New fan system

[google]

Hi
I am installing an in-line extractor fan with timer, which will serve 2 bathrooms with timer can please advise .both bathrooms are in same circuit.

 

[Murdochcat]

Best to fit 2 separate fans …..

 

[ericmark]

There are two reasons to fit fans, one to comply with building regulations, the other to help the bathroom dry. I don't know how you combine two rooms to comply with building regs, and I have found fans if switched on at the wrong time can make the room wetter rather that drier.

There are heat recovery units which can serve multi rooms, but the idea is to move the moisture outside not into the rest of the room, so unless directly over the shower, it wants to switch on after you have finished in the shower so it does not drag the moisture in the shower area into the rest of the room.

To arrange a shutter system is not impossible, but I would agree with @Murdochcat easier to have two independent fans.

 

[SUNRAY]

One fan, suck from both rooms simultaneously, wire both lights as a common 2 way circuit.

Seems to becoming standard practice in some new builds

 

[JohnW2]

One fan, suck from both rooms simultaneously, ...

I imagine that one of the issue eric was referring to is the uncertainty, if one does what you say, of knowing what proportion of the total air extraction will be from one room rather than the other. In a 'bad case scenario' (e.g. with very different duct paths) little air might be extracted from one of the rooms.

wire both lights as a common 2 way circuit.

Can you clarify what you mean by that?

 

[flameport]

Double pole light switch in each bathroom, 1 pole for the light, the other for the extractor.
Or a PIR / microwave detector in the ceiling of each room, both wired to the extractor.

 

[JohnW2]

Double pole light switch in each bathroom, 1 pole for the light, the other for the extractor.

Indeed - that's the obvious way to do it - but I asked him to clarify what he meant, since I would personally not have described what I was thinking of (and you have described) as "a common 2 way circuit", would you?

 

[SUNRAY]

Indeed - that's the obvious way to do it - but I asked him to clarify what he meant, since I would personally not have described what I was thinking of (and you have described) as "a common 2 way circuit", would you?

Double pole is definitely a correct way of doing the job and probably the simplest.

I've seen several new builds where I assume the 'electricians' are 4 hour wonders and not capacle of anything outside of the half day tuition on a whiteboard. Bathroom and ensuite are commonly adjacent to each other and they have wired lights in both rooms together with 2 way switching at the doors.
I think I've mentioned it on here before. Due to the way it's been wired and not wanting to spoil decor my fix has been to fit a pair of relays.

EDIT: I suppose the issue may have been they are not permitted to use any different accessories to those supplied in bulk.

 

[JohnW2]

Double pole is definitely a correct way of doing the job and probably the simplest.

Indeed, as I said 'the 'obvious' way - provided,of course, both lights aree on teh same circuit (otherwise we would be in the territory of the fan 'borrowing a neutral!)

I've seen several new builds where I assume the 'electricians' are 4 hour wonders and not capacle of anything outside of the half day tuition on a whiteboard. Bathroom and ensuite are commonly adjacent to each other and they have wired lights in both rooms together with 2 way switching at the doors.

I'm still a little confused by your reference to "2-way switching". Are you saying that switching off the light in one bathroom (and the fan) would result in the light in the other bathroom also going off?

Kind Regards, John

 

[SUNRAY]

Indeed, as I said 'the 'obvious' way - provided,of course, both lights aree on teh same circuit (otherwise we would be in the territory of the fan 'borrowing a neutral!)

Not neccessarily

I'm still a little confused by your reference to "2-way switching". Are you saying that switching off the light in one bathroom (and the fan) would result in the light in the other bathroom also going off?

Kind Regards, John

Yes exactly that.

 

[JohnW2]

Not neccessarily

Agreed - but if the lights are on different circuits, the switches certainly needs to be wired by someone "who understands what they are doing" and,even then, there is a potential issue.

If the lights are on different circuits, then at least one of the switches needs an L feed from the 'fan circuit' for it's 'fan pole' (both switches if the fan is on yet a third circuit ), as well as the L feed for its'light pole'. However, if that is done correctly, then one has Ls from two (possibly even three!) circuits present at the same face plate, which could represent a potential hazard for someone subsequently working on it.

Yes, I know, proper 'testing for dead' should address/eliminate that hazard but, given that people are human, having two or more circuits present at an accessory will increase the potential risk.

Yes exactly that.

How daft

Kind Regards, John

 

[SUNRAY]

Agreed - but if the lights are on different circuits, the switches certainly needs to be wired by someone "who understands what they are doing" and,even then, there is a potential issue.

If the lights are on different circuits, then at least one of the switches needs an L feed from the 'fan circuit' for it's 'fan pole' (both switches if the fan is on yet a third circuit ), as well as the L feed for its'light pole'. However, if that is done correctly, then one has Ls from two (possibly even three!) circuits present at the same face plate, which could represent a potential hazard for someone subsequently working on it.

Yes

with the more likely situation on the right

Yes, I know, proper 'testing for dead' should address/eliminate that hazard but, given that people are human, having two or more circuits present at an accessory will increase the potential risk.

How daft

Kind Regards, John

I agree but other solutions far too complicated for some of the 4 hour numpties we sometimes find.

I had something very similar in an office block where they fitted PIR sensors for the lights in the toilets on every floor and wanted the rooftop 2KW fan controlled by them too. The contractor had the sense to fit a contactor but simply took the SL from every room and linked them. It was only discovered due to the different rooms being on different phases. Contractor suggested the solution of a current switch or NC contact of a dusk to dawn sensor in every room into an input of a PLC. I did it much cheaper and easier with relays.

 

[JohnW2]

Yes <diagram> with the more likely situation on the right

Agreed - that's obviously what I was describing (but couldn't be bothered to draw diagrams )

I agree but other solutions far too complicated for some of the 4 hour numpties we sometimes find.

Again agreed. As I wrote (in a slightly more specific context) ...

,,,,, the switches certainly needs to be wired by someone "who understands what they are doing" ....

I still remain a little uneasy about the possibility (if more than one circuit were involved) of their being Ls from two (or three) circuits at the same 'light switch'. One could avoid that problem (at the switch) by doing it with ('remote') relay(s) (and one would then only need standard SP switches) - but, even then, a similar issue would exist wherever the relays were located.

Kind Regards, John

 

[SUNRAY]

Agreed - that's obviously what I was describing (but couldn't be bothered to draw diagrams )

Again agreed. As I wrote (in a slightly more specific context) ...


I still remain a little uneasy about the possibility (if more than one circuit were involved) of their being Ls from two (or three) circuits at the same 'light switch'. One could avoid that problem (at the switch) by doing it with ('remote') relay(s) (and one would then only need standard SP switches) - but, even then, a similar issue would exist wherever the relays were located.

Kind Regards, John

But a warning on the relay enclosure will be in a location where aesthetics are unlikely to be an issue and several supplies expected. I would add an internal warning in the switch if suitable.

 

[plugwash]

One option I've heard of people using is to use "grid plus", then put the label between grid and faceplate. This hides the warning from normal users of the installation but means somone working on the installation is likely to see the warning while the wiring is still mostly enclosed.