Question: I'm using relays to drive a circuit of solenoids. Do I really need flyback diodes on the controlled circuit if there are only solenoids on it? The driving circuit is already protected by flybacks.

![schematic](https://i.stack.imgur.com/Xvlay.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fXvlay.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)

Answer: 
A MOV or snubber or bipolar TVS will usually extend the life of the relay contact. At 24VAC it may not be that important. Personally, I would consider a bipolar TVS. 

It won't affect the relay directly, but if the controlling circuitry is poorly designed you may see effects from switching such an inductive load (microcontroller resets, flakey behavior increasing in frequency as the contacts age and so on).
The relay contacts should be snubbed with a (bipolar) TVS device or R/C snubber network; this will protect the contacts from arcing damage/wear (pitting, etal) and extend their life *dramatically* in this service. See Chapter 7 of [Electromagnetic Compatibility Engineering](http://rads.stackoverflow.com/amzn/click/0470189304) for more snubbing advice.