Baxi 105 HE combi boiler question

VEEMAN_3

Hi i wonder if anyone can provide me with a liitle bit of information. I have the baxi 105 He combi boiler which has developed a fault. Can any one confirm to me that when the central heating fires the boiler, reaches the room stat temperature, boiler shuts down , pump over runs. I know the pump over runs for a short period, but my pump runs constantly until the boiler fires up again with in 2 mins. It seems to me that the pump is going all the time. Pump housing is getting very hot due to this.
Is this constant pump running a charateristic of this boiler? Any one with any thoughts.
Hot water functions are working fine, as well as the rads are heating up o.k.
Cheers
Veeman

Canucklehead

Hi

Pump will stop after overrun if the room stat is satisfied.
If the boiler fires up again after two mins. then the stat is not satisfied.
You either have a faulty stat or pump overrun stat.
You could also have no or insufficient bypass.(pump cannot dissipate the heat so will run and run, AKA dead heading.)

Corgi Guy.

VEEMAN_3

Thanks for the info it's appreciated. Can you please expand on the following:-
1. I could put the link back into the boiler wiring and remove the room stat from the cct. Then try the boiler to eliminate the stat.
2. Where do you locate the over run stat? Is this the CH temp sensor, if so have already renewed it.
3. Your comments on no or insufficiency bypass. Would this cause the pump to heat up enough for not to keep you hand on it. I've noticed that the pressure does not increase as the boiler temp increases. Do you think the impellor is jammed with crud and not allowed to rotate, hence worth pulling out to have a look, or just renew the pump.
Once again you effort is appreciated.
Cheers
Veeman

Canucklehead

Hi

It sounds as if you have no programmer or it's faulty.
As Agile says it's working properly as it will fire up every few mins. like it's supposed to when there is a call for heat.

Now you say you've changed the ch stat and the pressure gauge doesn't move.
This suggests that you have either (and there is no suggestion otherwise)....
had the boiler fitted by a DIYer, or a cheap, unregistered/incompetent fitter: either way the system was probably not flushed . If this isn't the case
You need to spend the money you saved on the installation to get it up to scratch and it might work for few trouble free years.

Corgi Guy.

VEEMAN_3

Thanks for your reply once more. As for the installation, was done by corgi registered plumber and certificate was issued for installation. I watched him install the combi, and remember that he flushed the system with a susbstance in a bottle, drained the system and put inhibter in the system when it was refilled.
Today I linked out the room stat and put the boiler back to if there was no room stat fitted. Used the boilers controls, boiler fired up , pump ran, temp went up to 70 degrees on display. Heating ran then shut down once the temp of the water in CH system had reached the required temp. Pump kept running, temp dropped to 60 degrees boiler fired back up. Same situation as with room stat fitted.
So if you say programmer, are you refering to the PCB?
As to my original question, does the pump shut down after a short period once this heating sensor reaches the 60 degrees ( stop boiling in the heat exchanger) until the room stat requests the boiler to fire back up. I assume I'm correct, but could be shot down in flames!
Thanks once more for your answers it's appreciated.
Cheers
Veeman

Canucklehead

Hi...after the installation was completed your 'installer' should have explained the workings of the boiler and associated controls: if you look in your Benchmark book gas commissioning checklist you will see the relevant sections i.e. 'For all installations confirm the following...'
PCB= printed circuit board
Programmer= central heating controlled by time clock to your desired settings. Check your boiler manual for further details or ask your CORGI to explain all when the boiler has an annual service.

Corgi Guy

VEEMAN_3

Had the corgi guy round today and explained all the controls ect after the boiler service. So a quick note to thank you for all your suggestions and help in my boiler problem.
A happy New Year to one and all.
Cheers
A warmer VEEMAN