Here’s a shot of one of my basics and the CE certificate from iTead.
Where do you put the 3rd wire? I always say that sonoff basic can’t be used with hugh power devices like heaters, cause one of the think left on many sonoff devices is ground input/output terminals.
That’s easily solved with a wire nut or screw terminal and has nothing to do with the load carrying capacity.
Apparently the pilot wire on some heaters is smarter than just an on/off signal and depending on the polarity and pulse width can perform more than one function:
Pilot wire current is typically less than 100mA.
So my guess would be a cracked dry solder joint causing arcing.
What I do is run the ground wire behind the Sonoff solder it together and heat shrink the whole thing. Might not be the most electrically compliant way but the earth is connected from one side to the other.
I could be wrong but I’d be horribly surprised if an arcing current of 100mA caused that much heat/damage.
We still need a drawing of the circuit…
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For all the Canucks here, the CE rating is not recognized in Canada. If the device does not have CSA, UL, or ETL markings then it does not meet the standards set by the Standards Council of Canada. If the device damages or destroys your property (or worse) your home insurer will take a dim view of your decision to use unapproved electrical equipment.
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I’ve just realised my panel heaters have the same pilot connection. The manual is a horrible mash of French Russian and English but it’s pretty simple to understand.
There are three terminals. Phase, neutral and pilot. wouf is taking the positive phase cycles (via the diode) and feeding them to the pilot terminal when the sonoff relay is on. This switches the heater off.
With the sonoff relay off there is no connection to the pilot terminal which results in the heater functioning in comfort mode (controlled by heater’s thermostat setting).
A IN4007 diode is appropriately rated for this application. Though the reverse dv/dt rating could be exceeded by noise spikes produced by arcing.
Even allowing for half wave rectification, 240V @ 100mA is 12W that could be dissipated in the arc/dry joint. I’ve seen 2W power resistors char FR4 PCB laminate eventually (takes months to a year) if they are not appropriately cooled.
yeah, I could see the 12w arcing in a small area causing a localized (very localized) high temp causing the the solder to melt and browning the board. But as soon as the solder connection fully melts = no more current since a 240v/100mA arc isn’t likely to be maintained thru the resulting air gap. Especially not long enough to cause that much heat to cause that much damage.
I’ve seen 480v 10 amp loads on a high resistance connection that didn’t cause that much damage.
But since there’s no way to really tell what happened it’s all just speculation at this point.
Moral of the story:
- Make sure you properly hack devices with good solder joints.
- Make sure you know what your doing with this kind of thing because the ramifications if done improperly could be devastating.
Or the solder could melt and bridge something it shouldn’t. There are many failure modes.
Agreed.
What we need @wouf to do is take some high resolution photos of the circuit board.
- In the case with the case cover off
- Board removed, top and bottom side photos
- Board washed, top and bottom side photos
Ideally you’d wash the board with foaming PCB cleaner but water and gentle rubbing with a toothbrush would do.
Also wear gloves or wash your hands thoroughly with soap and water afterwards. There could be some nasty compounds in that soot.
Worth repeating:
Any electrical item can fail and burn. Doesn’t mean the whole company and their products are bad unless it is a documented issue and not a single instance. Also everything put into a wall with power requires an approved electrical box/housing for just this case. And proper wiring for the 110/220 power to the SONOFF.
So what in that certificate makes you believe it is electrically safe? It all seems to relate to RF emissions.
And I don’t believe a CE certificate makes it legal to use in Australia. AU and NZ have their own certification codes.
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I’m not saying that I’m an expert on this stuff but reading through the 52 page report on iteads site it mentions numerous over temperature, short circuit, current, over voltage and electrical isolation tests performed.
From my perspective of the device it satisfies my criteria (maybe not a lawmakers) enough to make it for me a safe device to use. Australian law does state however that a RCM compliance is needed that states the product complies to Australia electrical standards however this is closely based on the CE certification used by the EU. Based on this the device may upon further research may not be 100% law compliant as I stated earlier but I am happy with the certification that have and expect others to be aswell.
Riley.
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This is the top of the pcb, did a really quick wash without tools, I can do better later if needed, but I think it’s clear enough : problem come from 1n4007.
I had other heaters more powerfull and connected the same way for more than one year, without any problem, I think all was ok but I probably had a faulty 1n4007 (aliexpress one…).
Other side :
@wouf Your diagram above, is the Wago connected to the pilote wire or the main feed into the heater ? Also, I’m assuming that the heater output cable is three core ?
Sonoff basic should be illegal to sell, they don’t follow various electric codes.
I advice all NOT using them.
The POW it’s much better (although not 100% code proof)
All Bullshit
Guess why it doesn’t satisfy the law maker : because you can kill people, relatively easy, with those devices
The DESIGN is flawed to begin with. The Basic is bad bad bad device for its use.
