DIY Doctor UK DIY Forums

HI, HOPE YOU CAN HELP ME? WE HAVE A
GLOWORM HIGH EFFICIENCY CONDENSING COMBINATION BOILER 30cx,
GAS FEED 22mm PIPE, WATER 15mm SUPPLIED TO THE BOILER,

CENTRAL HEATING WORKING FINE,

!THE PROBLEM IS!
WHEN WE TURN THE HOT WATER ON FULL THE DIGITAL DISPLAY (AS NORMAL) GO'S FROM 1.0 bar TO 30 DEGREE THEN OVER THE NEXT MINUTE THE TEMPERATURE CREEPS UP AND DOWN (FLUCTUATES) TO 40 DEGREE THEN STARTS TO DROP DOWN TO ABOUT 20 DEGREES.
BUT WHEN WE TURN THE HOT TAP ON HALF WAY THE HOT WATER GETS TO FULL TEMPERATURE, WE CAN NOT PUT THE HOT WATER TAP ON FULL.

SAVE ME PLEASE
(WASHING MACHINE ENGINEER)
THANK YOU
JOHN.

John, I would check the diverter valve initially + have you tried with just hot water on ie no ch?

What's the flow rate like with the tap only half open ?

Sometimes the water flow rate can be too much for the boiler, when you think the water is cold entering the boiler and comes out hot. Particularly in the winter months when the mains cold water temperature drops you tend to find you need to turn up the boiler temperature or reduce the rate that the water is flowing through the boiler.

The boiler will tell you the flow rate, this flow rate will ensure the boiler will produce hot water. If the flow rate is greater then this may be the problem.

Also, when the system is cold - check the central heating flow pipe when the hot water is running, this pipe should not get hot - if it does then it's the diverter at fault and the heat is being lost to the central heating side.

Hope this helps