UHA S
TANDARD
U
NIT
H
EATER
I
NSTALLATION
O
PERATION
AND
S
ERVICE
M
ANUAL
6 of 51
SECTION 3: CRITICAL CONSIDERATIONS
3.1 Basic Information
UHA[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
u
nit heater
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
u
nit 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 corriosion that
may shorten its life.
3.3 Location and Suspension
All models:
• M
u
st be installed indoors.
• 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 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 49, Section 16.2
.
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.
See Page 7, Figure 4
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 7, Figure 4
and
Page 13, Figure 6
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
on Page
11, 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
on Page 19, Section 9
.
3.7 Electrical Supply
A permanent 120 V / 60 Hz / 1 Ø 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
See Page 21, Section 10
.
3.
8
Vent
Choose heater orientation to allo
w
for the 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 11, Section 7
.
