Frequently Asked Questions
What does a contactor board do in a grow room?
It lets one 24 hour timer switch all your grow lights at once. The timer switches a heavy duty 40A contactor, and the contactor carries the load, so the timer is protected from the surge of current lights pull at switch-on. Fans and extraction go on separate always-on sockets.
What do the numbers 12/14, 16/18, 20/24, 24/28 and 24/32 mean?
Timed sockets / total sockets. A 12/14 way board has 12 sockets on the timer for lights and 2 always-on sockets for fans. The 16/18 has 16 timed and 2 always-on, the 20/24 and 24/28 have 4 always-on, and the 24/32 has 24 timed and 8 always-on plus a built-in consumer unit.
Does the contactor board come with a timer?
Yes. Every board has a built-in 24 hour timer that switches the timed sockets. The always-on sockets stay live for your fans and extraction.
Can I use a contactor board with LED grow lights?
Yes. LED drivers pull a surge of current at switch-on just like HID ballasts, which is what burns out standard plug-in timers. The contactor takes that load instead.
Can I fill every socket on the board?
Only if your supply can carry it. Socket count is not the same as safe load. Add up the wattage of everything you plan to plug in and have a qualified electrician check your supply before you fill the board.
Do I need a contactor board or a plug-in contactor?
For a tent with a couple of lights, a 4 to 8 way plug-in contactor is usually enough. If you are filling a room with lights or plan to expand, a board gives you more timed sockets, dedicated fan sockets and one tidy wall-mounted unit.
Description
Once you're running more than a couple of lights, a contactor board is what keeps the whole room on one timer without cooking it. Lights go in the timed sockets. Fans and extraction go in the always-on ones. The 24 hour timer clicks the 40A contactors in and out, and the contactors take the load.
It's all built onto one MDF board that goes up on the wall. A lot tidier than a tangle of extension leads behind the tent.
Why not just use a plug-in timer?
Grow lights pull a big spike of current the second they switch on, and a cheap plug-in timer isn't made for it. Put up with that every day for a few weeks and the contacts start to weld. Sometimes the lights stick on. Sometimes they don't come on at all.
With a contactor in between, the timer only switches a small control circuit and the contactor does the heavy lifting. Same story whether you're on HPS ballasts or LED drivers, as both give that inrush at start-up.
Which size do I need?
Read the numbers as timed sockets / total sockets. So a 12/14 gives you 12 on the timer and 2 that stay on all the time for fans.
| Board | Timed sockets | Always-on fan sockets | Contactors | Timer |
|---|---|---|---|---|
| 12/14 Way | 12 | 2 | 1 x 40A | 24 hour |
| 16/18 Way | 16 | 2 | 2 x 40A | 24 hour |
| 20/24 Way | 20 | 4 | 40A | 24 hour |
| 24/28 Way | 24 | 4 | 2 x 40A | 24 hour |
| 24/32 Way | 24 | 8 | Built-in consumer unit with circuit breaker | 24 hour |
The 24/32 is the big one. It has a consumer unit built in with its own circuit breaker, and 8 always-on sockets instead of 4. Plenty for all the fans and extraction in a full room.
One tent and two lights? Then a plug-in 4 or 6 way contactor will do you fine, and there are a few below. A board starts to make sense when you're filling a room, or you know more lights are coming.
A word on load. More sockets doesn't mean your supply can feed them all. Add up the wattage of everything going on the board and get a qualified electrician to check your supply before you fill it.
Smaller setup? Plug-in contactors
