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.

2011

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?

Assuming that the shower is an instantaneous type the cable will be at least a 6mm^2

That would mean installing a contactor fed by a 6mm^2 cable that supplies two separate 6mm^2 cables. This would require quite a large contactor to terminate the cables properly on the load side. If I had to do this I would use large d=DIN rail terminals & busbar. It is not likely that this would all fit in the distribution board and therefore an additional enclose would be required.

What you have described is not impossible task but it would be difficult to do in such a way that would comply fully with ET101:2008, be cost effective and practical.

The rules to look at in particular include:
● 133.2.1
● 133.2.3
● 134.1.1
● 134.1.4
● 134.1.5
● 433.1

I admit that my current sensing relay is not the most straight forward of solutions either, but it would cleaner and far more compact. I think that this simple problem is being over analysed. The simplest solutions are often the best, such as:
1) Feed a fan with an overrun timer from the light switch
2) Buy a quality humidity sensor and feed the fan from it.

Par1

2011 wrote: »

Assuming that the shower is an instantaneous type the cable will be at least a 6mm^2

That would mean installing a contactor fed by a 6mm^2 cable that supplies two separate 6mm^2 cables. This would require quite a large contactor to terminate the cables properly on the load side. If I had to do this I would use large d=DIN rail terminals & busbar. It is not likely that this would all fit in the distribution board and therefore an additional enclose would be required.

What you have described is not impossible task but it would be difficult to do in such a way that would comply fully with ET101:2008, be cost effective and practical.

The rules to look at in particular include:
● 133.2.1
● 133.2.3
● 134.1.1
● 134.1.4
● 134.1.5
● 433.1

I admit that my current sensing relay is not the most straight forward of solutions either, but it would cleaner and far more compact. I think that this simple problem is being over analysed. The simplest solutions are often the best, such as:
1) Feed a fan with an overrun timer from the light switch
2) Buy a quality humidity sensor and feed the fan from it.

Well said 2011 hopefully this is the last post on this topic. Also the regulations are there as a guide to promote safety, the regs can not stipulate every circumstance that is why competence is recommended and insisted in the restricted works paper.

There are many reasons why the above should not be done and there is no point in stating any more regs (which we can do) instead lets bring this topic to a close and move on, as the original poster has more than enough recommendations at this point. Our time would be better spent advising people on other aspects of electrical queries and most importantly advising on Safe electrical practise. We will all make recommendations that another individual will query, that's productive criticism and the joy of asking opinions.

Next topic please!!
Cheers.

Sir Arthur Daley

2011 wrote: »

Assuming that the shower is an instantaneous type the cable will be at least a 6mm^2

Ok lets purpose use same cross section cable as shower cable to feed the coil on a contactor. The fan would be switched via the open contacts of the contactor.
Regardless of the economics or practicality of this proposal I don't believe its breaching any rules or regulations as other posters are suggesting.
Im open to correction on this.

2011

Sir Arthur Daley wrote: »

Regardless of the economics or practicality of this proposal I don't believe its breaching any rules or regulations

Agreed, it would be possible to do this and fully comply with the rules (I said this in my last post). However it would not make sense on any level.

mikeyjames9

Sir Arthur Daley wrote: »

Ok lets purpose use same cross section cable as shower cable to feed the coil on a contactor. The fan would be switched via the open contacts of the contactor.
Regardless of the economics or practicality of this proposal I don't believe its breaching any rules or regulations as other posters are suggesting.
Im open to correction on this.

it's a bad idea attempting to use shower isolating switch as a means of switching a fan

the switch is liable to give trouble when you break into it with new wiring or the consumer starts using it as a fan on/off switch

I don't think there's any specific reg against it

occupancy sensor or the other automatic methods, flow switch or current sensor(in DB) are preferable if the humidistat doesn't work properly

Sir Arthur Daley

I agree its not the best idea, just want to resolve the issue that another posters say its against regulation.
Its bad enough if one gives advice and its incorrect but alot worse giving correct advice and being told its incorrrect. Causes alot of confusion for nothing.

Par1

That is why the words 'Competent' is used a lot now in describing electricians as qualifications can lead people to think 'Oh hes an electrician, he must know his stuff' - not necessarily in some circumstances. Give me competence over qualification any day but competence combined with qualification is really the key i think.

mikeyjames9

using an appliance isolating switch for control/switching of another device

now that I think of it there definitely should be a regulation against it, if there isn't already

Sir Arthur Daley

mikeyjames9 wrote: »

using an appliance isolating switch for control/switching of another device

now that I think of it there definitely should be a regulation against it, if there isn't already

A single cooker switch feeding a seperate oven and hob is widely a case of this.

mikeyjames9

Sir Arthur Daley wrote: »

A single cooker switch feeding a seperate oven and hob is widely a case of this.

That's a common (shared) isolating switch

A different matter

2011

mikeyjames9 wrote: »

using an appliance isolating switch for control/switching of another device

now that I think of it there definitely should be a regulation against it, if there isn't already

What is your concern?

I don't see why this would be dangerous or in breach of any regulation if done correctly.

mikeyjames9

2011 wrote: »

What is your concern?

I don't see why this would be dangerous or in breach of any regulation if done correctly.

It's just bad practice imo

"separate isolating switch " for an appliance should only serve to isolate the supply to the appliance/s and not control of other devices

2011

mikeyjames9 wrote: »

It's just bad practice imo

"separate isolating switch " for an appliance should only serve to isolate the supply to the appliance/s and not control of other devices

The shower will be safely isolated by the isolator.
The fan can still have a dedicated local isolator.
All poles of both devices can be safely isolated by a local isolating device, that is the important bit.

I think that this is a strange and not very practical solution, but it can work safely.

Do you have a particular safety concern?

mikeyjames9

What will happen if that starts up is someone thinks

Hey, I'll wire the fan and shower cubicle lighting from the shower isolator

That's a cool idea

So next thing you know you have to work in the dark if you need to fix the slower

2011

mikeyjames9 wrote: »

What will happen if that starts up is someone thinks

Hey, I'll wire the fan and shower cubicle lighting from the shower isolator

That's a cool idea

So next thing you know you have to work in the dark if you need to fix the slower

That has nothing to do with this thread.
Besides electricians often have to arrange temporary lighting, its really not that difficult.

Sir Arthur Daley

Maybe my idea for the op is making more sense than its credited for. Its a solution to his problem.

mikeyjames9

2011 wrote: »

That has nothing to do with this thread.
Besides electricians often have to arrange temporary lighting, its really not that difficult.

It has everything to do with

In the example being discussed

The shower isolating switch is proposed as a method of controlling/switching a seperate device

If this was a good idea there would be everyday examples of this

There are none

2011

mikeyjames9 wrote: »

If this was a good idea there would be everyday examples of this

I never said it was a good idea!
In fact I said quite the opposite.

In post 32 I said "What you have described is not impossible task but it would be difficult to do in such a way that would comply fully with ET101:2008, be cost effective and practical" and in post 44 I said "I think that this is a strange and not very practical solution".

However that does not mean that it would be dangerous or in breach of ET101.

Par1

Id agree with mikeyjames9 with posts 39 41 and 43

2011

Par1 wrote: »

Id agree with mikeyjames9 with posts 39 41 and 43

I agree that it is not a good solution (for many reasons).

But the fact remains; so far nobody has been able to say why it would be dangerous or against the regulations.

I would still go with one of my earlier solutions:
1) Feed a fan with an overrun timer from the light switch
2) Buy a quality humidity sensor and feed the fan from it.