question

The relay, on the GlobalLink 520, will only handle 125vac max, according to the spec sheet. Ergo, you can’t connect 220vac directly to it.

However, you could use the GL520 relay to switch another auxiliary dc relay which can handle 220vac mains.

[Note that this advice is provided as a guide. If you are not competent with electrics, don’t do it. You undertake this entirely at your own risk.]

So, let’s say you utilise a 12vdc auxiliary relay, whose contacts are rated to at least 220vac.

Connect 12vdc to the common terminal of the GL520 relay. Connect the NO terminal, on the GL520 relay, to one side of the coil on your dc auxiliary relay. Connect the other side of your auxiliary relay coil to negative (ground).

Connect your 220vac live to the common contact terminal of your auxiliary relay and your greenhouse ventilator live to the NO terminal of your auxiliary relay.

Thus, what will happen now, is that you can send a command to the GL520 instructing it to close its relay. This will occur within 15 minutes if the GL520 operates normally.

When the GL520 relay closes, it will switch 12vdc to your auxiliary relay, causing its contacts to close, putting 220vac on the live connection on your ventilator, thus switching the ventilator on.

Thanks Jolir for your kind reply. I wouldn't qualify myself as competent, but I'm eager to learn, whatever the consequences!

If I understand you well a 12v positive power source should be connected to the COM contact of the GL520 relay, and the other side of the auxiliary relay should be connected to the negative of the same 12v power source. As the default relay state on GL520 is OPEN the coil of the auxiliary relay receives current and keeps the relay closed. Am I correct?

I can’t follow your answer; it’s not clear.

I believe my careful step by step exclamation is clear on how to wire it and what happens.

Basically, the GL520 relay will be OPEN until you send it a signal to close. This connects the GL520’s relay COMMON connection to its NO connection.

This will pass +12v through to your auxiliary relay’s coil which, in turn, will close its contacts and pass 220vac to your ventilator.

If my instructions are not totally clear to you, find someone else to wire it up for you. A mistake could be costly and dangerous.

I just wanted to know what following means: 'Connect 12vdc to the common terminal of the GL520 relay'. Does it mean you have to connect a 12vdc positive wire to the COM terminal?

Yes. As per my original post….

Connect +12vdc to the common terminal of the GL520 relay. Connect the NO terminal, on the GL520 relay, to one side of the coil on your dc auxiliary relay. Connect the other side of your auxiliary relay coil to negative (ground).

Based on your question, it’s reasonably clear that you don’t understand this simple circuit. You need to be aware that getting this circuit incorrect could damage your devices or even kill you.

You're absoltely right to warn me and I appreciate your concern. Meanwhile I also realise that the meaning of OPEN and CLOSE was not understood by me. OPEN means a circuit is interrupted, not the opposite.

I assume that if the GL520 is OPEN again the auxiliary relay will disconnect its contacts so that the ventilator stops working.

That’s absolutely correct. The NO (“Normally Open”) contact interrupts the circuit in its original state.

The relay also has a “Normally closed” (NC) contact too. So, for other projects perhaps, the GL520 relay can be used in the opposite sense.