At 09:31 PM 3/13/04 -0500, Ken Law wrote:
" How do I hook up two compressors (120V) without blowing a hose or something. Is it just a matter of 'T'ing them together and let each pressure swith operate as it will?"

Very easy. Just connect a hose directly between the two tanks (bypassing any output regulators). Do not ever try to force air flow backwards through a regulator. And you will need enough electrical supply capacity to run both units at the same time (assuming you intend to do that). Connect them to two different fused circuits if you can (less likely to blow the line fuse).

You will be able to draw air from either unit, and the tank capacity will be the sum of the two tanks. The first one to hit the low pressure switch pressure level will kick on first. If you're not drawing any more air than the one unit can pump, the second one would never kick on, as the first unit can supply all the air you need.

If you are drawing more air than the first unit can supply, then the pressure will continue to drop until the second unit kicks on. Then you get the combined output of the two units working together to recharge the tanks. If you are not using more air than the two can supply together, then the pressure may eventually rise to the point where one unit will shut off. The other unit would continue to run as the pressure drops, and the second one will kick on again at the low pressure switch setting.

If you are using more air than the two units combined can supply, then you run into the duty cycle and trigger time calculations. Add volume of the two tanks and treat it as one. Add output of the two compressors and treat it as one.

At 11:04 PM 3/14/04 -0700, Ken Law wrote:
"If I hook two compressors together that have 120psi each does the pressure add to 240 or just 120?"

No, just 120 psi. They will be in parallel to double the volume at the same pressure.

"When you said add output and treat as one, what terms of output are you speaking?"

Compressor output is expressed in CFM (Cubic Feet per Minute) which is a bit of a misnomer. It is really SCFM (Standard Cubic Feet per Minute). They usually have two noted outputs at different pressure, such as 7 CFM at 40 PSI, and 4 CFM at 90 psi. If both of the units were the same, this would add up to be 14 CFM at 40 PSI and 8 CFM at 90 PSI. Just add the rated outputs and treat it as if it was a single compressor. The tanks are similar, just add the volume of the two tanks and treat it as if it was a single tank on one compressor.