Vaillant boiler noise after British Gas visit

[blueplanet]

Hello I have a Vaillant Eco Fit Pure 418 boiler. It was installed in 2021 and was not used mush for one year. It has been used since but I am a very low user and I had a solar thermal system until last year so the boiler has seen minimal use.

More or less when it gets cold I get two fault codes F.83 and F.72. The system is mains pressured with an unvented cylinder. The boiler was in excellent virtually new condition. It operated quietly and efficiently and I could barely hear it when on. I called British Gas due to the two fault codes and they could not identify the cause of the fault codes.

The engineer opened up the front case, and removed the black pipe on the left side to access something. Other than that I do not know what else he did. I do know he adjusted the temperature control on the cylinder and turned it up to 60c.

However, after he left the boiler is now noisy. It makes a constant humming and whirling sound. Before when it switched on it would power on, display an egg timer and about 20 seconds fire up but remain nice and quiet when running.

Now, it powers on and fires up quickly, with what sounds like perhaps a fan running constantly, it makes this noise continuously while operating, the fan (or whatever it is) seems to run for about 2 minutes after it switches off. The noise is irritating and at night prevents me sleeping (bedroom above boiler).

Any idea on what has caused this or what the issue is likely to be? I've raised it with British Gas and then are to send someone else over but that is taking time. Thanks in advance.

 

[John.g]

Can you check the flow/return temps, D.40/D.41 preferably with the boiler off.
Could be a flow or return sensor fault, surely they tested the resistances of both?.
Does the circ pump run as soon as you start up?.

 

[blueplanet]

I will check and confirm the D40/D41.

BG attended again today and could not locate the issue. The engineer did say he had checked the flow and return though. He has ordered the following parts simply to eliminate them (although he says they seem to be fine) as the cause:

H28706 Sensor NTC C/H 2
738133 PCB 1

 

[John.g]

And, of course, the obvious, if a OV system, check F&E cistern has water in it, and if pressurized to 1.0/1.5bar if sealed.

 

[blueplanet]

And, of course, the obvious, if a OV system, check F&E cistern has water in it, and if pressurized to 1.0/1.5bar if sealed.

Its a sealed system, unvented cylinder running off the mains. The flow return temperature when off were: D40 - 24c and D41 - 19c. The pump comes on when the boiler is switched on but before it fires up if that makes sense. Also the pressure is correct at around 1.25 bar. Thanks for your help.

 

[John.g]

Its a sealed system, unvented cylinder running off the mains. The flow return temperature when off were: D40 - 24c and D41 - 19c. The pump comes on when the boiler is switched on but before it fires up if that makes sense. Also the pressure is correct at around 1.25 bar. Thanks for your help.

Yes, quite normal for the pump to come on before fire up. Not sure if you mean (from the below) that the boiler does run continuously and the noisy operation carries on for a further 2 minutes?, a normal, programmed off or roomstat/cylinderstat satisfied off means the circ pump will run on (pump overrun) for whatever its setting is, (D.01), I think the fan runs on for maybe 10secs or so as well but not sure.
Can you alternatively check between D.40/D.41 a few times while the burner is firing.

"Now, it powers on and fires up quickly, with what sounds like perhaps a fan running constantly, it makes this noise continuously while operating, the fan (or whatever it is) seems to run for about 2 minutes after it switches off. The noise is irritating and at night prevents me sleeping (bedroom above boiler)."

 

[blueplanet]

I ran the boiler for about 30 mins. The D40/D41 readings (once heated up) were consistently D40 - 57 and D41 50. Occasionally, 57 and 49.

It terms of the noise since the BG engineer attended the boiler has been noisy.

Before: It was quiet, it would turn on and then for about 15 seconds remain you would see an egg timer but it would not ignite the gas. Then it would ignite the gas and then continue operating but was quiet. You would not hear the fan going but it worked well. When the boiler reached the programme end (say 30 mins or 1 hour) it would turn off.

Now: when you turn it on the gas seems to ignore almost instantly. however, as soon as it goes it seems like the fan starts and you hear a constant humming or whirling sound. Its very annoying and the boiler is now not quiet. On the bedroom above you cannot sleep because of the noise. When the programme reaches the end of the 30 min or 1 hour the fan seems to operate for about 2 minutes afterwards.

 

[John.g]

I ran the boiler for about 30 mins. The D40/D41 readings (once heated up) were consistently D40 - 57 and D41 50. Occasionally, 57 and 49.

It terms of the noise since the BG engineer attended the boiler has been noisy.

Before: It was quiet, it would turn on and then for about 15 seconds remain you would see an egg timer but it would not ignite the gas. Then it would ignite the gas and then continue operating but was quiet. You would not hear the fan going but it worked well. When the boiler reached the programme end (say 30 mins or 1 hour) it would turn off.

Now: when you turn it on the gas seems to ignore almost instantly. however, as soon as it goes it seems like the fan starts and you hear a constant humming or whirling sound. Its very annoying and the boiler is now not quiet. On the bedroom above you cannot sleep because of the noise. When the programme reaches the end of the 30 min or 1 hour the fan seems to operate for about 2 minutes afterwards.

The noise problem and any sensor problems should be unrelated, the dT, 24-19, 4C, boiler off, theoretically should be the same but the boiler may have to be off overnight for this to happen, the dT, 57-50. 7C, boiler running, seems reasonbable enough, but changing the sensors (+the PCB) might show up something, whatever about the noise. issue.

 

[DevsAd]

Hi BluePlanet.

I'm guessing the service guy turned off the anti-cycling feature; Vaillant Anti-Cycling Mode Explained - Compare The Boiler Market - https://comparetheboilermarket.co.uk/vaillant-anti-cycling-mode possibly as part of the service and checks.

Why this might cause additional noise, tho', haven't a scooby. Where's the pump - in the airing cupboard? Could you check what speed it's at?

 

[blueplanet]

The Pump speed is set to 1. The pump is a Groundfos UPS 15-50 circulator Pump SELECTRIC.

The BG guy turned up and did not replace the sensors or the PCB. He called Vaillant and they claimed 1) wiring issue between boiler and pump 2) when Boiler's frost protection kicks in, the pump does not trigger the valve to open.

BG claimed "the pump wont trigger the valve to open as that is controlled by the thermostat. Basically its a fundamental design fault by the installer. " I've so many posts of Vaillant making excuses and this seems like another one but I would welcome thoughts.

 

[blueplanet]

I have given this more thought. I live in a modern house and it is highly unlikely for the temperature to drop significantly. However, what makes the pump and honeywell valve turn on? The BG guy said the honeywell valve will not operate while the thermostat is not switched to go on. I thought the boiler triggers the pump and then that water going pushes the honeywell valve on.

Vaillant claim that the honeywell should have bypass and its a design fault. This seems nonsense to me. I would welcome your thoughts.

ps. The BG gas referred to the pump in the airing cupboard but there is also a pump in the boiler.

 

[RBG]

Hello, Just to confirm. You are saying there is a pump in your boiler and also a pump for the central heating in the airing cupboard?

 

[blueplanet]

Hello, Just to confirm. You are saying there is a pump in your boiler and also a pump for the central heating in the airing cupboard?

The manual for the Ecofit Pure 418 refers to a pump in the boiler

 

[RBG]

do you have a link to the manual or a product code for the boiler? all i can find is
ecoFIT pure 412 - 435 manual and it is a heat only / regular boiler i.e. without a pump in it

 

[blueplanet]

I think its the same one. here's the manual: https://www.freeboilermanuals.com/assets/pdf/vaillant/ecoFITpure1.pdf

Looking at the picture again there is no pump - my apologies I must have been looking at the wrong manual first time.

 

[RBG]

No problem. So basically the only pump is in the airing cupboard. The sequence of operation is the the boiler is last on the line, before that the pump and before that the zone valve.

Timer - stat - zone valve - pump boiler

So yes if the stat is "off" then you won't get anything from valve as BG says

 

[blueplanet]

Thanks. So I do not operate it on a timer. I use a drayton wiser kit and turn the hot water or heating on via an app - like say 30 mins before I return home. Other than when I select it to go on it is off at all other times. What appears to be happening is that the boiler turns itself on (I assume the frost protection but could be other reasons). It seems from my Octopus App that there is some small gas usage. Then in the morning I notice the F..83 fault displayed.

Thus if the boiler is kicking on by itself it may not be getting the flow into it and thus must switch off. I've noticed this issue tends (but not always) to be when the weather is colder. So the BG guy is saying I need a bypass so that when the boiler switches itself on it needs to have water flowing into it and that the honeywell valve is not opening as its operated by the thermostat. Does this make sense? Would you agree with the analysis? Is there a simple fix? Thanks again.

From the order you have quoted "Timer - stat...." it seems that the boiler should come on, that activates the pump and the water should trigger the honeywell valve to open. Is it likely that the honeywell valve would remain closed?

 

[RBG]

As you have an unvented cylinder you will have at least one 2 port zone valve. I am assuming that the other zone valve for you central heating is also a 2 port. And so that you have 2 x 2 port zone valves. Can you confirm?

 

[RBG]

From the order you have quoted "Timer - stat...." it seems that the boiler should come on, that activates the pump and the water should trigger the honeywell valve to open. Is it likely that the honeywell valve would remain closed?

No, the water does not trigger the valve to open The valve opens and then the pump runs. The valve is open electrically / mechanically not by water

 

[blueplanet]

Here's some photos. Cylinder 1 is of the system. Cylinder 2 - I have marked the two valves. One is a Honeywell silver thing. The other is a Drayton (cannot recall of 2 or 3 port but will confirm later). Also attached is a close up near the pump.

 

[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.