Too often I see people stumped on how to properly get power to their pump. Not only that, but people also want the pump to turn on and off with the computer, and let's face it, it is the best option.
Too often I see people stumped on how to properly get power to their pump. Not only that, but people also want the pump to turn on and off with the computer, and let's face it, it is the best option. The relay that I have been using for about 2 years can be found here at D-Tek Customs and at Cooltechnica. This kit has everything you need and is pretty inexpensive, just $18.
Before we even start installation, we need to find a suitable place for the relay power plug socket to go. I try to have it as close to the PSU's power plug, this way you won't forget to plug it in! Unfortunately on my new Cube case, it was not possible to place the relay socket near the PSU. Once you find a good spot, hold the square bracket up and trace around the inside of it with a pencil. Then, eyeball the center of the box you just traced and drill a small pilot hole. You will need a hole saw or something that can make a 1.25" hole. If you only have a large drill bit and a dremel, then you could make the hole to 1.25" that way if you had to but a hole saw will be the easiest and make the best hole.
Once you have your 1.25" hole drilled, hold the square mounting plate over the center of the hole and now take you pencil and mark the 2 mounting holes for the screws that will hold the plug in place. Grab you drill and get a 1/8" bit and drill the 2 holes. In the particular relay I just installed, the metal square bracket was too tight for the socket plug to go into, I had to file the bracket out a bit, not a big deal but worth noting and could be a nightmare if no suitable file is on hand.
Now mount the socket into the metal mounting frame, once in, tabs on the socket hold it in place securely. Install the plate with the socket with the 2 screws. The good news is that the hardest part is over!
Now take the actual relay, and mount it somewhere near the socket you just installed as a wire from the relay needs to go to the socket. You also want the relay somewhere accessible because if you change one wire, you can have the pump turn on instantly WITHOUT the computer being on. This is extremely important and this option is much needed so you can leaktest/bleed etc. without the whole machine needing to be on. Like I said, it is one wire that you move to a different slot in the relay, more on that later.
Now there is one very important decision you need to make regarding your pumps power cord. If you want to leave the plug on the end of it and not slice it off there is an option! Go get a short extension cord and slice that up. It won't be as clean looking as you will have to huge plugs in your case but your pump won't be hacked up either. I choose to cut the plug off the end of the pump for a cleaner look but it is up to you.
The wiring is pretty simple and the directions that are supplied with the relay are pretty good. I want to help you avoid any confusion - some pumps have 3 wires and some pumps have 2 wires (My Iwaki for example only has 2) but it makes no difference. The black wire that comes wired into the relay with the fitting plugs into the socket. The BLACK wire from the pump power cord goes to the COM slot in the RELAY. The neutral wire (White) from the pump goes to the socket as does the ground (Green). The molex pass through connector attached to the relay MUST BE PLUGGED INTO THE PSU!!! This is VERY important! This molex connector is what tells the relay that the computer is on, once it senses the power from the PSU, it sends power to the pump. Conversely, when the machine is shut down, the relay kills power to the pump. A perfect solution if you ask me!
To switch the relay to power the pump WHENEVER the relay socket is plugged in, all you need to do is move the black wire in the N/O (Normally Open) position to the N/C (Normally Closed) position. As I said earlier, this is essential for bleeding and filling and leak testing.
VERY IMPORTANT!!! Once you are ready to fire up the machine YOU MUST MOVE THE WIRE BACK TO THE N/O POSITION OR THE PUMP WILL NOT TURN ON WITH THE PSU, THE PUMP WILL TURN OFF WHEN THE PSU STARTS UP!!!!
In my opinion, there is absolutely no reason NOT to use a relay to power your pump. You don't need to worry about running the pump plug out of the case, no need to wonder if your pump is going to turn on and off with the whole machine. The ONLY drawback to some maybe the price of the relay. At just $18, I think it is a very wise investment not only for it's ease of use, but once installed, you just forget about it, it is there doing it's job and no more wondering if your pump is on or off.