Fitting a bathroom fan...again.

[amfisted]

Right.. I was absolutely sure that I understood the wiring diagram that came with the fan to the letter and line, and that I'd absorbed everything I've been told here.

I connected everything up this afternoon and Voila...the fan runs permanently, even when the pullcord switch is off.

I know the switch is working because when you pull it once the power light on the fan comes on, and when the cord is pulled again the light goes off. But... whatever position the switch is in, the fan continues to run on, and I don't think its the timer because I've sat and watched the damned thing whirring away happily for 20 minutes with the timer interval turned down to minimum.

Presumably the humidistat function doesn't work when the external switch is off, so does anyone have any idea what I might have done wrong?

Cheers.

 

[EFLImpudence]

Of course the humidistat controls it when 'off'; how else could it work.

Turn it up to maximum. It's 82% outside here today.

 

[JohnW2]

Of course the humidistat controls it when 'off'; how else could it work.

With reference to the original wiring diagram we were shown that obviously depends upon whether we are talking about the isolating switch or the over-ride one. If the latter, then I agree with the above, and with:

Turn it up to maximum. It's 82% outside here today.

Kind Regards, John

 

[amfisted]

So...just to recap, if I fit an external pullcord switch on a humidistat fan and turn that switch off, the fan will continue running as long as the humidity level remains high, notwithstanding the setting on the timer?

 

[EFLImpudence]

if I fit an external pullcord switch on a humidistat fan and turn that switch off, the fan will continue running as long as the humidity level remains high,

Yes.

notwithstanding the setting on the timer?

Not sure what you mean.

It will continue for the set time after the humidity reaches the set value.

 

[amfisted]

Ah, I see...thank you.

What I meant was "does the timer override the humidistat: ie, even when the humidity hasn't yet reached the required level, the timer will turn the fan off".

Maybe all is not lost after all.

 

[JohnW2]

So...just to recap, if I fit an external pullcord switch on a humidistat fan and turn that switch off, the fan will continue running as long as the humidity level remains high, notwithstanding the setting on the timer?

Yes, assuming we are talking about that 'over-ride' switch. The only way you could stop the fan working when the humidity was above its 'trigger' level would be to turn off the isolating switch (if you have one). That 'over-ride' switch is only there so that you can turn the fan on when humidity is to low for the humidistat to turn it on. My understanding of the timer is that it determines how long the fan continues running after the humidity level has fallen to below the device's trigger threshold and/or after you have operated the over-ride switch.

Kind Regards, John

 

[EFLImpudence]

What I meant was "does the timer override the humidistat: ie, even when the humidity hasn't yet reached the required level, the timer will turn the fan off". .

Yes, but that wouldn't be overriding as the humidistat wouldn't be 'on'.

 

[AndyPRK]

I didn't think or know the timer had an relationship to the humidity sensor.

I assumed it was a case of a timer fan (timer letting the fan run on, after light/switch turned off) with a humidity sensor added on. As soon as the humidity threshold is reached the fan would go off (assuming light off, timer expired)

What reason could there be to let the fan continue to run on a bit after the humidity level was reached?


With regard to the OP's problem. Turn off the isolator, turn the humidity adjust to max one way. Turn isolator on. If fan is still on.
Turn isolator off, turn the humidity adjust to max the other way. Turn isolator on.

 

[JohnW2]

What I meant was "does the timer override the humidistat: ie, even when the humidity hasn't yet reached the required level, the timer will turn the fan off". .

Yes, but that wouldn't be overriding as the humidistat wouldn't be 'on'.

I think the vocabulary may be introducing some confusion. As I understand the functionality it does 'override' the humidistat for its timed period, in the sense that it causes the fan to continue running even after the humidistat goes 'off' - but then the fan stops after the end of the timed period.

As I said, 'over-riding' of the humidistat (by either manual switch or timer) can only work in that direction (turning the fan on when the humidistat is 'off'). As I said in terms of 'the other way around', the only way to turn the fan off when the humidistat was 'on' would be to operate an isolating switch (if there was one).

Kind Regards, John

 

[EFLImpudence]

What I meant was "does the timer override the humidistat: ie, even when the humidity hasn't yet reached the required level, the timer will turn the fan off". .

Yes, but that wouldn't be overriding as the humidistat wouldn't be 'on'.

I think the vocabulary may be introducing some confusion. As I understand the functionality it does 'override' the humidistat for its timed period, in the sense that it causes the fan to continue running even after the humidistat goes 'off' - but then the fan stops after the end of the timed period.

Ah yes, I was thinking what was meant was the humidity 'on the way up'.

If 'on the way down' then the timer will continually be 'reset' until the humidistat turns off.
The same if the light switch is turned on and off in quick succession (frequent visits).

 

[JohnW2]

I didn't think or know the timer had an relationship to the humidity sensor. ... I assumed it was a case of a timer fan (timer letting the fan run on, after light/switch turned off) with a humidity sensor added on. As soon as the humidity threshold is reached the fan would go off (assuming light off, timer expired)

The instructions are a bit ambiguous, but seem to imply that there is a timer-controlled run-on after a period of either manually- or humidistat-initiated 'fan on'.

Operates either when triggered automatically by the humidity sensor or when turned on using the integral pull cord switch (light indicates when fan is operating in manual mode). Built-in timer automatically operates fan for a preset delay of up to 20 minutes.

What reason could there be to let the fan continue to run on a bit after the humidity level was reached?

If that does happen, I suppose it would just be to provide a bit of user-programmable hysteresis in the control (in addition to whatever hysteresis may exist in the humidistat itself).

Kind Regards, John

 

[EFLImpudence]

I think that is how they generally work although, obviously, difficult to test.

I presume the humidistat just triggers the timer in the same way as the light switch.

 

[JohnW2]

I think that is how they generally work although, obviously, difficult to test. ... I presume the humidistat just triggers the timer in the same way as the light switch.

Yes, it would actually be impossible to test (without delving into the innards with a meter) unless there was some way of knowing whether the humidistat itself was 'on'or 'off' (which I presume there normally isn't). Like you, I had presumed that the humidistat probably triggered the timer in the same was as with a manual (over-ride switch) or light-circuit trigger.

Kind Regards, John

 

[AndyPRK]

Yes its a fair point. It could be designed that way.

I guess if one wanted to know you could fiddle with the 2 pots, and it maybe possible to work it out from that.