worcester 240 combi - no hot water & lukewarm heating

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My daughter's combi boiler fires up on request for hot water and central heating. The diverter valve spindle travel is good and instant. Microswitches are both activated. Flame comes on, pump is turning (removed the bleed cap and the spindle is spinning). But there is no discernible increase in the temperature of any of the pipework around the pump or heat exchanger. The outlet to the rads is lukewarm at best. The pump head was the warmest thing after switching everything off. The pump spindle spins but I don't know if it is at the normal rpm? I noticed the spindle could be pushed inward against the magnetic field a few mm, I assume that is normal. Could the problem still be with the pump and a lack of circulation? The pump is a Grundfos, and is almost silent in operation. Don't want her to buy a new pump head on my advice if it is unlikely to be faulty.
 
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take the pump head off and check the impeller



Flame comes on, pump is turning (removed the bleed cap and the spindle is spinning). But there is no discernible increase in the temperature of any of the pipework around the pump or heat exchanger.

heat must be going somewhere or the boiler would overheat :idea:
 
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Thanks Kev,
Pump is working ok, the radiators are all increasing in temp when the boiler is on, but they are getting no more than lukewarm. Pipe coming directly from the boiler is only lukewarm, there is nothing that is too hot to hold your hand on. Like you I am now wondering where is the heat going if not into the circulating water?
I guess I either have a reduced burner flame? Or the heat from the burner is being diverted straight out to atmosphere? Or there is no heat transfer due to dirt?
Are any of these options a possibility in your view?
I am returning to the site tomorrow and will remove the covers on the furnace to see if anything obvious pokes me in the eye. If not; it is time to call an expert, there is no way I am touching anything on the gas side.
Thanks again for coming back.
 
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Sounds under-gassed, if the boiler continues to run (flame on) without heating up, you will need a RGI to sort that.
 
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Sounds undergassed to me as well, but before calling a RGI out check noone has nearly turned the ecv (meter valve) nearly off.
Do you have a gas hob?
Is that working ok? Do the flames get smaller when the boiler lights?
If so switch everything off at meter and get Transco in to change meter regulator or check gas pressure.
Phone no 0800 111999
 

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