I'm putting an energy recovery ventilation (ERV) system in my new construction. I already put one in the shop/garage that uses a 120V timer set to come on several times a day. In the house, I was thinking about putting in a manual override on the timer.

Here's my thoughts on how to wire it using a double box with the timer on one side and the switch on the other. I feed the box with power and pigtail the hot to the timer and to the switch. The hot coming out of the timer and the switch are then reconnected. The neutral just goes on through the box to the ERV. Ground as necessary. It would only require a single 12/2 wire up to the ERV in the attic.

So, if the timer comes on, power is sent to the ERV. If the switch is on, power is sent to the ERV regardless of the timer. When the switch is off, the timer goes back to running the ERV. Seems right to me, but this configuration isn't in my electrical wiring for dummies book.

Mark