OBA pulling more than 50 amps?

[saburai]

Hi Gang,

in finalizing the set up of my OBA in the XJ I've run in to an interesting situation. The OBA blows every fuse I put in the system! 30, 40, and last try 50 amps:Wow1:

I'm running a puma pd1006 compressor - 1 HP, 30amp draw, 100% Duty Cycle, 125psi.

here's a link:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380139416070

I'm stripped the tank and pressure switch. I built it up with a Viair 90110 Pressure Switch with Relay, a check valve, a 30 amp rated switch, 10 gauge wire and a remote tank. There is no short. It functions fine when run directly to the battery. However, when I add a fuse to the circuit, initially it turns on and with the 50 amp fuse at least, cycles a few times before tripping the fuse.
Could it be that it's normal for it to draw 50 plus amps kicking on and overcoming the 80 or so lbs. behind the check valve?

Many Thanks...

 

[R_Lefebvre]

Uh, well, they're claiming 1hp. 1HP=745 Watts. 745 Watts at 12V requires 62 amps. And that is not counting for the startup current either. You're going to need a bigger fuse.

I'm sorry but that's just how the math works out. Either their claim of 1hp, or the claim of 30A is crap.

 

[SunTzuNephew]

Uh, well, they're claiming 1hp. 1HP=745 Watts. 745 Watts at 12V requires 62 amps. And that is not counting for the startup current either. You're going to need a bigger fuse.

I'm sorry but that's just how the math works out. Either their claim of 1hp, or the claim of 30A is crap.

Thats also assuming 100% efficiency, which only happens in first-year science exams.

 

[saburai]

Math to the rescue!

Thanks Rob!

Well, it's drawing more than 50 amps and it's quite robust...

Next question, where do I source a 65 amp or higher fuse?

Uh, well, they're claiming 1hp. 1HP=745 Watts. 745 Watts at 12V requires 62 amps. And that is not counting for the startup current either. You're going to need a bigger fuse.

I'm sorry but that's just how the math works out. Either their claim of 1hp, or the claim of 30A is crap.

 

[ExpoMike]

Personally I have used these many times in different rigs. Here is an 80 amp version.

You can find them other places but here is one, http://order.waytekwire.com/productdetail2/M37/46983/HI%20AMP%20MANUAL%20RESET%2080%20AMP/

 

[SunTzuNephew]

You can get circuit breakers like that on Amazon, too - one brand is Blue Sea, sealed, waterproof, marine grade ++

 

[spencyg]

You will also want to make sure your primary switching relay is up to the task. The primary switch and your pressure switch in the tank should be wired in series to trigger the relay. None of your switches should be seeing any load other than switching the relay. The circuit breaker should go between the load side of the relay and your power source.

Just thought I'd throw that in there...

Spence

 

[dustboy]

You don't want the compressor to have to fight back pressure when it starts, I would wager this is the cause of your problem. Air compressors with tanks have a release valve between the compressor and the check valve to relieve the fill line.

I have a cheap portable compressor for my nail gun that just has a tiny hole that leaks out the pressure behind the check valve. Not the most efficient method, but effective.

If this doesn't help, you need a slow-blow type of fuse that can handle the initial current spike. Also if your 10-gauge wire is long, you will be seeing a significant voltage drop with that kind of load. You may want to go to something like 6 gauge.

 

[soonenough]

I was gonna say the same thing about wiring. Depending on how long your run is, 10-gauge may not be sufficient; not even taking into account the voltage drop due to wire length (as dustboy mentioned), but purely from the amperage being drawn by the compressor. 65+ amps is a lot for 10-gauge wire (AWG rating tables found here show that you'd need probably 8-gauge minimum).

Next question, where do I source a 65 amp or higher fuse?

For the main power lead to my auxillary fuse block, I use a Sea Fuse (made by Blue Sea Systems) that I bought from West Marine. They go from 100A up to 300A in 25-amp increments, and are mounted in a Sea Fuse holder (also from Blue Sea Systems) that is rated for 300A @ 32V. Marine grade electrical equipment is generally higher quality than the stuff available at Pep Boys, etc (and is probably higher quality than a lot of the OEM electrical components on the car). The downside is that it's not cheap.

For your application, the smallest one of these (100A) might still be too large, but you could go with a Maxi Fuse, which are available from 30A to 80A in 10-amp increments. They look like an overgrown version of a normal ATO/ATC fuse. One benefit to this is that you'll have a much easier time finding these locally than something like a Sea Fuse, especially if you live in an area where boating isn't popular.

 

[R_Lefebvre]

Big fuses should also be available at big car stereo stores. Working on your side is the fact that the "1 hp" rating might be the "peak" rating, which IS the startup current.

Thats also assuming 100% efficiency, which only happens in first-year science exams.

Ah, 220, 221, whatever it takes.

Seriously, yes, but given we don't have very much info, let's just base it on what we *do* know.

 

[dustboy]

Ah, 220, 221, whatever it takes.

I was gonna suggest more ball bearings.:snorkel:

 

[LandCruiserPhil]

For over a year I have run a PUMA on #10 with no issues.
30 Amp RLA (running load amps) but it will start at a much higher amperage(double is not uncommon with a loaded motor. One time fuses blow when the rated amperage is reached or excessed. You need a time delay fuse or a breaker that is designed to handle the starting load.

Does the pressure switch you are using bleed the head pressure off? The factory PUMA set-up does. If not starting amperage will be much higher then normal starting amperage. Also #10 would be the minimum size you will want to use and with a 30A load you will have voltage drop except for the shortest run. How long is the feed from the battery to the compressor. When ever you have voltage drop you will get amperage increase, guaranteed. This why it is best to have your vehicle running (13.5+volts)when your compressor is in use.So you may be experiencing a multiple of problem keeping you from running.

 

[Cody1771]

if he is using the VIAIR pressure switch it does bleed off, they are a great system. about the 13.5V thing though there is a setup you can buy from most auto parts suppliers that with a flick of a switch it kicks your motor up to a high idle or desired RPM, they generally are used for trucks that are running a PTO of a sort, they work really well though. especially well when you are giving someone a boost hehe

 

[BIGdaddy]

Personally I have used these many times in different rigs. Here is an 80 amp version.

You can find them other places but here is one, http://order.waytekwire.com/productdetail2/M37/46983/HI%20AMP%20MANUAL%20RESET%2080%20AMP/

so, I don't know electricity very well, but if there's a spike that is around 75amps that doesn't trip that 80amp fuse, will that backfeed and hurt something like the engine CPU? I thought thats why you see mostly 20-30amp systems in cars?

I guess high powered stereo's are the same, but I had thought that the amplifier acts as both a boost/buck station and a fuse, protecting the stock circuitry upstream.

 

[rickc]

Hi Saburai and all:

Your choice of a fixed range pressure switch is a good idea but from what I could see yours does not have an unloader port to connect to the check valve. This ensures that at max pressure, when the compressor switches off, the pressure is relieved between the compressor and check valve. This makes it much easier for the comressor to restart at lower load.

I agree with others that the load for your system should be much higher than advertized. I bet the "30A" draw is at the 40psi level. With your set-up running a higher tank/system pressure you are hitting those higher amps.

I'm also in agreement that the Cooper Bussman marine ciruit breaker/ isolators are the way to go.