Aurora pvi 3000 RCD requirement

[m$park]

I have posted this question on another forum.

Hello calling any experts.

I have three systems to install and am trying to work out RCD requirements, not used Aurora inverters before and can't find any information in the installation instructions.

System 1
Farm with 100A TNCS supply I have already wired some buildings which are fed by sub main and are TT <100 ohms with 100mA S type main switch and 30mA for sockets. System will be connected to submain with XLPE/SWA. Does the Aurora PV1 3600 inverter require a type A or B RCD, array frame will be main bonded 6mm cable to TT MET.

System 2
House with 100A TNCS supply and Earth rod/buried 25mm copper cable connected to MET <200 ohms, array frame main bonded 10mm cable to MET. AC cable In Nexans Allsecure NXS (cable with full earth screen) Does the Aurora PVI 3000 inverter require a type A or B RCD.

System 2
House with 100A TNCS supply and earth rod/buried 25mm copper cable connected to MET <100 ohms. Array mounted on steel frame steel profile roof detached garage with main equipotential bonding exported in 10mm 3core XLPE/SWA to garage. Inverter SB4000TL I have designed this with a 100mA type A RCD as per SMA instructions.

Any comments greatfully received

 

[m$park]

No response to my question yet, I have found some information which I hope may be usefull to other on the forum. see attached

 

[BruceB]

The key point to note is that the inverters do NOT require an rcd.

But if you do use one for other reasons, eg agricultural or TT, then as you have discovered, Power One recommend 300mA type AC. SMA recommend a min of 100mA. Both Power One and SMA say type B is unnecessary. Using a 30mA rcd, eg for additional protection for cables buried in walls, is not recommended because of the possibility of nuisance trips. But some people say they have done so successfuly.

In you scenarios:
-SYSTEM 1. Probably ok, but does not match the 300mA Power One recommendation.
-SYSTEM 2. No rcd required unless cable is buried in wall. Or is that cable exempt? DTI Guide V2 does not allow array framework with TL inverter to be bonded to MET with TNCS (in most circumstances)
-SYSTEM 2 the second. Read the SMA instructions more carefully. They do not require an rcd. They say if you have one it should be at least 100mA.

Regards
Bruce

 

[m$park]

From the DTI guide

Where an electrical installation includes a PV power supply system
without at least simple separation between the a.c. side and the d.c.
side, an RCD installed to provide fault protection by automatic
disconnection of supply must be type B RCD according to BS EN 60898
(IEC 60755, amendment 2).

I thought simple separation was a transformer to BS3535 in which case a transformer less inverter will need an RCD

 

[BruceB]

That is not what it says.

An RCD "installed to provide fault protection by ADS" means a TT situation or where Zs is too large for the mcb protecting the circuit. But if you do not need an rcd to provide ADS because your mcb can do it then type of rcd is irrelevant because there is no need for one.

That requirement is reflected in 712.411.3.2.1.2, which also then has the exemption where an inverter cannot by design feed dc to the ac side, which the SMA and Power One TLs are stated to fall within, then no type b needed.

 

[GaryM]

Would you also apply that logic to the Fronius IG TL range?

 

[SolarCity]

Would you also apply that logic to the Fronius IG TL range?

Absolutely

 

[SibertSolar]

Just fyi, but if anyone's planning to visit Ecobuild in March then come and see us on our stand (N3367) and we'll have a demo unit running to show what happens to Type-A and Type-B RCDs when subjected to pulsed and pure DC leakage currents.