Replacement Parts List

70
HS-300D-PL
TROUBLESHOOTING HYDRONIC SYSTEM PROBLEMS
1
Below and on the following page are four guides for troubleshooting various problems found in typical hydronic heating
systems. Each guide was developed by Bob DeWyze, Director of Training and Education for ITT Fluid Handling Division
(retired). Familiarization with this information may provide insight in preventing future repairs required for pumps, valves
and other hydronic accessories found in this service parts catalog.
1
PUMPING SYSTEM TROUBLE ANALYSIS GUIDE
COMPLAINT POSSIBLE CAUSE RECOMMENDED ACTION
No circulation Set screw not tight, coupler loose on shaft
Impeller slipping on shaft
Air-bound system
Air-bound pump
Broken pump coupler
Clogged impeller or piping
System valve closed
Pump electrical circuit broken
Tighten set screw in shaft recess.
Check to see if impeller is placed on the key way of the shaft.
Tighten impeller nut.
Vent system
Vent pump casing
Replace; check alignment
Locate and remove obstruction
Open
Check all related low and line voltage circuits.
Inadequate circulation Air-bound system
Air-bound pump
Clogged impeller or piping
Clogged strainer
Pump impeller damaged
Insufficient NPSH (net positive suction head)
Pump too small
Partially air-bound pump
Pump running backwards (three phase)
Improper motor speed
Vent system
Vent pump casing
Locate and remove obstruction
Remove and clean screen
Replace
Lower pump or raise pressure or relocate
Replace pump or impeller
Vent pump casing
Reverse any two motor leads
Check wiring and voltage
Pump or system noise Entrained air
Pump cavitation
Pump misalignment
Worn pump coupler
Excessive water velocity
Poor foundation (base-mounted pumps only)
Pipe vibration
Vent system
Lower pump or raise pressure or relocate (see note below)
Re-align pump
Replace; check alignment of shafts - replace sagging motor mounts
Install balancing cocks or parallel piping.
Provide rigid foundation with adequate grouting.
Provide adequate pipe support.
Premature failure of
pump components
Improper pump (size/type)
Improper pump location
Pump misalignment
Excessive water treatment
Over-oiling of pump
Under-oiling of pump
Pump operating close to or beyond end point of curve
Excessive piping load
Replace
Relocate
Re-align
Check manufacturer’s instructions
Check manufacturer’s instructions
Check manufacturer’s instructions
Balance system
Provide proper pipe support
Seal failures within 1
year period or less in
a closed system
Excessive dirt, sand and oxides
Excessive or improper water treatment
Pump Cavitation:
1. Improper selection
2. Compression tank location
Air-seal without lubricant (water)
Excessive temperatures
Pumps run without fluid
Clean system
Check for proper water treatment recommendations from pump
manufacturer.
Check pump operation on its curve - overloading
High head pump must have compression tank on suction side of pump.
Vent air from pump volute
Check type of seal and max. operating temperature from manufacturer.
Pumps must be primed before operation.
Seal pitting
Oxygen corrosion
Magnetic iron oxide
Caused by wear and excessive amounts of free oxygen.
Fresh water feeding carries oxygen into the system.
Check if system has a constant leak.
Note: Cavitation can be identified by low rumbling or sharp rattling noises. This situation is created by the lack of available net positive suction head (NPSH). The pressure at
some point in the pump falls below the vapor pressure of the water causing flashing and the formation of bubbles, which are carried into the volute where the higher pressure
causes them to implode. This can eventually destroy the pump.
AIR CONTROL SYSTEM PROBLEMS
COMPLAINT POSSIBLE CAUSE RECOMMENDED ACTION
Waterlogged
compression tank
Gravity circulation between boiler and tank
Leak in tank
Leak in gauge glass. Top gasket dries out allowing air to
escape.
Install air control system
Check with soap solution - replace
Check tapping - would most likely be in upper tapping
Insufficient air control in
air control devices
Boiler top outlet fittings
Dip tube not 2½” below water line in boiler This is almost impossible to find without taking the supply piping on the
boiler apart.
In-Line fitting not working
properly
Velocity too high through fitting for air separation.
Initial system start-up not performed properly
Improper pitch in piping to the tank
Leaks in system piping
Check size of fitting - it should be the same as the pipe size
Check manufacturer’s instructions
Check to make sure horizontal pipe is pitched towards the
compression tank.
Check for leaks
No heat radiation Air-bound Vent