MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Connecting two air compressors

I want to connect two air compressors together to give longer trigger time. I’ve read Barney Gaylord’s useful posting on connecting compressors, but I am still unsure of a couple of things. I attach a photo of my two compressors. The red one is a direct-drive Sears 30 gallon, and the black one is a belt-driven Kobalt 60 gallon.

To connect the two tanks, do I need a ‘T’ connector in place of each of the two vertical pipes in the picture, with a hose running between them? The pictured vertical pipes are the places where the air first comes out of the tank, before getting to the two regulators. Do I have this right or should the connection be somewhere else?

From which of the two tanks should I draw the air?

Thanks in advance for your advice!
Mike Whalen


M.E. Whalen

Mike,
I have been investigating this myself. You can draw air from either tank, and putting both outputs to a common header is a better idea yet, as it would keep the moisture in the tanks, which you can blow down. If hyou are taking directly from the compressor tank, I would use the smaller tank, if the compressor motor is smaller. The idea is to have the smaller compressor come on at a higher pressure than the larger compressor, so the smaller one will run during normal operations, but the larger one will kick in if needed. The savings is in the electricity used.
Mike Parker

Mike, you need to make the connection AFTER the regulators.
Art Pearse

Had a big thing about this on the TD board a few months ago. Started by LaVerne Downey and Huib Brujstens. A lot of stuff re intercoolers and hookups. Check archive.

Basically, hook them together where you take air off, just a hose with QD couplers. Set the smaller to turn ON first, and the bigger to come on if the little one can't keep up. This gives cheapest running, since the bog one never runs for small jobs. Or you might want to reverse it if you have one of those annoyingly noisy little ones!

FRM
Fletcher R Millmore

Mike, just to protect the regulators I think I'd also add a check valve in the output from each regulator such as this one from Grainger. http://www.grainger.com/Grainger/items/4X828?Pid=search

This would ensure that pressure from one compressor couldn't back into the other one if it was at a lower internal pressure for some reason. Regulators are not designed to protect from reverse flow, especially at high pressure differentials. That would allow you to shut down one compressor if you wanted without any risk of damage.
I'd plumb the system with a regulator on each compressor outlet followed by a check valve and then connect the two lines together with a T fitting. Set each regulator to the desired output pressure with that set up or add a third regulator on the common output to set operating pressure for your tools or paint gun.
Bill Young

Just connect the tanks together. Tee in the vertical pipe next to the tank is a good place to do it. That makes the two tanks serve as a single larger tank with two compressors, and both tanks always have equal pressure. If you install a disconnect coupling between the tanks, be sure it has a shut-off poppet on BOTH sides of the coupling. Male coupling with shut-odd poppet is a bit harder to source, maybe not found at the cheap tool shops.

You could connect the two tees to a remote manifold, just don't put any check valve or restrictor or regulator anywhere between the tanks or manifold. The tanks must breath freely between each other to serve as one. A manifold between the tanks is not at all necessary, as you can draw air from either original output, even using two air tools at the same time with different regulator pressure settings. An intermediate manifold just makes a third output (with or without a regulator). You can run one compressor while drawing air from the other, makes no difference which as it serves as a single tank.

Do NOT connect together after the regulators. As tank pressures change this would make the unit with higher pressure force air backward through the regulator on the tank with lower pressure, which is a VERY bad idea.

By adjusting switch-on pressure settings you can make one compressor (either of your choice) switch on first and do all of the work while the other never runs, as long as the one compressor will always keep up with the demand. When demand exceeds capacity of the one compressor, pressure will eventually drop low enough to switch on the second unit. It is also good to adjust the switch-off settings to make the second unit shut off first. That is, the second unit will only run when needed to supplement demand.

Smaller compressors are not necessarily more efficient. In fact it is more often the other way around. A high speed direct drive compressor is almost always less efficient (and more noisy) than a low speed belt drive compressor. Larger compressors may also be multi-cylinder two stage for much better efficiency at higher pressure. In short, the larger compressor will commonly produce more air flow for a penny's worth of electricity (and less running time). A single stage compressor, regardless of displacement or number of cylinders, might produce slightly more air flow per penny at low pressure, less than 50 psi, but the tanks seldom run pressure that low.
Barney Gaylord

It seems that all you really need is more volume, rather than an actual second compressor. Since you have two compressors, you have the option of running either one.

I am looking around for a second large tank - maybe a compressor that has a burned out motor that someone is trying to get rid of...definitely in the 30 gallon or larger range - not a portable compressed air tank or something propane-tank sized. Maybe 10 grill propane tanks plumbed together and mounted along a shelf near the ceiling would work - I could get them free at the dump!



AJ Mail

I think propane tanks are only rated at 75 psi
Art Pearse

This thread was discussed between 06/04/2010 and 10/04/2010

MG MGA index

This thread is from the archives. Join the live MG MGA BBS now