No hot water. Heating OK. Vitodens 100-w wb1b 30 kW combi

[Duncs35]

All cleaned out no blockages present. Clean heat exchanger. Clean flow switch. Tap symbol appears when hot tap on , fan runs but no ignition. Temp display goes lower as water flows through and gets cooler. Once tap is shut off boiler kiks in to bring up to set temp of 50 deg. Heating works fine. Can see director valve motor operation pushing piston back and forth. Just no ignition when hot water flowing. Any ideas appreciated

 

[simond]

How do you know the heat exchanger is clean, and do you mean both?

WB1B has a flow switch on the main hex on the sealed models, we don't fit Viessmann combis so not sure if they are thr same, but I expect so.

If the plate hex is partially blocked ( eg: someone didnt have a powerflush when the boiler was fitted) and if your combi has this switch it will prevent burner ignition if the flow rate is low.

 

[holty]

blocked plate. does temp reach around 86 or above when water is on. probably find the rubber hose is stiff and crunchy as well. set boiler to eco rather than comfort to see if it lights after demand

 

[Duncs35]

I have had the unit to pieces. Heat exchanger cleaned and blasted through. Rubber hose removed and all crunch cleaned out. Hose and manifold \ pipe work is all clean. Flow from tap is brilliant 15 LTS a minute easily. Temp does not reach anything as boiler does not kik in only goes down as water cools through system. Only ignites when tap is off to heat up to preset 50 deg. Unsure how boiler went to comfort mode so no idea how to get to eco mode. Advise me please!

 

[holty]

are you registered?

 

[Duncs35]

I thought it would be a flow switch but as tap symbol appears when hot water is running , maybe not. Not registered no




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