Baxi Duo Tec 40 HE A Fluctuating Hot Water Temperature

[MasterMech]

Hello All,

I am currently having an issue with my Baxi Duo Tec 40 HE A not maintaining a constant temperature for the domestic hot water.

With a thermometer under a tap & the domestic hot water thermostat set to 43 °C I get a fluctuating temperature from 51 °C to 38 °C which is clearly not acceptable as it goes from warm to scalding.

I have uploaded a video of the boiler to YouTube below showing what happens when you create a hot water demand by turning a tap on.

As you can see the burner does not stay on but cycles on & off because it seems to me the primary water in the boiler is getting to hot so the PCB is turning the burner off?

What I have found is that if I turn two taps on at the same time the problem is fixed!

The boiler modulates the temperature correctly & I get around 43°C at the tap give or take 2 degrees.

I have boiler cover plan so I contacted them & they sent an engineer out & so far they have changed the following components:

1. Diverted Valve

2. Domestic Hot Water Thermistor

3. Plate Heat Exchanger

4. PCB

All genuine Baxi parts & I still have the same problem so clearly non of these components were faulty.

The warranty company is now saying that because they have spent all this money on these components & it has not fixed the problem the I need a new boiler!

At this point I have lost all trust in them & the engineers capability to diagnose the problem.

I am currently trying to get recommendations for a gas engineer in my area but am struggling to do so & am wanting others opinions on what could be causing this.

This has taken place over a four month period due to COVID.

Here is the video of the boiler with one tap running creating a hot water demand:
View: https://www.youtube.com/watch?v=f_6SGMUkAU0&feature=emb_logo


As you can see the burner switches on & off causing the temperature to fluctuate.

Here is a video of the boiler with TWO taps running creating a hot water demand:
View: https://www.youtube.com/watch?v=DyzUVARBvdI&feature=emb_logo


& here the burner stay lit constantly fixing the problem!

Any ideas what could be causing this & why it is fixed by turning two taps on?

Many thanks

Adam
[automerge]1592268441[/automerge]
Can an admin or moderator please move this thread to the gas engineers forum please?

Sorry I posted it in the wrong section.

Thank you

 

[Aquarius]

Hi Adam,

I’d be asking to speak to a senior manager or engineer with the cover plan company as it’s clearly unacceptable that you require a new boiler on the grounds that they are unable to repair it. It’s probably a circulation issue, and opening the other tap is an additional outlet for getting rid of the heat from the boiler.