BAXI COMBI 105E. DHW HOT FOR 30 SECS THEN STONE COLD

[TonyElyod]

A Heads up would be appreciated Guyz.

The Microswitch seems to be operational when drawing off water.ie push pin opens/shuts when water is on/off.
But DHW stays hot for 30 secs then stone cold altho Temp Lights show 80C.
Am I right in thinking renew DHW Thermister.???

And Are these Thermisters both the same part Number for CH & DHW, as I bought CH Thermister & replaced but didnt rectify problem from last year, so can I use previous CH Thermister to replace DHW thermister?

And I see DHW Thermister isn,t that easy to get to?
Any tips or "Look Out For!!!..lol

Thanx In Anticipation
Tony

 

[sandybeach]

You'd need a multi meter to check the resistance across the sensors but my guess would be the plate heat exchanger is partially blocked.Poor heat transfer will cause the limit stat to shut the burner off when the primary water temperature reaches 80 degrees c.

 

[ukrobj]

Water to Water hex needs cleaning.

 

[Agile]

Measure the flow and return temps to the plate HE.

Should be about 15 C if its clean!y