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WaWaWa · Joined: 03 Oct 2005 Posts: 1 Location: Midlands.

I have installed a mechanical heat recovery ventilation unit in the loft.
I have connected the ducting for two bathrooms and the kitchen to it.
The (two, one inlet the other expel) fans in the unit draw a total of about 100W at 240V on the lowest setting and up to about 250W at the highest setting.
This has been working fine for over a year.

This set up is fine during the winter months when the windows are generally closed.
During the summer it is wasteful because it runs continually and I chose a unit which is too powerful for my size of house!

I would like to change the way it is controlled.
I would like it to be off most of the time unless one of the following happens:
-> one of the bathroom lights is turned on.
-> I turn it on with a separate switch.

The unit is in the loft, so what I need is a device which sits between the unit and its (domestic 13A socket) power supply to which I can connect the original fan activiation wiring from both the bathrooms and also a third switch (regular pull cord or similar), so that when any one of them is on the unit is powered, but all three are isolated from each other.

This could either work with the 3 switches providing a signal only and the unit getting its power as it does now, or with the 3 switches actually providing the power too.

A sort of mains spec. OR gate is what I'm after.
Ideally it would also have a timer circuit in so that the fan would continue to run for a period after the last light or switch is turned off.

The house is 8 years old, single phase.

So my questions are:
-> does such a device exist?
-> what name would I look under?
-> who would be a good brand?
-> where would I get one in the Coventry area?
-> what sort of price am I looking at?

Don't worry about the rights and wrongs of MHRV or the risk of humidity build up in the bath rooms without their conventional fans, this unit can easily exceed the displacement of the previous inline fans.

Thanks in advance.

dj-paul-c · Joined: 17 Oct 2004 Posts: 23 Location: edinburgh

to switch the unit with the bathroom lights wont work properly with 3 switches in the circuit as when you switch the bathroom lights on the unit will work,but if you switched the unit from another location the bathroom lights would come on as well when not necessary,i presume you want a switch at both your bathrooms and one at your kitchen

but

you say you could turn it off with a seperate switch,yes you can do that, you could controll the unit from 3 seperate points anywhere in the house and work the unit with any of those switches,you can do this with a 2 way and intermediate switching arrangement

please contact an electrician to undertake the work

hope this helps

vince knight · Posted: Thu Oct 06, 2005 6:27 am Post subject:

Why not place a spur in your airing cupboard on the top floor taking the supply from the water heater spur, then you could switch it on an off without getting in the loft. This is the easiest way without making up a relay set.

Vince