I've just fitted Boostmaster FBT5 switched, fused, spur timers to a couple of dual-heat towel rads. They work well and are easy to use BUT the LEDs that indicate the timing progress are lit whether or not the switch is "on" or the fuse is fitted, and without these there's no power to the rad. Seems daft!
Lin and Lout and Nin and Nout the wrong way around?
I thought that too, but their "internal schematic" shows the timing circuit before the switch, and the fuse in series with Lout.
I discovered the same (or a consequent) problem when I wanted to use a timer with an isolation switch to isolate a circuit that also needed untimed always on (when not isolated) live from the switched side of the isolator switch (for a frost stat). This can't be done because the timer output relay is on the mains side of the isolating switch. On mature reflection I realised there is no safe way to put the relay contacts on the output side of the isolating switch without using a very expensive relay with a safety rating for coil to contact insulation equal to that of the isolating switch (3mm gap?), because the timing circuit needs to be supplied with power even when the isolating swich is off. So I needed an FCU as well.
That also means that although they could put an indicator on the isolated side of the switch it could only light when the timer and switch were both on, and, unless it was a neon, would need an extra low voltage LED supply isolated from the mains side one.
That would seem wrong, if the circuit went short the fuse would be pointless tripping the whole circuit.. Brian
I haven't put real thought to it but it feels as if the closure of the switch neutral contacts could be detected and used to enable the LEDs ... or a simple mechanical linkage to operate a microswitch when the D/P switch is operated ... or an opto-isolator used ... but an output neon would be the simplest thing to add. I like the FBT5's simple indication of selected time intervals, but the usability aspect hasn't been thought-through IMnsHO.
The MCB will protect all to the FCU and the fuse will protect all after the FCU
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