Motion Sensor for Electric Shower - What Relay? Ask questions and find answers to many subjects relating to electrics and electrical work

[jim the plumb]

Hi guys.

Typing this again as I lost the lot a few minutes ago.

I've nearly finished my bathroom install and I've put the light pull cord in the loft for a smooth ceiling. The cord still works but now there's a pir sensor that turns on the lights when the door is opened.

I've also put the electric shower pull cord in the loft. Again this is still working but means that if I want to turn off the shower I have to go in the loft. I want to keep the isolation in the loft but use a second pir to send power to the shower.

The only way I can think of is to use a high capacity relay 45amp in-line for the shower cable and use the pir to power the relay from NO to CLOSED. When motion is no longer detected, the relay returns to NO.

What do you think? And which relay?

Jimbo

[proptech]

Hi jim the plumb
Funny, I just lost my reply too, so let's try again.
I might be missing something, but to my mind, the isolation must be accessible, and if you were to use a relay, then you would still need isolation before it. So what's the point ?
The isolation doesn't have to be a pull cord, and depending on location, could be outside the bathroom, but not in the loft.

[ericmark]

To use any automated system would not be allowed for isolation just can't see the point in turning off a shower anyway. Isolators are designed to isolate a supply so it can be worked on not to switch it on and off and in the main they will have some means to lock off. I have used remote operation of an isolator it was called an emergency stop and there are rules with vary according to the damage likely if it fails. But if you wanted a PIR to open isolator that would be OK but you would need a manual reset in the same way as a motor stop and start is wired so a button or momentary switch would need to switch power on and the PIR would hold power on with another switch to break power in an emergency so you would have a stop, and start switch plus PIR. Just can't see the point?

[jim the plumb]

Thanks for the reply.

The point is that I don't want an isolation switch on the wall outside the bathroom as this wall at the top of the stairs, will be tiled. A switch will spoil the clean minimalist look of the house. All our lighting is dimmable motion sensing downlights. As you walk around the house, lights come on and off as necessary and as programmed.

I would never remove the shower isolation - I just want to keep it in the loft out of site. The reason for the motion sensor is to remove electricity from the shower when not in use. Obviously when someone uses the loo, the power will be turned on to the shower and the led will illuminate.

In the meantime I have found a relay from Farnell but it needs a 12v pir supply to power it. Is there a 240v relay out there that can do the job?

[DIYorNot]

You would need to use a contactor not a relay. The contactor would fit in a DIN enclosure and you'd use the PIR to switch the contactor on.

Alternatively, look at the remote/wireless shower switches that some of the electric shower manufacturers such as Mira, Aqualisa and Creda offer.

[ericmark]

The word relay normally refers to up to 16A and contractor above 16A but this is a loose thing and there is some crossover but at 40A contractor would be the term used. However a three phase 16A relay with all contacts in parallel could handle 48 amp but the term is of little importance 63A contractors can be DIN rail mount.

What is more important is basic reason for isolation. The whole idea is for fault or maintenance the supply can easy be removed. If to remove the supply it is easier to switch off at consumer unit than isolator then clearly no point in having the isolator.

Isolators should be visible from the item it controls and lockable otherwise rather pointless. Having an isolator which would remove the supply when some one entered an area may make some sense however you are looking for the reverse. This rather defeats to point.

Return to basics and work out why you want an isolator. What you are protecting against is some one turning on the shower and walking out of the room with the shower running. If some one is so intent on wasting energy then likely what ever system you install they will find a way to defeat it. Cameras and a monitoring station is only option.

Showers do not rotate in fact have no moving parts so isolators are not strictly speaking required the RCD in the consumer unit is enough. So clearly something missing. Is this shower in the home of the insane? Be it alzheimer's or other then clearly one has to do a careful risk assessment but unless protecting against some mental problem one has to ask why is this required?

[jim the plumb]

[quote="ericmark"]The word relay normally refers to up to 16A and contractor above 16A but this is a loose thing and there is some crossover but at 40A contractor would be the term used. However a three phase 16A relay with all contacts in parallel could handle 48 amp but the term is of little importance 63A contractors can be DIN rail mount.

What is more important is basic reason for isolation. The whole idea is for fault or maintenance the supply can easy be removed. If to remove the supply it is easier to switch off at consumer unit than isolator then clearly no point in having the isolator.

Isolators should be visible from the item it controls and lockable otherwise rather pointless. Having an isolator which would remove the supply when some one entered an area may make some sense however you are looking for the reverse. This rather defeats to point.

Return to basics and work out why you want an isolator. What you are protecting against is some one turning on the shower and walking out of the room with the shower running. If some one is so intent on wasting energy then likely what ever system you install they will find a way to defeat it. Cameras and a monitoring station is only option.

Showers do not rotate in fact have no moving parts so [b]isolators are not strictly speaking required the RCD in the consumer unit is enough[/b]. So clearly something missing. Is this shower in the home of the insane? Be it alzheimer's or other then clearly one has to do a careful risk assessment but unless protecting against [b]some mental problem[/b] one has to ask why is this required?[/quote]

Because it's cool!

Maybe I am mental. I prefer 'thinking outside the box'. You place/ hide the cables for something electrical then dangle a cord from the ceiling to operate it - that spoils the clean lines of what I am trying to achieve.

Why have a pull cord switch in this day and age? The big Klunk as you pull it! Why is it so noisy anyway?
And if the circuit breaker can be the isolator, why have a pull cord in the first place?

That's just mental.

[proptech]

"Because it's cool!" ? How about the clunk from a contactor every time the room is entered. I just hope this installation gets to be correctly inspected and tested for safety.

[jim the plumb]

It will be tested. So a contactor makes a clunk as well eh?

Back to the silent drawing board then.

Thanks for the replies and advice guys.

[plumbbob]

I just hope this installation gets to be correctly inspected and tested for safety.

I don't see how it can be if any isolaters are put in the loft. IEE regulation states they must be placed in a visible location adjacent to the equipment they protect. The other stipulation for a shower isolater is it must not be within reach of anyone in the shower.

Also, I can see problems with the pir not sensing someone in the shower cubicle and turning the power off.

[ericmark]

The IET regulations are not easy reading with references pushing one around the book in circles as they all cross each other. As far as isolators go there are on load and off load isolators 537.5.2.3 but most of the requirements are in the case of rotating machines of a rating exceeding 0.37 kW (522.1.2) which does not include a shower.

537.2.1.5 in the 17th and 476-02-02 in 16th both refer to remotely placed isolators and the ability to lock off. Also 537.2.2 refers to securing and unauthorised operation.

514.1.1 talks about visible and switch gear. 537.2.2.2 also refers to visible also 537.3.2.2.

So because of the visibility requirements using contactors as isolators and also it would need to comply with BS EN 60947-4-1 to be used as an isolator BS EN 61095 would not comply so one would have to be very careful selecting. See Table 53.2.

However I can’t find any regulation saying there must be an isolator with a shower. But reading the manufacturers instructions they say isolator must be fitted and 134.1.1 says we must follow manufacturers instructions however most manufacturers instructions also require local supplementary equipotential bonding but 701.415.2 has removed the requirement if conditions (i) to (iii) are met so one has to decide if the manufacturer is advising or requiring as they often repeat BS7671 regulations as advise rather than a requirement.

So down to nitty gritty of regulations it is all dependent on what the manufacturer of your shower has written in their installation instructions as to if an isolator is required. However if it is required then there must be visible indication and clearly a manually operated switch would be required and a contactor complying with BS EN 60947-4-1 or Isolator complying with one of the BS numbers listed in table 53.2 and this would not allow a PIR to work it.

[DIYorNot]

Also, I can see problems with the pir not sensing someone in the shower cubicle and turning the power off.

Most PIR sensors have an 'on' timer which can be adjusted. So once triggered, it will keep the output 'on' for a set period. However, if the bathroom also has a toilet or someone is just is in there but not using the shower, the PIR sensor will still switch the output. This may be wasteful.

You will indeed hear a clunk from the contactor. Since high current is involved with an electric shower, I doubt whether you will find a quiet solution as you need to switch a hefty load.

[DIYorNot]

You may want to consider a remote wall control in another room as I mentioned previously. Many of the shower manufacturers offer this for walk-in showers.

Here is one by Mira:

http://www.mirashowers.co.uk/platinum/index.htm

[ericmark]

[quote]High-pressure valve for mains pressurised systems or combination boilers[/quote]
Not sure how this would ever require a contactor as water is not instant electric heated. The idea of using either stored water or gas heated does have many advantages main one being reasonable quantity of water not a trickle mine is 27kW clearly far bigger than any instant electric can be.

However much depends on what supplies the water. We have a Main 7 boiler which once the flow rate goes below a set rate will switch off and if you were to use an instant electric type shower head it would repeatedly cycle from hot to cold as not enough water to keep boiler running.

My mother has similar problem in her case there is a small store of hot water in the combi boiler so on switch on it is cold until this store of hot water gets to shower then there is a second cold supply where the store has run out but boiler has not warmed up.

It does not really matter what the electronic mixer tries to do unless it is supplied to constant hot water supply it can't supply a constant hot water at the shower. From a heat store it will depend how it is supplied some you use the water direct others have a heat exchanger built in and again quantity of water being drawn will likely alter temperature so fast acting mixers are only any good with a boiler or store able to supply it.

Personally after using a 27kW shower I would never consider electric instant heat type I like a reasonable supply of water not a dribble but I will admit there are times where the instant electric can be better option.

However the question has to be why have an isolator? Although we will normally fit isolators on shower and cooker supplies there is nothing as far as I can see which says you have to have one. Look at a gas cooker and often there is no isolator either you switch off main supply or use a plug and socket arrangement which self seals as the spigot is released. How they get away with it I don't know but as far as I can see there is nothing to say you must have an isolator.

So back to basic why do you want the supply to be removed from the shower unit when no one is in the room? When I have had an electric shower I never bothered turning it off.

I am sure something is being lost in the writing and there must be something I have not envisaged but just can't see why you need an isolator at all if it's not manual operated.

A RCD at the consumer unit would isolate the supply far better than anything hidden in a loft. So please try to explain why you want something in the loft.

[jim the plumb]

Crikey - so many replies I've had to break out the laptop!

The reason for keeping an isolation switch is the Triton manual states, "After phased shutdown the unit [b]MUST[/b] be isolated via the 45amp-isolating switch.

In order to maintain the minimalist look of the bathroom, I have moved the isolation pull cord into the loft. For ease to get it out of the way and have a smooth ceiling. That's it - no other reason for it to be in the loft.

So, to save me from going into the loft every time - I either leave the isolator on constant or get creative and 'think outside the box'.

The shower does have it's own breaker under the stairs which I could use but that again is a manual switch and at some point I'll forget to turn it on before getting undressed.

So you can see my reasoning for a motion sensor to create the isolation for me.

But if a contactor is noisy, then I won't use it.