Fried Travel Power

[nb Innisfree]

I also believe an RCD would work as intended on the TravelPower, as has been said, its a current sensing device sensing a current imbalance between L and N and so it does not have any care as to what the voltage is.

I do not know how external RCD testers work but I hypothesise that they might be based upon a resistor to earth that creates a current flow to trip the RCD. If this is the case then because the voltage is lower a tester might incorrectly "fail" an RCD???????.

 

...........Dave

 

 

Introducing a resistor to earth is the same as if someone gets a shock, their body is also introducing a resistor to earth.

[nicknorman]

Introducing a resistor to earth is the same as if someone gets a shock, their body is also introducing a resistor to earth.

However the resistor required to produce the 30mA to trip the RCD would be smaller if the voltage were 120v. As stated earlier, it is the current that is the killer, and the current that defines when the RCD trips. Therefore I can easily see that an RCD tested would not trip the RCD since only 1/2 the current would be flowing, say 15mA, not enough to trip. But that has no bearing on the level of protection to humans.

 

Just putting my 2 penn'th in here, we use a TP with a Victron multiplus and run a washer/dryer with it.

When we are doing locks, it's difficult to keep the engine revs up enough for the TP to give a full output, in fact the load almost stalls the engine. So, what we do is use the turn down facility (to about 8 amps, so that the combi supplements the power from the TP. We have no trouble with trips using this system. It works smoothly and you can hear it working in the engine note. Our first TP lasted 5 years before failing. This one has been going for 2 so far.

Thats useful info for the OP - his configuration should work!

[nb Innisfree]

However the resistor required to produce the 30mA to trip the RCD would be smaller if the voltage were 120v. As stated earlier, it is the current that is the killer, and the current that defines when the RCD trips. Therefore I can easily see that an RCD tested would not trip the RCD since only 1/2 the current would be flowing, say 15mA, not enough to trip. But that has no bearing on the level of protection to humans.

 

 

Thats useful info for the OP - his configuration should work!

So how can a RCD be tested? Does the voltage have to be monitored while the tester is operated?

 

We need a proper expert here, where is he?

 

GIBBO!

 

Another double post edit.

Edited February 8, 2013 by nb Innisfree

[by'eck]

So how can a RCD be tested? Does the voltage have to be monitored while the tester is operated?

 

An RCD's own test button usually just momentarily connects live to neutral through a resistor. It doesn't check leakage from either leg to earth, so may give a false sense of security.

 

This RCD tester schematic suggests it checks live to earth scenarios as well as providing various indications.

 

[Keith M]

In my experience you can not test a RCD using an RCD tester when the supply is via a TP

Because the type of of tester required looks at the incoming supply and if it does not conform as would be found using a TP it will just not do the test.

 

Also for a RCD to function correctly the out of balance is respect to earth. it is just not an out of balance between the L & N

 

It may be that the new TP with the two fans on the front or bottom may be E / N Bonded?

 

With any Inverter / charger that has the ability to power assist when the unit detects an incoming AC supply being a grid supply or a TP supply the E / N bond will be removed and will not be replied even when in power assist as it will relies on the incoming earth.

 

If using a TP you will not have and Earth therefore total unprotected

 

The use of a IT has be known for many years unfortunately most boat builders do not install TP correctly

 

Keith

Edited February 8, 2013 by Keith M

[Philippe]

Did I offend?

 

Apologies if so.

 

No, not at all.

[nicknorman]

In my experience you can not test a RCD using an RCD tester when the supply is via a TP

Because the type of of tester required looks at the incoming supply and if it does not conform as would be found using a TP it will just not do the test.

 

Also for a RCD to function correctly the out of balance is respect to earth. it is just not an out of balance between the L & N

 

It may be that the new TP with the two fans on the front or bottom may be E / N Bonded?

 

With any Inverter / charger that has the ability to power assist when the unit detects an incoming AC supply being a grid supply or a TP supply the E / N bond will be removed and will not be replied even when in power assist as it will relies on the incoming earth.

 

If using a TP you will not have and Earth therefore total unprotected

 

The use of a IT has be known for many years unfortunately most boat builders do not install TP correctly

 

Keith

 

Hi Keith, I know you are an expert on these matters so I hesitate to argue with you but...

 

RCD functioning: I was always under the impression that it just detected an imbalance between L and N, such as is shown in Richard's diagram above (you can see the E just goes straight through). Wikipedia agrees with me (and we all know that is always correct!) Could you point me to any reference that shows how current in the E line affects an RCD?

 

As I mentioned before, the TP centre tap is connected to hull and therefore there is an earth - its just that L and N are both 120v~ or so away from it, rather than 1 being at earth and the other being at 240v.

 

I do have the new TP with 2 fans. To be honest I haven't checked that it is still centre tapped with mid-point bonding to earth, but the behaviour of the iPad seemed to suggest it was. I'll check, down to the boat next Wednesday. I'll also check that the RCD trips when I connect either the L or N to earth via a suitable resistor (to give 30mA at 120V, if that's what I find).

Edited February 8, 2013 by nicknorman

[Philippe]

Just putting my 2 penn'th in here, we use a TP with a Victron multiplus and run a washer/dryer with it.

When we are doing locks, it's difficult to keep the engine revs up enough for the TP to give a full output, in fact the load almost stalls the engine. So, what we do is use the turn down facility (to about 8 amps, so that the combi supplements the power from the TP. We have no trouble with trips using this system. It works smoothly and you can hear it working in the engine note. Our first TP lasted 5 years before failing. This one has been going for 2 so far.

Great to see that someone is successfully doing exactly the same as the setup on my boat. Which makes it more and more likely to be a fault rather than a fundamental issue.

 

All this discussion is great stuff! Pointing my mechanic at it and hoping it helps track the problem down before I smash the damn thing up and throw it in the bin!

[Justme]

No, see my previous post on the subject. Unless you can explain to me why the RCD wouldn't work, I will continue to believe that it will work since the supply is not floating.

 

My thinking is that the RCD needs to see the current in the L & N the same.

 

Now remember that this is AC so if you have a fault to earth via a insulation fault the current will be leaking in equal amounts from both the L & the N to earth (unless you have cut either the L or the N & was holding the end).

 

As the current is equal there would be no imbalance.

 

Great to see that someone is successfully doing exactly the same as the setup on my boat. Which makes it more and more likely to be a fault rather than a fundamental issue.

 

 

 

They could have turned the N&E bond off completely?

[nicknorman]

An RCD's own test button usually just momentarily connects live to neutral through a resistor.

 

It normally works by momentarily connecting a resistor across live and neutral via an extra coil around the core, thus introducing a non-zero magnetic field which the trip system detects. This is surely pretty indistinguishable from the non-zero magnetic field from an imbalance in the main conductors?

 

My thinking is that the RCD needs to see the current in the L & N the same.

 

Now remember that this is AC so if you have a fault to earth via a insulation fault the current will be leaking in equal amounts from both the L & the N to earth (unless you have cut either the L or the N & was holding the end).

 

As the current is equal there would be no imbalance.

?

No, if one conductor is connected to earth via some resistance, only the current in that conductor is affected (how could the current in the other conductor be affected) and so an alternating magnetic field is produced, which is detected and cuts the RCD. If the leakage was equally from both conductors to earth (hard to see how that would happen) then of course the RCD wouldn't trip. Nor of course would it trip if you touched L and N simultaneously (and were well insulated from earth) but I think in that case, Darwinism kicks in!

[Philippe]

Not sure if this will work or not as I've never done it before, but here are some photos of the boxes. These were taken before the Filax was removed.

 

 

 

Edited February 8, 2013 by Philippe

[by'eck]

In my experience you can not test a RCD using an RCD tester when the supply is via a TP

Because the type of of tester required looks at the incoming supply and if it does not conform as would be found using a TP it will just not do the test.

 

Also for a RCD to function correctly the out of balance is respect to earth. it is just not an out of balance between the L & N

 

It may be that the new TP with the two fans on the front or bottom may be E / N Bonded?

 

With any Inverter / charger that has the ability to power assist when the unit detects an incoming AC supply being a grid supply or a TP supply the E / N bond will be removed and will not be replied even when in power assist as it will relies on the incoming earth.

 

If using a TP you will not have and Earth therefore total unprotected

 

The use of a IT has be known for many years unfortunately most boat builders do not install TP correctly

 

Keith

 

Sorry Keith, both the highlighted statements are wrong.

 

You do need some means of triggering the RCD if your body in contact with boat hull, also touches live though. Hence having inverter neutral/earth bond when working, and with earth circuit itself bonded to boat hull, so you have similar protection when on shore power.

 

The RCD will trip by detecting an imbalance between live and neutral though, nothing else.

 

Apart from only having half the fault current, a centre tap earthed TP will still function with RCD correctly.

[nb Innisfree]

All I know about RCD is that a N/E bond provides a path back to neutral so that any missing current can bypass the mechanism for detecting an imbalance.

[nicknorman]

Not sure if this will work or not as I've never done it before, but here are some photos of the boxes. These were taken before the Filax was removed.

Thats the older type of TP, almost certainly centre-tapped.

 

ps good pix but maybe make them smaller next time!

[by'eck]

All I know about RCD is that a N/E bond provides a path back to neutral so that any missing current can bypass the mechanism for detecting an imbalance.

 

Surely its to provide a reference for the neutral leg which would otherwise be floating with an inverter output. This to give a firm trigger if your earthed body touches live.

[Philippe]

ps good pix but maybe make them smaller next time!

 

Oops! Sorry

[jonathanA]

It normally works by momentarily connecting a resistor across live and neutral via an extra coil around the core, thus introducing a non-zero magnetic field which the trip system detects. This is surely pretty indistinguishable from the non-zero magnetic field from an imbalance in the main conductors?

 

 

No, if one conductor is connected to earth via some resistance, only the current in that conductor is affected (how could the current in the other conductor be affected) and so an alternating magnetic field is produced, which is detected and cuts the RCD. If the leakage was equally from both conductors to earth (hard to see how that would happen) then of course the RCD wouldn't trip. Nor of course would it trip if you touched L and N simultaneously (and were well insulated from earth) but I think in that case, Darwinism kicks in!

 

Extra coil- thats a new one on me. I wouldn't use such a device as its not a valid test at all. the usual self test arrangement that I've seen on every RCD I've dealt with is a resistor between Live after the current sensing element and neutral before the current sensing element

 

Thus creating an imbalence between live and neutral current and causing the trip to trip. Which is exactly how they are supposed to work and therefore a valid test.

[TNC]

 

 

We have the older black box TravelPower which I believe is tougher than the new silver one.

Its just failed after over 10,000 engine running hours. Bearings went and rotor hit stator.

Resurrected by Cox's!

We try to keep the revs on in locks but often forget. So far this has caused no trouble other than washing machine looses its plaoe in wash cycle and breadmaker makes wet bricks instead of bread.

 

..............Dave

 

I belive Gibbo also thought this.

Our 1999 black box TP, with similar hours to yours, is indestructable...I have even been known to use it to power my 16A Clarke mini welder!

If it gets upset, it just cuts out.

It has got through 3 sets of brushes and the bearings are just beginning to show a little play. I have a bearing set to fit, probaly get around to it soon.

I do not use power assit in NB Eranest's Multiplus, from the TP, but do from shoreline (switched with 12v / 240v relays.)

[nicknorman]

Extra coil- thats a new one on me. I wouldn't use such a device as its not a valid test at all. the usual self test arrangement that I've seen on every RCD I've dealt with is a resistor between Live after the current sensing element and neutral before the current sensing element

 

Thus creating an imbalence between live and neutral current and causing the trip to trip. Which is exactly how they are supposed to work and therefore a valid test.

Thats a perfectly valid way to test as well. I think both methods are "in circulation". TBH I am only going by what I quickly found on t'internet, but its not the first time I have come across a test coil. But in what way is it not a valid test? I guess a resistor is cheaper than a resistor plus coil, that's probably why its more common.

 

Surely its to provide a reference for the neutral leg which would otherwise be floating with an inverter output. This to give a firm trigger if your earthed body touches live.

Without a N E bond on an inverter output, if you touch live it won't trip the RCD. But on the other hand, you won't get a shock of course! I think the issue is that without a N E bond, you can have a fault with L connected permanently to Earth without anything happening. So then you go tinkering, expecting N to be at earth potential, but whoopie you get a belter! Ditto if N is connected to E in the equipment (which it shouldn't be) the RCD will trip if the inverter has N E bonding, not if it doesn't. So I think the inverter N E bond is more about detecting permanent single faults that wouldn't show up otherwise, rather than protecting the user from a single fault such as touching something that is or has become live.

 

For those not wanting to take my word for it, type Gibbo as the author, Neutral as the key word and return posts, not topics in advanced search. A quick browse of His Highnesses utterings on the subject will convince.

Edited February 8, 2013 by nicknorman

[bizzard]

Is ''The fried Travel power'' a new tasty item on the ''Little Chef'' menu?

[nb Innisfree]

Ok my take on an RCD and N/E bonding with regards to our Victron Multiplus.

 

Touch live and current will still pass back through RCD via neutral but it will be minus 30 milliamp which cannot be lost, it has to go somewhere, that somewhere is through your body to earth and then back to neutral via E/N bond and so by-passing RCD which will detect that 30 milliamp by-pass and trigger.

 

Connected to inverter but without N/E bond if you touch live or neutral current will pass through your body and back to hull earth to comple the circuit but as there is only 120v on live and neutral you might live. In this scenario RCD can't detect an imbalance. If you are totally insulated from hull touching just live or neutral will have no effect as circuit has nowhere to go. If you are still insulated from earth and touch live and neutral current will pass through your body but RCD won't trigger because there is no missing current so it's goodbye cruel world. If boat is connected to grid, return path of 30 milliamp will pass through onshore E/N bond to complete circuit and activate RCD.

 

In the case of touching live and neutral itcwould seem that a RCD will not give protection but in reality some current is likely to escape to earth and back to neutral via N/E bond and trigger RCD. If in this scenario you are totally insulated from earth, quite unlikley I would think, then RCD won't trigger and you will die.

[nicknorman]

Ok my take on an RCD and N/E bonding with regards to our Victron Multiplus.

 

Touch live and current will still pass back through RCD via neutral but it will be minus 30 milliamp which cannot be lost, it has to go somewhere, that somewhere is through your body to earth and then back to neutral via E/N bond and so by-passing RCD which will detect that 30 milliamp by-pass and trigger. True

Connected to inverter but without N/E bond if you touch live or neutral current will pass through your body and back to hull earth to comple the circuit but as there is only 120v on live and neutral you might live. In this scenario RCD can't detect an imbalance. If you are totally insulated from hull touching just live or neutral will have no effect as circuit has nowhere to go. No, without N E bond both live and neutral are floating, there isn't really a live or neutral. So if you touch either and are earthed, nothing will happen. There is no circuit.

If you are still insulated from earth and touch live and neutral current will pass through your body but RCD won't trigger because there is no missing current so it's goodbye cruel world. True - RCDs cant protect you if you touch both L and N and there is no leakage anywhere else. One advantage of NE bond is that if you did do that (though I maintain Darwinism applies) chances are you would be partially connected to earth, enough to trip the RCD so you might be saved. If boat is connected to grid, return path of 30 milliamp will pass through onshore E/N bond to complete circuit and activate RCD. Only if you are connected to earth in some way, not if you just touch L and N and are unearthed

In the case of touching live and neutral it would seem that a RCD will not give protection but in reality some current is likely to escape to earth and back to neutral via N/E bond and trigger RCD. If in this scenario you are totally insulated from earth, quite unlikley I would think, then RCD won't trigger and you will die. True

 

 

Sorry, only partially correct! I have inserted my comments in red above!

Edited February 8, 2013 by nicknorman

[nb Innisfree]

Sorry, only partially correct! I have inserted my comments in red above!

 

Great I have got it right with the exception of floating mains.

[nicknorman]

Great I have got it right with the exception of floating mains.

Yes, I wrote the post saying you had got it mostly wrong, then once I had added the red bits I realised you had got it mostly right and had to change it!

[dmr]

I belive Gibbo also thought this.

Our 1999 black box TP, with similar hours to yours, is indestructable...I have even been known to use it to power my 16A Clarke mini welder!

If it gets upset, it just cuts out.

It has got through 3 sets of brushes and the bearings are just beginning to show a little play. I have a bearing set to fit, probaly get around to it soon.

I do not use power assit in NB Eranest's Multiplus, from the TP, but do from shoreline (switched with 12v / 240v relays.)

 

Oh a chance to make one of those silly pedantic posts that have no value and just upset people...but I just can't resist.

Gibbo THOUGHT this????, it should Not be in the past tense???? Although this forum is the centre of the universe and Gibbo is not posting here, he is not dead!!!!!!!

But seriously, replace your bearings NOW, a failure is expensive. Mine only gave a short warning that they were near their end and it was not that obvious either. Despite quite a bit of experience with these things I failed to spot the warning signs (sounds).

Really good news that the TP will drive a welder, I have thought about this but not been brave enough to try. All the talk of needing to isolate everything when welding, and the TPs odd grounding scheme, thought it might be asking for trouble.

 

..........Dave

 

.........Dave