I seem to remember that these Tomzn units were discussed some time ago. The video shows what the insides are like.

 

https://www.youtube.com/watch?v=FQXecTM8yuo

 

 

 

I love bigclive teardowns and reverse engineering.

 

No real surprises in there, the MOV does look a little small for the 10/20kA rating but it is naked and the other PCB mounted ones I've seen are coated which would disguise the actual size of the active element.

 

Heating the overheat protection with a soldering iron isn't really a fair test. When they trip in real life only a very thin layer of the "solder" around the hot bit melts and the joint pings apart leaving almost a socket in the unmelted bit. I don't have one that's actually tripped to take a photo.

Why are they offered in 2 voltages- 275 and 385v ?

 

https://www.aliexpress.com/item/32268052079.html?spm=a2g0o.productlist.0.0.3d9965d3fKjF10&algo_pvid=c71cc7ce-f73f-46a2-8852-54ee4bc328cb&algo_exp_id=c71cc7ce-f73f-46a2-8852-54ee4bc328cb-3

 

Also, are 2 poles really necessary as they also sell 1p units.

 

https://www.aliexpress.com/item/4000169115438.html?spm=a2g0o.productlist.0.0.3d9965d3fKjF10&algo_pvid=c71cc7ce-f73f-46a2-8852-54ee4bc328cb&algo_exp_id=c71cc7ce-f73f-46a2-8852-54ee4bc328cb-0

 

 

275V for single phase, phase-N (TNC-S) or phase-N+E (TT), 385V for 3-phase, phase-phase.

 

2 pole for TT systems (it never hurts even if TNC-S, gives you a spare cartridge).

 

 

 

Thanks.