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 occupant of the room was awake, because this happened in a bedroom. 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.
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.