ARB Twin Compressor

[coyotearms]

Originally Posted by ridintall

I too went with the dual ARB compressor. I mounted mine in the rear Aluminess bumper and used a Kilby manifold and 2.4 gallon air tank kit.

There are sure a lot of smart people out there! An incredibly interesting install---bravo.

[coyotearms]

Originally Posted by BroncoHauler

I would look carefully at the question raised about venting. Batteries can off-gas and those gasses can be explosive in certain situations. Adding an electrically switched item like a compressor in the same space only increases the odds that you could have an explosive situation. Herb

Food for thought might start by asking why the van came from SMB with the Sure Power battery isolator located in the battery cabinet. When it is connecting the engine and house batteries together it is hotter than anything you want to touch! The batteries came in battery cases, which had vents and drains going to the outside but the cases were not sealed from the battery compartment.

As far as I can tell the big no-no is a battery is in a battery box that is not vented in any way. No matter how little hydrogen may leak from a battery, if contained in a small closed space long enough, that is an issue! What I have done appears consistent with AGM batteries since the batteries are completely open to the battery cabinet and the cabinet is now open to the inside of the van because I took the door off. The means for what little gas may come out of the batteries eventually dissapating to the outside if something goes wrong (with the charger or whatever) is the same means by which we don't run out of oxygen sleeping in the van over night. An AGM battery has no acid to leak out and is not filled with liquid acid that would be the source for lots of hydrogen. This situation would have to be revisited if the AGM's were replaced by wet acid batteries.

I tend to look to the boating community for questions like this, and the topic of battery venting is covered by standards such as ABYC and USCG. There is also the NFPA, and even the RVIA, which seems like a joke IMHO. On the Blue Sea website there is mention of specific ABYC and USCG regulations for battery boxes (http://bluesea.com/productline/overview/351) by the United States Coast Guard Code of Federal Regulations, Title 33, Subpart I, Part 183.420 and the American Boat and Yacht Council Standards and Recommended Practices for small craft, section E-10.7.

If you want to see a typical debate about battery venting in the boating world (and learn a lot in the process), look at http://www.cruisersforum.com/forums/f14 ... 33757.html.

I would expect this issue might also come up in the "dust" post viewtopic.php?f=2&t=5101&start=15 where I describe closing the battery box vents and drains open to the outside. Or maybe this topic should exist as a separate thread all together if it doesn't exist already?

[coyotearms]

Originally Posted by BrianW

For your battery bank, is that three batteries? Are they in sealed, vented boxes (or box)? Hard to tell. I need to redo my battery bank (2 batteries) from the OEM SMB build of two plastic boxes that are showing their age. The current boxes are separate but connected by a vent hose, with the rear box then venting to the outside through the van wall. Both boxes are not really sealed, though, so the vent really isn't doing anything.

One of the photos shows three AGM's, that came in boxes and had lids, but were not sealed from the battery cabinet. They also had vents AND drains to the outside. You probably have drains too. See my response to Bronohauler above and the reference there to another post of mine for more details. If I were completely redoing the battery arrangement and still using AGM's, I would still want them inside and would consider simple battery trays to physically hold down the batteries and leave it at that, making sure everything was fused properly and any other equipment in the cabinet solidly mounted to not contact the postive battery terminals. Wth vents and drains to the outside as the alternative, it would be a major problem to completely seal the batteries from the inside of the van in order to address the resulting major dust entry issue if you want to get off the pavement whenever that seems like more fun. Using trays would also allow more space in the same cabinet for more/bigger batteries if one desired more AH capacity.

[ridintall]

Here are some more pictures as promised:

[coyotearms]

Originally Posted by ridintall

I too went with the dual ARB compressor. I mounted mine in the rear Aluminess bumper and used a Kilby manifold and 2.4 gallon air tank kit. Since I didn't have an ignition on source in the rear of the van and didn't want to run a long wire to the front, I'm using two switches...one to arm the compressor and the other to turn it on.

I like the switch arrangement using a standard wall plate---you must be a high level interior designer! I am curious why the arming switch, although it looks cool. I believe the wire on the ARB harness that is supposed to go to an ignition-on source assumes one is powering from an engine battery, which(?) encourages one to run the engine when using the compressor---probably a good idea. Just so others are not confused, I connected that wire via a 10 A fuse directly to the house battery bank (seen on the uppler left of the first photo of my install). Of course, either way works.

[Tapatio]

If you have lockers or are planning to get lockers it's more useful to have the switch up front. I mounted them on the left side of the plastic knee panel below the steering wheel. Won't work unless the ignition is on.

[ridintall]

I don't plan on running an ARB Locker any time soon. Because of that I didn't want to extend the wiring harness all the way to the front of the van when the battery connections were in the rear. I specifically wanted to run the compressor off the house batteries due to the large amp draw and since all batteries are charged by the alternator I'm not worried about draining the battery. I mounted the switches in the rear of the van b/c of the close proximity to the batteries and not wanting to extend the wiring harness. Besides, the rear bumper cover needs to come off to run the compressor and my air line is stashed in the back of the van so it made sense to put the switches there. I could have easily run the ignition hot wire directly to the battery and just used one switch, but my concern was the compressor switch accidentally getting switched on. If I ever developed a leak in the system and was driving I would never hear the compressor running. If I was parked and not around and developed a leak the compressor would run until my batteries were dead. The arming switch just adds an extra safety layer. I've considered getting an ARB, but honestly that would probably only happen if I ever swapped in a full floating rear end. In that case it'll be easy to extend the wiring harness and the switches to the front and tap into an ignition hot source. I'll just cover the hole in the back with another switch plate cover.

[coyotearms]

In a previous contribution on this thread I detailed the installation of an ARB Twin Cylinder compressor mounted in my battery cabinet to have a very capable compressor in a very clean environment with essentially no added space taken up inside our van. The installation included the removal of the door to the cabinet to take into account the heat generated by the compressor. However, during airing up after deflation the compressor seemed to loose some oomph by the time I was on the fourth tire. I consulted with ARB, and they concluded that even with the cabinet door off, the input air to the compressor was probably becoming hot enough to affect performance. So I have modified the installation by adding tubing from the compressor input to outside the cabinet.

I followed the directions in the install manual regarding mounting the inlet filters away from the compressor and the diameter of tubing for a given length and chose 1/2" ID 5/8" OD, found a 1/4" MNPT to 1/4" FNPT elbow to redirect the inlet path from vertical to horizontal with a brass Watts A-739 (labeled as a street elbow 1/4" MIP x 1/4" FIP) from Lowes and a straight nylon 1/4" MNPT to 1/2" barb fitting at a local marine supplier (Fisheries supply, Seattle, WA SKU #69409) after not having any luck finding a single piece elbow to do the job. I had enough room to make nice holes in the cabinet with a right angle drill and a 5/8" Forstner bit. I was not able to find FNPT 1/4" to 1/2" barb adapters to use to attach the filters, which have a 1/4" MNPT fitting, so I just pressed/twisted them into the tubing, which seems fairly secure given that I terminated the tubing at the point where it just comes out of the cabinet and cannot expand. That should do until I find what I need to make it more bullet-proof. Note that there is normally a 3/4" plywood sheet that covers the top of the cabinet for the bed, which should be enough of a separation between the compressor and its air source that the inlet air is cooler than in the original configuration even with the cabinet door off. Note the equipment, wires and fuses seen outside the cabinet are part of the solar system.



This arrangement should result in cooler air entering into the compressor and improved performance. The darn compressor is so compact even with the 1 gal aluminum air tank I am using (to help cool things), it is tempting to install it into places where you can get in trouble with heat. Hopefully this new arrangement will improve things and result in the ability to inflate at least four tires without reduced performance.

EDITED 6/20/2013:
Getting air from outside the battery cabinet did not improve performance and after more sniffing around more I realized (dah) that one of the compressor motors was not even getting warm, i.e. the compressor was just not working correctly even though it was getting 12v! Fortunately, the one and only ARB service center in the U.S. is just outside of Seattle, so I brought it there. The motor thermal breaker had burned out on the side that wasn't working and the electrical connector had partially melted on the other motor, apparently working overtime to overcome the non-working side.

Those guys were great! They walked me through the rather tricky procedure for field replacement of the bottom piece of the motor that houses the thermal switch and replaced both of them. In my case the switch did not reset automatically. So if it happens again I can just send away for the part and do it myself, although as I said above it is a rather tricky procedure. One has to be very careful to not misalign the crank shaft of the compressor at the top end of the motors and also be careful with bearings and brushes when the part is replace at the bottom end.

They also looked at my installation and thought I might consider putting the cabinet door back on and adding auxiliary fan on the rear end of the cabinet to draw fresh air through it and past the compressor. But that door would be very leaky without a major effort to seal it, and I doubt a fan would do much to exchange the air in the vicinity of the compressor any better than without the door. So I did some testng where I measured the temperature of air right under the compressor where the cooling fan blows air upward over the compressor and also near the air intakes outside of the cabinet while simulating the presence of the bed board that is normally in place that covers the top of the cabinet as shown in the photos below. After airing up all four tires (2 from 30 to 60 psi and 2 from 40 to 80 psi) the air temperature in the cabinet was only 73 degrees F while near the air intakes it remained at 70 degrees. Given that and noting the inflation times were less than two minutes for 30 to 60 psi and less than three minutes for 40 to 80 psi, I am VERY happy (finally) with this setup!



The compressor does get hot, however, with the temps at the hottest spots on the blue motor heat sinks reaching about 120 to 130 degrees F and the black compressor heat sinks reaching about 170 degrees F, but this is normal behavior. The exact places these temperatures were measured with a non-contact temperature gun are shown on photo below.

[Tapatio]

My compressor blew the 40a inline fuses a few weeks back. I thought it was a goner but after removing it I noticed the connectors that lead to each compressor had partially melted causing a short. My assumption is the blade connectors were causing resistance which generated enough heat to melt the plastic housings. Rather than replace the connectors I soldered the wires together. Filled a few tires and didn't feel any heat at the splice so I think that fixed the problem.

While I was at it I took the compressors apart, inspected all the moving parts and lubed the needle bearings. It is a very well built piece of equipment and if something broke you could easily replace the parts.