
FAUL
T CODE THUMBNAILS –
PAGE
F 9
FAUL
T CODE THUMBNAILS –
PAGE
F 9
Heater System Solving Guide
Fault Code Thumbnails HS
Maximum R
eturn W
ater T
emp Ex
ceeded
F
AULT
C
ODE
T
HUMBNAILS
HS M
AXIMUM
R
ETURN
W
ATER
T
EMP
E
XCEEDED
HS
M
AXIMUM
R
ETURN
W
ATER
T
EMPERATURE
E
XCEEDED
UHS, IDL2, IDL, ED2
If water temperature exceeds 105°F, the heater will shut down and
go into lock-out.
Automatic restart is 2 minutes after water temp drops below 105°F.
P
ARTS
T
HAT
M
AY
B
E
N
EEDED
• Control Module
• External Thermostat (if system uses one)
NOTE:
In most cases, no replacement part will be needed.
D
IAGNOSTIC
S
EQUENCE
A. Verify water flow is adequate.
Low water flow will cause high temperature.
(Generally, 25 gpm is needed by smaller heaters, while 300,000 btu/h
heaters may require 40 gpm or more. See heater’s operating manual.)
B. Verify set point setting of remote thermostat us below 108°F. If external
control is used, verify that external thermostat is set below 104
o
F. (Exter-
nal thermostat may be faulty and need to be replaced.)
C. Verify integrity of exchanger.
D. Check for possible bad ignition/control module.