# Doubling Up Compressors or Fans

When you link two fans or compressors together, what's the effect on pressure and airflow? January 18, 2007

Question
Would two 15 scfm at 90 psi compressors equal 30 scfm at 90 psi? Or is there more to it than that? Further, how would two identical dust collectors perform wired together? I do have two Dbl bag collectors that are rated at about 2300 cfm and 16" static. I'm sure that 4600cfm and 32" is out of the question, but what would be expected by hooking both up to my widebelt? It isnt enough, but if the math works out I'd rather implement a third dust collector, rather than buying a single new, very expensive (large) dust collector.

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
If you've got the room, a dedicated collector close to the machine seems like a simple solution.

From contributor L:
Yes on the 2 - 15 cfm to 30. No on the 2300x 16 to 4600x32. Your static pressure would not increase. 2300x16 should be enough for most widebelts. The usual catch with wide belts is they fill the porosity of the bags with the fine dust reducing the airflow. Solution: more bag area, different fabric.

As a side note I replaced two 38 CFM recips with one 25hp x 105cfm screw (both at 90psi) and am still short on air sometimes, everything down stream is rated larger than 105cfm, very disappointing.

From contributor W:
For the simple case of 2 machines that are identical, if ran in parallel, the flow-rates add but the pressure does not change. If ran in series, the pressures add and the flow-rates do not change. The two 2300 cfm at 16" collectors, if ran in parallel on the same system, would equate to 4600 cfm at 16".

From the original questioner:
Would you describe a practical installation of parallel vs. series for dust collectors? Also, what if the collectors were not identical? I bought an 80 gal 2 stage compressor that is rated at 27cfm/100psi - if I simply hooked up an additional 120 gallon tank what gains would be expected, and how is this calculated?

From contributor W:
If you needed more static pressure developed in your system, you would put the collectors in series. This might be the case if you had a really long run, or a lot of bends or whatever. If you just need more volume/velocity, you would put them in parallel. It depends on the system.
Looking at the fan curves for the two collectors (in parallel), the smaller of the two would not start making a contribution to the flow until its maximum static pressure was reached, then the two flow-rates for the fans (at each static pressure) would sum.