Worcester Bosch

Silverbird65

Just had boiler in but it reaches therm set temp 19 and then fires on and off  instead of remaining of till room temp drops. I have Honeywell tr3  thermo. Can anyone explain why or is the boiler faulty. Or am I doing something wrong?
Cheers

[Deleted User]

Modern boilers do cycle as they have flow sensors to detect the temperature of the returning water. If the temperature of the running water is above a set limit, the boiler flame will cease until the returning flow temperature falls but the pump will continue to circulate water around the system. This 'cycling' will continue until the thermostat set temperature is reached. You can check if things are working normally by turning down the thermostat temperature. The boiler should shut down: turn it up, and the boiler should start up again.

Silverbird65

Thanks I must seem daft but I thought  once the set thermo temp was reached the boiler went off untill room temp dropped then boiler switched on again to maintain temp. My previous combi did that. Surely this is not economical?😊

Tallerdave

It does sound weird. If the thermostat isn't calling for heat, the boiler should be off (after a pump overrun period to cool things down).

Is the thermostat wireless and a long way from the boiler? If they lose radio connection with the remote thermostat some receivers default to an 80%/20% emergency cycle to stop you freezing. Is there a green led on the receiver that shows you when it is calling for heat from the boiler?

The thermostat may also have a setting for cycle times/frequency. I'm afraid that's going to be a case of reading the installation/user manuals and getting into settings mode.

The combi boiler may have a water pre-heat setting that causes it to fire randomly, but it wouldn't be for long.  Again,  read the manual and check the settings. 

Brewer20

Silverbird65 said:

Thanks I must seem daft but I thought  once the set thermo temp was reached the boiler went off untill room temp dropped then boiler switched on again to maintain temp. My previous combi did that. Surely this is not economical?😊

I've got a WB boiler, condensing Green Star, my programmer/stat sits downstairs in the lounge. 
As you say you expect it to switch on when the temp has dropped and off when the desired temp has been reached. Mine doesn't keep recycling.
You can set all this up on the programmer mine switches on automatically when the temp drops to 18.5 deg and off when 19.5 deg has been reached. 
Just check your settings, presumably you have the destructions for both boiler and programmer/stat?
And just to add, you can set it for hot water on demand. This pre heats the hot water side of things, the boiler will cycle up as necessary to heat the water for when needed, is it this that's happening with yours? Mine was set to not preheat the hot water, it can be changed in the boiler controls by the consumer.

Silverbird65

Thanks again. There is no led light  just a flame symbol. The symbol doesn't always show . The boiler is on eco so no water reheat. I have been through thermo settings. Just don't know what to do,?☺️

Silverbird65

Ok mine has tr3 Honeywell thermo. I set daily settings on twice a day morning and evening on 19° off at set time 5°. Goes on set time reaches temp they cycles on and off every 5mins or so sometimes shows flame sometimes not. Very disconcerting. Give me back my old boiler it just did what it was told.

MWT

Also the Honeywell T3R has some 'fuzzy logic' features which aim to maintain the set point before it falls rather than just reacting to a fall, so even if it is at the set temperature it may still call for heat.

It will show it is calling though so look for that, not just the current temperature.

Silverbird65

How does it show? Can I turn the fuzzy logic feature off?😊

MWT

Silverbird65 said:

How does it show? Can I turn the fuzzy logic feature off?😊

When it is calling you will see the little flame symbol to the right of the temperature.

You can turn off things like the optimal start/stop time features but the basic temperature maintenance aspect is not an option I believe, nor would you really want to turn it off as it should result in better stability and more efficiency.

If the flame symbol is not there and the boiler is not just in pump over-run mode then something else is not right.

Silverbird65

So back to installers to see what they can do. Eon used NG installations govt backed scheme I rue the day never again,😊