Vaillant boiler noise after British Gas visit

[RBG]

Thank you. From the installation manual and also what BG man has said. You do need a bypass as if both the valves are closed the water has no where to go if boiler and pump are running. This may also account for the f83 issue. The boiler needs flow to dissipate heat from it. If it doesn't have this it doesn't like it

 

[blueplanet]

OK, thanks for your help. Is fitting a bypass likely to take long or is a quick job?

 

[RBG]

Really depends on how it can be fitted in the system in that cupboard pipe access etc How much needs draining or not etc

 

[blueplanet]

Yes, there isn't much space really and its quite tight. I will get some quotes and see if its economically worth doing or do I just need to live with until I either change boilers or move. Thanks very much for your help.

 

[John.g]

Yes, there isn't much space really and its quite tight. I will get some quotes and see if its economically worth doing or do I just need to live with until I either change boilers or move. Thanks very much for your help.

First, the external circ pump should be controlled by the boiler since the boiler PCB tells the pump how long its to run (pump overrun) when all zone valves close, so first check that, whatever method you are using to start your boiler, that the circ pump (and boiler) starts about 6 to 10 secs after you request a start, since its a (end) switch on each of the zone valves should do this once any zone valve is fully opened.
There should be a external ABV (automatic bypass valve) installed between the boiler flow and return to cool down the boiler heat exchanger when all zone valves close and gives a circulation path to do so. However this should not cause any noise problems or flag any alarms during normal operation or during start up since the boiler and pump do (should) not start until one of the zone valves are fully open, You may get kettling noises and ultimately damage the heat exchanger from the boiler on shutdown if no ABV installed.

Also suggest increasing the pump speed from 1 to 2.

 

[blueplanet]

Thanks John.g. I will check the start up time when I return home later and report back. Unfortunately, there is no ABV installed on the system. I will also turn up the pump speed.

 

[John.g]

Thanks John.g. I will check the start up time when I return home later and report back. Unfortunately, there is no ABV installed on the system. I will also turn up the pump speed.

What you might also consider doing sometime is, (ensure HW cylinder not calling for heating, switch off) with the CH is on and calling for heat, boiler on, switch off the CH demand or turn down the roomstat to shut down the boiler, see does the circ poump run on for a few minutes, 5 minutes is its default overrun time. Manually latch open the CH zone valve then refire the boiler, check for any noise or boiler codes.

 

[blueplanet]

Update: I've been away and since had BG turn up again and this time changed the flow and return sensors on the boiler. They also changed the pump head for the newer UPS 3 model. However, it made no difference. The f.83 fault does still appear and it seems to be happening when the water temperature drops below 12c - that is the threshold for the frost protection to circulate water.

I still need to do the test John.g suggested and will update again.