Combi boiler problem

[confusedplumbingnovice]

Hi All,

Just bought my first place. 3 weeks in and the boiler has started playing up - please help me!

I have a Glow Worm Hot Water Express combi boiler.

Problem is, when the heating is on, the hot water starts off hot for a few seconds, then goes cold. Especially bad in the shower (due to higher pressure required?), but happens on all taps after about 30 seconds.

Water pressure in the shower seems to be ok - just goes cold.

Odd thing is, the boiler's currently set to 'Hot Water'. If I set it to 'Central Heating and Hot Water', the heating stops working.

Any advice greatfully received!

TIA

 

[PEDANTICVINDICTIVEMAN]

sounds like a diverter valve problem, others on here will have more experience than me with this particular model, Express is the last thing these are if I remember correctly.

 

[kevplumb]

heating working when set to hot water only ?

 

[confusedplumbingnovice]

Hi there. Yes the heating does work when set to 'Hot Water', but not when set to 'Heating and Hot Water'.

Also, this morning I had the heating set to turn off 10 mins before I got up, as I thought the hot water was fine if the heating was off. However, the shower ran hot for about 5 minutes, then went cold.

Does this give anyone any further clues?

Any advice would be greatfully received!

 

[ArtfulBodger]

As PVM already said, you have a duff diverter valve, or a stuck DV microswitch

 

[DP]

Boiler does not have a diverter valve. HE is composite i.e. same unit heats primary as well as secondary water. Boiler has a lever center of panel for HW only or CH+HW. This is a mechanical device that isolates the rads when set in HW mode.

Boiler has a flow switch that detects HW demand, which starts the boiler. When the boiler stops supplying HW (after aforementioned 5 minutes), is the fan running? What about the pump and the burner. Does the pilot go out? More info would help.

 

[confusedplumbingnovice]

Hi guys, thanks for your interest.

I will do some further investigation this evening.

I know that the pilot light remains lit at all times. What's the easiest way to determine if the fan, pump and burner are still running?

Sorry I am a complete novice...

 

[confusedplumbingnovice]

Hi Guys,

As far as I can tell, the fan is still on and the boiler still burning when the water runs cold.