a BigClive discussion and tear-down of an Automatic Transfer Switch

[RichCor]

Since we haven't had a knock-down drag-out fight over Transfer Switches, oh, since

Transfer switch gone amuck
By bankruatsteve, July 21 in The Electrical Forum 

 

thought I might post this recent YouTube video where UK BigClive talks about and does a tear-down of an automatic changeover switch for a backup generator supply. This is for those interested in safelier (yes, not a real word) doing a power hookup combining Live Mains and a Power Generator.

 

 

 

the more you know, the scarier things are

[carlyai]

On transfer switches@Crossy, have you got a dummy load on your automatic setup?

With your automatic setup how do you provide 90% load, if it starts? For me I need an air conditioner or two on for the load, so if I went automatic and we had an incoming power fail this time of year is definitely not air con. weather.

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[Crossy]

42 minutes ago, carlyai said:

On transfer switches@Crossy, have you got a dummy load on your automatic setup?

 

Nah, no dummy load, it's not needed for normal operation, just run with whatever happens to be operating at the time. Our standing load is about 8A (1,700W) anyway (5.5kVA generator).

 

During the monthly (ish) test run I boil the 2kW kettle a few times (leading to higher tea consumption) to exercise things somewhat.

 

[carlyai]

 
Nah, no dummy load, it's not needed for normal operation, just run with whatever happens to be operating at the time. Our standing load is about 8A (1,700W) anyway (5.5kVA generator).
 
During the monthly (ish) test run I boil the 2kW kettle a few times (leading to higher tea consumption) to exercise things somewhat.
 

Ok thanks again......sand bags come in handy?

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[wayned]

The last time that I used a "dummy load", I got knocked off the ladder and broke my hip!

[Crossy]

Interesting video, I've seen these units on Aliexpress but never bought one.

 

The simple manual transfer switch he showed is very good and is only $9 for the 63A version from Aliexpress  https://www.aliexpress.com/item/2P-63A-MTS-Dual-power-Manual-transfer-switch-Circuit-breaker-MCB-50HZ-60HZ-400/32786129292.html

 

The automatic (Tomzn branded) unit he dismembers is $33

https://www.aliexpress.com/store/product/2P-63A-230V-MCB-type-Dual-Power-Automatic-transfer-switch-ATS/300086_32786834934.html? for the single-phase unit or $47 

https://www.aliexpress.com/store/product/4P-63A-380V-MCB-type-Dual-Power-Automatic-transfer-switch-ATS/300086_32788923528.html  for the 3-phase.

 

What would be useful is an indication of the change-over (mains fail) threshold voltage and how to connect it to auto start your genset.

 

I suspect that it doesn't have a well defined "mains fail" level (the mains "sense" is simply the relay coil), which is a shame because it means we need to provide something to do that and something to control the genset.

 

My experiences using a relay as a mains fail sensor weren't particularly successful, it works fine if the mains is actually off, but if it's down at 120V (HV phase out) then the relay doesn't drop out and the genset fails to start.