts reading was showing the fridge as pulling about 400w on cycle. That cant be right can it? Its an 85w 240 fridge. I was only running on tickover today and it was very noticeable when the inverter supplied the fridge. The fridge was the only 240v demand today.

 

Biggles

[Theo]

Finally my inverter Watts reading was showing the fridge as pulling about 400w on cycle. That cant be right can it? Its an 85w 240 fridge. I was only running on tickover today and it was very noticeable when the inverter supplied the fridge. The fridge was the only 240v demand today.

 

Biggles

 

We run a fridge and a freezer from on 1800W MSW Sterling inverter and it is very noticeable when the fridge cuts in. Fridge motors take quite a belt on startup. That's why you would normally fit a 13A fuse in the plug.

 

As to the 400W. Are you checking it with one of the plug in energy meters? It may be that the meter does not like to waveform and is reading falsely. If you have a clamp meter it would be useful to compare Watts out as measured by the energy meter and Watts in as calculated from input voltage (measured, not just taken as 12V) and multiplied by the current through the 12V input wires as measured using the clamp meter. Remember that inverters are not 100% efficient and have their own quiescent input current (when not supplying any output).

 

Nick

[alan_fincher]

Sure enough a small fuse had blow. Can't see the rating cos not got my glasses with me.

 

Interestingly there is a tiny resistor between the N&E inside the inverter. What's that for?

 

Are you aware of the previously published material from the experts about which types of inverter can be safely modified for an earth - neutral bond, (assuming not already), and which can not.

 

Gibbo gave me an excellent run through on this, and I wonder if you are trying to modify one of the inverter types where he says it cannot be done ?

 

See

 

Link to previous thread.

[blackrose]

Interestingly there is a tiny resistor between the N&E inside the inverter. What's that for?

Are you sure the inverter isn't already N-E bonded by the manufacturer?

[Biggles]

I have just read the previous thread. Kinda wish I hadn't now. My head is hurting

 

The tiny (physical size) resistor between E&N what is that doing? forming an earth bond?

 

Now I'm home (with my glasses) I can see the fuse now says P5A 250v, and in fact 2 of them are blown. Inside my inverter it seems to be lie 2 units in one, almost a mirror image of components.

 

The microwave has previously run from the inverter without issue. Could the earth bonding I have introduced cause the internal fuses to blow?

 

Biggles

[MoominPapa]

I have just read the previous thread. Kinda wish I hadn't now. My head is hurting

 

The tiny (physical size) resistor between E&N what is that doing? forming an earth bond?

 

Now I'm home (with my glasses) I can see the fuse now says P5A 250v, and in fact 2 of them are blown. Inside my inverter it seems to be lie 2 units in one, almost a mirror image of components.

 

The microwave has previously run from the inverter without issue. Could the earth bonding I have introduced cause the internal fuses to blow?

 

Biggles

Did you reach a conclusion about where your inverter sits in Gibbo's taxonomy? If your inverter is of the type which has a centre-tap earthed and you then bonded N+E then that could indeed blow fuses.

 

MP.

[Guest]

Not sure what inverter you have, but my Sterling pure sine was NOT neutral-earth bonded, nor was it centre tapped. I checked with Sterling who confirmed it was OK to link thus. My RCD now functions on a test, whereas it didn,t before and was useless. As my inverter is a UPS and shore power passes "through" it, I installed a switch so that the "link" can be switched out (credit to someone who gave me the idea).

[Biggles]

No I haven't yet. It only blew the fuse when I turned on the microwave. The fridge was fine, and the RCD problem went. I also ran an angle grinder from it in the morning.

 

Centre tap being the earth pin on the outlet and the earth being the wing nut I have on the chassis of the inverter?

 

My head always hurts when electronics are mentioned.

Edited July 12, 2009 by Biggles

[MoominPapa]

No I haven't yet. It only blew the fuse when I turned on the microwave. The fridge was fine, and the RCD problem went. I also ran an angle grinder from it in the morning.

 

Sorry, I didn't read your first post well enough. If the inverter was of the centre-tapped type it would have blown the fuses straight away.

 

I've also not found your original post about the RCD popping, but it's possible that the microwave is faulty: some faults will have different symptoms with the bond in place.

Could you try the microwave at home, or, best of all, get it PAT tested. If you have the right sort of job, sparks departments can often be persuaded to so that as a favour.

 

Just to check: where exactly have you bonded N and E?

 

MP.

Edited July 12, 2009 by MoominPapa

[Biggles]

Sorry, I didn't read your first post well enough. If the inverter was of the centre-tapped type it would have blown the fuses straight away.

 

I've also not found your original post about the RCD popping, but it's possible that the microwave is faulty: some faults will have different symptoms with the bond in place.

Could you try the microwave at home, or, best of all, get it PAT tested. If you have the right sort of job, sparks departments can often be persuaded to so that as a favour.

 

Just to check: where exactly have you bonded N and E?

 

MP.

 

 

I bonded the E&N in the plug that exits the inverter. The microwave works OK on the marina power.

 

The other 2 appliances worked fine. The MW popped it all as soon as I hit the power button. I'll fix the fuses and start again and try by elimination assuming the inverter is otherwise OK.

 

It is a 2kw MSW of Chinese decent. Not that I know much about these things, but inside it looks nicely made.

[Graham_Robinson]

Just to throw a spanner in the works, are non of these inverters double insulated?

 

Some of the smaller wattages must come in a 'plastic' housing.

 

Just checked some older posts on this subject, make very interesting reading to a land locked 'spark' like myself. Hope you all sleep soundly on your super conductive tin boats floating on super conductive water with 240v lurking all around!!!!!!!!!!!!!! :lol:

 

Not that I want to alarm you all in any way of course Mind you we've got water cooled extension leads at the yard, haven't they all. It's amazing how much faith people put in an RCD!!!!! I must have replaced dozens of faulty ones over the last 30 years.

 

I'll stick with 12v for now until I get more information. I'm sure it's going to come flooding in. Reaches for S'wester.

Edited July 13, 2009 by sparky2