Repair or not, electrical heater switching circuit

Submitted ⁨⁨2⁩ ⁨days⁩ ago⁩ by ⁨BigDanishGuy@sh.itjust.works⁩ to ⁨askelectronics@discuss.tchncs.de⁩

https://sh.itjust.works/pictrs/image/2fab08dd-7e2f-4219-a4e6-01816ca23e12.jpeg

Two questions

But would you trust a repaired board?
What makes a triac short out like this?

In the linked picture there are two power supplies from two 400V electrical heaters. Brandname ADAX, model clea. The thermostats have been removed.

The heaters are supplied with two phases only, no third phase and no neutral.

The terminals on triac in the power supply on the right shorted out during the night, luckily the heater was mounted in a bedroom and the occupant was awake. The power supply on the left was pulled from a functioning heater for reference.

I’m fairly certain that only the resistor, triac and board have been damaged. And I’m also fairly certain that I can fix it.

The burned heater is only 1200W, but there’s a lot of vias stitching the two layers together. So while it’s only 3A, and the board is housed in fire resistant plastic, inside a metal and glass casing, it’s also 400V and I don’t know if I want to trust the solution. Even if I can get all the parts, including shipping, for a tenth the cost of a new heater.

If I decide to repair the board I’m going to be replacing the triac, R8, R9, C9, and the varistor.

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Comments

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stevestevesteve@lemmy.world ⁨2⁩ ⁨days⁩ ago
As much as I’m a proponent of DIY fixes, in this case the PCB itself could be burned and potentially conductive, especially at 400v. Is it possible to contact the manufacturer for a new power control board rather than replacing the entire unit?

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- BigDanishGuy@sh.itjust.works ⁨2⁩ ⁨days⁩ ago
  I was thinking about contacting the manufacturer, but they don’t really have any post sale customer support. That’s all on the stores, and besides the heater has been in operation for almost 6 years now. So I’d they’d tell me to go away at best.
  
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  - IsoKiero@sopuli.xyz ⁨2⁩ ⁨days⁩ ago
    Doesn’t hurt to ask. Not related to anything electrical, but “a while” ago my office chair mechanism started to make really annoying noise, metal grinding on metal screech. It was at least 6 years old at that point and isn’t high-end model by any stretch. I sent email to manufacturer if they could point me to a retailer who sells spare parts but instead they just shipped me a new mechanism for free, no questions asked.
    
    Obviously if the model isn’t available anymore it might be a different story, but if it’s still on the market they might give a surprise.
    
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  - espentan@lemmy.world ⁨2⁩ ⁨days⁩ ago
    I’ve actually had success getting support directly from Adax before. Broken wifi unit, sent them an email and they ended up sending me a new one free of charge.
    
    Drop them a line and see, maybe you’ll get lucky.
    
    From Adax.no Image
    
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litchralee@sh.itjust.works ⁨2⁩ ⁨days⁩ ago
My experience is mostly with repairing lower voltage devices (eg 12v to 54v PoE). In your case, a phase to phase short has made quite the mark on that PCB, and being a much higher energy event than low-voltage DC, its possible that some delamination has occurred, with downstream effects on expected trace resistance, capacitance, and leakage/creepage.

Were this a low-voltage board, I personally wouldn’t be worried about those downstream effects. But for AC line voltage, I’d rather buy myself the peace of mind. Do keep parts from the dead board that are salvageable, but IMO, a thermal event on the AC side of a 400v board would disqualify it from continued service.

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- BigDanishGuy@sh.itjust.works ⁨2⁩ ⁨days⁩ ago
  I don’t know what stopped it. I wrote the occupant, but it was really just me. Neither RCD or fuses were blown. There’s a fuse (bimetal in a plastic box positioned above the heating element inside the heater) in series with the heating element, but that’s 400mm from the short, and its probably only there to prevent overheating and setting clothing coverie the heater on fire.
  
  A new heater is 200€, because it has to be 400V as there’s no neutral wire available. That’s why I’d even entertain the idea of repairing the board.
  
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  - litchralee@sh.itjust.works ⁨2⁩ ⁨days⁩ ago
    Would it be possible to rewire the supply wires so that it provides 230v line and neutral? That should make it easier (and hopefully cheaper) to select a heater, although the heater would not be as powerful.
    
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redlemace@lemmy.world ⁨2⁩ ⁨days⁩ ago
400v gives quite a spark when shorted. It’s not worth the risk, replace the board especially if any on it is charred.

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- BigDanishGuy@sh.itjust.works ⁨2⁩ ⁨days⁩ ago
  But you managed to pack my thoughts into 3 sentences. Unfortunately that means a new heater, because I don’t have a source for the board.
  
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