Concerning Sonoff Mini Switches and Circuit Protection

What’s up with Sonoff’'s directive to add 6A or 10A circuit protection to their devices? In most cases these are being installed on circuits that are wired with 14 gauge wire and 15A circuit breakers. That does not meet the specification of either 6A or 10A circuit protection (Sonoff says both 6A and 10A in their manuals).

Here are the statements verbatim from the Sonoff ZBMINIL2 Quick Guide and the ZBMINIL2 and MINIR4M User Manuals:

ZBMINIL2 Quick Guide V1.0 (still being shipped from ITEAD in December 2023) –

“To ensure the safety of your electrical installation, it’s essential either a Miniature Circuit Breaker (MCB) or Residual Current Operated Circuit Breaker (RCOCB) with an electrical rating of 6A has been installed before the ZBMINIL2.”

ZBMINIL2 Quick Guide V1.1 (2022-11-18) –

The above language has been completely omitted, but in the User Manual there is still (December 2023) a directive in the ZBMINIL2 User Manual to add 10A of circuit protection.

ZBMINIL2 User Manual V1.0 (from Sonoff website on 12/15/2023) –

“2.Wiring instruction:
Before installing the device, please install an air switch as the protective device (Air switch: 10A/250V).”

|Model| ZBMINIL2
|Input| 100-240V AC 50/60Hz 6A Max
|Output| 100-240V AC 50/60Hz 6A Max
|Max. load| Resistive load: 6A Max LED:150W Max @100V, 300W Max @240V

MINIR4 User Manual V1.0 (from Sonoff website on 12/15/2023) –

“Wiring instruction
To ensure the safety of your electrical installation, it’s essential either a Miniature Circuit Breaker
(MCB) or a Residual Current Operated Circuit Breaker (RCBO) with an electrical rating of 10A
has been installed before the MINIR4M.”

|Model| MINIR4M
|Rating| 100-240V~ 50/60Hz 10A Max Resistive Load μ
|Max. power| 2400W@240V”

So, which is it that is required?
Is it a 6A Miniature Circuit Breaker (MCB)?
Is it a 6A Residual Current Operated Circuit Breaker (RCOCB)?
Or is it a 10A/250V Air switch?

If we go just by what is presently (12/15/2023) available at the Sonoff website (ZBMINI-L2-DOC - SONOFF Official) the only directive is to install a 10A/250V Air switch, and it seems that would have to be inside the electrical box along with the ZBMINIL2, right? I think we need to qualify the terminology

Let’s qualify what is meant by an “air switch.” This would not be the kind of switch used with some garbage disposals or hot tubs. I believe the Sonoff engineers are a referring to what’s known as any mechanically operated device that produces a gap (of air) in the electrical path.

Let’s look again at the language from the User Manual, from Step 2:

“Before installing the device, please install an air switch as the protective device (Air switch: 10A/250V).”

We must assume this means a 10A breaker (generically described as an air switch) since they refer to it as a “protective device.” In Step 1 they already instructed to turn the power off, so this is not for shock protection of the installer. We have to assume they mean overload protection for the 6A rating of these devices.

Now let’s qualify what a Residual Current Operated Circuit Breaker (RCOCB) is. These are typically used with DIN rails in industrial automation scenarios, but Residual Current [Device] (an RCD) refers to what is essentially a Ground Fault Device (ground fault being American terminology) that protects against current leakage. What? The following is a clue from Wikipedia:

A pure RCD will detect imbalance in the currents of the supply and return conductors of a circuit. But it cannot protect against overload or short circuit like a fuse or a miniature circuit breaker (MCB) does (except for the special case of a short circuit from live to ground, not live to neutral).

However, an RCD and an MCB often come integrated in the same device, thus being able to detect both supply imbalance and overload current. Such a device is called an RCBO, for residual-current circuit breaker with overcurrent protection, in Europe and Australia, and a GFCI breaker, for ground fault circuit interrupter, in the USA and Canada.

Okay, there’s a direct reference to the Miniature Circuit Breaker (MCB), and the only exact terminology to match the Sonoff documentation. So can we assume the Residual Current Operated Circuit Breaker (RCOCB) is a combination of an MCB and RCD (or GFCI)? I think so.

Now let’s define Miniature Circuit Breaker (MCB). Is this a tiny device that’s supposed to fit inside the electrical box with the ZBMINIL2? I don’t think that’s what Sonoff is trying to say, but who knows. There is certainly no off-the-shelf device like this being sold in the U.S. or Canada., that I could find. Here’s a couple definitions from Wikipedia, concerning what low-voltage and MCB mean:

Low-voltage (less than 1,000 VAC) types are common in domestic, commercial and industrial application, and include:

Miniature circuit breaker (MCB)—rated current up to 125 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation.

It seems to me that this all (Sonoff documentation) refers to the circuit breaker found in one’s typical electrical breaker panel, but the specification for 6A or 10A is not in line with what we typically have in our (U.S.) residential installations. For most of us (in the U.S., anyway) we’re going to find a 15A breaker installed on our lighting circuits. Does this mean we should change the 15A for a 10A breaker if we are using these Sonoff Mini switches?

If so, this will create other limitations in load capacity for a lighting circuit. For instance, if your bathroom light is on the same circuit as the outlet your wife uses for her hair dryer, the Sonoff Mini switches will not be suitable for such a circuit. The same goes for any 120V circuit load that goes over 10A/1200 watts. Remember Ohm’s Law: V/I=R, I=V/R, V=IR and IV=W (10A x 120V = 1200W).

These 10A breakers are not at all common in the U.S., and will likely need to be special ordered.

Looking forward to hearing the thoughts from the Community…

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My thoughts:

  1. their devices are typically designed for EU/Asia, not the US, and that brings up some of these issues

  2. these questions are best directed to Sonoff. Let us know what they say

  3. although their documentation does say “air switch“ I’m pretty sure this is a translation error, and what they meant to say was “air break” switch. Also called a “disconnector” and not at all the same as the air bubble switches used in areas with a lot of water, like for a garbage disposal. (In some countries, it is called an “isolator.“) Given the context, I suspect they specifically mean arc chutes in miniature circuit breakers, but I don’t know for sure. :thinking:

  4. speaking just for myself, I don’t wire anything into the mains which isn’t UL/ETL safety certified Shelly has A good line of inexpensive models with UL certifications.

When Shelly first made the decision to go for UL certification, they thought their devices already met all the requirements, and their executive staff said they were quite surprised by the number of changes they did have to make. :thinking:

Details are included in the following

FAQ: Does UL Certification matter?


When you say “they” in the paragraph following #4, do you mean Shelly?

On a side-note from the larger question, the ZBMINIL2 and MINIR4M carry the “TUV Rheinland” label, though not with a US or C, as outlined in your UL FAQ.

I think the deciding factor for many of us will be the insurance exclusion mentioned in that FAQ. So much for the $100 I just spent on $13 Sonoff Mini switches, and for the idea that I would free up a bunch of $30 Z-WAVE and Zigbee rockers for locations where they are more useful…

Yes, sorry for any confusion.

For Sonoff, The TUV Rhineland mark will be issued contingent on following all of the manufacturer’s installation instructions. It may also be contingent on being installed in a European system, it depends on the details of the Mark grant.

Does Shelly make Z-Wave or Zigbee? I’m just not comfortable yet with go WiFi, though I did get some MINIR4Ms to experiment with.

If not, then from a money-savings standpoint, the only US certified solution (for Zigbee or Z-Wave technology) that I can find would be the Zooz ZEN52 Double Relay if one has a switch box where two non-dimming switches are applicable. This gets the cost down to roughly $18 a switch.

Shelly makes WiFi, mostly.

I like the engineering on the zooz devices. Leviton is also good.

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Sadly, most people don’t read that. Or understand. The potential is there for someone to be seriously disappointed when their insurance claim–should it come to be–is potentially denied for failure to comply. (Another big one many folks don’t understand/heed in areas covered by a local, state, or national fire code that requires a barbeque grill to be located some distance–often 15 feet or more–from the insured structure. The grill melts the siding? Starts a fire? Insurance claim denied!)

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