Mastervolt (and Sterling) chargers tripping RCD

[Slim]

Has anyone had experience of this happening?  I know the immediate response will be that  it's a wiring problem but EVERY thing I can think of has been checked with an insulation tester ( chinese megger) or by removing / substituting. 

I'll try to give some facts.

Supply RCD is shared by two others neither of whom have a multi stage charger Both are residential (I'm not)

Mastervolt is a 100/2000 Combi and the Sterling(s) are 2 x75 a in a common casing but with seperate supplies, switches, status indicators and

outputs.All 3 are switched indepentantly. The Mastervolt is adjusted to 10 a a/c demand.

Leaving aside what I 've done in the recent past trying to resolve the matter the set up at present is landline to boat, landline via plug type RCD to multi-socket, boat 'ring main' , immersion heater and all 3 chargers 'hard wired' via 13a plugtops. Obviously not are all plugged in at the same time. Everthing is fine until I try to introduce any of the chargers. When I do the site RCD pops. Flick the RCD on and it trips again. If you turn it on had hold it on for a few seconds it often latches on.

The obvious next step is to replace the RCD. Unfortunatly it's not that simple. The site owner has a "qualified electrician" son-in-law who thinks it's my chargers at fault.(to the best of my knowledge he's not done any checks).

On my last visit with the setup much as it is I plugged into a totally independant supply, everything worked fine with no tripping.

Since the probem first became an issue and before i started modifying the setup I spent 3 seperate weeks on other supplies without issue. Over the summer it ran faultllesly on my RCD protected Paguro 4000 generator.

Sorry to go on, it may take me time to respond to questions as my only reliable wifi while I'm on the boat is in the pub

 

Frank

Should have stressed that the present setup is short term so please spare me a lecture on safety

Edited September 20, 2017 by Slim

[OldGoat]

Some RCDs are more sensitive than others. Electronic power devices take quite a large current for a tiny fraction of a second and that's enough to cause a trip.

That's what you have reported by testing alternative sources.  You can get less sensitive RCDs - but that defeats the object of the protection.

I had something similar at home which I fixed by changing a RCD - however I did notice that one of the connections was a bit loose and that may have contributed... 

[WotEver]

As above really. If it works on all supplies except X then there would appear to be a problem with X. In this case, an over-sensitive RCD which is probably popping on the small leakage to earth caused by the charger's noise reduction circuitry. 

[GUMPY]

Get hold of an rcd tester and test the supply rcd this will confirm if its bad or not!

[Keeping Up]

I had exactly the same problem with a Sterling charger last year. As it was quite old, and had a few other minor faults, I decided to replace it - particularly as at the time I was taking no chances while trying to find out what had caused my hull to have been electrolysed away in the previous 2 years.

Replacing the charger with a brand-new Numax charger cleared the fault immediately - at that location. However on arrival at a new location (ie a different mooring) the RCD there occasionally trips when I first switch on the charger, or when I first apply mains to the charger even if it switched OFF at the time. It really does seem as if it is a feature of the chargers. My next step is to measure the currents to earth (including possibly crucially any current from mains live to battery negative) when it is on and when it is off. The problem is that measuring the steady-state current is easy, but measuring the initial surge is not.

[Slim]

Thanks to everyone for their comments and suggestions.

Had another word with the site owner èarlier today and told him i might be causing some disruption tomorrow after I've returned the boats wiring to it's original configeration and re-connect the power. I also told him of the comments made on this topic over the last 24 hours. His eyes just glazed over and he admitted he was fed up with the matter. He did make a half hearted commitment to get his son in law to look at things but I've no idea when. 

I think that crunch time comes when I try to re-connect. I do have a few thoughts

[Slim]

Follow up / update to my original post with further question.

No matter what I did the issue continued into the autumn. Due to a health issue (now resolved) I was forced to leave the boat over the winter with the charger switched off. A recent week on the boat showed that the batteries, 5 x 110ah Lucas AGMS just 5 years old, are down to about 50% capacity and need replacing. This is in hand. I've also found another mooring but circumstances mean I won't be able to move until late May. In the meanwhile I'll be fitting the new batteries and would want them on float charge immediately.

My question is, would fitting an Isolation transformer in the supply prevent my chargers from 'interfering' and tripping the suspect shore based RCD? 

I've already noted that several moorers at the new site have ITs fitted so one would have a long term benefit.

 

Many thanks

 

Frank       

Edited March 30, 2018 by Slim

[WotEver]

4 minutes ago, Slim said:

My question is, would fitting an Isolation transformer in the supply prevent my chargers from 'interfering' and tripping the suspect shore based RCD? 

Yep. 

[Slim]

21 minutes ago, WotEver said:

Yep. 

There goes another 450 quid

A quick fix too.

I was thinking of fitting an Airlink IT, in a locker at the point where the incoming supply socket is. So, shore supply - supply socket - isolation transformer - onboard RCD - demand. (would remove existing galvanic isolator) Do you see any issues  ?

 

Frank

If I knew how to insert a link to the Airlink site I would

Edited March 30, 2018 by Slim
forgot about VAT

[WotEver]

9 minutes ago, Slim said:

If I knew how to insert a link to the Airlink site I would

https://airlinktransformers.com/post/airlink-waterproof-isolation-transformer

 

10 minutes ago, Slim said:

I was thinking of fitting an Airlink IT, in a locker at the point where the incoming supply socket is. So, shore supply - supply socket - isolation transformer - onboard RCD - demand. (would remove existing galvanic isolator) Do you see any issues  ?

I would make it a wooden locker to avoid any arguments about earthing the incoming. 

[GUMPY]

Technically wood is not an insulator especially if its damp 

[WotEver]

5 minutes ago, Loddon said:

Technically wood is not an insulator especially if its damp 

But the transformer is in a plastic case anyway. 

[Detling]

If the trip is caused by the charger's inrush or an overload it will still trip via an IT. You mention a 100 amp charger, that is going to pull over 6 amps on it's own, on a shared RCD if all 3 of you try to do that it will trip. I don't know about the Mastervolt charger but my Victron has a dirty great transformer, which I suspect can easily have an inrush surge double or treble the continuous load, my 90 amp charger has tripped our bollard which has a 10A trip when the batteries are low. One trick you can try is to have the engine running when you plug the charger in (with nothing else on the 240V) this will hopefully ensure that the charger starts softly as the battery voltage is high and the current rush into them is lower, once the charger is OK you can stop the engine as the big connection surge is over.

[WotEver]

42 minutes ago, Detling said:

 

If the trip is caused by the charger's inrush or an overload it will still trip via an IT.

 

A very good point that I hadn’t considered

[Iain_S]

Although the inrush should be limited a bit by the inductance of the transformer.

[nb Innisfree]

If SP has separate RCD and MCBs then latter should trip with overload and not the former, if it's a leakage then only RCD will trip. If RCBBOs are fitted instead then it could be an overload or leakage but difficult to differentiate. 

Or am I talking out of my tradesman's entrance? 

Edited March 30, 2018 by nb Innisfree

[Detling]

I have never seen a marina bollard with separate RCD and MCB, they probably exist, but usually there is just one trip device per plug/socket so presumably combined.

[Slim]

8 hours ago, Detling said:

If the trip is caused by the charger's inrush or an overload it will still trip via an IT. You mention a 100 amp charger, that is going to pull over 6 amps on it's own, on a shared RCD if all 3 of you try to do that it will trip. I don't know about the Mastervolt charger but my Victron has a dirty great transformer, which I suspect can easily have an inrush surge double or treble the continuous load, my 90 amp charger has tripped our bollard which has a 10A trip when the batteries are low. One trick you can try is to have the engine running when you plug the charger in (with nothing else on the 240V) this will hopefully ensure that the charger starts softly as the battery voltage is high and the current rush into them is lower, once the charger is OK you can stop the engine as the big connection surge is over.

The RCD was tripping even when the other 'subscribers' had little or nothing switched on. I also had the Mastervolt charger adjusted to demand a maximum of 10 amps.  It was also tripping even when the batteries were as near as damn it fully charged.

4 hours ago, nb Innisfree said:

If SP has separate RCD and MCBs then latter should trip with overload and not the former, if it's a leakage then only RCD will trip. If RCBBOs are fitted instead then it could be an overload or leakage but difficult to differentiate. 

Or am I talking out of my tradesman's entrance? 

The shore power supply has an RCD and separate MCB/Fuses. It is not a conventional marina bollard. 

[smileypete]

If it's just for keeping batteries topped up, maybe just fit a smaller plastic cased charger that doesn't use an earth. A modest solar setup won't produce anything really worthwhile in winter, but should still be enough.

If the problem is purely down to inrush and not loose connnections, iffy filter caps, then an inrush limiter might work, eg:

https://www.ebay.co.uk/itm/Inrush-current-limiter-230V-16A-for-transformers-power-supplies-LED/231650038237

https://www.amazon.co.uk/Inrush-current-limiter-transformers-supplies/dp/B00OZLSVB0

I've seen much cheaper chinese sourced ones but they're just a bare board, no nice case etc.

Edited March 31, 2018 by smileypete