Hi all,

I have axpert clone(5star) without internal bond relay. My question relates to external bond relay activation.

I use solar panels, no simple activation of bond relay contact(no) when eskom drops out.

Will it be ok to

a) connect bond relay coil in parallel with bypass relay coil(not sure if driver transistor can handle 2 coils in parallel)

or b) get signal from before driver transistor of bypass relay and employ my own (2n3906 or cmos? ) transistor for activation of bond relay - should there be a delay (500ms?) after activation/deactivation of bypass relay?(rc timing needed)

I was wondering if b), if there is a way to pick up signal from control board (CN11?) without having to take out main board.

You thoughts will be appreciated.

5 minutes ago, Beugleuce said:

I use solar panels, no simple activation of bond relay contact(no) when eskom drops out.

Why can't you utilise the Eskom supply to operate a relay/NEB?

1 hour ago, frivan said:

Why can't you utilise the Eskom supply to operate a relay/NEB?

My 2c you only want to do it when the AC will be supplied by the inverter not when the inverter is not on and has an output.

49 minutes ago, Scorp007 said:

not on and has an output

My proposal doesn't create a NE bond if Eskom is present at all.. But doesn't the inverter blend solar in phase with Eskom? Then it may still work.

2 hours ago, frivan said:

Why can't you utilise the Eskom supply to operate a relay/NEB?

Exactly my thought - that's how mine is set up.

I don't have any knowledge of this 5Star inverter, but by law no inverter is allowed to push back power into the grid when grid power fails, and inverters normally have a relay that opens to disconnect the "non-essential" loads, and the grid input to the inverter. In addition, many inverters make use of CT coils to limit feedback even when grid power is available.

Just hook up a suitable (normally open (NO) type) contactor or relay's coil to the grid side of the inverter (make sure the relay is rated for 230V AC...) and connect Neutral and Earth to the NO terminals Obviously one should first confirm that there is no power on the grid inlet side if the gird is switched off, and that the relay switches correctly before connecting the N and E wires (oh, and these must come from the load side of the inverter...

On 2026/05/07 at 1:06 AM, Beugleuce said:

a) connect bond relay coil in parallel with bypass relay coil (not sure if driver transistor can handle 2 coils in parallel)

The bypass relay is already actually two relays, possibly (depending on the model and power rating) with their coils already in parallel; both live and neutral are switched. I would not put a third load on that relay driver. MAX models seem to have one driver per relay coil, due to the higher power and heavier relays.

I note that the outputs from the control board are open collector and active low. So you'd need an extra inverter stage, or change to an emitter follower arrangement as per the MAX models.

The relay driver circuits are a bit tricky; I can't follow them myself.

On 2026/05/06 at 6:15 PM, Scorp007 said:

My 2c you only want to do it when the AC will be supplied by the inverter not when the inverter is not on and has an output.

Using Grid to supply the relay and connecting N/E to N/C contact. If the grid drops, N/C will close, connecting your N and E. Simple

31 minutes ago, hoohloc said:

Using Grid to supply the relay and connecting N/E to N/C contact. If the grid drops, N/C will close, connecting your N and E. Simpleland

Edited May 9May 9 by Beugleuce
Reformulating...

Below Relay configuration for Neutral/Earth bonding using utility(Eskom) to drive the relay coil. Use a 1 amp fuse on the live leg of the relay coil.

9 hours ago, TaliaB said:

Below Relay configuration for Neutral/Earth bonding

I don't think the Neutral In is needed, but check if earth leakages trip without it.

9 minutes ago, frivan said:

I don't think the Neutral In is needed, but check if earth leakages trip without it.

The Neutral IN shown in the diagram is there because the relay logic depends on the neutral reference during transfer/bypass operation, not merely for bonding the output neutral itself.