Transformator Smart machen

I would try the following.

Equipment

1. one Shelly Pro 4 PM or
2. two Shelly Plus 2 PM

I would code a script that ensures that only one of the four outputs is switched on at a time. As soon as you want to switch, all outputs can be switched off for safety reasons and then the desired output can be switched on.

I don't know if this can be imlemented without a script.

Edit: After a reboot, all outputs must be configured to “off”.

Edit 2:
I mistakenly saw the 80V connection being used. Of course, three outputs are sufficient.
Compared to the electrically safe series connection of relay outputs ( thgoebel), my script solution uses slightly less energy...

In theory, you could do this with 3 relays. However, the 3 relays must be interlocked against each other.

In practice, I would advise against such tinkering and will therefore not provide any further information.

Welcome to the forum!

To your issue: It is absolutely essential to switch one tap of the autotransformer only to the ventilation motor. Two tap must not be connected together cause the transformer would be damaged. Thus, I would recommend to use three or four NO/NC relays, like these:

https://www.amazon.de/Eltako-2078023…aps%2C93&sr=8-7

Connected with this circuit diagram

each tap is switched exclusively to the motor. You may use a Shelly pro 3 for three speeds or a Shelly plus 4PM for four speeds.

Please be aware to place three or four snubbers in parallel to the relay coils. If a Shelly pro 4PM shall be used, NO power measurement will be available cause the Shelly indicates the power consumption of the relay coil(s).

A separate on/off switch can be implemented with the fourth contact of a Shelly pro 4PM or a single Shelly plus 1PM, which can be used for power monitoring:

Zitat von Captain_Byte

In practice, I would advise against such tinkering and will therefore not provide any further information.

This would be the end of this forum: Tinkering (with hard- and/or software) is the clue for evolution. Otherwise we should refer to the manuals provided by Shelly Europe Ltd. …