1. CH works
2. HW does not. Used to work but hasn't since a few weeks ago and I have opened all hot water taps and can hear/feel water running through the boiler, but the secondary heat exchanger never gets hot.
3. Actuating lever that registers a call for hot water does not move so the microswitch is never activated
4. When I push the microswitch manually and run the taps, the water still runs cold but the radiators get hot.
Based on the above, I believe the diaphragm needs to be replaced.
1. Do you think my diagnosis is correct or at least a good starting point?
2. If I am to replace the diaphragm, do I need to drain the boiler first?
-The manual says to shut off boiler which includes: close off the CH valves, close DHW cold water supply valve, close gas inlet valve, then open taps, then remove the housing and replace the diaghragm.
It won't take much longer to do, but if I can get away with not draining it, then I will. Seems like I would have water spilling out when I get to the diaphragm if I don't drain the boiler.
Thanks in advance.