Worcester 240 too hot

TALU · 14 Sep 2005

Water is always burning hot, temp control makes no difference, but the electrics of it are funtioning fine.

Could it be the diverter or microswitch?

chrishutt · 14 Sep 2005

Which water (DHW or CH)? What temp. is "burning"? Go on, give us a few more clues.

TALU · 14 Sep 2005

It heats both HW and CH till its steaming, way too hot to touch!

There is a temperature regulating variable resistor on from that makes no change to the temperature, but it is still functioning.

ChrisR · 14 Sep 2005

but it is still functioning

it seems that it isn't !

TALU · 14 Sep 2005

When i say it is still functioning, i mean that it is electrically, ie it changes resistance (0-256 ohms) but it has no effect on the boilers water temperature output.

ChrisR · 14 Sep 2005

Need the M.I. to see how many temp sensors there are. If there are two (ch, hw) it smells like the pcb..... I bet COG knows.

(The water flow rate on HW must be pretty low for it to be able to make the water that hot!)

TALU · 14 Sep 2005

Don't like the sound of PCB problem, they cost £70.

How could i be sure if this?

What outputs should change? (voltage changes etc)

Could it be the Gas regulator? would obviously get Corgi guy to change that if it was needed.

kevplumb · 14 Sep 2005

whats the flowrate

ChrisR · 14 Sep 2005

they cost £70.

rrp is about £260!

B.O.B DOLE · 14 Sep 2005

sounds to me that the mod valve or the thermistors or faulty

jiminblack · 14 Sep 2005

Pull one of the yellow wires off the gas valve solenoid while on full flow hot watre demand. Does the boiler go to low flame?

COG · 15 Sep 2005

The temp dial on the front is only for CH hot water is set on the board at 54dec C . The boiler should give a temp rise of 40degC at a flow rate of 9lts per min (9 lt flow restrictor fitted ) if your flow rate is low then the temp will rise above 54 but it should come back down ,if the modureg or min setting on the gas valve is out it will just shut down then re fire ,could be the dhw sensor ,you can test by checking the temp at the senser and testing the resistance(dont have the data handy) but its a bit time consumeing easyer to just swap it for the ch / primary sensor and if faulty the symptoms will change.

TALU · 15 Sep 2005

jiminblack said:
Pull one of the yellow wires off the gas valve solenoid while on full flow hot watre demand. Does the boiler go to low flame?

YES it does, what would this mean?

jiminblack · 15 Sep 2005

The modulating solenoid can sometimes stick in high flame. By pulling the yellow wire off the boiler should go in to low flame ( approx 2.0 mb ) burner pressure. You've proved it's not sticking but are the burner pressures set right?
++++++++++++++++++++++++++++++++++++++++++
COG are you a Worcester engineer?

MOD
please use the edit button

TALU · 16 Sep 2005

Ok now that is eliminated, whats next to test?

What triggers the change in voltage to the modulating solenoid? Temperature sensor, or just PCB?

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Worcester 240 too hot

B.O.B DOLE

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