Logic Combi C24 - loud noise every hour

Ingo23

Hi,
We recently had a Logic Combi C24 installed. We haven't had any problems but recently we noticed that every hour it makes a loud noise for about 5 - 10 seconds. Not sure how to describe the noise but it's quite loud, starts suddenly and then stops and as I say it happens every 60 minute.
Anyone have any idea what it might be?
Thanks

K.Flyer

Ingo23 wrote: »

Hi,
We recently had a Logic Combi C24 installed. We haven't had any problems but recently we noticed that every hour it makes a loud noise for about 5 - 10 seconds. Not sure how to describe the noise but it's quite loud, starts suddenly and then stops and as I say it happens every 60 minute.
Anyone have any idea what it might be?
Thanks

It is caused by the Hot Water pre heating system in the boiler being left on..

Summer conditions - i.e. DHW (Domestic Hot Water) only required.
Set the mode knob control to Summer (tap symbol).
Set the CH external controls to OFF.
Preheat will operate with the preheat switch (A) set to ON.
The boiler will fire periodically for a few seconds to maintain the DHW calorifier in a preheated condition. The average time period between firing is 90 minutes. This may vary considerably due to the surrounding ambient temperature of the boiler. The boiler will fire whenever there is a demand for DHW.
The boiler preheat facility can be immobilised by turning the preheat switch (A) to OFF. This will stop the boiler operating for short periods.

Ingo23

HI,

Thanks for the reply. There is a pre-heat option on the controls which is set to off at the moment but the noise continues. So, if I move the knob to the tap symbol (as opposed to tap and radiator) there'll be no heat from the radiators but the noise will stop?

Thanks

K.Flyer

The pre-heat is for the hot water part of the system, so seeing as you already have it switched off then thats not the issue.
Is it a loud knocking type of a sound?
What is the pressure reading on the pressure gauge?

Ingo23

Hi,
Yeah, it's a quite loud knocking sound which happens whether the system is on or not. The pressure gauge is under 1

K.Flyer

Ingo23 wrote: »

Hi,
Yeah, it's a quite loud knocking sound which happens whether the system is on or not. The pressure gauge is under 1

With a random knocking sound I would have thought the system may be over-pressurised with the filling valve left open and the noise was the pressure relief valve opening and shutting.
Keep a watch on the gauge over an hour and see if it is creeping upwards towards 3 bar.
Either ways, it sounds like you need to get a Registered Gas Installer to look at it.

Ingo23

Ok will keep an eye on it. Thanks for your help.