I'm trying to select a relay for a IoT project that will control a water boiler.
I took a look at the HF32F-G relay, but some of the specifications in the datasheet weren't making any sense to me.
Specifically, the given contact rating for a resistive load is 10A@250VAC, which naturally translates into the specified max switching apparent power of 2500VA.
However, the specified figure for max switching real power is merely 300W, which doesn't seem to agree with the given contact rating for a resistive load of 10A@250VAC.
Can anyone shed some light on this apparent discrepancy?
Best Answer
The difference is AC vs DC.
For DC, the rated voltage is only 30V, which at 10A comes to a 300W max load.
For AC, the rated voltage is 250V, which at 10A comes to a 2500VA max load. Note that this is Volt-Amps which for a pure resistive load is equivalent to Watts.
The datasheet is not saying that for AC, you can have 2500VA active power, but only 300W resistive power. Rather it is giving two specifications, one for AC and one for DC.
I've tried to highlight how these specifications link together in the annotated diagram below.