Extractor fan relay for two independent light switches

metanet · Mar 27, 2024

Thinking a 240V AC relay activated by two independent light switches could be used to switch power to a shared inline extractor fan. The fan serves two bathrooms, just needs to be activated from two different switched live lighting circuits.
I'm aware double pole light switches could be used in this scenario but the light switches didn't pass wife test.

Anyone know of a dual input relay I could use for this purpose?

Thanks
Meta

oscar21 · Mar 27, 2024

Just use 2 relays, I did similar in a small apartment referb where they wouldn't knock the toilet and bathroom into one.

metanet · Mar 28, 2024

Would these work? HF105F-4/240A1ZSTF | Hongfa Europe GMBH Flange Mount Power Relay, 240V ac Coil, 20A Switching Current, SPDT | RS - https://uk.rs-online.com/web/p/power-relays/1218077

oscar21 · Mar 28, 2024

The look like they would work, not too keen on the spade terminals though, you will have to start crimping spade lugs onto the ends of the cable . I've used these sorts before now in various projects.

230v AC 8 Pin Relay 2 Pole

bill01803 · Mar 28, 2024

How about 2 of these
Fusebox INC202 - 20A 2P N/O 230V Contactor | Express Electrical - https://www.expresselectrical.net/fusebox-20a-2p-n-o-230v-contactor?gad_source=1

DefyG · Mar 28, 2024

Why 2 relays when 1 would do?

mainline · Mar 28, 2024

metanet said:
Thinking a 240V AC relay activated by two independent light switches could be used to switch power to a shared inline extractor fan. The fan serves two bathrooms, just needs to be activated from two different switched live lighting circuits.
I'm aware double pole light switches could be used in this scenario but the light switches didn't pass wife test.

Anyone know of a dual input relay I could use for this purpose?

Thanks
Meta

Just use a double pole single gang switch, it's much easier.

Or if you're adamant on not using switches, then you could use a two input solid state relay.

oscar21 · Mar 28, 2024

DefyG said:
Why 2 relays when 1 would do?

From my point of view they are 10 a penny, simple to use and I've not come across a dual input relay before.

DefyG · Mar 28, 2024

oscar21 said:
From my point of view they are 10 a penny, simple to use and I've not come across a dual input relay before.

Still cant see point of using 2 relays though

oscar21 · Mar 29, 2024

DefyG said:
Still cant see point of using 2 relays though

Well lets say I needed to do the above job, I've just been on google, typed in dual input relay and then clicked products, this is what came up.

dual input relay - Recherche Google

I'm none the wiser which relay I should buy out of that lot, so I can either take a guess and end up with the wrong thing costing me a days work or I could buy 2 relays and do it that way very easily. Is that a good enough point.

mainline · Mar 29, 2024

oscar21 said:
Well lets say I needed to do the above job, I've just been on google, typed in dual input relay and then clicked products, this is what came up.

dual input relay - Recherche Google

I'm none the wiser which relay I should buy out of that lot, so I can either take a guess and end up with the wrong thing costing me a days work or I could buy 2 relays and do it that way very easily. Is that a good enough point.

I can't see how using a pair of relays/contactors are going to be in any way easy.

They would need to be mounted properly in an enclosure that's suitable.

Contactors in the consumer unit is going to be no easy task and also costly.

The easiest, cheapest, quickest, and Compliant way is to use a pair of 1 gang dp switches as already said.

mainline · Mar 29, 2024

DefyG said:
Still cant see point of using 2 relays though

Are you talking about a dual input one ?

mainline · Mar 29, 2024

oscar21 said:
Well lets say I needed to do the above job, I've just been on google, typed in dual input relay and then clicked products, this is what came up.

dual input relay - Recherche Google

I'm none the wiser which relay I should buy out of that lot, so I can either take a guess and end up with the wrong thing costing me a days work or I could buy 2 relays and do it that way very easily. Is that a good enough point.

Why don't you try "two input solid state relay", like i posted #7

[ElectriciansForums.net] Extractor fan relay for two independent light switches

Simon47 · Mar 29, 2024

Sorry, no diagram, but here goes.
Relay coil to one light S/L, relay pulls in when that light is on.
Contact (needs to be C/O) common to fan S/L input.
Connect contact N/O to same S/L as coil.
Connect N/C contact to S/L on other light.

Switching one light on pulls in the relay, changes over the contacts, and applies live to fan control. Fan runs.
With that light off, tge fan is controlled by the other light as if the relay wasn't there.

The above assumes bith lights on same circuit. If on different circuits, relay coil S/L & N come from one circuit. The N/O contact must connect to the permanent L the fan is connected to - needs an extra cable core.

Simon47 · Mar 29, 2024

Oh yes, the relay will hum when on. It's possible to add a couple of diodes so the coil operates on DC, and it's inductance will smooth out the half wave and eliminate the hum.

Also, depending on the fan, it may be possible to just use two diodes so when either light is on, the fan control input is fed with half wave DC. This will be sufficient to trigger the timer on many fans.

Extractor fan relay for two independent light switches

metanet

oscar21

metanet

oscar21

bill01803

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DefyG

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mainline

oscar21

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oscar21

mainline

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mainline

Simon47

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Simon47

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