Two collectors in parallel?

[BobH]

I just bought 2 HF dust collectors and was thinking that running them in parallel would increase the volume to take advantage of a 6" whole shop system still to be built. A drum separator with Phil's baffle then splitting with a Y to each collector with cartridge filters on the outlet is what I had in mind. I wound up with 2 units because I can't pass up a good deal. The stores near me will take the internet price at http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=97869&xcamp=google&utm_source=googlebase&utm_medium=cpc&zmam=13262200&zmas=12&zmac=112&zmap=97869
as a price match then, because it's not a "coupon", you can use the 20% off coupon. $111 each.

[recky]

Hi Bob

Parallel doesnt work they cancel each other out, Series works, check this out.

http://www.ukworkshop.co.uk/forums/triple-extractor-wip-t39564.html

HTH

Allan

[BobH]

As they say on that UK web site "smashing good". I would have thought that series would have only doubled the suction but thinking about it, more suction is just more volume trying to get through the same size restriction. I think I'll run these two in series for my wood materials and pick up one more for my metal grinders! Thanks

[zzzzdoc]

I'm still thinking of the electricity analogy here.  Won't putting 2 HF in parallel increase flow and two in series keep the same flow but essentially act like a greater horsepower motor and withstand greater pressure?

Basically, series increases voltage and parallel increases current.

Also, as air isn't very compressible at these pressures, I think that the pipe cross sectional diameter will make a big difference as to whether two collectors will work together in an additive fashion.

I was planning on two HF 2HP collectors in parallel going through 6" pipe (presently flex, but hopefully rigid in the future.)  I can't see how two 1550CFM DCs in parallel wouldn't produce more flow than one if it is going through non-restrictive piping.  Maybe not through 2.5" or 4", but through 6" I think it should help dramatically.

[Master53Yoda]

Paralleling fans to increase air flow is a common practice.

Paralleling 2 fans will provide close to double the volume at the same pressure.    Series connections will double the pressure at the  volume of one fan.   Inlet piping is important to getting the flow correct.  The inlet needs to be piped into the center of the Tee or Wye preferably or they won't load evenly.  the length and configuration of the inlet piping between the Tee and the blowers needs to be as identical a as possible.   I would only use enough flex to absorb vibrations.  3  to 4" long on each blower.     A good example would be the piping configuration between the fan and the multiple bags on the larger dust collectors.   The discharge is individual into the surrounding air, but the discharge piping configuration needs to be the same on each blower.

One thing to remember that in dust collection there are two factors that must be meet.  One is sufficient air velocity to keep the collected material entrained in the air flow.  The other is enough volume to generate the velocity to overcome the chip  velocity that is placed on the chip by the cutting tool.   the finer the chip the more air volume is necessary to overcome the initial chip velocity.   This is why dust collection on miter saws or radial arm saws is much harder to obtain because the chip velocity is not directed effectively by the saw.  It also requires a higher air flow to effectively collect dust above the table on a table saw.

piping methods and  sizing uses up the available static pressure.   a 4" pipe run on a 2 hp and a 5 hp collector will move almost the same amount of air.

Delivered HP is related directly to CFM X Static pressure.    A 4" hose takes about 1 1/3 Hp to provide full airflow.   I if you measure the amp draw X voltage on each motor you would find that the 2 hp and the 5 hp are using the same amount of power when connect to the same piping system as in  he case of a 10' piece of 4" flex.

So in conclusion the only reason to Parallel 2 blowers is to be able to use more tool runs open at the same time.   If you wanted to get the dust collectors to draw air like a vacuum cleaner does then putting the blowers in series would increase the available static pressure and move about 1/3 more air through the same 4" piping system, this appears to be making it a better collector but you would accomplish the same thing by increasing the duct size to a 5" and it would use less power then increasing the pressure does.

I hope this makes since and us usable information.   Please give me some feedback if not.