Worcester Heatslave 9.24

[MarkGibson]

Following on from my earlier question.

I am still having trouble with my hot water from the above machine.

So I have at least ruled out the water temp sensor (on the Heat Ex outlet)

So I have been doing more thinking!! and have come up with the following possibly flawed reasons for still not working.

The gas valve (which I know next to nothing about) has 4 wires, I guessed that 2 of these are for the spark and the other 2 are to control the gas to the valve? Now i guess this means my valve cant be faulty due to the fact the central heating is working, and the electronics must control the valve on the central heating side of things in a similar fashion to the hot water side. i.e regulating the flow etc. (also the above should also rule out the electronics etc being faulty??)

It cant be my pump overrun thermostat because that side of things seems to be working correctly.

Therefore I have come to the conclusion that the over heat thermostat may possibly be broken or sending the wrong signal back to the valve? (next to the pump overrun stat) and causing my boiler to cut off prematurely?

Any help from any of you guys would be greatly appreciated.

Mark

 

[COG]

Two of the four wires to the gas valve open the main opperater (coil) the other two increase and decreas the burner pressure at the burner. T he limit stat you mentioned is an interupter thet will shut of the gas by interupting the output from the thermocouple to the gas valve, its worth replaceing if its old but my question is why people assume something is wrong with the stats when they are just doing there job ? that is telling yuou things are getting too hot ! if you want to do things properly splash out on a surface temp probe and take the temp at the stat you should get around 78degC and not more than 84degC on DHW on full it should trip out at around 104 +/- 4

 

[MarkGibson]

Cog thank you for your reply,

So if the temp is 104 or there abouts then the over temp sensor is working, what would you suggest would be the problem if this is the case?

The hot water will run for about 15 mins then the boiler cuts out.

Am i right in saying the gas valve must be OK due to the fact the central heating is working?

Also 3 years ago was having the same problem, took to bits and the over temp sensor was loose, tightened it up and the problem went away, now its doing the same but the sensor is not loose.

Any help would be greatly appreciated.

Mark

 

[COG]

From what you say your gas valve sounds ok. Your boiler is at least 15 years old so overheating fom poor circulation is very posable, the trick is to find the restriction but after 15 years that will include both heat exchangers the diverter valve and the pump and the only way to test for certain is take temperatures at various points but you could have more than one restriction. If you can undo the shaft end screw on the grundfoss pump it will spin freely , if the speed is reduced to 1 it will still spin freely if its in good health if it stops or labours then its had it. . If tghe diverter valve has white spots of corrosion comeing thru then its had it,.