Boiler keeps turning on

[Sakir]

Hi there

Some help and advise would be greatly appreciated.

I have a Worcester Greenstar 18i boiler with a unvented hot water cylinder. I have two issues with my central heating system:

1. When the hot water is switched on, a few of the radiators get very hot.

2. When the central heating is on, the display on the boiler shows the system temperature. As it heats up, the temperature increases. Once it reaches the desired temp, the boiler stops heating and switches off. The system temp starts to decrease quite quickly and within a few minutes the boiler will start back up again. So essentially, my boiler is constantly turning on every 5 mins or so. Does anyone know what the issue could be?

Thanks in advance!

 

[Chuck]

1. Is very likely a phenomenon known as 'reverse circulation'. This happens if the standard rules for plumbing the system have not been followed and the CH and DWH returns are tapped into the boiler return in the wrong sequence.

2. Is behaviour known as 'short cycling'. It happens when the minimum power the boiler can deliver, around 8kW from memory, is more than can be transferred by the emitter system, usually because the TRVs on most radiators are shut. Tends to affect systems in the autumn and spring when only a couple of kW are needed to keep the house at the correct temperature. The cure, which is known as a buffer tank, is large and relatively expensive so most people live with the problem.

I'd expect the full on-off cycle to be 10 minutes on a Bosch boiler.

 

[Scott_D]

Do the radiators heat properly when heating is selected?
Open all TRVs to maximum, does it still the same?

 

[king of pipes]

How many radiatord do you have ? Are they all open to allow the flow , post a few pictures of the system . Regards kop