EUD12NPN-UC from Eltako Electronics 

I was installing the EUD12NPN-UC for a friend and like your opinion on the following.

Before there was an Eltako impulse relay (Eltako S12-100-230V) for the corridor lights.  Several light points and 3 impulse switches.

My friend asked me to help him remove the impulse relay and replace it with a dimmer (EUD12NPN-UC from Eltako Electronics) and as soon as I put it in and truned the fuse, the fuse it blew all the trip switches (2) in all the circuits too.

I wired it in as per diagram (see enclosed) and as soon as I flipped the fuse, it tripped both the trip switches.  I did some checking and in the end found that if I only connect live and neutral (see diagram of the EUD12NPN-UC marked in red) to L and N on the EUD12NPN-UC the same thing happened.  

My assumption is this thing is dead on arrival, or there is a minuscule leakage but that should not be.  Am I right? Any experience with these units? Any tricks?  

Thanks. 

Sounds like a dead short .       I presume your lights go in the   X   terminal ?   

If it wasn't dead before it probably is now. Electronic switches don't generally like being involved in short circuits or overloads.

I find your diagram hard to interpret. Are the two upper rails just for the switches?

In your installation, are the upper terminals ONLY connected to the switches? An original stepping switch would probably have one side to supply.

I was guessing a1 & a2    were  the remote switching pair ....and   X  was the light fittings  . Never fitted one of these TBH.

Yes, I was making the same assumption but the diagram really is unclear regarding terminals A1 & A2.  I just wondered if the OP had connected one of them to supply, either deliberately or accidentally.

A1 & A2 are the standard markings for a relay coil connections.

If this is commercial, perhaps there are two phases across the device, one phase for the L & N for the load, and another for the control supply which has created an issue?

I would say the A1 & A2 from the impulse relay need to go to the A1 & A2 on the dimmer.

The 1 & 2 on the impulse relay, one of these is line, one load, the line (L power supply) needs to go the L on the bottom of the dimmer.

The other to the load connection with the lamp symbol (X in a circle).

You will then need to pull a N in from the same supply as the L, unless the control on A1 & A2 is from the same breaker.

In which case the A1 & L are equipotential, and A2 & N are equipotential.

Lamps still to the lamp symbol and on to the same N as above.

Finally the switches are as shown.

You might have the circuit supplied from 2 RCBO's and you may have a shared or crossed N, in which case you will trip both.

Is the control (switching/dimming/retractive switches) on the same breaker as the lamps?

If the control is on a different breaker and they are RCBO's where have you got the N from?