RCD Trips

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RCD Trips

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steve58

Two jobs both identical with panels and invertors ect. Ie: Aurora 3.6 TL , 14 panels 235w. Both using Wylex garage boards 16amp mcb and 63a 30ma RCD 4mm T&E. One starts up and works no problem the one next door trips RCD. Done all checks and test all ok. Invertor goes through start up all ok then after about 2 mins trips RCD. Any ideas please
 
any tl inverter will take out 30ma rds all day long. Either scrap the rcd all together of change to 100ma at least - obviously provided installation method of cable allows or its a tt system
 
mmccx said:
any tl inverter will take out 30ma rds all day long. Either scrap the rcd all together of change to 100ma at least - obviously provided installation method of cable allows or its a tt system
Click to expand...

Really? I have not noticed this, what evidence do you have? I need to ensure our installers are not doing something wrong, saying that we have not had an influx of complaints about RCD trips either which I am sure we would of had with the amount of installs carried out :(
 
The amount of ones I have had to change in recent months! Also all manfacturers I use recommend Atleast 100ma SMa solarmax eversolar fronius etc. 30ma rcd's will generally go randomly and from experience will happen mostly on duel tl inverter setups and the larger size inverters 3.5 kwvand up although it has happened on the smaller ones.

Also never put an inverter on a shared rcd's just in case you didn't know
 
I would not expect you to and our company has installed 30ma Type B RCDs for over 7 years and out of all the installs only had to replace about two which were on tin roofs.

Is this not just masking a problem within the houshold or the design? Why would you have residual current on a class II product ??

As a quick question how many other installers increase the RCD size to combat tripping ?
 
It's the residual current from the inverters and not the modules that are the issue I believe. Tl inverters appear to have a high residual current on them particularly on startup shutdown and well whenever they seem to please. As long as the cable is installed without the need for 30ma protection the I would not use one or use are larger rated rcd otherwise IMO you are asking for nuisance tripping when installing a tl inverter
 
Sorry, I am quite new to the forum, How is the residual current created? most inverters have an IP rating don't they? and they would be sited according to their IP rating (I assume). I am trying to get around the fact that a TL inverter would have more leakage than a transformer inverter.

Transformer inverters are the old reliable inverters however I would dispute the fact that TL inverters have more Residual Current / Inballance and in practice I would have to disagree with you.

I know as that we have only facilitated approximately 2000 installs this year, this does not make me an expert, however we have not had a problem due to undersized (as you say) RCDs
 
All I can speak from is my experience and you can only speak from yours, and what I have found is that tl inverters will trip 30ma rcd's. Why for sure I cannot say but if manufacturer recommendations are anything to go by the ones we install reccomend Atleast 100ma and no less. A good example would be an SMa 4000tl.
 
Too many loaded questions/comments Glen, in my opinion....I would hazard a guess that you know what the guy is getting at though to be honest. The fact is that TL inverters have an inherent AC leakage current, ask each manufacturer what it is and they will normally tell you. Let's say, for argument's sake, that it is 20mA. On start up, especially on moist/misty mornings, where parasitic capacitive leakage currents can be naturally generated by the PV array, these currents when combined with the inherent leakage current generated by the TL inverter can exceed the 30mA trip limit and "nuisance" trip the RCD. SMA and others recommend a trip limit of at least 100mA because of this. PowerOne recommend 300mA.

Is the discussion about whether it is possible to increase the RCD trip limit without contravening any applicable requirements for "human protection" under BS7671? Or is it about whether TL inverters have inherent leakage current? No-one suggested that the auto-response was the increase the trip limit regardless. I think there was a mention of conforming to reg's and/or having a TT supply.....

I'm pleased to read that you use Type-B RCDs when fitting TL inverters, can I ask whether you would like to share why you do that please? Is that something you do for all TL systems or just ones where you deem it necessary to fit an RCD according to BS7671? Just curious, thanks.
 
My response was really got serious with this comment

any tl inverter will take out 30ma rds all day long. Either scrap the rcd all together of change to 100ma at least - obviously provided installation method of cable allows or its a tt system
Click to expand...

Scrap the RCD all together, OK lets do that,

On the serious note why do we use Type B RCD, if you do or if you dont this is up to the installer, there are so many shades of grey in regs, so if I install a sunnyboy and the protection fails the type B RCD covers me under governing law. we can argue manufacturers guidelines supercede all other regulations but I can't really be bothered wasting a day in court to explain that. I can't really be bothered explaining to trading standards how it all works and reading manuals to them.

If it does not hinder the performance of the system then no harm done!!
 
Glen Powell said:
My response was really got serious with this comment



Scrap the RCD all together, OK lets do that,

On the serious note why do we use Type B RCD, if you do or if you dont this is up to the installer, there are so many shades of grey in regs, so if I install a sunnyboy and the protection fails the type B RCD covers me under governing law. we can argue manufacturers guidelines supercede all other regulations but I can't really be bothered wasting a day in court to explain that. I can't really be bothered explaining to trading standards how it all works and reading manuals to them.

If it does not hinder the performance of the system then no harm done!!
Click to expand...

Completely agree! Most on here would know that I am a proponent for the use of the DC sensitive RCDs where TL inverters are concerned.....good to get someone else's take on it.
 
Not sure it just says. RCCB 30ma. It's in it's own mini CU.


From memory sunny explorer usually displays residual current of 8ma never seen it change.
 
Last edited by a moderator:
Forgot to post the new RCD decision process as recommended in the new Guidance Note 7:
RCDs.jpg
 
That decision tree matches with how I see it.

A type B RCD is only required for fault protection if the inverter hasn't got means of preventing leakage of DC current onto the AC side.
 
Bit too simplistic if you ask me.....not entirely sure that the statement "isn't able to feed DC fault currents into the AC side of the installation" is all-encompassing or enough to satisfy all potential scenario's where DC fault currents might exist. I'll take the fifth on this for now I think....
 

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