Secondary heat exchanger.

[Knappers]

Personally I’d be checking the DHW NTC sensor

I think that one's just a heat exchanger

 

[Mastermixlee]

I think I’m going to get the secondary heat exchanger changed on my Baxi Platinum 28HE as my heating engineer has already cleaned it out a few year ago. My hot water is now once again fluctuating warm/hot as it did before. As a point of curiosity is there much difference between a 16 plate and 20 plate replacements available. Just trying to keep cost’s down too, thanks for any replies ?

As others have said I'd let the GSR engineer get the parts as the heat exchanger is sized to Rubbish the specific design and output of the boiler it is fitted to. Multiple different sizes of plates normally just indicates there are various output models of that boiler range.

Fitting a different type can negatively impact performance.

Also as mentioned get a filter put on at the same time. The system will already be drained for plate replacement so best to get one fitted at same time.

 

[EvilDrPorkChop]

Personally I’d be checking the DHW NTC sensor

Also had it before where the DHW temp fluctuates and it's the DHW NTC sensor. You can tell this as the burner is constantly modulating other than getting up to 80oc+ then cutting off and firing back up.