Having just fixed a boiler fault (with agiles help) I now have a second problem. The domestic hot water is getting nowhere near hot enough, have put the thermostat on full, waited for the boiler to stop firing and measured the water temp at tap. Am getting 110 degrees F, i think thats about 50 c. As far as im aware temp range should be 55-80 degrees c. Dont think its the diverter valve as the flow pipe to c/h isnt getting hot. Is it the control thermostat/thermo phail and if so how do i prove it???. Also someone mentioned a paddle switch might be faulty?, again how do i test it?. boiler is worcester heatslave 20-25. Any info would be greatly appreciated.
Domestic hot water fault on heatslave boiler.
- Thread starter boilerslave
- Start date
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Water from a combi is not expected to exceed 50° C .
I would therefore say that its correct.
Its not just a matter of the termperature though. The performance of the boiler is to heat a specifiec flow rate by a temperature rise.
e.g. a 24 kW boiler will heat 9 litres/minute to give a temperature rise of 35° C.
Tony
I would therefore say that its correct.
Its not just a matter of the termperature though. The performance of the boiler is to heat a specifiec flow rate by a temperature rise.
e.g. a 24 kW boiler will heat 9 litres/minute to give a temperature rise of 35° C.
Tony
hi Agile, heatslave manual says, and i quote, "tank temp is controlled by the domestic hot water control thermostat and is variable between 55-80 degrees c. Either way shower water is only hot for 15 seconds and is then just tepid no matter how long the water has been on. Any more thoughts?
All those technical minds out there and no answers !!! Come on chaps.
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H
holty
have you tried just turning the temp stat up for dhw
Thanks for your suggestions, will look into the flow switch h/e issue (and yes the temp stat is on max). 
H
holty
the flow switch is a paddle type, make or brake one on the 20/25 so that could be ruled out with a continuoty test,id loke more at the temp stat or scale etc
The boiler may store water between 55° and 85° but the heat in that store is then transferred into the DHW which flows out at a lower temperature of 40°-50°.
I would have to see the book to be sure of your particular boiler but most have a blending valve to set the actual DHW temperature. Those blending valves often jam!
Cornwall is generally very soft water so lime scale on the secondary of the plate HE would not be expected but rusty dirt on the primary is a very likely culprit. The boiler is only designed to give water out at up to 50° C.
A thermal survey under steady state operating conditions would usually identify where the fault lies.
Tony
I would have to see the book to be sure of your particular boiler but most have a blending valve to set the actual DHW temperature. Those blending valves often jam!
Cornwall is generally very soft water so lime scale on the secondary of the plate HE would not be expected but rusty dirt on the primary is a very likely culprit. The boiler is only designed to give water out at up to 50° C.
A thermal survey under steady state operating conditions would usually identify where the fault lies.
Tony
Thanx for all the comments, after a bit more "prodding about" i am thinking the same way as Holty, ie temp stat. Have been told theyre only £25, quite cheap in boiler part terms, so will order one and hope that cures it. Agile," A thermal survey under steady state conditions" has gone a bit over my head unless you meant a temperature reading at the labour party head office!.
Fitted a new temp stat today, fired up the dhw and...... back to square one. boiler only fired for about 5 minutes then shut off. water from tap only runs hot for about 5 seconds then goes tepid. Dhw tank should hold 46 litres according to book. The only way to get the bioler to fire again is to open a hot tap. What can i do next???? help please.
where is and what does a blending valve look like? Does a heatslave 20-25 have one?
Thanks for your comments, i understand what you are saying but something must still be wrong. It cannot be right that a modern boiler is only capable of providing a tepid shower? It seems to me that the boiler is shutting down before the whole dhw tank is up to temp. A question, if the hw tank thermostat is at the top of the tank, how can the boiler make sure the whole tank is up to temp?.
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