Worcester Bosch Greenstar 8000 Life problems....Or are they???

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It might be these new energy saving pumps. I’ve just put my boiler central heating temp up from 68 degrees to 71, forget condensing mode. A few years back on an energy efficiency course, we were advised to set the boiler to max and control the room temperature with the trv’s and room thermostat. Put it on max, it fires up once and gets up to temperature quick and then goes off makes sense. I’ll revert back to the old way and see if it makes any difference.
 
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without looking at the system installation it is often difficult to determine all of the probable causes. I have well over 50 of the 8000 boilers installed with 2 that have complained about similar issues to yourself. one is because they have a large household all getting ready for school and work and they are continually demanding hot water for about 90 minutes on and off. ( they should have had a hot water cylinder but they knew best!) the other had a dripping hot water tap and they had preheat enabled.
I have solved a few others that i hadn't installed and there systems hadn't been balanced properly or they had more than one heating zone and the thermostat settings were incorrectly set in the back ground.

I appreciate what you're say snb, but none of this applies to me. For example the boiler we have is 35KW for DHW and 30KW for CH and it runs 11 radiators max. We don't have any dripping taps at all. The system as per the advice on this forum was balanced, but this issue is simply the fact that if no one runs the DHW, the boiler runs fine, but if you make the mistake of opening the tap, then the boiler just pauses for ages before continuing the heat. That means if I run the heating for 3 hours and open the taps 2-3 times within those hours, it'll waste a good 20 minutes just sat there, waiting to switch back to CH. That's a waste of energy and resources IMHO as the rooms never properly heat up.

It might be these new energy saving pumps. I’ve just put my boiler central heating temp up from 68 degrees to 71, forget condensing mode. A few years back on an energy efficiency course, we were advised to set the boiler to max and control the room temperature with the trv’s and room thermostat. Put it on max, it fires up once and gets up to temperature quick and then goes off makes sense. I’ll revert back to the old way and see if it makes any difference.

Yes it sounds about right that it's the new energy pumps. Isn't putting the boiler on max going to waste lots of energy? My boiler is set to 75C. Please do let us know how you get on.
 

snb

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If the unit is waiting 20 minutes to return to heating after a demand for hot water then either you don't have the boiler settings as per the changes i suggested or you have altered them from the factory default because that would give a max of 5 minutes between a demand for hot water and the heating resuming. These boilers when asked for a heating demand go straight to 75% of max heating power for 10 minutes before going to 100%. This is only throttled back if the difference between the flow and return is less than 20 degrees ( poor flow around a system or poorly balanced) if the flow temp gets to within 6 degrees of its set point then it will also start to reduce output. once it has reached temp it wont restart until the flow is at least 6 degrees below the set point. this is to reduce cycling. if difference between flow and return goes above 20 degrees it goes into 5 min waiting period.

The only other problem we have is with small systems like yours with only 11 rads and a central heating output at 30kw is that it would try to heat up too quickly at 75% of 30kw. 22.5kw is the kind of output we would be using on a system with about 25 rads dependant upon size.

How big is the overall size of your house in square meter and its age ?

If you were to reduce the output for heating in 3-b1 to 50% you may find that it heats up faster because it won't keep going into waiting periods. ( when we put a boiler in max rate it bypasses most energy settings and only stops when it hits the flow temp setting).
Everytime currently when your boiler has demand for hot water it will revert afterwards central heating input at 22.5kw but if it hits a flow and return differential above 20degrees it will put it into a 5min waiting period and the cycle just continues.
 
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Apologies if I wasn't clear snb, but I didn't mean that it stops for 20 minutes each time - I meant 20 minutes in total if we open the tap 2-3 times.

Unfortunately, I don't know how big our semi-detached house (built in 1935) is in square meters.

I have changed the 3-b1 setting which was on 100% to 50% now.
 

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