Motion Sensor for Electric Shower - What Relay?


Postby plumbbob » Sun Dec 15, 2013 5:42 pm

jim the plumb wrote:But if a contactor is noisy, then I won't use it.


For sure, a 40amp contactor will make a loud “thud” when it pulls in!

ericmark wrote: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.


Well, according to my little book of the IEE Regs, it states for electric showers, “The heater must be controlled by a double pole linked switch. In the case of a shower heater, if this switch is not built in to the heater itself,” (which it isn’t) “ a separate pull switch must be provided adjacent to the shower……”

To be honest, I can’t be bothered to search the book for the exact wording, but as far as I am aware, all kitchen appliances are required to have isolators (usually a fused spur) in view above the worktop. Fine, built in hobs or ovens may be plugged in to a 13amp socket in a cupboard, but will still require the protection above.

ericmark wrote: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.


Yeah, I wondered that too. I never turn mine off. There is no instruction to do so in the user handbook. The isolator is only for safety only. Some of the electronic showers have internal circuitry that will waste energy, so from that point of view, I could understand it may be desirable to kill the supply.

If the noise of a contactor is a problem, how about a solid state relay????
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Postby ericmark » Sun Dec 15, 2013 8:01 pm

I see a little more now so isolator is to comply with manufacturers instructions rather than any IET/BSi or building regulations. The PIR would switch on shower even when not required and to have any switch would likely have the same displeasing effect. Or would it? Swapping the light switch for a double switch one can use a contactor as you said without the problems that the PIR would activate contactor even if the shower is not required.

I have fitted contactors in guest houses as people would walk out of the bath room and leave shower running so a simple pneumatic timer would switch off the shower.

The point is of course unless one was to put a huge notice in the bathroom shower must be turned off at isolator after use then most people would not bother so for a manufacturer to require the isolator to be used after every shower use would require a complete re-education of all electric shower users. To fit a means of double pole isolation some where so if the shower goes faulty it can be isolated so it will allow the RCD to be reset in the consumer unit is a good idea where the RCD used does not only supply the shower. But be it in the loft or by consumer unit it really does not have to be turned off after each shower. Only with fault.

So if it were me I would leave enough cable to add an isolator or contactor but would try it without first.

Double pole switching is required with TT supplies but with TN not really required but likely manufacturer thinks does the guy fitting it know what TT is. Clearly he should but in practice he may not so easy thing ask for double pole anyway.

Last shower I fitted had a row of switches at the door. From bottom under floor heating isolator, under floor heating thermostat, lights, shower isolator, fan isolator and yes the strip of switches does not look the best. And looking back today under floor heating never used, power shower now removed and a standard thermostatic shower from combi has replaced it so switch redundant, lights are of course used but now 6W LED no longer 150W tungsten so no real sweat if left on 24/7, and fan is never switched on so only switch really needed is light switch.
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