CTHN-S
ERIES
I
NSTALLATION
, O
PERATION
AND
S
ERVICE
M
ANUAL
78 of 91
18.1 Troubleshooting Flow Chart - Unitary
Depr
ess s
w
itch.
Chec
k
v
olt
a
ge
.
Is it 1
2
0
V
?
Chec
k
v
olt
a
ge
b
et
w
e
en
door s
w
itch and
b
ur
ner
neutr
al (whit
e).
R
e
place S
w
itch
N
o
Chec
k w
ir
ing and
Diag
ram.
R
emo
v
e o
b
str
u
ction.
Chec
k w
ir
ing t
o
the
b
ur
ner
.
Mak
e
sur
e the
b
ur
ner is
plugged in.
C
o
rr
ect g
as pr
o
b
lem.
See Gas Piping Section
f
or det
ails
.
Is ther
e
po
w
er (1
20
V
)
b
et
w
een contr
ol panel
BH and B
N
t
e
rm
inals of
the z
one
calling f
or heat.
Is ther
e po
w
e
r (1
20
V
) at
the
b
ur
ner r
ecept
acle?
Is ther
e pr
oper g
as
pr
essur
e
and f
lo
w
t
o
the
b
ur
ner
s?
Is
b
lo
w
e
r side
door in place?
R
emo
v
e door
. Is
v
olt
a
ge
at door s
w
itch 1
2
0
V
?
Chec
k
v
olt
age
b
et
w
een
door s
w
itch and
b
ur
ner
neutr
al (whit
e).
Disconnect w
ir
es fr
om
MBR
and MBR-COM.
Is
ther
e at least 1
2
V
DC
b
et
w
een the t
e
rminals?
R
econnect MBR and
MBR-COM.
Ar
e
the
v
acuum pr
o
v
ing and/or
mot
or end s
w
itches
oper
ating pr
oper
ly?
R
eplace appr
o
pr
iat
e
z
one r
e
la
y on main
b
oar
d.
(P/
N
9043
8
1
00,
Omr
o
n
G2R-1
-S
, or
e
q
ui
v
alent)
R
eplace Door
.
R
eplace main contr
ol
b
oar
d.
(P/
N
90437500)
R
e
pair or R
eplace
s
w
itches
as necessar
y.
N
o
Ye
s
Y
e
s
Ye
s
Y
e
s
Ye
s
Y
e
s
N
o
No
N
o
N
o
Ye
s
No
N
o
N
o
N
o
Ye
s
Is ther
e
po
w
er (1
20
V
) t
o
the contr
ol panel H and
N
t
e
rminals?
T
est ther
most
at
b
y
placing a jumper w
ir
e
b
et
w
een COM
and
appr
opr
iat
e ther
most
at
T(1,2,3,4) t
e
rminal.
Does
the pump tur
n on?
Is ther
e
po
w
er (1
20
V
)
b
et
w
een the panel
MH and M
N
t
e
rminals?
Is the mot
or hot?
Mot
o
r ma
y ha
v
e tr
ipped
o
v
er
load s
w
itch.
W
ait
1
0-1
5 min
u
tes f
o
r
aut
o
matic r
eset.
Chec
k cir
cuit
b
re
ak
er
and/or fuse on panel
suppl
y
cir
cuit.
R
e
place fuse
.
(P/
N
9043
8
200)
250
V
3A siz
e 3A
G
Is the fuse on the cir
cuit
b
oar
d
b
lo
wn?
Disconnect po
w
e
r t
o
the
mot
or
. Does the mot
or
tur
n fr
eel
y
?
Is the pump impeller
o
b
str
uct
e
d?
R
eplace main contr
ol
b
oar
d.
(P/
N
90437500)
Is ther
e at least 1
2
V
DC
at the pump r
e
la
y coil?
(
W
2 and
W
1 on cir
cuit
b
oar
d.)
R
e
place pump r
e
la
y.
(P/
N
90437900, Omr
on
G4B-1
1
2T1
-US
, or
e
q
ui
v
alent)
Mot
or
b
ear
ings ma
y
ha
v
e f
ailed.
R
e
place
mot
or
.
Chec
k ther
most
at w
ir
ing
and r
eplace ther
most
at if
necessar
y.
Is the mot
or connect
ed
pr
oper
ly? R
e
fer t
o
the w
ir
ing
diag
ra
ms on the mot
o
r and
in the inst
allation man
ual
N
o
N
o
N
o
N
o
N
o
N
o
N
o
Ye
s
Ye
s
Ye
s
Ye
s
Ye
s
Ye
s
Ye
s
N
o
N
o
N
o
Ye
s
Af
te
r a 45 pr
e-pur
ge
per
iod, does the
b
ur
ner
light?
T
u
rn
up ther
most
at.
Does the pump tur
n
on?
N
o
Ye
s
