24VAC transformer has 3 wires instead of 2

[ramblinwreck]

Hi,

I’ve just ordered an Opensprinkler unit + expansion board. I’m reading up to prepare for the install soon as it arrives. It will be replacing a Hunter Pro-C controller that was installed by the guys who installed a 9-zone irrigation system recently.

I’ve noticed that the Opensprinkler board is expecting a 2-wire connection from the transformer, yet the Hunter transformer that I’ve already got is a 24VAC/1-AMP unit, having a 3-prong electrical plug and three wires going to the Hunter Pro-C controller: AC1 (yellow), AC2 (yellow), and GND (green).

This is shown in page 9 of the Pro-C manual, here:
http://www.hunterindustries.com/sites/default/files/om_proc_dom.pdf (I’m using the indoor model)

Can I use this transformer for Opensprinkler? Is the 3rd wire a problem? Do I simply leave the GND wire unconnected? Or should it be connected elsewhere? Or alternatively would you recommend picking up a 2-prong/2-wire transformer like the $15 model from home depot that is mentioned on the product page?

EDIT: Transformer appears to be Hunter model # 526500

Thank you,
Chris

[biaggi]

I am using the exact same transformer and I did not connect the green-gnd wire. The importance of the ground is for safety reasons and specifically when plugging/unplugging near wet/damp areas, but it will not damage the unit. It is a fail-safe, ie, if there is an open on the neutral wire, the gnd provides a path for the current to go to gnd vs through you.

[ramblinwreck]

Thanks Biaggi. I appreciate the explanation. 🙂 Glad that I’ll be able to reuse my existing transformer.

[Author]

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