wire gauge and 110VAC amps
 

Ok, I have yet another annoying question ;). While wiring up my pump relay w/ mostly solid core wire (left over from wiring our house), I also used one piece of wire off of a molex. Now looking at that one peice of wire, it just looks too small. I'll be running a Ehiem 1250. So I just want to make sure the wire isn't going to heat up and melt down too much.

So if you could lemme know if I should swap that peice out for the other stuff, I would appriciate it.

The 1250 is not going to draw more than an Amp. (I'd guess 0.5 Amps is probably a more realistic maximum.) Assuming the gauge of that wire is typical of PSU drive cables, there won't be a problem.

The voltage rating of the insulation might be a different issue, but I seriously doubt there is much risk there either.

Ok, so when I'm ready to boot up I'll just flip the switch and look for smoke (like always). Unless someone else wants to add something.

House wiring is usually 10-12 AWG gauge or better (right?), and can handle 15 amps, easily.

The gauge of the molex wire ought to be between 14 and 18, which can still take 0.5 amps, very easily.

Voltage is well covered here. As Since87 accurately pointed out, you're also not likely to spark through the wire insulation: these things are usually good up to 300 to 600 Volts (safely, and spec) in general, but if you have an unusually thin insulator, you might opt to use something else.

I believe that you're good to go.

Otherwise, in selecting a wire, one may look for a number of other things, like corrosion protection (for harsh environments), insulation hardness, water-proofing, etc... none of which apply here, but do cover up your wires (heatshring, electrical tape, etc.)

The thing we must remember is, if the pump were to short circuit them the wire must carry how much current before the fuse or breaker kicks out. With a 1 amp fuse then 16- 22 gage should be fine. But without a fuse you could start a good fire long before a 20 amp breaker would trip if it ever did trip.

I bought a relay to turn off my pump, but decided not to install it.

PRO 1 Its cool
CON 1 It may fail

PRO 2 longer pump life
CON 2 If anything should short the AC to +12 or +5
every part in the computer is toast!

PRO 3 Same energy
CON 3 If it were off 8 hours a day .25Amps X 120 volts
= 30 watts X 8 hours X 368 days = 85,440watt
` hours per year = 85.44 kilo watt hours per year X .07
` dollars per KWH = 5.98 dollars per year

That's a good point. A fuse, properly selected, would blow and protect the pump, to some extent.

Otherwise, the idea of 120V AC crossing into the DC circuitry is a little far fetched: you can just be careful.

As for the wear on the pump, most of them don't have any friction that is significant to warrant turning it off, but the high temperature that some pumps may reach, could be a concern. Then again, those temp cycles (on/off) are a source of wear themselves.:shrug:

A few points...

1. US House wiring is typically 14 or 12 guage for normal 110VAC wall sockets, lights, etc. 14 is good for 15A circuits, 12 is needed for 20A. 10g or heavier is usually only found on 220VAC, and other heavy duty circuits.

2. House wiring is not really suitable for use inside a PC. It is solid core wire, very stiff, and not intended to be used in applications where it will be subjected to vibrations or flexing. In a PC you should be using stranded flexible wire. (such as found in a power cord)

3. The pump is very low current draw, and could safely be wired with 18g wire (i.e. lamp cord). In theory it could even be wired safely with thinner wire (22g?) from a current standpoint, however wiring standards say that 18g is the thinnest wire permitted for use w/ 110VAC for reasons of mechanical strength as much as current handling ability.

4. From a failure standpoint, 18g wire will carry enough current to blow the fuse before the wire will get hot enough to cause a fire. The connected device might get hot, but that is not a wiring related issue.

5. The discussion of the wiring left out one important question about the location of the thin wire from the molex plug - Namely where the thin wire is located in the circuit! Remember that there are really two (or more) different circuits in a relay, the coil circuit and the switched circuit. The switched circuit in this case will be 110VAC, probably having a 10A rating on the contacts, and should be wired with at least 18g wire. (Larger wire is OK, but overkill) The coil side is probably going to be 5 or 12 volts DC (from the PSU) and have power through it on the order of milliAmps. Nearly any size wire would be fine from a current standpoint, but at least 18-20g should be used to give enough mechanical strength.

Hope this helps
Gooserider

what gauge of wire is on a standard molex? The ground for 12V is what it actually was.

Also, everytime I flip my switch between always on and relayed, but sub puts out a bit of a kick. The sub is 4' away and the speaker wires aren't that close. Why is there this discharge when I switch? oh and also when My comp turns off.

Depends on the PSU to some extent, there aren't as many standards as there are in the AC world where things are ruled by the National Electrical Code (among others) However typical is either 16 or 18 guage, with a few cheapies going for 20 (also they tend to use 20 on the little FDD style connectors)

Either way, it shouldn't be a problem. As I mentioned in the previous post, that is the coil side of the relay, with a probable current draw in the 10's of milliamps range. The molex wiring should be plenty for that sort of load no matter how cheap the PSU might be.
By 'sub' I assume you're refering to a subwoofer in your speaker setup?

I am guessing, but it seems likely to me that you are putting a bit of a spike on the line which is getting back into the audio amp on your sound board.
The most likely cause that I can think of is possibly a back EMF pulse coming from the relay coil when it changes state. Try momentarily unplugging the pump and flipping the switch to see if the noise still occurs. If it does, the relay is the cause. Try putting a small signal diode across the coil terminals of the relay to get rid of the pulse (actually not a bad idea regardless...)

Gooserider

small signal diode = 1N4001 or 1N4148 :), either would be fine for your purposes.