help selecting best inverter for tt system 4kw

[crawf.9]

hello all,
struggling to find the right inverter for this job.its our first one with a tt supply.we usually use sma 4000TL on these size jobs,but i can't see a way of satisfying manufactures
100ma max rcd and current regs.
to my mind,a transformerless inverter doesn't seem suitable for a tt power supply,
any thoughts?

 

[yellowvanman]

You can use a 100mA RCD on TT as long as the cables is not concealed in a wall!

 

[SolarCity]

You should be careful installing a TL inverter on anything system that has a high Zs - which is almost certainly the case with a TT system.

 

[crawf.9]

thanks for that yellowvanman,just been reading the spec of a sma 4000TL inverter and it does say suitable for TT sytems if
Un PE<15V i'm now thinking what that is,time to cast my mind back

it would be an armoured cable if in the wall and 100ma trip to satisfy the tt regs though.

help with the test requirement above will be very much appreciated though

 

[yellowvanman]

Not familair with the 'Un PE<15V' term!

 

[crawf.9]

thanks for your thoughts,biggsolar.
i did read somewhere that an earth loop greater than 1 ohm would make a TL unsuitabe,but now can't find this on sma 4000TL inst. manual,unless it was fronius?!

using a 4000TL would be a better efficiency than the isolating transformer equivalent,can you recommend an isolation transformer inverter that has similar efficiency?

 

[crawf.9]

has anyone fitted a sma sb4000TL inverter to a TT supply,and if so,can you advise on earthing arrangement and rcd protection used

 

[SolarCity]

I'm not sure about Un PE<15V. It appears to be talking about earth leakage or something but I'm probably wrong.

I have used 4000TL inverters on TT systems but I've always made sure that the Ze is as low as possible. I'm not sure exactly how low it needs to be - I have asked the manufacturers previously - but if it seems too high then I make an effort to bring it down.

 

[BruceB]

I suspect that means the voltage between protective conductor and true earth (or N line)