Boiler pump turning itself on for 30 second bursts randomly

[ChrisLondon5]

Hi this is my first post here.

We have a gas boiler that serves our central heating and water cistern for hot water. We have a Honeywell dual channel programmer and a Nest Smart Thermostat. Everything has been functioning well for a while but recently we've had this new issue:

When neither the HW or CH are running we randomly hear the boiler start up and make a sound for 30 seconds. I believe this to be the pump running because the gas flame is not firing up, and the noise runs for 30 seconds exactly after which it quickly fades down. This is a slightly different sound to when the boiler switches on properly which is a much louder.

The time the pump comes on for is always exactly the same, 30 seconds. However when this occurs seems to be random. Sometimes it will do it five times in the space of 30 minutes. Sometimes it doesn't happen for hours on end. Seems completely random. I have used the programmer to turn the HW and CH schedules off completely, but the random pump activity continues to happen.

Boiler Model: Myson Apollo Fanfare 15/30 S

Any help would be greatly appreciated. Thank you

Chris from East London.

 

[Dean744PiN5]

make and model of boiler would be a great help, please.

 

[ChrisLondon5]

Boiler Model: Myson Apollo Fanfare 15/30 S

*original post edited.

Thanks

 

[lightning]

Faulty 2 port or 3 port valve

Paul

 

[Wernamgas]

Are you sure it's the pump? The fan on this boiler will come on occasionally for 30 seconds to get rid of the heat from the pilot light. If the noise is only coming from the boiler it's unlikely to be the pump as that is not fitted within this boiler.

 

[ChrisLondon5]

Are you sure it's the pump?

No. I just presumed. Thank you for this advice. If I do have a fan that turns on randomly, what would you recommend as a solution please? This never used to happen...

 

[Wernamgas]

The fan should come on at low speed for half a minute every 5 minutes. If not it could be a problem with the fan timer PCB.

 

[ChrisLondon5]

OK so there is every chance that this has always happened but it's recently just become louder. Maybe the fan is broken or has become loose? Is this possible?

Is replacing the fan an easy job?

 

[Wernamgas]

The fan can get louder with age. I'd recommend getting someone qualified to repair or replace it as it's not a DIY job.

 

[Andehh]

Sorry to bump an old thread, but this is exactly the problem I am having with my Worcester Bosch System boiler, a Greenstar CDI 34kw. Only a year old.

During the night, the pump (or could be the fan?) activates for 30 seconds or so, then quickly dies off and repeats this every 20minutes or so?

The system isn't calling for heat but this only seems to happen after the central heating has been on & has since turned off and the pipes are ''warm'' (but NOT hot) - whether that makes any difference or not.

Last night was one of the first nights the boiler has come on during the night to top up the temperatures and due it it being near the bedroom, is something that is waking me up. ECO Mode is off (where it keeps the loop warm) and the boiler does not ignite itself - something I check at 1.40am this morning!

When I stick my head in the airing cupboard - 5 meters or so from the boiler it does sound like water is being circulated - but the pipe are warm/luke warm at best.

 

[The831Bunny]

The eco light needs to be lit (ON) to turn the preheat off. Eco meaning it uses less gas and electric....

 

[Andehh]

The eco light needs to be lit (ON) to turn the preheat off. Eco meaning it uses less gas and electric....

The ECO button is lit, which I was told meant it was ''off'' by Worecester Bosch last year (never made sense to me, but I followed what she said). Leaving it unlit apparently meant the boiler circulated hot water through the system to improve response times? Does that sound right?

Now it is this pump/fan noise that has unfortunately sparked my curiosity.

 

[The831Bunny]

Y

The ECO button is lit, which I was told meant it was ''off'' by Worecester Bosch last year (never made sense to me, but I followed what she said). Leaving it unlit apparently meant the boiler circulated hot water through the system to improve response times? Does that sound right?

Yes, that's right mate.

Have you got a thermostat you set to an overnight temperature? It may be set to 18C or so and is coming in when the house cools down. You need 15C or less to usually ensure the heating is off on all but the coldest nights.

 

[Andehh]

Y

Yes, that's right mate.

Have you got a thermostat you set to an overnight temperature? It may be set to 18C or so and is coming in when the house cools down. You need 15C or less to usually ensure the heating is off on all but the coldest nights.

Due to our young son, his room is kept at 17 degrees as a minimum, which the room was hovering at for most of the night. We have an Evohome system that allows us to control individual rooms.

I have not yet ruled out the fact that the room was at 17 degrees & stat was set at 17 degrees as a possible cause for these random fluctuations of the boiler. Going to ring Honeywell later and see if it *could* be the slight flicker of the room temp hovering just above & below the stat.

I doubt it is this though due to the regularity of it, the Fan/Pump noise was almost too uniform in how long it sounded for & how often it occurred. It seemed very regular over the 40 odd mins I was stuck wondering about it. The boiler also wasn't firing during this time - something I was checking as well.

 

[The831Bunny]

More than likely the evohome was requesting a very cool flow temperature for just one room and the 'on' time was extremely short. The only way to confirm would be to lower that room temperature if possible.