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PROBLEM POSSIBLE CAUSES SOLUTION
No hot water
1. No power to unit
2. Circulator air-bound
3. Faulty circulator or zone valve
4. Faulty control
5. Boiler inoperable
1. Check circuit breaker, boiler emergency switch and boiler reset switch.
2. Purge air. Ensure circulator is on Boiler Supply. Check air vents.
3. Check circulator and zone valve. Repair or replace if necessary.
4. Check continuity. Switching circuit should close. If not, replace control.
5. Check boiler system. Boiler must operate to generate hot water.
Insufficient hot water
1. Demand exceeds capacity
2. Temperature too low
3. Boiler lacks output for simultaneous heat &
hot water
4. Fouled heat exchanger
5. Insufficient heat exchanger flow
1. Check sizing based on household size and boiler output.
2. Increase temperature setpoint.
3. Set up for priority. If problem persists add storage or increase tank size.
4. Check Boiler Supply/Boiler Return during cold startup. If difference is less
than 20°F, clean heat exchanger as outlined below. Install water treatment
equipment to prevent recurrence.
5. Check for undersized or faulty circulator, stuck or undersized zone valve.
Ensure all shutoff valves are open. Check for stuck flow check valve.
Purge boiler loop to remove air.
Water too hot
1. Improper plumbing
2. Temperature set too high
3. Temperature sensor bulb not fully inserted
4. Stuck zone valve
5. Flow check valve stuck open
1. If Boiler Return is plumbed to the suction-side of a heating circulator,
overheating will occur when the home’s heat is on. Fix plumbing.
2. Reduce temperature setting.
3. Re-insert temperature sensor bulb.
4. Repair or replace.
5. Clean, repair or replace.
Relief valve dripping
or opening
1. Thermal expansion tank undersized or missing
2. Thermal expansion tank set improperly
3. City pressure too high
4. System over temperature
5. Faulty relief valve
1. Install the properly sized thermal expansion tank.
2. Ensure precharge air pressure matches static water pressure.
3. Install a Pressure Reducing Valve (PRV) if city pressure is over 80psi.
4. Determine cause of over temperature condition and correct problem.
5. Replace relief valve.
Discolored water
at faucet
1. Poor water quality
2. Sediment or suspended particles
1. Have water tested for contaminants.
2. Install sediment filter, purge unit more often to avoid future problems.
Boiler will not operate
when calling for
hot water
1. Improper or loose wiring
2. Boiler high limit has been reached
3. Problem with boiler system
1. Check connections against wiring diagrams in this manual.
2. Boiler will periodically cycle on and off during operation.
3. Have boiler diagnosed for proper operation.
1. PURGE HEAT EXCHANGER: The heat exchanger should
be free of large air pockets to allow the circulator to operate
properly. Using the diagram below as a guide, isolate the
boiler return line and flush the loop until large air pockets are
purged. After this, the air elimination equipment will collect
smaller air bubbles.
2. FILL TANK: Open the hot water fixture furthest from the
heater. Open the cold water supply and allow the water to
run until air stops emerging. Air pockets may appear at any
hot water fixture. This is considered normal and will clear
as hot water is used.
3. START HEATER: Turn power on to the unit. Mechanical
controls should have the knob rotated to the 120°F mark.
The circulator or zone valve should operate and the boiler
should start.
4. CHECK OPERATION: The water heater will begin to heat.
Depending upon the size of the water heater, output of the
boiler and the space heating load, the unit should typically
reach set temperature within 15 to 60 minutes. If heating
does not occur, consult the troubleshooting section in this
manual. Note: Large heaters coupled with small boilers
may exceed this time period upon initial startup.
5. SET TEMPERATURE: The control should be set to the
minimum temperature consistent with the user’s needs. This
maximizes efficiency and reduces scald potential.
Painful scalding with possible serious
and permanent injury can occur if the
temperature is set too high or the thermostat is not
functioning properly.
6. MAINTENANCE: The water heater and system should be
periodically checked by a licensed professional at least
annually and more often as system ages.
Startup Procedure
Troubleshooting
Warranty
WHS Series and DC Series:
10 Year Limited Warranty Residential
5 Year Limited Warranty Commercial
Visit www.amtrol.com for complete warranty details.