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SECTION 3: C
RITICAL
C
ONSIDERATIONS
5 of 47
SECTION 3: CRITICAL CONSIDERATIONS
3.1 Basic Information
UHD[X][S] heaters have a
u
tomatic ignition b
u
rners
for ON/OFF operation only.
3.2 Manufactured Units
Gas-fired, po
w
er-vented d
u
ct f
u
rnace
w
ith t
u
b
u
lar
heat exchanger. Units shall have a minim
u
m of 82%
thermal efficiency. The standard
u
nit shall consist of
a non-separated comb
u
stion design
w
ith an
al
u
minized heat exchanger. Design and heat
exchanger alternatives shall be offered as follo
w
s:
• Separated Comb
u
stion: A separated
comb
u
stion
u
nit shall feat
u
re an enclosed,
sealed b
u
rner box. A piece of flexible air d
u
ct
connects this b
u
rner box to a flange on the
cabinet. Comb
u
stion air sho
u
ld be d
u
cted from
o
u
tside the heated space,
w
ith the d
u
ct
w
ork
connecting to the
u
nit
w
ith the
u
se of the flange.
• Stainless Steel Heat Exchanger: A stainless
steel heat exchanger
u
nit shall consist of heat
exchanger t
u
bes, heat exchanger t
u
be s
u
pports,
heat exchanger t
u
be plates and vent box
prod
u
ced of 409 stainless steel.
The
u
se of stainless steel heat exchanger is
recommended
w
hen air inlet temperat
u
res are
belo
w
40° F (4.4° C) or temperat
u
re rise is less
than 40° F (22.2° C) as condensation may form
on the heat exchanger res
u
lting in corrosion that
may shorten its life.
3.3 Location and Suspension
All models:
• M
u
st be installed indoors.
• M
u
st be installed on the positive press
u
re side of
the air circ
u
lation blo
w
er.
• M
u
st be installed in a level position
w
ith
horizontal discharge.
• May be mo
u
nted on a shelf of non-comb
u
stible
material
u
sing shelf mo
u
nting brackets.(
See
Page 11, Figure 6
and Page 11, Figure 7
for
details.)
• Drop rods m
u
st be a minim
u
m of 3/8" diameter
mild steel. Fo
u
r s
u
spension points (3/8" n
u
ts)
are located on top of the heater.
• May be s
u
spended from above (
See Page 10,
Figure 5
) or from
w
all brackets of s
u
fficient
strength to s
u
pport the heater as listed in the
Technical Data Table
on Page 45, Section 16.2
.
• M
u
st be installed in a manner
w
hich allo
w
s
access to all serviceable components.
See Page
6, Figure 3
for details.
3.4 Minimum Re
q
uired Installation Clearances
Clearances aro
u
nd the heater and vent m
u
st be as
indicated
on Page 6, Figure 3
and
Page 14, Figure 8
to ens
u
re access for servicing, and correct
operation.
3.5 Ventilation
It is important to ens
u
re that there is adeq
u
ate air
space aro
u
nd the heater to s
u
pply air for
comb
u
stion, ventilation and distrib
u
tion in
accordance
w
ith local and national codes.
See Page
12, Section 7
.
3.6 Gas Supply
It is important that the gas s
u
pply pipe is sized
correctly to provide the inlet press
u
re as stated on
the heater data plate. The gas s
u
pply pipe and
electrical connections m
u
st not s
u
pport any of the
heater's
w
eight.
See Page 20, Section 9
.
3.7 Electrical Supply
A permanent 120
V
/1 Ø/60 Hz electrical s
u
pply is
req
u
ired for the main electrical po
w
er. The heater
also req
u
ires s
u
itable controls in accordance
w
ith
Page 22, Section 10
.
3.
8
Vent
Choose heater orientation to allo
w
for proper
location of the vent. Each heater m
u
st be fitted
w
ith
a correctly sized sealed vent system.
If vented horizontally, no other appliance may be
connected to the vent.
See Page 12, Section 7
.
Summary of Contents for UHD 125
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