Thermostat on Central Heating.


3yr old Worscester Bosch, when the thermostat is set to 18 deg. it cuts off after about 1 hour, when set on 20, it seems to be on continuously, the heat setting is on number 3 at the boiler.
Any thoughts?
Thanks.
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Is there a thermostatic radiator valve on the rad in the same room as the wall thermostat? If so, turn the thermostatic rad valve up to max, or better remove the head.
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The wall thermostat is in the hall, and when it was installed we were told not to have the radiator with a thermostat valve in the same room.
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Sheila wrote:

enough heat to lift the temperature in the room where your thermostat is located above 20 degrees You could try raising the boiler thermostat and see if that helps. if not the problem could be because all the heat is going into other rooms perhaps - radiators un-balanced
or you have thermostatic radiator valves set below 20 in that room.
One question is did the system used to work OK and just started this behaviour? Have the radiator valves been adjusted eg by decorator or visitors?
hth
Bob
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Thanks for that, we will try raising the temp on boiler tomorrow.
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Sheila wrote:

I would suggest that the boiler heat setting is too low because it is currently incapable of raising your room temperature to 20 deg - and hence your boiler is running continuously while struggling to achieve the task!
It will be more economical to raise your boiler heat setting and allow the boiler to be controlled by the room stat. I also have a Worcester Bosch boiler (a 30 CDi combi) and have the boiler heat setting on 6. Rooms heat up very rapidly and then the boiler switches off promptly. So, although the heat setting on the boiler is higher - my boiler will be firing for shorter periods than yours.
Kev
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On Nov 9, 9:48am, "Ret." <xxx> wrote:

Is that true for a condensing boiler, in terms of efficiency?
Jonathan
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The comment about being more economical is wrong for both condensing and non-condensing* boilers. Most efficient operation is with the boiler temperature set low enough that the room stat never quite switches off. Trouble is this boiler temperature setting will vary with outside temperature, and would need to be boosted to heat up the house from cold, and so it doesn't lend itself to manual adjustment. However, this is what an intelligent control system with weather compensation will do for you automatically.
*Non-condensing boilers have an additional constraint that the return temperature must be high enough to prevent condensing, normally at least 60C.
--
Andrew Gabriel
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Andrew Gabriel wrote:

Yes - I stand corrected. I had this response from Worcester Bosch when I queried what heat setting I should put my boiler on:
"Thank you for your enquiry.
Whilst using your room thermostat it is important to obtain the most efficient flow and return temperatures to extract the highest output from the boiler with the lowest temperature of flow. Please see diagram below from installation instructions:
Central Heating Max. rated heat input: kW 30.9 Max. rated heat output net 40/30deg C kW 32.1 Max. rated heat output net 50/30deg C kW 31.8 Max. rated heat output net 80/60deg C kW 30.0
From 1 to MAX on your CH control knob on the boiler work in 8C increments starting from 35C-88C MAX.
This table shows of the higher kW gains achieved by reducing flow temperature and achieving a more balanced return. Certainly having the boiler short cycling at full output will reduce the economy so by setting your CH control knob to a lower temperature over a longer demand period will improve the efficiency. It may take slightly longer to heat the property but once heating the boiler will be producing more efficient flow/return temperatures therefore increasing the condensing process making the demand more efficient."
We hope this answers your query satisfactorily.
Kind regards
Technical Support Worcester, Bosch Group
Not sure that I fully understand the table, but I now accept the concept that the boiler heat setting should be at its lowest to achieve the necessary warmth in the house.
Kev
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