Baxi duo tec2 ga 28 kw combi hot water temp fluctuating .

[Allgoode]

Hi guys,
Was at a customers recently & they had problem with fluctuating hot water temperature.

On the initial repair visit I changed the hall sensor & the flow turbine as this was quite cruddy when I dropped it out to check condition.

New one came with brass block so just removed old one from block, vacuumed out block area for debris & fitted new item to it.

Once done I re-tested boiler & all was running ok.

Been a couple of weeks now & had a call - water on blink again.

Checked thermisters at 25degree's & were reading 9.65/9.72kohms against 10k/ohms guide.

Checked signal from hall sensor & showing 4.99vdc so ok there.

No fault codes at all displayed but boiler slightly slow to light up from demand input although displays hot water demand as soon as tap turned on & flow is above 2lpm.

Location in a soft water area - Cornwall.

Any ideas gratefully received as its getting on my goat & I like to get to bottom of this.

Thanks,

Andy

 

[SavageW]

If you run hot water tap are you getting the MI's flow rate to temp rise ok? If you then leave the tap running for a period of time is the boiler constantly alight, or does it shut down an then re light (giving you the fluctuation in hot water) the delay in responding to demand could be that it has a preheat function so that the boiler may not actually light until the tap has run for some time as there is a small store of preheated water.

 

[townfanjon]

What temp difference are you getting in and out of the plate ?

 

[RoryD]

As implied above, there's a good chance that the plate to plate heat exchanger is blocking up. That would have the boiler cutting out and re firing. Also often overlooked is the DHW filter.

 

[king of pipes]

I would drop the plate heat out to check for debris on the heating side , i place it in a bucket and fire water through it with a pressure washer i even took one to a local garage once and used their jet wash to flush it through you will be suprised what you get out do it in a bucket though . Cheers kop