Weil-McLain WM97+ Product Manual page 35

CWH
companion water heater
Troubleshooting
CWH Temperature/pressure relief valve lifting or weeping
1 Undersized or missing domestic water side expansion tank?
• Is there a thermal expansion tank installed on the domestic supply piping and is it properly sized?
• A thermal expansion tank is required if the domestic supply piping includes a backflow preventer or pressure reducing
valve.
• Ensure the potable water expansion tank is properly sized according to the water heater volume and supply pressure.
• During long periods when there are no draws from the tank (i.e. overnight), the T&P relief valve may lift or weep due to
thermal expansion, but may function properly during normal periods of tank draws.
2 Faulty domestic water side expansion tank?
• Is the expansion tank defective, water logged or improperly charged?
• Check for failed gaskets or bladders, or a faulty Schraeder valve.
• Use a tire gauge to check the charged pressure of the tank.
• Tank must be isolated and pressure relieved when testing.
3 Faulty T & P relief valve?
• Is the temperature/pressure relief valve functioning properly? Dirt and water deposits can accumulate under the valve seat.
4 High domestic water supply pressure?
• Check the domestic supply pressure entering the water heater.
• If the pressure is over 70 psi it is recommended to install a pressure reducing valve. A thermal expansion tank is required
if a PRV is installed.
• This will prevent any pressure spikes or increases in pressure due to thermal expansion which may cause the T&P valve
to lift or weep.
5 Possible water hammering or pressure spikes?
• Check the domestic system for possible sources of water hammering or pressure spikes.
• Some appliances such as clothes washers and dishwashers utilize fast acting valves which may cause water hammering or
pressure spikes through the domestic water system.
• Install water hammer arrestors as required per the manufacturer's instructions, or install flexible connectors to isolate the
tank from the domestic system
6 Check boiler operating temperature.
• If the boiler operating temperature is too high, stacking can occur in the water heater raising the domestic water tempera-
ture close to the boiler operating temperature. — Reduce the boiler operating temperature to 180°F. Also follow page 33
suggestions if the problem persists.
Part number 635-500-156/0113
— Product Manual
(continued)
35