Bathroom Fan

65535

Hi,
I would like the bathroom fan that I have fitted to come on when the shower is actually turned on.
Without running a cable down into the shower for to 'trigger' the fan is there a device that can be fitted by clamping on or by 'teeing' into the shower cable that will allow the fan to come on.

The fan has a steam detector but it's not great, I would like just for the fan to come on when the shower is operating and turn off afterwards.

Any ideas - thanks !

65535

I think a current sensing relay is the job for it.

mikeyjames9

probably way too much hassle

they use them for the shower controllers


if i remember they're all N/C so you couldn't even switch the fan direct if it was rated for it

mikeyjames9

the humdistat type should be the solution for your needs


do they not work effectively then? i haven't seen them

Par1

There is a lot of options i.e magnet contacts on shower door via relay, point to point beam (N/C), directional motion sensor...etc but the IP rating will be an issue along with temprature - (PIR detection) and also finding supply for the fan via RCD or RCBO may be an issue as the shower is fused at 40 amps (or should be) therefore eliminating that as the power source.

You could consider a fan isolation switch with time delay? its not fully automatic, more semi automatic.

65535

Thanks everyone for the ideas.
Yes it already has a humidity stat built in but it takes a while for the steam to reach it, so at the minute it's either on or off with a switch.
Probably will have to look at one of the options suggested but it's not mad urgent

Sir Arthur Daley

Is there attic space over your shower and where fan is?

65535

Yes it's a single story with access to the attic over the bathroom.
I installed the fan in the ceiling and ducted it to the outside via the attic.
I installed the shower a few years ago as a replacement for an older model but did not put in extra cable to run the fan from the shower at that time.

Sir Arthur Daley

Have you a pull cord on ceiling for isolation or is it a wall mounted switch?

65535

I have a pull cord on the ceiling next to the (higher rated) pull cord for the shower.

Sir Arthur Daley

Why not get your switching supply for the fan from the pull cord, get this to pull in a contactor, fuse appropriately of course.

65535

Thanks for that Arthur.
There is a switching wire to the fan which I can wire to the shower pull cord.
Now all I have to do is to get everyone to use the pull cord

Sir Arthur Daley

Second thought there if the pull cord is normally left on then that suggestion is not much good. What you need is to tap into shower after the switch itself on the unit. Sorry for not getting that.
I cant commmit to say is it ok to get a supply for a contactor off say the pump or solenoid inside the shower. Have you a conduit used in the wall that is feeding the shower or is it a stud wall?

65535

Yeah that is what I was aiming for - when the shower is turned on (at the shower) that the fan would turn on.

That is why I was thinking there must be a 'current flow detector' either clamped on or 'teed' in to the shower feed that would in turn switch the fan on/off.

From memory the cable is fitted in trunking but fairly tight.
I did not replace the cable the time I changed the shower as it was fine and rated correctly.

I will have a chat with an electrician guy that I work with now and then when I meet up with him.

Par1

Sir Arthur Daley wrote: »

Second thought there if the pull cord is normally left on then that suggestion is not much good. What you need is to tap into shower after the switch itself on the unit. Sorry for not getting that.
I cant commmit to say is it ok to get a supply for a contactor off say the pump or solenoid inside the shower. Have you a conduit used in the wall that is feeding the shower or is it a stud wall?

A 'Shower Pullcord' is an isolation switch only - Not to be used for switching loads so this option is not recommended as to abide by regulations.

You should also NOT take a supply from the shower unit itself to supply another accessory again as to abide by electrical regulations.

Par1

65535 wrote: »

Yeah that is what I was aiming for - when the shower is turned on (at the shower) that the fan would turn on.

That is why I was thinking there must be a 'current flow detector' either clamped on or 'teed' in to the shower feed that would in turn switch the fan on/off.

From memory the cable is fitted in trunking but fairly tight.
I did not replace the cable the time I changed the shower as it was fine and rated correctly.

I will have a chat with an electrician guy that I work with now and then when I meet up with him.

Again it is not permitted to 'Clamp' or 'Tee' within a fixed appliance (spur) as to abide by current electrical regulations.

Par1

The easiest way to do what you require is to fit a flow switch onto the water main feeding the shower. The switch will only switch on flow of water (high or low varients available with various outputs). Once flow switch is fitted then it can be wired through relays etc but care should be taken to source suitable way of powering the flow switch.

GreeBo

Why not just put a motion sensor in series with the fan that points at the shower?
I presume the shower is only on when someone is in it.

In any case, you want the fan to remain on for a few minutes after the shower to remove the steam, a motion sensor would also work here as they are not immediate.

Par1

GreeBo wrote: »

Why not just put a motion sensor in series with the fan that points at the shower?
I presume the shower is only on when someone is in it.

In any case, you want the fan to remain on for a few minutes after the shower to remove the steam, a motion sensor would also work here as they are not immediate.

Good idea also...there would be an issue with the infa red when the room and the person heats up to similar temperatures though..would be fine for cold showers! A microwave detector is an option but nuisance activation would be an issue because of microwaves range i.e activation through stud walls

65535

Par1 wrote: »

The easiest way to do what you require is to fit a flow switch onto the water main feeding the shower. The switch will only switch on flow of water (high or low varients available with various outputs). Once flow switch is fitted then it can be wired through relays etc but care should be taken to source suitable way of powering the flow switch.

This could be a runner alright!
I will investigate them further.
Thanks everyone for all the assistance

2011

65535 wrote: »

Hi,
I would like the bathroom fan that I have fitted to come on when the shower is actually turned on.
Without running a cable down into the shower for to 'trigger' the fan is there a device that can be fitted by clamping on or by 'teeing' into the shower cable that will allow the fan to come on.

It is always best to avoid connecting into a cable carring a large current when possible.

Inserting a flow switch adds anothe layer of complexity. It means another join in the water pipe (potential point of failure), the switch will need to be accessible so that it can be replaced if required, if the switch operates at mains voltage the whole safety aspect will have to be looked at carefully. A mains voltage flow switch shoule be supplied from an RCD (not the shower RCD) in my opinion.

Another option would be to use a current sensing relay.

http://docs-europe.electrocomponents.com/webdocs/001b/0900766b8001bde0.pdf

This can be used to switch on the fan once a current is drawn by the shower, i.e. when the shower is in use.
An expensive way of doing it, but it would work.

IMHO the most simple solution is best; have the fan run anytime that the bathroom light is on.
Simple, cheap and effective

Sir Arthur Daley

Par1 wrote: »

A 'Shower Pullcord' is an isolation switch only - Not to be used for switching loads so this option is not recommended as to abide by regulations.

You should also NOT take a supply from the shower unit itself to supply another accessory again as to abide by electrical regulations.

You missed what i was saying completely.

Par1

Sir Arthur Daley wrote: »

You missed what i was saying completely.

My apologies, i taught you said to:
'tap into shower after the switch itself on the unit'

also
'Why not get your switching supply for the fan from the pull cord, get this to pull in a contactor'

I missed what you were saying completely?...could you please explain How?

mikeyjames9

2011 wrote: »

It is always best to avoid connecting into a cable carring a large current when possible.

Inserting a flow switch adds anothe layer of complexity. It means another join in the water pipe (potential point of failure), the switch will need to be accessible so that it can be replaced if required, if the switch operates at mains voltage the whole safety aspect will have to be looked at carefully. A mains voltage flow switch shoule be supplied from an RCD (not the shower RCD) in my opinion.

Another option would be to use a current sensing relay.

http://docs-europe.electrocomponents.com/webdocs/001b/0900766b8001bde0.pdf

This can be used to switch on the fan once a current is drawn by the shower, i.e. when the shower is in use.
An expensive way of doing it, but it would work.

IMHO the most simple solution is best; have the fan run anytime that the bathroom light is on.
Simple, cheap and effective

it might be possible for an electrician to fit one into the DB seeing as there's attic space and wire the fan from there

tapping into pull-cords and shower cables is a non-runner as a method

the sensor idea around the shower cubicle is a good idea if it will operate correctly

GreeBo

Par1 wrote: »

Good idea also...there would be an issue with the infa red when the room and the person heats up to similar temperatures though..would be fine for cold showers! A microwave detector is an option but nuisance activation would be an issue because of microwaves range i.e activation through stud walls

The scenario where it couldn't distinguish you from the steam is exactly when you would want it to be running though...the room is full of steam!

Par1

GreeBo wrote: »

The scenario where it couldn't distinguish you from the steam is exactly when you would want it to be running though...the room is full of steam!

Yes true but if the sensor can not see you then it would assume nothing is there and switch off therefore not ventilating the room hence my opinion but if a timer was used in conjunction then problem sorted. Its all a bit over the top really for a domestic situation not unless shower traffic was heavy which shouldn't be as most domestic showers recommend a 'cooling off' period between uses.

GreeBo

Par1 wrote: »

Yes true but if the sensor can not see you then it would assume nothing is there and switch off therefore not ventilating the room hence my opinion but if a timer was used in conjunction then problem sorted. Its all a bit over the top really for a domestic situation not unless shower traffic was heavy which shouldn't be as most domestic showers recommend a 'cooling off' period between uses.

I would have thought it would stay on as it would constantly "see someone" until the room cooled...?

Bottom line for me is that the fan should stay on for a few mins after the shower is off, otherwise its kinda pointless!

Par1

GreeBo wrote: »

I would have thought it would stay on as it would constantly "see someone" until the room cooled...?

Bottom line for me is that the fan should stay on for a few mins after the shower is off, otherwise its kinda pointless!

Easy mistake to make, the fan would switch off as there would be no temperature difference even if there's movement so open circuit on the switched side - fan is off. the reason the temperature is an issue is the sensor senses a difference in body temperature and ambient temperature therefore closing circuit to activate. If it cant see a difference in temperature movement is irrelevant - it remains open circuit - fan off.

I agree the fan should stay on for a few mins after the shower is off.

I think we have taken this issue as far as it can go the guy has plenty of options now....well done all!!

Sir Arthur Daley

What rules or regs are being breached by terminating in another cable into the switched side of the pull cord to power a contactor in an enclosure?

Sleeper12

65535 wrote: »

Hi,
I would like the bathroom fan that I have fitted to come on when the shower is actually turned on.
Without running a cable down into the shower for to 'trigger' the fan is there a device that can be fitted by clamping on or by 'teeing' into the shower cable that will allow the fan to come on.

The fan has a steam detector but it's not great, I would like just for the fan to come on when the shower is operating and turn off afterwards.

Any ideas - thanks !

Bathroom fans are designed for smells & not steam. If they actually sucked the steam out of the room, the steam would condense. You would get a drip from the fan if this happened.
They don't do any harm as they help create airflow (Very little) but they will never remove steam from a bathroom. Ideally if you are using a fan for airflow because of steam it should run for 20 minutes or more after the shower as the steam condenses on the ceiling & walls. This helps everything to dry out. But it will not remove steam.

Sleeper12

Sir Arthur Daley wrote: »

What rules or regs are being breached by terminating in another cable into the switched side of the pull cord to power a contactor in an enclosure?

Some shower manufactures say this shouldn't be done. I haven't a clue why.