I have a Hayward/Goldline AquaLogic PS-4 automation system. This system has an option for adding a fifth 120/240 volt relay output (in addition to the four that are part of the PS-4 system), but it requires that you aren't using the fourth valve actuator output. In fact, one could add a SIXTH 120/240 Volt relay output by using the third valve actuator output in a similar manner.
I just received the AQL-RELAY-AC-KIT from poolsupplyworld.com for $62.46 plus $7.95 s/h. I was 95% certain which relay was needed, but I wasn't completely sure so I went ahead with buying the factory relay kit. The reason for my hesitancy was that the normal four relays (8 relays for PS-8 or 16 relays for PS-16) use relays with DC coils (Omron G7L-2A-BUBJ-CB-24DC), but these add-on relays need to have AC coils since the valve actuator output is AC. Also, I really wanted to be sure which exact relay model that Hayward/Goldline was using.
It turns out that this AC relay kit has a few more parts than I had realized, with the main extra being a metal relay cover. The contents of the AQL-RELAY-AC-KIT is:
(1) Relay, 3 HP @ 240 VAC, 24 VAC coil (Omron G7L-2A-BUBJ-CB)
(1) Relay Wiring Harness
(2) 6-19 x .38" Screws
(2) 10-32 x .31" Screws
(1) Relay cover
(1) Label for relay
So unless one really needed the metal relay cover, one could just purchase the Omron G7L-2A-BUBJ-CB relay at Digikey or Mouser Electronics for about $16 as compared to the factory AC relay kit at $65.
The only other thing missing would be the "relay wiring harness" which has a 3-pin connector which connects the valve actuator circuit board location to the new relay. The supposedlly "industry standard" 3-pin connector may be an "industry standard" for pool valve actuators, but in reality it is a very hard to find, oddball connector. I had success in contacting Goldline technical support and requesting that they send me this 3-pin connector.