I've put a 4P Hager 2NO/2NC contactor to switch my geyser between essentials and non-essentials wired such that it is after the EL of each. The coil is wired into the non-essentials as well, so when the grid drops it puts the geyser onto the inverter.

But sometimes when the geyser is powered while the grid supply falls away or comes back it will trip the ELs. Sometimes one, sometimes the other, sometimes both. 

I'm assuming there is a bit of cross-over in the contactor creating enough difference between L&N to trip the EL? Or am I mistaken?

24 minutes ago, rinners said:

I've put a 4P Hager 2NO/2NC contactor to switch my geyser between essentials and non-essentials wired such that it is after the EL of each. The coil is wired into the non-essentials as well, so when the grid drops it puts the geyser onto the inverter.

But sometimes when the geyser is powered while the grid supply falls away or comes back it will trip the ELs. Sometimes one, sometimes the other, sometimes both. 

I'm assuming there is a bit of cross-over in the contactor creating enough difference between L&N to trip the EL? Or am I mistaken?

This is not ideal , in fact it's dangerous , and COC will not approve . Even if the contactor is break before make , which is normally the case with contactor.

You need a dual mechanically interlocked contactor arrangement. When energizing the coil of one contactor, it first unlocks the other mechanically.

EDIT: actually the contactor does not  get mechanically unlocked, the mechanical interlock just proves mechanically that the other contactor is already de-energized before you can operate the contactor.

There are manufacturers that actually sell a mechanical interlock kit in order to upgrade certain types of their single  contactors  .

 

Edited May 25, 20233 yr by BritishRacingGreen

@BritishRacingGreen

Thanks.

Those contactors you are referring to, I think I know them, but not sure they will fit under a din front panel? They look pretty chonky.

What if I used one of these instead? I assume there's some sort of delay built into it to avoid cross over?

https://www.takealot.com/automatic-changeover-switch-2-pole-63a/PLID91215945

 

1 minute ago, rinners said:

@BritishRacingGreen

Thanks.

Those contactors you are referring to, I think I know them, but not sure they will fit under a din front panel? They look pretty chonky.

What if I used one of these instead? I assume there's some sort of delay built into it to avoid cross over?

https://www.takealot.com/automatic-changeover-switch-2-pole-63a/PLID91215945

 

Yes automatic transfer switches  will do the job , they  also have mechanical interlocking inside, or at least they should. 

Just make sure that the device is approved locally , make sure you COC official will pass it.

7 minutes ago, BritishRacingGreen said:

Yes automatic transfer switches  will do the job , they  also have mechanical interlocking inside, or at least they should. 

Just make sure that the device is approved locally , make sure you COC official will pass it.

The following must be noted on this switch:

When one power system turns off, the switch will automatically connect to an alternative.
Use a known solar or backup power installer

So make sure this will work for you. I would have preferred to actuate it remotely via my control system,but that's just a preference.

Edited May 25, 20233 yr by BritishRacingGreen

On 2023/05/25 at 9:51 AM, BritishRacingGreen said:

Yes automatic transfer switches  will do the job , they  also have mechanical interlocking inside, or at least they should. 

Just make sure that the device is approved locally , make sure you COC official will pass it.

Ok, then I need to know what devices are locally approved, how do I tell?

Would this be?

https://www.geewiz.co.za/smart-plugs-switches/192524-automatic-changeover-switch-2p-single-phase-220v-100a-50hz.html?

But I see the number of cycles on this is low, 2000 cycles could easily be done in a year with load shedding.

So I'm thinking of adding another din rail contactor with some delay on timers. Just need to figure out the wiring, not sure if I need NO+NC on both or just NO on one and NC on the other.

Would this set up be able to pass a CoC using probably this delay timer:

https://acdc.co.za/products/delay-on-timer-10-120s-230v-din?variant=30482310732

Great chat and good info around what could pass a COC. I haven't read of the mechanical interlock system for a long time. Also worth noting that it is essential to use a normally closed contact of the other source in series with the coil to create electrical interlock so 2 coils cannot be energized at the same time. 

Another option is to use a fail save relay where the design is of such a nature that if any contact welds other contacts cannot move.

I just cannot remember the make and model and hope someone can fill in on this. 

@BritishRacingGreen

Who and how are electrical equipment approved to satisfy use for getting a COC. 

Edited May 27, 20233 yr by Scorp007

1 hour ago, Scorp007 said:

.

Ok , I don't know of COC  type approval per se, that why I recommend that the OP  passes it by the COC official. My COC contact  that checked my integration of small inverter  supply to my lighting circuits a number of years back insisted on either a manual changeover or in the case of electrical operation , that the dual contactor be mechanically interlocked.

He pointed out to me that electrical interlocking (rest contact of one contactor in energizing circuit of another) is not safe enough.

I tend to agree with him, the inadvertant  connection of non synchronised supplies leads to catastrophic failures.

 

3 hours ago, BritishRacingGreen said:

Ok , I don't know of COC  type approval per se, that why I recommend that the OP  passes it by the COC official. My COC contact  that checked my integration of small inverter  supply to my lighting circuits a number of years back insisted on either a manual changeover or in the case of electrical operation , that the dual contactor be mechanically interlocked.

He pointed out to me that electrical interlocking (rest contact of one contactor in energizing circuit of another) is not safe enough.

I tend to agree with him, the inadvertant  connection of non synchronised supplies leads to catastrophic failures.

 

Thanks. I thought that some transfers actually have a timer that allows a generator to 1st stabilise and then the transfer of load takes place. I have to say I have not worked on transfer switches for a long time. I use a manual unit between inverter and whole house after I have switched off some hi power loads. When I go away then these high loads remain off and essential loads can stay on the inverter. 

The ATS have a few down sides:

1) They are big
2) They are loud
3) They don't have a lot of cycles. Assuming an average of 2 auto switchings per day that's less than 3 years lifespan (yes I know they are cheap enough)
4) They physically move when changing over. Sometimes enough to trip the EL or breaker either side of it.

What are the thoughts on this mini transfer switch? Other than the build quality, is it enough of an interlock? would it pass CoC?