rbdimmer 1CH 4A module gets very hot after ~20 minutes of operation.
Setup:
After 20 minutes the TRIAC is too hot to touch. I measured with thermocouple — 85°C on the package.
Is the module defective? What is the safe operating temperature?
Not defective — the module is overloaded for continuous use. I calculated the power dissipation as follows:
Your load current: I = P / V = 600W / 230V = 2.6A
The 4A module is rated for 4A peak, but for continuous operation you need to apply a derating factor. The general rule for TRIAC modules is to not exceed 60% of rated current for sustained loads. For the 4A module:
4A × 0.6 = 2.4A safe continuous current
Your 2.6A load exceeds this by about 8%. Doesn’t sound like much, but here’s the thermal problem:
TRIAC on-state voltage drop is approximately 1.2V (typical for BTA16-class devices). Power dissipated in the TRIAC:
P_diss = V_t × I_load = 1.2V × 2.6A ≈ 3.1W
The small TRIAC package on the 4A module without a heatsink can only dissipate about 1.5–2W continuously before the junction temperature climbs into dangerous territory. At 3.1W, the package will reach 85°C+ exactly as you measured — and that’s just the case temperature. The junction is even hotter.
Put it in a sealed plastic box with no airflow and it gets worse.
You need an 8A module for this load. The 8A module derating: 8A × 0.6 = 4.8A continuous, which handles your 2.6A with plenty of margin. It also has a larger TRIAC package with better thermal characteristics.
Also — open that plastic box or add ventilation holes.
Clear. Ordering 8A module. Will add heatsink and drill ventilation holes in the enclosure.
The 60% derating rule is very useful — I did not find this in the datasheet summary. I was looking only at the 4A maximum rating and assumed 2.6A is safe because it is below 4A. Now I understand that continuous operation needs extra margin.
For future reference: my application runs the heater 8-10 hours per day in a workshop. With the 8A module and proper ventilation this should be reliable long-term.
Thank you Vincent and rbdimmer team.