Can sprinkling zone valves be directly controlled by the voltage relays on the xp-8?
Any help would be greatly appreciated.

That depends on the voltage and current requirements of the valves. What are their electrical specifications?

Electrical Specifications
• 24 VAC 50/60 Hz (cycles per second)
solenoid power requirement
• 0.30 A (7.2 VA) inrush current
• 0.23 A (5.5 VA) holding current
• Solenoid coil resistance: 38 Ohms

And what are the electrical specifications, current-wise, of the XP-8 relays?

I don't mean to be tedious or to be a smart-ass, but comparing the current carrying and switching capability of the XP-8 with the required current for the sprinklers is the way to answer this question.

If you find that the sprinklers require more current than the XP-8 relays can safely switch and carry, then the answer is no. In that case I would get some Bosch automotive relays, that you can find at almost any auto parts store. The XP-8 can switch them and they can safely handle the current of the sprinklers. Those intermediate relays can be next to the XP-8 or next to the sprinklers or wherever in between is most convenient. Be sure to have a 12 volt supply with enough current to hold all of the Bosch relays on at the same time.

Apparently, this just flew over my head. As I understand it, the xp-8 outputs 30 volt dc, and the valve uses 24 volt ac. Is there somewhere I can learn how to do this?

I think you're misunderstanding the relay specification, and what you are concluding is totally logical, but unfortunately not correct. Just like a light switch on a wall, that is rated 250 volts and maybe 10 amps, a relay's spec does not indicate that it puts out any voltage or current -- the light switch doesn't put any out, it just lets it go through or not -- instead the specs show the upper limit of what you can put through it.

Two things come to mind: First, you would use the XP-8 to turn on relays that can handle the AC current of the sprinklers.

Better yet, call RTI or email them and ask for the AC characteristics of the XP-8 relays. In general, relays can switch higher AC voltages than DC...I forget whether higher or lower AC currents. Understand that the guys at RTI might be scared as hell to let AC loose on any of the terminals on the XP-8. If they are, don't hassle them, just get external relays to switch the sprinklers on and off.