I need to control the on/off state of 6 centrifugal fans with 220v 150w/0.66A AC motors, individually. Previously I have controlled many 220v things with relays and Arduinos but they were all without earth and pretty low wattage. These fans have a 3 pole earthed wire (see picture below) and do pull a few more watts than I usually work with.
In the picture below is one of the fans, showing how the wires on the right come from the wall plug and connect to the motor and a 2.5uF capacitor.
I just glanced at the SE post, it seems like the cascading of the relays is just to isolate your low voltage circuit from mains voltage. Although I've been under the impression that you can get optocoupled relay modules. Maybe this is just an extra security layer.
I'm just a hobbyist, not an EE, so I could be wrong:
I would assume that 150 W should be still in the area of what these relays should be able to handle. But personally I never switched anything with them above 40 W or so (light bulbs). However as mentioned in the SE post, quality relays start around 10 USD, when in doubt go for quality. Especially if you can't really asses how safe your devices are. That's probably the road I would take here: better safe than sorry.
Just connect phase and neutral to your relay, leave earth as is, i.e. never break that connection. You can get away with only switching one wire, however in my country we don't have polarity protection so I'd never know which is which and from what I've read it's better practice to switch both anyway.
Just a personal note: If you don't really know what you are doing or feel uncomfortable, don't work with mains yourself and get a professional to do it.
Edit: what's with the blue and brown cable coming from the terminal with no input? Also it seems like a bad idea to have brown and blue coming from th same terminal when on the input side one of them should be neutral.
Also the wires get thinner after that. Can't really telly but are they still thick enough for 150 W?
The earthed wire, yellow with green stripe, is only connected to the fan frame, not the motor. I have a whole shelf of those fans that came from an old convection oven.
The motor is a split phase motor with one 220 volt line going directly to the motor and through the capacitor to another winding on the motor. If the fan turns up to a good speed as you have it wired, just add the relay as you are intending. Good thing you have lots of them. Best to use a solid state relay.
Since some of you asked about the wiring - it was wired by the guy who sold it to me who is an electrician working with installing (and removing) them, so I just assume that's how it should be. Also they work great and seem to push a lot of air.
So, I gather it is safe to use the relays I have as long as I use two relays per fan. I might buy some 2 pole relays. Are there any advantages to using a solid state relay apart from it being noiseless?
Follow up question - is it safe to use them with a dimmer used for stage lights (i.e. a powerful one)? Should I in that case be careful with running it on low dimmed levels?
Motors are highly inductive loads, you will need a snubber network to avoid heavy arcing on the relay
contacts normally. Relays will usually specific a derated current specification for inductive loads too.
gorgon:
Chuckyx, Paul_KD7HB, LMI1 thanks for chiming in!
Since some of you asked about the wiring - it was wired by the guy who sold it to me who is an electrician working with installing (and removing) them, so I just assume that's how it should be. Also they work great and seem to push a lot of air.
So, I gather it is safe to use the relays I have as long as I use two relays per fan. I might buy some 2 pole relays. Are there any advantages to using a solid state relay apart from it being noiseless?
Follow up question - is it safe to use them with a dimmer used for stage lights (i.e. a powerful one)? Should I in that case be careful with running it on low dimmed levels?
You only need a single contact relay for the motors. Just need to open and close the circuit. But the tiny contacts on the Chinese relays won't be very reliable. A SSR is quite reliable for your project. All depends on what you need.
A dimmer such as you are suggesting is used for a resistive load. Will not work for your fan motors. Don't even bother to try. If you want to reduce the air flow, add a moveable cover to the intake side of the fan. Adjust the opening for the air you need.
