UHA S
TANDARD
U
NIT
H
EATER
I
NSTALLATION
O
PERATION
AND
S
ERVICE
M
ANUAL
28 of 51
11.2 Be
g
in Start-Up
11.2.1 Before Operatin
g
the Heater
To ens
u
re that all the controls are in safe
w
orking
order, operate the heater for the first time
w
ith the
isolating gas valve t
u
rned off and po
w
er s
u
pply
t
u
rned on.
1. T
u
rn off the isolating gas valve.
2. T
u
rn
u
p the thermostat above room
temperat
u
re. The a
u
tomatic ignition
seq
u
ence
w
ill no
w
begin as described
on Page 28, Figure 13
.
There
w
ill be no ignition of the b
u
rner and locko
u
t
w
ill occ
u
r,
w
hich proves the controls are operating
correctly.
Fi
g
ure 13: Automatic Burner Control Se
q
uence
Burner Se
q
uence for Ignition Control
Flame Signal
Start Gas
V
al
v
e
Ignition Spark
Thermostat 24
V
SHUT DO
WN
RU
N
START
ts = 10 Seconds
Signals Output By Control
Re
q
uired Incoming Signals
Flue Blower
Pressure
Switch
P
C
N
O
N
C
30 Seconds Purge*
*Purge time
b
egins at pressure switch change o
v
er.
Axial Fan
30 Seconds Delay
90 Seconds Delay
30 Seconds Post Purge
If at any stage the flame fails, the control
w
ill retry
for ignition. The control has fo
u
r trials for ignition
before a one ho
u
r locko
u
t.
