# How to reduce the leakage current of a solid state relay?

I have a zero-cross solid state relay (Crydom CKRD2420) that regulates the power output of a 2kW@240V heater using 10Hz PWM (e.g. here to illustrate). I need the power output of the heater to be under ~2W when OFF. However I measured the leakage current is 25mA RMS (2.5 times the 10mA garanteed in the datasheet, by the way...), which means that the power leakage is about 13W (the mains supply voltage reads 264V).

My first thought was a current divider, but the bleed resistor would reduce by a factor of 10 the available power, and reduce significantly the efficiency. I can't use a normal relay because of the lifetime required (I need at least 50-100M cycles of operation), and power MOSFETs would be tricky to implement. Are there any simple-ish fixes I have overlooked?

• To me, the leakage current being out of spec says the SSR is damaged. Dec 16, 2015 at 14:35
• To me as well, but I've got 4 of them and they all show the same leakage current - I don't see how they could all be damaged in the same way, especially given that they are used correctly... Dec 16, 2015 at 14:35
• Perhaps they are not? Dec 16, 2015 at 14:36
• BTW, Are you sure an AC SSR is the right thing for PWM? I would say you need a DC relay here... Also I am not quite sure how do you modulate AC with PWM. Can you provide some kind of schematic? Dec 16, 2015 at 14:41
• @MisterMystère: use some relay in series that you PWM with <1Hz frequency when in the lower enegy requirements range? Dec 16, 2015 at 15:00

The load resistance is R = 240^2/2000 = 29$\Omega$, so with 25mA leakage you'll have a power in the heater of 18mW (I^2R), which is not a problem. The '13W' you calculated is actually 13VA, almost all leading in phase and does not represent power either in the relay or the load.