System construction

[Nicola Peron]

Hi everyone, I’m new to this irrigation system, but I really like it. I purchased an OpenSprinkler PI board and two extenders to connect my 24 solenoid valves. However, when I open the solenoid valves, the pump should start. Here’s a diagram of what I think is correct. Can you help me if everything is OK? The biggest problem is connecting the pump to the relay.
I posted diagrams A-B-C. Which one is correct?
Thanks
Nicola

Attachments:

1. 

   Schermata-2026-03-28-alle-18.59.49.png
   

2. 

   Schermata-2026-03-28-alle-19.48.11.png
   

3. 

   Schermata-2026-03-28-alle-19.50.07.png
   

4. 

   Schermata-2026-03-28-alle-20.03.43.png
   

[Ray]

Version C looks more correct. The other versions all have a common problem: one wire of the 24VAC transformer goes simultaneously to the orange terminal block and the COM terminal – you should NEVER do this – this can create a direct short of the 24VAC transformer causing it to shutdown, or its internal fuse to burn. The two wires from the 24VAC transformer should only go to the orange terminal block, which is what Version C shows.

[Nicola Peron]

Thanks, Ray.

Now I’m really happy and I made a good purchase.
I wanted to ask if the VEMER TMC 30/24 transformer is sufficient or if a larger one, such as a VEMER TMC 40/24, is better.

Thanks.

[Ray]

By “VEMER TMC 30/24” I suppose it means 30VA (Watt), 24VAC? It’s more than sufficient. Ultimately the power rating needed depends on how many valves you need to open simultaneously / concurrently. No matter how many valves you have, if you never need to open 3~4 valves at the same time, even a 20VA adapter would be sufficient.

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