I am currently running a 400C with an 8.5 gallon tank. I know this is not recommended, which leads me to my question. Is the power wire ( I think its a 10 gauge, whatever it came with from HB) that I currently have big enough to run two compressors? I highly doubt it but had to ask. What size wire do you recommend for running 2? The run is about 12-15 feet if that helps. Below is a pic of the battery connection. It’s melting the wire loom
That is with 1 compressor, the loom is melting?
With that footage at 30A worst case, it should have 8 gauge minimum for 1 compressor. For 2 400c compressors, 60A, 4gauge wire. Stranded wire!
You might want to check the resistance of your wire or something to see why it is getting so hot at that terminal. Corrosion.
In regards to running 8.5 gallons off 1 compressor; If you are into saving money and the warranty for the compressor is out, do what I did and attach a 220cfm 12V computer fan to the side of the compressor with zip ties and hot glue. If there is adequate room around the compressor, it will keep the temperature of the compressor near ambient.
delta tfb1212ghe fan or similar.
Great info here Dan!!! I like that chart, will have to print for future reference. Really looking for a little faster fill time and to take some load off of the one compressor. Also, it is mounted under my toolbox in the bed of the truck so it gets plenty of ambient cooling I would think (I’ll post a pic). I may just go ahead and run a 4 guage to the one compressor for now then it will be there when I add another. What do you think about that??
Sounds good. If you decide to stay with 1 compressor, the compressor will heat up pretty fast if it’s on for a long time. It’s need airflow not just cool air around it. Make sure the connections have no corrosion and you should be set.
It’s suspicious why that terminal is getting as hot as it is right now. Even with slightly small wire it shouldn’t get more than warm. That chart is a bit aggressive with thick wire. The main reason why they recommend such thick wire for DC current is because of the voltage drop since 12 volts isn’t much to drop. For something huge like an electric clothes dryer or hot tub, I’d doubt it’s more than 4 gauge, maybe just 6 gauge because of 220 volts AC
I’m going to clean the connection tonight and see if that helps with heat.
Clean the ground connection at the compressor too. If it is marginal, it can draw more amperage.
Will do. I cleaned the battery connection this afternoon, I’ll look at the ground tomorrow. Thanks bud
What you’re showing in your picture there is no doubt a bad earth in my book. Looks badly corroded. Nothing to do with the compressor I reckon… the most likely culprit will be your starter motor.
BTW… for the upgrade to your compressor, have a look at the comparison chart to see the options in one easy hit 
http://www.trainhornforums.com/showthread.php?t=6219&highlight=chart
DBO, great job collecting that info and putting it in one place!!! That helps a lot to put things in perspective.
I have 2 444’s ran with 4Ga wire almost 18 feet from my battery to my toolbox, from there the 4ga goes into a wire block and each compressor is using 10ga through all the relays, works wonderfully. Although the 20ft of 4ga was a pretty penny…
That’s what I’m planning on doing, 4 ga to a distribution block then 8 or 10 from there? How big a tank do you have and how long does it take to fill with the two 444’s? Does your battery connection get hot? Thanks
I have a 12 gallon tank, from 0-150 PSI takes roughly 8 minutes, I’ve never timed it exactly. I am very happy with the dual 444’s and the fill time really impressed me. Also I have never noticed the 4ga getting hot.
Thanks for the input. I think dual 400’s should work for me. Already have the 4 gauge left over from an amp install.
Update- I cleaned the ground connection today and it is running much faster than it was. I didn’t realize it was running slow before, guess I was used to it??
Also the battery connection barely gets warm. Looks like you guys advice fixed it!!! Thanks to all who contributed
Also, I timed it from 100-150 psi and it took 2:29. Not too bad
An Oasis can completely fill it in less time. (blatant plug…lol)
I have no doubt that you speak the truth sir… maybe one day 
It’s my understanding that what heats up a wire is wattage, not current. Since 5,000 watt hot tubs and clothes dryers often use 6 gauge or maybe 4 gauge at 220 volts AC, I think all the way from the fuse box to the device or GFI, that’s leads me to believe that.
The reason why you need thicker wire for lower voltage applications(12V) is because there isn’t much voltage in the first place (potential) and so a little resistance will really start to add up. I don’t think the wire heats up any more because I think all that matters with heat is wattage (volts*amps) and resistance specs for the conduit and the same thing with automotive fuses. They are rated for an amperage, but they blow at a certain wattage area, so a certain voltage is assumed in that rating.
If there is a highly resistive section of the circuit, like a corroded battery terminal, that can create a lot of localized heat because it’s in such a small area.
Can anyone clarify that?
/nerdism
You’re right - in a way. Power is the output (in this case used by a resistor to generate heat). In this case though you want to focus on the resistor (because that is where the heat will dissipate). The wattage is therefore calculated on Voltage squared divided by the resistance (in Ohms). As the resistance builds up, the power output will increase across the area of resistance and turned into heat.
In the case of the faulty earth, the wire is a resistor, but the rusted part is an additional resistance. It’s that section resistance which causes the high heat at that point. By that I mean that for most parts the wire will have little to no resistance, but at the point of bad contact, a high resistance spot creates the trouble.
The reason why you need thicker wire for lower voltage applications(12V) is because there isn’t much voltage in the first place (potential) and so a little resistance will really start to add up.
Sorry… you lost me there. Lower voltage will not make things worse and you certainly won’t need thicker wire - quite the opposite. If your voltage climbs the power output will be appropriately higher as well (remembering that V squared over resistance gives you the power). The reason for thicker wire in 12V applications is that you will have higher amperage devices (e.g. the starter motor drawing several hundred amps) and power is linked to amperage (W=I(amps) x V). That’s why you have low amp household circuits (traditionally 20A max), otherwise the wiring required would be massive gauge at 110 or 240V.
Well, current along with voltage MAKES wattage. You can have 2 scenarios that take the same wattage and require hugely different wires. Real world example:
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2000w/110v household heater that runs fine on a 14ga cord (20 amp circuit).
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2000w/12v car amp and you’re going to need 0ga (200 amp fuse).
The car amp would absolutely boil the insulation off of 14ga and it is using the same wattage.
Ever heard electricity compared to water through a pipe?