UHD S
TANDARD
D
UCT
F
URNACE
I
NSTALLATION
O
PERATION
AND
S
ERVICE
M
ANUAL
6 of 57
SECTION 3: CRITICAL CONSIDERATIONS
3.1 Basic Information
UHD[T][X][S][R] heaters have a
u
tomatic ignition
b
u
rners for ON/OFF or HIGH/LOW 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 and a single stage gas
valve. Design and heat exchanger alternatives shall
be offered as follo
w
s:
• Separated Comb
u
stion: [S] For Models 150-250,
a separated comb
u
stion
u
nit shall consist of a
sealed hinged enclos
u
re.
Comb
u
stion air inlet flange on rear of heater
allo
w
s for comb
u
stion air from o
u
tside heated
space to be attached.
For Models 300-400, 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 shall 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: [X] A stainless
steel heat exchanger
u
nit shall consist of heat
exchanger t
u
bes, heat exchanger t
u
be s
u
pports
and heat exchanger t
u
be plate prod
u
ced of 409
stainless steel.
Air inlet temperat
u
res belo
w
40° F (4.4° C) are
not recommended.
• T
w
o Stage Gas
V
alve: [T] A t
w
o stage gas valve
shall allo
w
heater to f
u
nction in HIGH/LOW
operation.
• Approved for Installation Do
w
nstream of a
Refrigeration System: [R] Installation allo
w
s for
u
nit to be installed do
w
nstream of a refrigeration
system. Unit design shall incl
u
de a 409 stainless
steel package. Stainless steel package incl
u
des
heat exchanger, t
u
be s
u
pports and drip pan.
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.
• May be s
u
spended from above (
See Page 11,
Section 6.2
) 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 53, Section 16.2
and Page 55, Section 16.5
.
• 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.
• M
u
st be installed in a manner
w
hich allo
w
s
access to all serviceable components.
3.4 Minimum Re
q
uired Installation Clearances
Clearances aro
u
nd the heater and vent m
u
st be as
indicated
on Page 7, Figure 4
and
Page 12, Section
7
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 code
on 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 19, 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 listed
on Page 21,
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 Combat UHD-Series
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