Clicking noise from Ri gas boiler, could it be a relay problem?

Question from William Heath, via email:
We have a greenstar Ri gas boiler, when the boiler turns off there is a clicking noise from the boiler which can last some 20 minutes?

It sounds like a relay turning on and off about every second. Could you please advise?

The boiler is about 7 years old and serviced 2011 before we moved in to this bungalow.

Thank you,


Answer from Martyn Bridges, director of marketing and technical support at Worcester, Bosch Group:
From your description it suggests that you may have a Y-plan system that is providing an electrical back feed back to the boiler which is making the PCB on the boiler respond. Unfortunately, with some of the older control systems – specifically the 3-port zone valve systems – even when the hot water and heating demands are satisfied, there is a voltage fed out of the wiring centre to the boiler. This voltage is insufficient to ignite the boiler but sufficient to “spike” the PCB.

To counteract this we have produced an optional extra which will ensure this electrical back feed does not get back to the boiler, this can be ordered from a spares stockist and is part numbered 8-716-109-275-0.

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