CWH companion water heater — Product Manual
Troubleshooting
(continued)
Boiler relief valve lifting or weeping
1 Undersized expansion tank?
• Insufficient allowance for expansion on the boiler side can cause the boiler pressure relief valve to lift.
• The tank must be sized to handle the total volume of water in the boiler system, the boiler and all inter-
connecting piping. The volume for the CWH boiler piping and heat exchanger is 1.4 gallons.
2 Faulty boiler expansion tank?
• Is the expansion tank defective, waterlogged or improperly charged?
• Check for failed gaskets or bladders, or a faulty Schraeder valve.
• Tank must be isolated and pressure relieved from boiler side when testing.
• Use a tire gauge to check the charge pressure of the tank.
• Turn the boiler limit up to a higher setting and let the system run at a higher temperature. This will
simulate maximum expansion in the boiler system.
• If the boiler relief valve lifts and/or there is a significant increase in the boiler system pressure, the
expansion tank is flooded or undersized.
3 Faulty boiler relief valve?
• Is the boiler pressure relief valve functioning properly? Dirt and water deposits can accumulate under
the valve seat.
4 Faulty boiler fill valve?
• Is the valve filling to the correct pressure?
5 Tank heat exchanger coil leaking?
• Turn the boiler power OFF.
• Close the boiler supply and return isolation valves.
• Isolate the water heater from the domestic water system by closing isolation valves.
• Attach a hose to the water heater drain valve (if not directly connected to a drainage location).
• Open the water heater drain valve to allow the tank-side pressure to drop.
• Watch the pressure on the boiler P/T gauge. If this pressure drops noticeably, there is a leak in the piping
or in the tank heat exchanger. Locate the problem and correct. Replace the CWH tank if necessary.
Part number 635-500-156/0113
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