pressure drop across 2 duct silencers
pressure drop across 2 duct silencers
(OP)
I have just completed a university project. Air balancing contractor is coming back with excessive resistance on REF1.
REF1 is a booster behind the mixing box on 30ton air handler. REF1 is rated for 11,000 cfm. On each side of REF1 I have and Industrial accoustics 5ES silencer 42x36-60 with a face velocity of 1000fpm and a static pressure drop of .24
The ductwork is the same size as the silencers so I cant see how this is correct or why they are not a little bigger to allow less static given the fact that there is 1 each side of the fan
AIr balance contactor states that of the 11,000 we are only getting about half that at the air hadler. Can anyone do a quick calculation on this to see if a mistake was made on the plans? system design is .75 TSP @ 11,000cfm current reading is 5,340cfm .73 TSP
REF1 is a booster behind the mixing box on 30ton air handler. REF1 is rated for 11,000 cfm. On each side of REF1 I have and Industrial accoustics 5ES silencer 42x36-60 with a face velocity of 1000fpm and a static pressure drop of .24
The ductwork is the same size as the silencers so I cant see how this is correct or why they are not a little bigger to allow less static given the fact that there is 1 each side of the fan
AIr balance contactor states that of the 11,000 we are only getting about half that at the air hadler. Can anyone do a quick calculation on this to see if a mistake was made on the plans? system design is .75 TSP @ 11,000cfm current reading is 5,340cfm .73 TSP





RE: pressure drop across 2 duct silencers
What is:
The fan size
Fan hp
Fan Type
The ductwork layout
Fan laws will be your friend.
RE: pressure drop across 2 duct silencers
RE: pressure drop across 2 duct silencers
RE: pressure drop across 2 duct silencers
If you are getting only half the flow, the DP will be much less.
So the question to ask is "what is eating the fan's pressure?"
Of course, it could be something stupid-simple. Like the fan turning backwards.
RE: pressure drop across 2 duct silencers
A good balancer hangs in there and helps trouble shoot the problem.
RE: pressure drop across 2 duct silencers
THis is a VAV system. with VF drives on REF1 and AHU1 driven by automated logic.
RE: pressure drop across 2 duct silencers
Tomorrow I am going to take a scan of this section on the print and post it.
RE: pressure drop across 2 duct silencers
If this stuff is too close to the fan outlet, the fan will not reach full capacity because the pressure drop is way higher than you think it is. First devices, including nasty fittings, should be 8-10 feet from the fan discharge on a straight duct to let flow develop.
A fan curve will also help with this problem; do you have one? Is this a FC, BI, Airfoil, Radial blade?