Combi DHW goes hot/cold/hot etc

[StevieV1]

Hi

I have a Potterton Performa 28 that is about 4 yrs old. Recently I have noticed that the shower goes hot/cold/hot/cold (thermostatic bar type). Other hot taps do similar but not as noticeable as the shower.

Now if I turn the flow down the situation improves so having searched on here and other forums the heat exchanger is suggested as being clogged up. My boiler has two, a plate HE at the bottom and another HE at the top. My question is which one is it likely to be or could it be both.

I am not a corgi person, but feel confident that I could remove both if need be, clean and reassemble.

Thanks in anticipation.

Steviev

 

[twgas]

plate h/e, replacement is preferable, but system cleaning may also be required/advisable

 

[StevieV1]

Thanks for that.

Whats the difference between them anyway?

Steviev

 

[Agile]

Thanks for that.

Whats the difference between them anyway?

Steviev

Presumably you mean the two HEs ?

If you dont know the answer to that question then I certainly dont think you would be competent to replace the primary HE as thats part of the gas train. Luckily its most likely to be the secondary which is the problem.

The primary HE transfers heat from the flames to the system water.

The secondary HE transfers heat from the system water to the hot water supply.

Tony

 

[StevieV1]

Thanks

Steviev

 

[SortedPlumbing]

change them before you even look at plate h/ex

could save u a small fortune

 

[lagunaglen]

Before changing heat exchangers have you checked the thermistor,i would test with a multi-meter first against manufacturers readings,these only cost about £15 .

 

[ChrisR]

change them before you even look at plate h/ex

I'll bet a quid it's not the sensors! The secondary h/ex for one of these isn't expensive - hardly worth trying to clean it.

 

[StevieV1]

Thanks for all your replies.

Ive found I can buy a new plate HE for about £40 so ill order one.

Thanks again

Steve

 

[StevieV1]

Had the new HE delivered today and just fitted it. Seems to have fixed the problem.

Many thanks for all the advice

Steviev

 

[Agile]

change them ( sensors ) before you even look at plate h/ex

could save u a small fortune

Just as well you did not take his advice !!!