Domus STF100-T Extractor Fan Overrun Timer Problem

[markjg123]

I've installed a Domus STF100-T extractor fan, which I bought as a like-for-like replacement for a broken Silavent GTF100-T. The fan has an overrun timer controlled by a jumper and 4 pins. It's supposed to be adjustable for 5, 15 and 30 minutes, but no matter which two pins I connect it runs for 30 minutes. Pins circled in photo. The fan is operated by the bathroom light switch, via a 3-pole isolation switch. So far Domus technical support haven't been able to resolve the problem, so I'm reaching out to you guys.

 

[EFLImpudence]

Many an hour wasted on faulty new products.

 

[markjg123]

Oh you think that's the problem? Damn. Was an eBay purchase. Doubt I'll get my money back.

 

[securespark]

Why?

 

[markjg123]

Private seller I think. Bought 2 of these.
I read in a related thread that the type of lighting can affect the timer, but I didn't understand the very technical explanation.

 

[markjg123]

I've got the extractor timers working by switching off the power at the consumer unit before moving the jumper to different pins. I had only switched off using the isolator switch before. I've no idea why this would make a difference but it has.

 

[EFLImpudence]

I've got the extractor timers working by switching off the power at the consumer unit before moving the jumper to different pins. I had only switched off using the isolator switch before. I've no idea why this would make a difference but it has.

Presumably your 'isolator' doesn't 'isolate'.

 

[Murdochcat]

Can you post the instructions?

 

[RandomGrinch]

Speculative thinking, but looking at this side of the PCB, there is an ELV side - shown by slots in the PCB and the 25V caps.
A simple variable timer could use the jumper links to select the small cap for @5 mins, the large cap for @15 mins and combine the two for @30 min fan delay.
It possibly wouldn't take much capacitive coupling to maintain a charge on these small caps even with the isolator switched off?

 

[markjg123]

Presumably your 'isolator' doesn't 'isolate'.

It turns off the fan, but switching it back on allows the fan to resume it's cycle.

 

[EFLImpudence]

Perhaps RandomGrinch has the right idea.

 

[markjg123]

Speculative thinking, but looking at this side of the PCB, there is an ELV side - shown by slots in the PCB and the 25V caps.
A simple variable timer could use the jumper links to select the small cap for @5 mins, the large cap for @15 mins and combine the two for @30 min fan delay.
It possibly wouldn't take much capacitive coupling to maintain a charge on these small caps even with the isolator switched off?

My head hurts after reading this

All I can say is they are working as required. I switch the light on and the fan comes on, then it goes off 5 mins after I switch off the light. If I switch off the isolator then the fan goes off. I'm not concerned about it resuming operation when I switch it back on, unless this were due to some major wiring issues, which it's not.