Rapid 2005, Installation, Operation & Service Manual

Page: 82 / 162

B-S
ERIES
I
NSTALLATION
, O
PERATION AND
S
ERVICE
M
ANUAL
72 of 147
SECTION 15: DUCT CONSIDERATIONS
The air handler has been designed to operate at the
specific air
v ol u me and external static press u re that
w as ordered (air handlers set- u p to accept an
external static press u re (ESP) of 1 in w c (2.5 mbar).
This static press u re is generated by any additional
components that are added to the heater (i.e. inlet
hood, filter section, dampers, d
u ct w ork, discharge
heads, etc). Additional static press u re beyond that
ordered w ill affect the performance of the air handler
and lessen the air v ol u me that can be deli v ered.
Proper engineering methods need to be employed
w hen calc u lating d u ct and component static press u re
(i.e. 2009 ASHRAE Handbook - F u ndamentals,
Chapter 21). Accessory press u re drops are a v ailable
on Page 16, Table 9 .
The system d u ct w ork m u st comply w ith Sheet Metal
and Air Conditioning Contractors Nationals
Association (SMACNA) or any other recognized
standards.
As a general r u le, all discharge d u cts sho u ld ha v e a
straight r u n of at least 3 hydra u lic d u ct diameters
after the air handler before adding any fittings,
elbo
w s, restrictions, etc. Ret u rn d u cts sho u ld ha v e
the same straight r u n before attaching to the u nit.
Hydra u lic d u ct diameter for ro u nd d u cts in inches:
Dh = d
Dh: hydra u lic diameter
d: ro u nd d u ct inside diameter
Hydra u lic d u ct diameter for rectang u lar d u cts (in
inches):
Dh = (2*H*W)/(H+W)
Dh: hydra u lic diameter
H: rectang u lar d u ct inside height
W: rectang u lar d u ct inside w idth
The air handler is not designed to s u pport the w eight
of d u ct w ork. D u ct w ork m u st be constr u cted in a
fashion that is self-s u pporting. D u ct w ork sho u ld be
straight, elbo w s sho u ld be minimal and any
transitions sho u ld be smooth.
Depending on the options ordered w ith the air
handler, flanges (either external or internal) may be
pro
v ided to facilitate connection of d u ct w ork. In
cases w here flanges are not pro v ided, flat s u rfaces
on the exterior skin of the air handler are pro v ided to
facilitate connection of d u ct w ork.
15.1 Inlet Duct Work
Inlet d u ct w ork height and w idth m u st be no smaller
than the air handler inlet height and w idth and s u pply
only fresh air to the air handler. ( See Page 11,
Section 5 for inlet dimensions).
15.2 Return Duct Work
Inlet d u ct w ork height and w idth m u st be no smaller
than the air handler inlet height and w idth and s u pply
only fresh air to the air handler. ( See Page 11,
Section 5 for inlet dimensions).
15.3 Dischar g e Duct Work
Refer to Page 73, Table 10 for minim u m discharge
d u ct sizes by model. Refer to Page 73, Table 11 for
discharge d u ct size req u ired for connecting to heater
(BD or RD), these dimensions pro v ide clearance for
d u ct flange to blo w er mo u nting bolts.
Cut/Pinch Hazard
Wear protective gear
during installation,
operation and
service.
Edges are sharp.
Falling Hazard
Use proper safety
equipment and prac-
tices to avoid falling.
WARNING
Failure to follow these instructions can result
in death, injury or property damage.