Position of Thermal Cutoff (Hi-limiter) in circuit

[jacklam2048]

Hi, may I ask if the thermal cutoff (or called the Hi-limiter) in a circuit must be put at the live wire ? I got an electrical diagram of an electric waffle maker from a factory. I found that they put the thermal cutoff at the neutral wire. Does this conform to the safety regulation ?
Anyone can help is very much appreciated !

 

[AnalogKid]

Rules vary by country, so there is not a single answer. There probably is a distinction between a fuse, which limits dangerous current levels in the wiring, and a thermal cutout, which limits overheating in the device caused by both overheated wiring and other, non-electrical things such as some sort of cover over the device, or the device operating inside a cabinet, where normally safe heat can build up to dangerous levels.

In the systems I've designed, we always put single-pole protection (breaker, thermal cutout, whatever) in the Line.

ak

 

[jacklam2048]

Rules vary by country, so there is not a single answer. There probably is a distinction between a fuse, which limits dangerous current levels in the wiring, and a thermal cutout, which limits overheating in the device caused by both overheated wiring and other, non-electrical things such as some sort of cover over the device, or the device operating inside a cabinet, where normally safe heat can build up to dangerous levels.

In the systems I've designed, we always put single-pole protection (breaker, thermal cutout, whatever) in the Line.

ak

Thanks for your quick reply !
I heard that If the thermal cutout comes in the neutral line. When the thermal cutout trips, it would appear that the circuit is dead where in fact it is still live. The waffle maker will still have 230V. This creates high risk of electric shock during maintenance procedures. But people from the factory defend and say whenever people do maintenance, they will unplug the appliance, so no danger happens. Do you agree ?

 

[AnalogKid]

"whenever people do maintenance, they will unplug the appliance" - ? No. They don't know that, and any liability lawyer can explain what that assertion will cost.

While an open circuit does not draw any current, and of course everything is safe when unplugged, an open Neutral means Line potential is present at exposed points such as connector pins, Fastons (quick-disconnect tabs), etc.

ak

 

[dave9]

Thanks for your quick reply !
I heard that If the thermal cutout comes in the neutral line. When the thermal cutout trips, it would appear that the circuit is dead where in fact it is still live. The waffle maker will still have 230V. This creates high risk of electric shock during maintenance procedures. But people from the factory defend and say whenever people do maintenance, they will unplug the appliance, so no danger happens. Do you agree ?

You are making no sense. There are a thousand different ways that someone can harm themselves if they open a device still plugged into mains AC, including devices that have no thermal fuse at all. No, there is little consideration whether a fuse placement will keep someone from doing something ignorant while taking apart a product they have no business taking apart. Besides if it has failed it's a repair not routine maintenance. Routine maintenance would be something one does to a working appliance with a fuse that isn't blown! And still needs unplugged from AC mains. Remember, it may not be the fuse that failed in the first place, normally some other fault causes it.

 

[Harald Kapp]

"whenever people do maintenance, they will unplug the appliance" - ? No. They don't know that, and any liability lawyer can explain what that assertion will cost.

For this reason usually the manual will state something along these lines:
- "no user serviceable parts inside"
- "Do not open."
- "Before opening the appliance disconnect completely from mains power."
- etc.
If it doesn't, the manufacturer may run into the problem you describe.

 

[Bluejets]

Thanks for your quick reply !
I heard that If the thermal cutout comes in the neutral line. When the thermal cutout trips, it would appear that the circuit is dead where in fact it is still live. The waffle maker will still have 230V. This creates high risk of electric shock during maintenance procedures. But people from the factory defend and say whenever people do maintenance, they will unplug the appliance, so no danger happens. Do you agree ?

Switching the neutral is not normally accepted.
Unit is covered by having a double pole switch and I'm guessing the unit plugs in to a power point.
Servicing anything while still plugged in would be a no-no anyhow.
In Aus at least, any electrical equipment should have a c-tick somewhere to show it is approved equipment.(now rcm compliance)
I'm guessing this device has none.
https://www.eess.gov.au/rcm/regulatory-compliance-mark-rcm-general/

 

[AnalogKid]

For this reason usually the manual will state something along these lines:
- "no user serviceable parts inside"
- "Do not open."
- "Before opening the appliance disconnect completely from mains power."
- etc.

Yeah, like that *ever* stopped me.

You?

ak

 

[dave9]

^ Yes, I have never disassembled something still plugged into the wall outlet. Once I have it open, I might need to plug it back in to test live, but with a plan to not electrocute myself.

 

[Harald Kapp]

You?

Not from opening. But I'm fully aware that I do this entirely at my own risk - and always after unplugging only!