Hi,

Currently, my bathroom has a fan which switches along with the light and
stays on on a timer afterwards. Most of the time, this is unnecessary -
if I fill up a glass of water before going to bed I don't need a fan
waking up everyone else in the house.

As part of my bathroom refit, I'm planning to disconnect the fan totally
from the lighting, and instead switch it via a flow switch on the shower
supply. I also want a manual button strategically positioned next to the
toilet flush :-). This would be a momentary switch so that the fan
starts and then runs-on on the timer.

My question is how to handle the wiring of this switch. I currently have
a nice brushed-steel button that would look the part. It happens to be
rated to 250v/5a, but AFAIK is not IP-rated. I also have a relay that
will switch a mains supply from a 6-12v signal current. One approach
would be to have the relay in a suitable enclosure in the roof space
above the bathroom, with the button controlling the low-voltage side
from below. This keeps mains out of the bathroom, but is it acceptable
from a regs point of view? I'm confident that I can built it safely, but
these aren't quite the same thing :-)

Alternatively, I could buy an IP-66 button (eg MP0031, http://is.gd/fdko
) and wire it directly. Would this be OK? The back of the button would
be inside a substantial piece of boxing-in, effectively a stud wall.
This would have access points in it, but not routinely openable (ie
require cutting sealant).

Cheers,

Pete

In article ,
Pete Verdon d writes:
Hi,

Currently, my bathroom has a fan which switches along with the light and
stays on on a timer afterwards. Most of the time, this is unnecessary -
if I fill up a glass of water before going to bed I don't need a fan
waking up everyone else in the house.

As part of my bathroom refit, I'm planning to disconnect the fan totally
from the lighting, and instead switch it via a flow switch on the shower
supply. I also want a manual button strategically positioned next to the
toilet flush :-). This would be a momentary switch so that the fan
starts and then runs-on on the timer.

What about a flow switch on the toilet cistern supply?

I'm also picturing a momentary action pullcord switch with the
end tied around the flush handle, and you could always operate
it early should something rather iffy happen;-) Probably all
rather too Heath-Robinson, but a plain momentary action pullcord
switch remains a possibility (they usually come with a long red
pullcord, as they're used for alarm callers).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel coughed up some electrons that declared:


What about a flow switch on the toilet cistern supply?

And the shower/bath cold feed. Now that *is* a good idea!

In article ,
Pete Verdon d wrote:
My question is how to handle the wiring of this switch. I currently have
a nice brushed-steel button that would look the part. It happens to be
rated to 250v/5a, but AFAIK is not IP-rated. I also have a relay that
will switch a mains supply from a 6-12v signal current. One approach
would be to have the relay in a suitable enclosure in the roof space
above the bathroom, with the button controlling the low-voltage side
from below. This keeps mains out of the bathroom, but is it acceptable
from a regs point of view? I'm confident that I can built it safely, but
these aren't quite the same thing :-)

Provided you use a suitable mains transformer to supply the low volts,
then yes. I have a similar idea to add in the shaving/makeup lights round
the mirror which aren't always needed. And I dislike pull cord switches.

--
*That's it! I‘m calling grandma!

Dave Plowman London SW
To e-mail, change noise into sound.

Tim S wrote:
Andrew Gabriel coughed up some electrons that declared:

What about a flow switch on the toilet cistern supply?

That's no good - I don't want the fan coming on when someone goes for a
pee at night. The switch next to the toilet is to be a manual one, with
a fan symbol etched on it.

And the shower/bath cold feed. Now that *is* a good idea!

That's what I am doing. I don't want steam blowing around the room
causing mould, so whenever the shower is turned on so will be the fan.

Pete

Andrew Gabriel wrote:
a plain momentary action pullcord switch remains a possibility (they
usually come with a long red pullcord, as they're used for alarm
callers).

....and look horrible :-)

I don't really want a pullcord for the main light either, though I might
have to settle for it. The continental habit of putting light switches
outside the room I find annoying, and IP-rated switches tend to be
designed for outside and would look wierd in a bathroom.

Pete

Pete Verdon wrote:
Hi,

Currently, my bathroom has a fan which switches along with the light and
stays on on a timer afterwards. Most of the time, this is unnecessary -
if I fill up a glass of water before going to bed I don't need a fan
waking up everyone else in the house.

As part of my bathroom refit, I'm planning to disconnect the fan totally
from the lighting, and instead switch it via a flow switch on the shower
supply. I also want a manual button strategically positioned next to the
toilet flush :-). This would be a momentary switch so that the fan
starts and then runs-on on the timer.

My question is how to handle the wiring of this switch. I currently have
a nice brushed-steel button that would look the part. It happens to be
rated to 250v/5a, but AFAIK is not IP-rated. I also have a relay that
will switch a mains supply from a 6-12v signal current. One approach
would be to have the relay in a suitable enclosure in the roof space
above the bathroom, with the button controlling the low-voltage side
from below. This keeps mains out of the bathroom, but is it acceptable
from a regs point of view? I'm confident that I can built it safely, but
these aren't quite the same thing :-)

Alternatively, I could buy an IP-66 button (eg MP0031, http://is.gd/fdko
) and wire it directly. Would this be OK? The back of the button would
be inside a substantial piece of boxing-in, effectively a stud wall.
This would have access points in it, but not routinely openable (ie
require cutting sealant).

Cheers,

Pete

I went for 2 pull cords. One (with a shorter string) controls the shower
light and the fan, the other controls the rest of the lights. This
system has been in use now in both bathrooms for several years and has
been very successful.

Dave
Dave

On Sat, 10 Jan 2009 19:28:22 +0000, Pete Verdon
d wrote:

Tim S wrote:
Andrew Gabriel coughed up some electrons that declared:

What about a flow switch on the toilet cistern supply?

That's no good - I don't want the fan coming on when someone goes for a
pee at night. The switch next to the toilet is to be a manual one, with
a fan symbol etched on it.

Perhaps a motion detector would help

;-)

--
Frank Erskine

Dave Plowman (News) wrote:

Provided you use a suitable mains transformer to supply the low volts,

I'm actually planning to use a PP3 battery. I know it sounds a bit odd,
but since it would only be energising the relay for a few seconds per
day it should last for ages, and it will be in my boarded-out loft where
I can easily change it when the time comes. All the transformers I
looked at drew a few watts of power even with no load - I'm far from a
tree hugger but knowing that something is sitting there taking power
while doing nothing would annoy me.

then yes

That's good to hear. Mind elaborating slightly on "how you know"? Is it
a common practice, or specifically mentioned in regs, or similar? I
wouldn't want to go trusting everything I read on the Internet now,
would I? :-)

Cheers,

Pete

Frank Erskine wrote:
On Sat, 10 Jan 2009 19:28:22 +0000, Pete Verdon wrote:

The switch next to the toilet is to be a manual one, with a fan symbol etched on it.

Perhaps a motion detector would help

Groan :-)

Pete

Pete Verdon coughed up some electrons that declared:

Tim S wrote:
Andrew Gabriel coughed up some electrons that declared:

What about a flow switch on the toilet cistern supply?

That's no good - I don't want the fan coming on when someone goes for a
pee at night. The switch next to the toilet is to be a manual one, with
a fan symbol etched on it.

Hmm - good point. What we need is the "smelly *******" sensor...

Tim S wrote:
Pete Verdon coughed up some electrons that declared:

The switch next to the toilet is to be a manual one, with
a fan symbol etched on it.

Hmm - good point. What we need is the "smelly *******" sensor...

I actually briefly flirted with the idea of putting something like
http://is.gd/fe4E on the switch instead of a fan symbol :-)

I thought the joke might not last.

Pete

On 10 Jan 2009 19:12:03 GMT, (Andrew
Gabriel) wrote:

In article ,
Pete Verdon d writes:
Hi,

Currently, my bathroom has a fan which switches along with the light and
stays on on a timer afterwards. Most of the time, this is unnecessary -
if I fill up a glass of water before going to bed I don't need a fan
waking up everyone else in the house.

As part of my bathroom refit, I'm planning to disconnect the fan totally
from the lighting, and instead switch it via a flow switch on the shower
supply. I also want a manual button strategically positioned next to the
toilet flush :-). This would be a momentary switch so that the fan
starts and then runs-on on the timer.

What about a flow switch on the toilet cistern supply?


To be honest I've had great success with these :

http://snipurl.com/9rfwk [cgi_ebay_co_uk]

(A 3 AA battery operated PIR & Photocell controlled LED Nightlight)

No clicking of lightswitches in the middle of the night, great if you
have elderly relatives staying who have to visit the bathroom
frequently and don't know where the lightswitches are. Battery
operated so not constrained by the need for a mains supply. The 3 AA
batteries seem to last us about 6months. Plenty enough light to light
a whole bathroom, landing or staircase to complete the "intended
function". ;-)

Only disadvantage I've found is that if you have them in the bedroom
in such a position that they can "see" head end of the bed, then they
come on everytime you scratch your nose during the night. However this
is easily avoided.

Derek

Pete Verdon wrote:

As part of my bathroom refit, I'm planning to disconnect the fan totally
from the lighting, and instead switch it via a flow switch on the shower
supply. I also want a manual button strategically positioned next to the
toilet flush :-). This would be a momentary switch so that the fan
starts and then runs-on on the timer.

Simplest way would be with a timber fan such as you already have -
however disconnected from the light switch. Plus an additional external
humidistat. That way you can trigger it either from the push button
(which will cause it to run for the timer duration) or from the
humidistat which will cause it to run until the RH falls below threshold
+ an extra timer duration.

My question is how to handle the wiring of this switch. I currently have
a nice brushed-steel button that would look the part. It happens to be
rated to 250v/5a, but AFAIK is not IP-rated. I also have a relay that
will switch a mains supply from a 6-12v signal current. One approach
would be to have the relay in a suitable enclosure in the roof space
above the bathroom, with the button controlling the low-voltage side
from below. This keeps mains out of the bathroom, but is it acceptable
from a regs point of view? I'm confident that I can built it safely, but
these aren't quite the same thing :-)

The main problem with a push button of inappropriate rating for the
location will be what effect the ingress of moisture will have on the
switch - regardless of any voltage exposure risk.

A momentary action pull switch may be better for the manual activation.

Alternatively, I could buy an IP-66 button (eg MP0031, http://is.gd/fdko
) and wire it directly. Would this be OK? The back of the button would
be inside a substantial piece of boxing-in, effectively a stud wall.
This would have access points in it, but not routinely openable (ie
require cutting sealant).

You can get momentary action rocker switches as well that look like
ordinary electrical accessories. These may prove somewhat more
maintainable.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Pete Verdon wrote:
Andrew Gabriel wrote:
a plain momentary action pullcord switch remains a possibility (they
usually come with a long red pullcord, as they're used for alarm
callers).

...and look horrible :-)

I don't really want a pullcord for the main light either, though I might
have to settle for it. The continental habit of putting light switches
outside the room I find annoying, and IP-rated switches tend to be
designed for outside and would look wierd in a bathroom.

You can use an ordinary light switch in a bathroom as long as its
outside zone 2 and is not going to get exposed to unreasonable levels of
moisture.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
Pete Verdon d wrote:
Provided you use a suitable mains transformer to supply the low volts,

I'm actually planning to use a PP3 battery. I know it sounds a bit odd,
but since it would only be energising the relay for a few seconds per
day it should last for ages, and it will be in my boarded-out loft where
I can easily change it when the time comes. All the transformers I
looked at drew a few watts of power even with no load - I'm far from a
tree hugger but knowing that something is sitting there taking power
while doing nothing would annoy me.

In my case the transformer is only powered up when the lights are on.
However, I'd not fancy using a PP3 and a standard relay - it won't last
long. You need a specialised motorised type which needs no holding
current. Like the type used on battery programmable thermostats etc.

then yes

That's good to hear. Mind elaborating slightly on "how you know"? Is it
a common practice, or specifically mentioned in regs, or similar? I
wouldn't want to go trusting everything I read on the Internet now,
would I? :-)

The regs don't cover every eventuality word for word, but operating mains
via an ultra low voltage relay is standard practice where safety matters.

--
*The problem with the world is that everyone is a few drinks behind *

Dave Plowman London SW
To e-mail, change noise into sound.

Andrew Gabriel wrote:
In article ,
Pete Verdon d
writes:
Hi,

Currently, my bathroom has a fan which switches along with the light
and stays on on a timer afterwards. Most of the time, this is
unnecessary - if I fill up a glass of water before going to bed I
don't need a fan waking up everyone else in the house.

As part of my bathroom refit, I'm planning to disconnect the fan
totally from the lighting, and instead switch it via a flow switch
on the shower supply. I also want a manual button strategically
positioned next to the toilet flush :-). This would be a momentary
switch so that the fan starts and then runs-on on the timer.

What about a flow switch on the toilet cistern supply?

I'm also picturing a momentary action pullcord switch with the
end tied around the flush handle, and you could always operate
it early should something rather iffy happen;-) Probably all
rather too Heath-Robinson, but a plain momentary action pullcord
switch remains a possibility (they usually come with a long red
pullcord, as they're used for alarm callers).

I am tempted to put a level sensor in the cistern, so it is activated only
when the toilet is full flushed, not the short flush!

Toby...

Dave Plowman (News) wrote:

In my case the transformer is only powered up when the lights are on.
However, I'd not fancy using a PP3 and a standard relay - it won't last
long. You need a specialised motorised type which needs no holding
current. Like the type used on battery programmable thermostats etc.

No - in mine the primary side of the transformer would be on all the
time, and the battery is only used (and relay energised) while the
button is depressed. The idea is that pressing the button looks to the
fan like someone flicked the light on and off, and it then runs for the
duration of its timer.

The regs don't cover every eventuality word for word, but operating mains
via an ultra low voltage relay is standard practice where safety matters.

Thanks. I was just concerned that this might be outlawed on the grounds
that a stray wire in the relay box could make the ultra-low-voltage side
live. Though the fact that the switch is actually mains-rated in this
case means you'd still need a second fault (or a lot of water) to get a
shock.

Pete

John Rumm wrote:

You can use an ordinary light switch in a bathroom as long as its
outside zone 2 and is not going to get exposed to unreasonable levels of
moisture.

So I see - zones are a relatively recent thing, aren't they? Seems very
weird to be able to put a normal switch in the room :-)

The switch would be at the other end of the room from the shower, but
might possibly be within 0.6m of the basin. However, I'm not sure even
then - I might well want to spray lots of water around for cleaning
purposes, so I'd prefer not to have to worry.

I saw a reference to an IP44-rated lightswitch that looked normal, made
by Clipsal, but I cannot find any more details.

Cheers,

Pete

John Rumm wrote:
Pete Verdon wrote:

Simplest way would be with a timber fan such as you already have -
however disconnected from the light switch. Plus an additional external
humidistat. That way you can trigger it either from the push button
(which will cause it to run for the timer duration) or from the
humidistat which will cause it to run until the RH falls below threshold
+ an extra timer duration.

Yep, that's almost exactly what I have in mind, except for using a flow
switch on the shower rather than a humidity sensor. Fan would be on
while showering, and for a timer-duration thereafter.

The main problem with a push button of inappropriate rating for the
location will be what effect the ingress of moisture will have on the
switch - regardless of any voltage exposure risk.

In this case I don't think it's likely to get water on it, and in any
case its design would discourage entry even though it hasn't actually
been certified.

A momentary action pull switch may be better for the manual activation.

Probably, from a practical purpose, but I really don't like the things.
One of them (for the light) is just about acceptable since it's so
common, but multiple dangling strings (a mate's bathroom has three)
drive me nuts.

Alternatively, I could buy an IP-66 button (eg MP0031,
http://is.gd/fdko ) and wire it directly. Would this be OK? The back
of the button would be inside a substantial piece of boxing-in,
effectively a stud wall. This would have access points in it, but not
routinely openable (ie require cutting sealant).

You can get momentary action rocker switches as well that look like
ordinary electrical accessories. These may prove somewhat more
maintainable.

I'm not worried about maintainability, more whether the inside of the
boxing-in counts as part of the bathroom, since this alternative
approach would mean it contains mains equipment (and the connections to
the back of the button aren't IP-sealed). I know that the space under a
bath is non-zoned only if there is a panel whose removal requires tools
- to have my studwork treated the same way I want access to be more
difficult, not less :-)

Cheers,

Pete

On Sun, 11 Jan 2009 04:26:30 +0000, Pete Verdon
d wrote:

John Rumm wrote:
Pete Verdon wrote:

Simplest way would be with a timber fan such as you already have -
however disconnected from the light switch. Plus an additional external
humidistat. That way you can trigger it either from the push button
(which will cause it to run for the timer duration) or from the
humidistat which will cause it to run until the RH falls below threshold
+ an extra timer duration.

Yep, that's almost exactly what I have in mind, except for using a flow
switch on the shower rather than a humidity sensor. Fan would be on
while showering, and for a timer-duration thereafter.

The main problem with a push button of inappropriate rating for the
location will be what effect the ingress of moisture will have on the
switch - regardless of any voltage exposure risk.

In this case I don't think it's likely to get water on it, and in any
case its design would discourage entry even though it hasn't actually
been certified.


You could use an external-type bell-push.

--
Frank Erskine

Dave Plowman (News) wrote:
In article ,
Pete Verdon d wrote:

Provided you use a suitable mains transformer to supply the low volts,

I'm actually planning to use a PP3 battery. I know it sounds a bit odd,
but since it would only be energising the relay for a few seconds per
day it should last for ages, and it will be in my boarded-out loft where
I can easily change it when the time comes.

You can do. FWIW though 4x AA batteries cost about the same and hold a
lot more charge. PP3s are especialy bad deals in terms of energy per
cost. And C cells are much better than AAs...


All the transformers I
looked at drew a few watts of power even with no load - I'm far from a
tree hugger but knowing that something is sitting there taking power
while doing nothing would annoy me.

You could use a switched mode wallwart, one of the small light ones
used for charging a mobile would be about right. No few watts wasted.


Pete Verdon wrote:
Dave Plowman (News) wrote:

No - in mine the primary side of the transformer would be on all the
time, and the battery is only used (and relay energised) while the
button is depressed.

yes, it has to be that way


The idea is that pressing the button looks to the
fan like someone flicked the light on and off, and it then runs for the
duration of its timer.

You probably wont want to, but you could use the fan rotor from a 1"
laptop fan as your press switch button. It would get the message
across in a cute way.

Re the proposed sign, 3d plastic turds are very easy to make. Let a
can of foam dribble the right amount out, it will fall/form like a
turd, and paint brown when set. Or not.


The regs don't cover every eventuality word for word, but operating mains
via an ultra low voltage relay is standard practice where safety matters.

Thanks. I was just concerned that this might be outlawed on the grounds
that a stray wire in the relay box could make the ultra-low-voltage side
live.

It could. That's true anywhere mains and LV coexist. A good method to
strongly discourage it is to have the 240v come in at a position where
the wires arent long enough to reach any low voltage part, make sure
theyre cord griped on entry, and cable tie L&N together so that if one
comes off it cant move far.

Grip & tie the LV wires similarly so they cant stray over to the mains
bits.

Then you can earth the secondary side as an added precaution.


NT

Pete Verdon wrote:
John Rumm wrote:
Pete Verdon wrote:

The main problem with a push button of inappropriate rating for the
location will be what effect the ingress of moisture will have on the
switch - regardless of any voltage exposure risk.

In this case I don't think it's likely to get water on it, and in any
case its design would discourage entry even though it hasn't actually
been certified.

Condensation/ damp may still affect it eventually. Picking a switch
with gold plated contacts would eliminate the main deleterious result.


NT

wrote:
Dave Plowman (News) wrote:
In article ,
Pete Verdon d
wrote:

Provided you use a suitable mains transformer to supply the low
volts,

I'm actually planning to use a PP3 battery. I know it sounds a bit
odd, but since it would only be energising the relay for a few
seconds per day it should last for ages, and it will be in my
boarded-out loft where I can easily change it when the time comes.

You can do. FWIW though 4x AA batteries cost about the same and hold a
lot more charge. PP3s are especialy bad deals in terms of energy per
cost. And C cells are much better than AAs...

I've often wondered about that - what are the crireia when designing a
torch, kids toy, whatever as to which size & number of batteries are best?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

wrote:

You can do. FWIW though 4x AA batteries cost about the same and hold a
lot more charge. PP3s are especialy bad deals in terms of energy per
cost. And C cells are much better than AAs...

Hmm, interesting. I don't know much about batteries, so I just picked
PP3 as the kind of thing that tends to hang around long-term in smoke
alarms and the like.

Unfortunately I've now built the box with a PP3-sized space in the
lower-voltage side, so I think I'll stick with it. If I find it needs
changing too often I can always stick a holder for four D cells to the
wall next to it, like an old-fashioned doorbell.

It could. That's true anywhere mains and LV coexist. A good method to
strongly discourage it is to have the 240v come in at a position where
the wires arent long enough to reach any low voltage part, make sure
theyre cord griped on entry, and cable tie L&N together so that if one
comes off it cant move far.

I've had a bash at actually making the thing, and what I've done is to
glue a plastic partition across the box - one half 9v, one half 240v.
The relay is glued into a hole in the partition, with the 9v half in the
9v cavity and vice versa. The connections to the relay are soldered, and
have then been covered in hot-melt so that any stray metal can't make
contact. These short connections go to terminal blocks for the in and
out cables.

Then you can earth the secondary side as an added precaution.

Interesting - not sure what you mean here. Just tie one leg of the
connection to earth, on the grounds that it won't make a complete
circuit with the battery? What about the other leg - I can't connect
them both to earth or I'd be connecting them together.

Cheers,

Pete

The Medway Handyman wrote:
wrote:
Dave Plowman (News) wrote:
In article ,
Pete Verdon d
wrote:

Provided you use a suitable mains transformer to supply the low
volts,

I'm actually planning to use a PP3 battery. I know it sounds a bit
odd, but since it would only be energising the relay for a few
seconds per day it should last for ages, and it will be in my
boarded-out loft where I can easily change it when the time comes.

You can do. FWIW though 4x AA batteries cost about the same and hold a
lot more charge. PP3s are especialy bad deals in terms of energy per
cost. And C cells are much better than AAs...

I've often wondered about that - what are the crireia when designing a
torch, kids toy, whatever as to which size & number of batteries are best?


As with many things there are 2 very different definitions of best...
Best in terms of run cost favours large expensive batteries that last
a very long time. 6v Lantern batteries are a good example.
Best in terms of lowest toy mfr cost and smallest size (cute factor)
favours small batteries that die quickly, often AA cells (or worse).

Re voltage, lower means shorter battery life and more trouble from
poor contacts. Higher means longer battery life but higher battery &
battery holder costs.
Some circuits are to some degree voltage specific, which overrides
other concerns. As to why they're voltage specific, thats getting into
circuit and IC design, which is a tad complex.


NT

Pete Verdon wrote:
wrote:

You can do. FWIW though 4x AA batteries cost about the same and hold a
lot more charge. PP3s are especialy bad deals in terms of energy per
cost. And C cells are much better than AAs...

Hmm, interesting. I don't know much about batteries, so I just picked
PP3 as the kind of thing that tends to hang around long-term in smoke
alarms and the like.

Unfortunately I've now built the box with a PP3-sized space in the
lower-voltage side, so I think I'll stick with it. If I find it needs
changing too often I can always stick a holder for four D cells to the
wall next to it, like an old-fashioned doorbell.

If you ever need to, a PJ996 might be easier to handle. 9v relays will
run on 6v.


It could. That's true anywhere mains and LV coexist. A good method to
strongly discourage it is to have the 240v come in at a position where
the wires arent long enough to reach any low voltage part, make sure
theyre cord griped on entry, and cable tie L&N together so that if one
comes off it cant move far.

I've had a bash at actually making the thing, and what I've done is to
glue a plastic partition across the box - one half 9v, one half 240v.
The relay is glued into a hole in the partition, with the 9v half in the
9v cavity and vice versa. The connections to the relay are soldered, and
have then been covered in hot-melt so that any stray metal can't make
contact. These short connections go to terminal blocks for the in and
out cables.

sounds like a very effective solution


Then you can earth the secondary side as an added precaution.

Interesting - not sure what you mean here. Just tie one leg of the
connection to earth, on the grounds that it won't make a complete
circuit with the battery? What about the other leg - I can't connect
them both to earth or I'd be connecting them together.

Cheers,

Pete

Just tie one of the transformer LV outputs to earth.
If mains meets that side of the LV supply, the fuse/mcb will trip.
If mains meets the other side of the LV circuit, the transformer
secondary will be low enough resistance to allow overcurrent, and
hopefully blow the fuse or trip the breaker, simultaneously frying the
relay.
You cant earth both of course

Someone else can hopefully remind us all of the regs on SELV, which
might say something else.


NT

In article ,
Pete Verdon d wrote:

The switch would be at the other end of the room from the shower, but
might possibly be within 0.6m of the basin. However, I'm not sure even
then - I might well want to spray lots of water around for cleaning
purposes, so I'd prefer not to have to worry.

I saw a reference to an IP44-rated lightswitch that looked normal, made
by Clipsal, but I cannot find any more details.


Dunno if any of the home easy stuff would be of use? A switch/dimmer module in
ceiling controlled by a battery powered light switch on the wall? Less risk
from wet fingers then...

No experience of them though - they might be crap for all I know

Darren

wrote:

Just tie one of the transformer LV outputs to earth.
If mains meets that side of the LV supply, the fuse/mcb will trip.
If mains meets the other side of the LV circuit, the transformer
secondary will be low enough resistance to allow overcurrent, and
hopefully blow the fuse or trip the breaker, simultaneously frying the
relay.
You cant earth both of course

Um - what transformer?

Presumably the same would apply with the battery though?

I'd wonder about the current-carrying capacity of the wiring on that
side, but I guess it would last long enough to trip an RCD.

Pete

Pete Verdon wrote:

You can use an ordinary light switch in a bathroom as long as its
outside zone 2 and is not going to get exposed to unreasonable levels
of moisture.

So I see - zones are a relatively recent thing, aren't they? Seems very

Not especially. They altered them with the 17th edition (deleting Zone
3), but the basic concept has existed for a reasonable time.

weird to be able to put a normal switch in the room :-)

You need to use common sense really - a large bathroom with the switch
well away from the wet bits might be ok. A smaller one or one with a
massive shower that will generate loads of steam, would be better with a
pull switch.

The switch would be at the other end of the room from the shower, but
might possibly be within 0.6m of the basin. However, I'm not sure even

Basins do not really count. Shower trays and baths do.

then - I might well want to spray lots of water around for cleaning
purposes, so I'd prefer not to have to worry.

Pull switch then...



--
Cheers,

John.

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Pete Verdon wrote:
John Rumm wrote:
Pete Verdon wrote:

Simplest way would be with a timber fan such as you already have -

oops make that a "timer fan" rather than a wood one!

however disconnected from the light switch. Plus an additional
external humidistat. That way you can trigger it either from the push
button (which will cause it to run for the timer duration) or from the
humidistat which will cause it to run until the RH falls below
threshold + an extra timer duration.

Yep, that's almost exactly what I have in mind, except for using a flow
switch on the shower rather than a humidity sensor. Fan would be on
while showering, and for a timer-duration thereafter.

The problem with that, is that the timer duration will probably not be
long enough to reduce the humidity completely. With a humidistat it may
need to run the fan for 40 mins or so to dry the room to normal levels.

The main problem with a push button of inappropriate rating for the
location will be what effect the ingress of moisture will have on the
switch - regardless of any voltage exposure risk.

In this case I don't think it's likely to get water on it, and in any
case its design would discourage entry even though it hasn't actually
been certified.

A momentary action pull switch may be better for the manual activation.

Probably, from a practical purpose, but I really don't like the things.
One of them (for the light) is just about acceptable since it's so
common, but multiple dangling strings (a mate's bathroom has three)
drive me nuts.

Alternatively, I could buy an IP-66 button (eg MP0031,
http://is.gd/fdko ) and wire it directly. Would this be OK? The back
of the button would be inside a substantial piece of boxing-in,
effectively a stud wall. This would have access points in it, but not
routinely openable (ie require cutting sealant).

You can get momentary action rocker switches as well that look like
ordinary electrical accessories. These may prove somewhat more
maintainable.

I'm not worried about maintainability, more whether the inside of the
boxing-in counts as part of the bathroom, since this alternative
approach would mean it contains mains equipment (and the connections to
the back of the button aren't IP-sealed). I know that the space under a
bath is non-zoned only if there is a panel whose removal requires tools
- to have my studwork treated the same way I want access to be more
difficult, not less :-)

Yup panels that need tools to get past count as if they are out of the
room. Obviously you don't want water getting under panels for all sorts
of reasons, so not getting your electrics wet is just another on the list.


--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
The Medway Handyman wrote:
You can do. FWIW though 4x AA batteries cost about the same and hold a
lot more charge. PP3s are especialy bad deals in terms of energy per
cost. And C cells are much better than AAs...

I've often wondered about that - what are the crireia when designing a
torch, kids toy, whatever as to which size & number of batteries are
best?

In general the smaller the battery the larger the cost per amp hour -
although economy of scale comes into this too. But perhaps the worst is
AAA against AA - they're often the same price despite being about half the
capacity. PP3s use 6 AAAA - not a common size on its own so difficult to
compare.

--
*El nino made me do it

Dave Plowman London SW
To e-mail, change noise into sound.

Pete Verdon wrote:
wrote:

Just tie one of the transformer LV outputs to earth.
If mains meets that side of the LV supply, the fuse/mcb will trip.
If mains meets the other side of the LV circuit, the transformer
secondary will be low enough resistance to allow overcurrent, and
hopefully blow the fuse or trip the breaker, simultaneously frying the
relay.
You cant earth both of course

Um - what transformer?

ummm


Presumably the same would apply with the battery though?

yes.


I'd wonder about the current-carrying capacity of the wiring on that
side, but I guess it would last long enough to trip an RCD.

Pete

It might not, but thats still a big improvement on it definitely wont.
Mind you in this case if there's no exposure of the LV side it may be
better to leave it uneathed and just equibond the push button front.
(Mains to the battery would be fun)


NT

Pete Verdon d wrote:

Tim S wrote:
Andrew Gabriel coughed up some electrons that declared:

What about a flow switch on the toilet cistern supply?

That's no good - I don't want the fan coming on when someone goes for a
pee at night. The switch next to the toilet is to be a manual one, with
a fan symbol etched on it.

There's no need to flush the toilet every time someone has a wee.

Daniele

D.M. Procida wrote:

There's no need to flush the toilet every time someone has a wee.

Maybe not, but I at least am in the habit of doing so, and I'm not going
to tell my lodgers that they shouldn't.

Pete

Pete Verdon d wrote:

D.M. Procida wrote:

There's no need to flush the toilet every time someone has a wee.

Maybe not, but I at least am in the habit of doing so, and I'm not going
to tell my lodgers that they shouldn't.

I guess it's easier to manage this en famille (especially when 50% of
the famille is prepubescent boy, and still wholly unabashed by bodily
functions).

Daniele
--
Your chance to own a nearly immaculate BMW C1 (Cardiff, UK)
http://search.ebay.co.uk/220341650190

On Sat, 10 Jan 2009 18:31:16 +0000
Pete Verdon d wrote:

Hi,

Currently, my bathroom has a fan which switches along with the light and
stays on on a timer afterwards. Most of the time, this is unnecessary -
if I fill up a glass of water before going to bed I don't need a fan
waking up everyone else in the house.
snip

One, totally orthogonal, thought is to have a heat recovery fan running
all the time. Needs no particular switchgear.

I'm considering one of these:

http://www.bes.co.uk/products/178.asp

R.

The message
from Derek Geldard contains these words:


To be honest I've had great success with these :

http://snipurl.com/9rfwk [cgi_ebay_co_uk]

(A 3 AA battery operated PIR & Photocell controlled LED Nightlight)

No clicking of lightswitches in the middle of the night, great if you
have elderly relatives staying who have to visit the bathroom
frequently and don't know where the lightswitches are. Battery
operated so not constrained by the need for a mains supply. The 3 AA
batteries seem to last us about 6months. Plenty enough light to light
a whole bathroom, landing or staircase to complete the "intended
function". ;-)

Have got a similar one in Lidl and have it on the upstairs landing.
Agree that it's an excellent idea and gives plenty of light to see one's
way around.

TheOldFellow wrote:

One, totally orthogonal, thought is to have a heat recovery fan running
all the time. Needs no particular switchgear.

Hmm, that's quite an interesting idea. I must admit, I was thinking what
a shame it was to blow all that lovely heat out of the house just to get
rid of the water. Not sure why I'd run it all the time - even at 80%
efficient it would still be spending all day pumping heat out of the
house compared to if it were turned off. Plus the running cost of the
fan itself. I guess that's necessary ventilation if you live in a modern
uber-insulated sweat-box, but my house, while not ancient, doesn't
really qualify.

Plus the fan has a dangly pull-cord on it, which looks really tacky :-).

And it's not cheap.

But still worth considering, thank you.

Pete

On Sun, 11 Jan 2009 04:09:19 +0000, Pete Verdon
d wrote:


No - in mine the primary side of the transformer would be on all the
time, and the battery is only used (and relay energised) while the
button is depressed. The idea is that pressing the button looks to the
fan like someone flicked the light on and off, and it then runs for the
duration of its timer.

Couple of practical points - don't place a push button within reach of 5 year
old sitting on toilet - pp3 will die quickly.
I found that my cheap fan only ran for about 10 minutes after "blipping" the
light on, even when the timer set for a nominal 20 minutes. It seems to require
a connection of about 4 seconds to charge the capacitor fully.


--
Geo