Diehl 3800s inverter and problems with 61009-1 B rcbo's??

[bigbob1]

I've installed a diehl platinum 3800's inverter, and it seems too be tripping an rcbo even when dark? anyone know if these inverters have a tendancy to not get on with rcbo's??

 

[saint]

Don't know about the Diehl, but i installed a SB4000TL recently and the instructions said if using an RCD not to be lower than 100mA. I put it on a standard MCB as the circuit supplying the inverter didn't need an RCD under BS7671.
You sure you need an RCD at all?

 

[bigbob1]

no it doesn't need an rcbo i'll get a normal 16A mcb and replace it i thinks

 

[edexlab]

Don't know about the Diehl, but i installed a SB4000TL recently and the instructions said if using an RCD not to be lower than 100mA. I put it on a standard MCB as the circuit supplying the inverter didn't need an RCD under BS7671.
You sure you need an RCD at all?

Transformerless Inverters like 4000TL have no galvanic seperation and should be protected by a B type Rcd (61008) Sma reccomend at least 100mA

 

[bigbob1]

Thing that gets me is the inverter was in standby last night it was dark at about 6pm, his main switch that is 80A 30mA tripped out but the rcbo didn't, and he switched the isolator off and then the 80A 30mA stayed in, round there just now and it's on, inverter is kicking out power the panels are kickin out power, everything tested out absolutely spot on on the radial and array tests. I've removed the rcbo and put in a 16A mcb, there is still a 80A 30mA rcd on there as the radial for sseg is 4mm t+e. Had the guy remove a time switch for an outside light that is meant to come on at 5.30, and all i can do now is wait too see what happens over the weekend. The guy is an ex elec engineer and has wired his whole house up himself and never had it certified, it is an absolute shambles of an installation and i have done all i need to do to be able to sign off my radial.

 

[matt666]

hi there ive fitted about 30 diehl heavy bloody units those 3800s i have never had any problem with these inverters apart form back ache!! never had rcd trip on us either do a ramp test on rcbo check its tripping times

 

[bigbob1]

the rcd is tripping fine, 26ms, i think it's somthing else in the house! i have even been thinking that it could of been the pulse meter? god knows!!

 

[Sonic280674]

Hi Matt,

I fitted a diehl 380s before xmas and it shown no signs of power even though I had 600+dc coming in from the array and 248v ac. I have wired the system in 6mm DC cable in 1 string as the roof is pure south and no shading, when I spoke to Diehl they said the inverter must be faulty and have sent me a new one out however am I ok to have this in 1 string and can the inverter take it (16 x 250w hj solar panels)

Cheers,
Craig

hi there ive fitted about 30 diehl heavy bloody units those 3800s i have never had any problem with these inverters apart form back ache!! never had rcd trip on us either do a ramp test on rcbo check its tripping times

 

[SolarCity]

With that set up you will have an open circuit voltage of 968v - higher at cool temperatures, which means that the panels themselves could possibly be damaged as they are only rated to 1000v. If the data sheet I am looking at is correct then the inverter you have has an MPP range of 315v to 630v and your array comes out at 809v.

The system is very badly designed and I would say that you have seriously damaged the inverter. The system should have been designed as two seperate strings of 8 panels.

 

[SibertSolar]

SolarCity is right about the spec's of the 3800S (MPP range of 315-630VDC), assuming they are the mono HJ panels, they have a 60V Voc so 16 panels in one string could be hitting between 800VDC and 1000VDC on a cold/crisp day (in theory). As advised, try splitting into 2 strings of 8 panels and re-connecting to the inverter but it is possible that damage has already been done to the inverter although I would have expected an overvoltage error to have been flagged up.

 

[Sonic280674]

SolarCity is right about the spec's of the 3800S (MPP range of 315-630VDC), assuming they are the mono HJ panels, they have a 60V Voc so 16 panels in one string could be hitting between 800VDC and 1000VDC on a cold/crisp day (in theory). As advised, try splitting into 2 strings of 8 panels and re-connecting to the inverter but it is possible that damage has already been done to the inverter although I would have expected an overvoltage error to have been flagged up.

Thanks for the info, would you suggest to change the inverter to one which can handle the load, Fronious 3.6 as it isn't possible to change the strings at this point?

Thanks again

 

[Sonic280674]

Sorry the model is the 3800tld which has a greater max MPP range 800+vdc ??

 

[SibertSolar]

The 3800tld has a 710vdc max for MPP tracking and max permissible input DC of 880vdc I think, still not ideal for a single string of 16 HJ250W mono panels. I think you are going to struggle to find a single phase inverter with the necessary voltage/mppt range suitable for 16 of those panels tbh. The fronius is no good and still wouldn't be suitable if you split the string as the max DC input current is only just over 10A. Are you the designer/installer or the end client/homeowner?

 

[Sonic280674]

Installer yet it has fell on our feet to sort it out, we have installed 100s of systems and have never witnessed a Max voltage going anywhere near the MPP max, have you?

 

[SibertSolar]

Best bet is to split the strings I'm afraid. Unless others on here are aware of an inverter that will suit such a high VDC string? Have you looked at the SMA or PowerOne offerings?

 

[Worcester]

Neither the SMA or the Power-one will cope with a single string the MPP voltages are too high in cold wether conditions. Fire it up as a single string and you will damage the inverter.

As the Diehl 3800TLD only has a single MPP tracker, it needs to be configured as two identical strings ( 2 x 8) to avoid damage to the inverter, although even then the MPP Voltage range is outside the tracking range of the inverter. This is in simple terms a very bad design and a mismatch with the inverter. Whowever designed it / specified it should have checked the parameters first.

As 2 x 8 , it won't blow up, however it will perform well below its capabilities. You should swap the inverter for a Power-one OUTD 3,6 or SMA 3600TL

See attached from PV*SOL output for the Diehl 3800TLD when configured as a single string.

 

[SibertSolar]

I think the 3800tld will be ok on 2 strings of 8 from a voltage/MPP point of view - max Voc will be approx 500vdc even in cold weather and the mpp range is 350-710vdc.... My only minor concern would be the 11.5A max input current. Although ok with the very low Isc on those panels (2x 5.35A) you wouldn't have much of a "safety margin" (ideally 25%) on top. An Eltek 3.8HE-t would be much better suited...and can be capped at 16A on the AC output if required.

 

[Worcester]

The problem with the 2 strings of 8 is the start up voltage when the panels warm up - i.e. the most sunny days when the most kWh should be generated, - IF they get to the top of the scale the Vmpp drops below the tracking voltage of the inverter.

The HJ Panels are good panels - we've used loads and loads of them, their high Voc does mean that you have to design the system properly. For the customers sake, let alone reliability, the Diehl shouldn't rally be used on this installation.

see screenshot of 2 x 8 panels:



The eltek 3.8Het is also a good match, so long as you configure it with 2 strings of 8.

 

[SibertSolar]

Fair point although I'd imagine those panels to output 50vdc pretty rapidly though. You're right though - the 3800tld is simply not an ideal match for those particular panels.

 

[Gavin A]

Installer yet it has fell on our feet to sort it out, we have installed 100s of systems and have never witnessed a Max voltage going anywhere near the MPP max, have you?

didn't you / your system designers realise that the voltage on those panels is around 50V vs 30V on the more standard 250Wp panels?

I suppose using the Diehl's with the wide voltage range maybe lulls you into a false sense of security on that front.