A.O. Smith AWH-35, Instruction Manual, Page: 27 / 48

27
TROUBLESHOOTING
PROBLEM POSSIBLE CAUSES CORRECTIONS
Heat pump is too noisy.
1. Sheet metal fasteners are loose.
2. Operating vibration is transferring to floor or
building structure.
3. 3. Blower pulley assembly loose or out of alignment.
Tighten fasteners.
Place vibration dampeners underneath unit.
Tighten or align pulleys.
Water on floor around
the heat pump and/or
water tank.
1. Tubing, valves, or fittings are leaking.
2. Heat pump is not leveled causing drain pan overflow.
3. Make sure the condensate trap has been properly
installed.
4. Drain pan is overflowing.
5. Condensation forming on the bottom of unit
(humid environments).
Repair leaks as necessary.
Shim unit to level. See installation section.
Condensate trap depth must maintain a water column during
operation.
Use pipe snake or compressed air to remove obstruction.
Cover bottom of unit with foam insulation.
Heat pump is not running -
electrical issues.
1. Circuit does not have adequate ampacity.
2. Short circuit or loose connection in field wiring.
3. Short circuit or loose connection in unit electrical
cabinet.
4. Thermostat failure.
5. Phase Monitor fault (red light on phase monitor lit)
6. Defective anti-short cycle timer.
7. Compressor burn-out.
Refer to nameplate for unit requirements.
Check field wiring diagram. Tighten all connections.
Check for loose wiring and tighten.
Replace thermostat
Reset phase monitor
Unknown
Replace compressor (refer to compressor change-out
page)
Heat pump is not running -
high pressure fault
1. Thermostat setting too high
2. Room temperature over 95 F
3. Low water flow causes
A. unit pump is not operating
B. piping between the heat pump and storage tank
exceeds 50 equivalent feet
C. heat exchanger has scale buildup
D. shut off valves are partially closed
Thermostat setting should not exceed 140 F.
Keep heat pump off until room temperature
is back in operating range
Low water flow corrections
replace unit pump
reduce piping or add booster pump
clean heat exchanger with a mild acid wash
open all shut off valves
Heat pump is not running -
low pressure fault
1. Room temperature below 50 F
2. Blower not operating at nameplate CFM - blower belt is
broken or out of alignment filters are dirty
3. Unit does not have adequate clearances obstructing air
flow
4. Loss of refrigerant
Keep heat pump off until room temperature is back in
operating range
Correct air-flow issue
i.Replace or realign pulley assembly; tighten belt
at the adjustable pulley
ii. Replace filtersw
iii. Relocate unit to allow for even air flow
Find source of leak, repair and recharge
Water is never hot enough.
1. Thermostat setting is too low.
2. Heat pump/storage tank undersized for application.
3. Heat pump is not properly connected to storage tank.
4. Unit cooling coil is overcooling the space.
Set thermostat for storage tank to a higher temperature.
Increase size of storage tank or install gas or electric heater
to make up for shortfall.
Refer to field piping diagrams for recommended piping.
If the room air temperature is too cool, a) use back up
water heating; b) duct cool air to another space; c) duct
warmer air from another space to the installed room.
Cooling coil is icing.
1. Insufficient air flow through the unit
2. Low room temperature
3. Partial refrigerant loss
4. Defective TX valve
5. Clogged filter dryer
Refer to “Heat pump is not running - low pressure fault”
section for correction suggestions.
If room air temperature is too cool, a) use back up water
heating; b) duct cool air to another space; c) duct warmer
air from another space to installed room.
Find source of leak, repair and recharge
Replace TX valve
Replace filter dryer
* Reset the heat pump by removing then restoring power to the unit at the breaker or from the manual switch. (There will be a three minute delay
before heat pump restarts.) If the heat pump cuts out again on LOW or HIGH PRESSURE, additional troubleshooting is necessary to find the cause
DO NOT CONTINUE TO RESET THE HEAT PUMP, AS CONTINUED SHORT-CYCLING MAY STRESS OR DAMAGE INTERNAL COMPONENTS.