Remote humidistat with timer fan

[PinkE]

I've been asked to fit a remote humidistat where there is already an inline fan with timer in place.

I have wired it as per the instructions on the supply side (i.e. L, SL and N). The output is a N and L to the fan. So, as the fan itself requires a permanent and switched live I have connect the L output from the humidstat into both lives on the fan. I was hoping that this would meant that the fan switches on with the light but also when humidity is above the preset level on the humidistat.

Problem: when the lights are switched off, they flick on off on off continuously.

What am I doing wrong chaps?

Is it not possible to have the fan come on with the light switch as well as the sensor because the fan requires a permanent live and switched live?
I read a post on here https://www.diynot.com/diy/threads/fan-controlled-by-light-switch-and-humidistat.342297/ (from 2003) where Ban All Sheds said to use a DP light switch to separate the fan (humidistat) live from the light switched live. Wouldn't this simply be the same as having no permanent live, the fan would always be off if the light switch was off?
One last thought, The instructions say it can be wired as a humidistat only, without the timer but there's no diagram to support this. I assume just don't connect at all the light switched live into the humidistsat? Will the humidistat still work if I do this?

Thanks

 

[ericmark]

When @ban-all-sheds talked about a twin pole switch the building regulations stated that where there was daylight available in the bathroom you needed to be able to turn on the fan without the lights. This was dropped, and when I looked for the old regulation I could not find it.

To be frank I did not have much luck with a humidistat switch, I found they were slow to come on, and when they did, they would then run for a very long time before they were dry enough to switch off. So as a result you do need a method to turn off should it end up running for a long time.

I did look at three homes, two no problem with mould, and one with a problem, and tried to work out why, I realised it was the design of the shower doors, one house had non, it was a wet room, and no problems, one house had doors which sealed at bottom, again no problem, and the last the shower was over the bath, so when used it circulated the moist air due to thermals getting whole room damp, and this one had a huge problem.

So when installing a fan we must be careful not to in doing so drag the air into the rest of the room, we also don't want room cold while having a shower, so the best would be if fan activated when we leave the room, not when we enter, then the fan does not draw the moisture laden air out of the shower cubical. Although this does not strictly comply with regulations, however there is nothing in the regulations that says the fan activation needs to be automatic. There is nothing wrong with a pneumatic timed push button which you can press when leaving the shower, all the regulations require is a run on I think 15 minutes from memory when you leave the room.

So a shower with a humidistat switch and push button in parallel would comply. And easier to wire. This was the method shown to wire fans and two way switches, and until the smart switch and LED bulbs, seems the best option.

However running the switch wires as shown can cause capacitive and inductive linking, using load capacitors can help, but not sure that is really a good idea? Some times we have no option. The use of switches which use a small current through the switch to power the switch has exacerbated the problem, with LED bulbs having a shimmer when switched on, and either staying on dim or flashing when switched off, where no neutral at the switch I have moved to Tapo (TP-Link) which has a battery in them to get around the problem.

I am not sure how your humidistat switch is powered, but if no neutral then likely it puts a small current through the load, and the big question was it designed to work with LED, so many switches of that type were designed to work with tungsten lamps.

If not your own house clearly you need to do what the customer wants, one needs to be careful with double pole switches, they look so like intermediate switches. I have needed to use a relay with central heating system, the problem is where to mount, some will fit in switch back box, but this one I used to work a landing lamp to give smart options, would need a very deep back box and a neutral, I fitted it inside the lamp, but since we don't know what humidistat switch you have tried to use, or how you tried to wire it, I can only talk in general terms and hope it gives you some ideas.

 

[PinkE]

Well you've touched on a lot there, thank you! In this case we don't have any singles, it's all t&e or 3-core+e. And there's no smart lighting either, the switches are bog standard light switch and fan switch (and yes, FCU before the light switch too, so both PL and SL are protected, nice). So unless there's something special about the bulbs (which I confess I didn't check), I don't think we've got an accidental capacitor. Also, the lights and fan were functioning as expected before we stuck a humidistat in there, so again that seems unlikely to be the problem.
There is a neutral, so none of this no neutral stuff. (I did agree to install a house full of no neutral smart switches a little while ago and hated every minute of it, though I'm probably a dinosaur).

What we've got here is pretty straightforward. Can't believe I forgot to tell you make and model of humidstat, sorry.
It is a Manrose 1361, remote humidistat and timer. I simply took the 3-core PL, SL + N that had previously been connected to the in-line fan, and connected them to the relevant supply side terminals of the humidistat. Then laid new L+N to the fan from the humidistat output.
I don't mind admitting I tried several other configurations and scratched my head, to no avail.
I can only think that somehow the humidistat is lighting up the SL to the light somehow.
Or if I've done something stupid please say!

 

[PinkE]

Hi again,
Are you able to recommend a relay? I can fit it in the loft so there will be plenty of space for it. The fan is a standard inline fan with timer. The humidstat is the Manrose 1361. I spoke to Manrose technical support and they said that it's a common problem, all humidistats will have the same problem with sending power back to the lights causing LED lights to flash even when switched off. The best they came up with is to disconnect the switched live to the humidistat therefore making it a humidistat only with no timer. But the client wants it to be activated by the light. A relay seems a bit more elegant than a capacitor

 

[EFLImpudence]

Wouldn't it be easier to fit a double-pole switch?

 

[EFLImpudence]

 

[PinkE]

Hi EFLI (always love your posts, thanks so much for responding!
I've presented this to the owner but she isn't keen on a DP switch unfortunately otherwise yes I would agree that that's the answer. A DP switch is that bit heavier to switch, she's got flush screwless brushed chrome switches and I can't find one that isn't chunkier and that requires a more positive press.
I've also presented the option of simply having the overrun controlled by the fan rather than the humidistat. I thought this was a good alternative because the humidistat works without the switched live, making it a humidistat only with no timer, so the switched live from the light could go to the fan rather than the humidistat so that the fan provides the overrun timer instead. The fan therefore receivesa switched live from the light and the permanent live terminal will have the feed switched by the humidistat.

But this will mean that the fan will only be activated when both the light is on and the humidity is raised, although it will continue to overrun when the light is turned off as long as the humidity level is still raised.
Hence asking for recommendations for a relay

 

[EFLImpudence]

Hi EFLI (always love your posts, thanks so much for responding!

Thank you.

I've presented this to the owner but she isn't keen on a DP switch unfortunately otherwise yes I would agree that that's the answer. A DP switch is that bit heavier to switch, she's got flush screwless brushed chrome switches and I can't find one that isn't chunkier and that requires a more positive press.

Ok. You can get DP pull cord switches.

I've also presented the option of simply having the overrun controlled by the fan rather than the humidistat.

That's always the case in that normally a humidistat just triggers the timer until the humidistat switches off.

I thought this was a good alternative because the humidistat works without the switched live,

No, that's not the case. The fan will not work with just the PL energised.

making it a humidistat only with no timer, so the switched live from the light could go to the fan rather than the humidistat so that the fan provides the overrun timer instead. The fan therefore receives a switched live from the light and the permanent live terminal will have the feed switched by the humidistat.

Ok. I think.

But this will mean that the fan will only be activated when both the light is on and the humidity is raised,

That is true.

although it will continue to overrun when the light is turned off as long as the humidity level is still raised.

It will but it will then turn off after the set time even if the humidity is still raised.

Hence asking for recommendations for a relay

Any suitably rated relay will do. I cannot recommend any.

 

[PinkE]

Any suitably rated relay will do. I cannot recommend any.

Agh. I'll confess I've never needed to fit a relay and there are endless choices on the market so was hoping for some guidance?
Looks like I'm going to have to go down the relay route because whilst this remote humidistat only requires a permanent live and the fan and the humidistat are operating as I described, it unfortunately doesn't meet the client's expectations as it doesn't clear the air after a number 2 unless humidity is raised and the light has been switched on.

 

[EFLImpudence]

@PinkE

I have no idea which makes are better than others but you only need the simplest of relays which operates a one-way switch; i.e. connects two separate contacts together; when activated.

 

[PinkE]

Just letting you know this was super easy when it came to it, thanks. I was just nervous having never worked with a relay before. Everyone's happy, thanks for talking me through it.

 

[EFLImpudence]