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.
I could rewire the heating circuit, but doing so without the backing of an authorized electrician would be illegal. I’m already on thin ice just installing the heater by self.
But the thought has crossed my mind, as I have noticed there being an order of magnitude more 230V heaters on the market than 400V. On top of having to rewire everything, I’d have to put in a new 3 phased breaker, otherwise I’d be pulling way too much current… Let’s just say that this 1200W heater isn’t the only one we have in operation in my house.
I see. Given those constraints then, I don’t see any option besides a new heater. Ideally, the new heater would be built with less circuitry, so there would be fewer things to break.
Looking at the Adax Clea product description, it seems overly complicated for a radiator, IMO. I’m not sure I’d want triac switching for something like a heating appliance. Resistive heating doesn’t strictly require silicon switches, when a relay should work. But I suspect an equally-svelt radiator that’s also simple may be hard to find.
I whole heartedly agree with you on the virtue of simplicity in design, and this heater is a bit over the top for its basic function. But we wanted something that
and at the time that narrowed it down to either the Clea or neo series from adax, and I believe one other product line from a second manufacturer. The remote control part was really hard to find in 400V.
A relay would do the job, but they also wear out faster and the sound is noticeable.
While writing that, I found myself thinking about how significant the life span difference is. So I did some back-of-the-envelope calculations.
The defective heater had been installed for roughly 2100 days. Sometime during April we shut the heaters off, and they’re not powered up again until October, so let’s call it 50% of the year. The schedule for the heaters is usually two power on cycles daily. Again let’s call it 50% of the time. The house is pretty OK insulated, but let’s say that the heating element is powering up 4 times each hour. In reality it’s probably closer to 25-30% and twice an hour, so I’ll use that as the lower bounds for this calculation.
1050 days is 25200 hours, meaning that the heaters will have done between 12k and 50k power cycles in the almost 6 years of operation. I’ve seen relays weld shut before 10k, but MTBF for suitably rated relays on RS starts at 50k power cycles.
So maybe a relay could actually do the job. But then there’d still be the issue of the noise, which, while negligible, could still be annoying for some, especially in a bedroom.