Built Up Air Handler
Built Up Air Handler
(OP)
In a built up air handler,what governs the distance between the fan and the cooling coil,and the distance between the filter and the coil?
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RE: Built Up Air Handler
If it is draw through, you most likely need space for the motor, then some working clearance between the motor and the coil like 6 inches. If the blower frame is internally isolated this may encroach a bit also.
upstream of a coil, I do not think you really need much clearance at all if the face area for a flat filter section, or the 'projected face area' (for lack of a better term) of an angle filter section are roughly the same as the coil(s).
Sometimes, if you want to plan ahead for good service on a big air handler, you allow an access section rather than having a tech remove filters and reach through the filter track to clean the coil surface. Access section will most likely add 2 feet to the length.
With heating and cooling coils in series, you may want to add access between the two coils.
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Built Up Air Handler
I am wondering if I need to keep a certain minimium distance between the fan and coil in order to minmise the possibility of preferential air flow through the middle portion of the coil.If that happens,it might render the coil periphery areas ineffective.
I was thinking of a perforated plate between the coil and the fan.The plate need not cover the full coil face but only the central area where preferential air flow can take place.What do you think?
RE: Built Up Air Handler
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Built Up Air Handler
Attention must also be given to the path that the airstream follows in approaching the fan inlets. If this is such that the airstream enters the inlet unevenly or if spin is generated, loss of performance will result. If it is not practical to alter the flow pattern ahead of the inlet, some improvement can usually be obtained by the use of baffles at the fan inlet.
For velocitie outlets to 2,500 fpm, the 100 percent effective duct length is 2-1/2 duct diameters (or diameters of equivalent rectangular area). As the blast area (area over the cutoff) decreases in proportion to the outlet area, the flow distortion increases, and potential system effect losses increase. The blast area normally has to be obtained from the manufacturer.
RE: Built Up Air Handler
Rule of thumb is to allow at least 3 fan diameters from coil to centre line of fan. For a large build up AHU I like to allow at least 600mm between the condensate trays and edge of the fan/motor base.