Vokera Linea 24 Boiler Issue, Advice Required Homeserve problem

[PlumbPunter]

Hello Forum,

I am hoping some of you fine professionals can offer me some friendly advice.

Ok, so I have boiler cover with Homeserve. Had issues with them before trying to claim my boiler was a 'beyond economic repair' when all that was required a was £90 part, which was resolved after eventually speaking to a director, and not being fobbed off.

I have a new issue, The hot water on my Vokera Linea 24 is intermittent, IE: When running hot water, it goes cold, then hot, then cold, etc. etc.

So I called Homeserve, they sent the subcontracted engineer who seemed clueless; so I mentioned I had researched the problem on the net, and it was suggested the 'primary thermistor' could be the issue.

Anyway, the same Homeserve subcontractor comes back today and replaces:

a) Primary thermistor
b) DHW Thermistor.

The issue is STILL there, cold, then hot, then cold, then hot.

So the Homeserve guy say's "Well, you must have limescale in the plate to the heat-exchanger, and your Homeserve insurance 'does not cover it".

Hmmmm. This is why I have come here today, to ask your professional opinion.

A few facts:

1) The central heating works fine

2) The hot water goes from hot, to cold, to hot, to cold.

BUT, and this is what caught my attention:

I timed the distance between the burners going on (hot water coming through), and going off (cold water coming through), when running the hot water consistently.

The times are EXACTLY the same between burners on, and then burners going off. Like this:

1) Turn hot water tap on.

a) Burners run for exactly 30 seconds - producing hot water.
b) Burners then turn off for exactly 12 seconds - producing cold water.

And the above times are repeat identically until the water tap is turned off, therefore repeating the cycle of cold, hot, cold, hot, with the burner times being totally consistent.

I would appreciate your thoughts on this, and I would absolutely appreciate your comments as to what the cause is, or whether the Homeserve guy is fobbing me off, due to lack of know-how, before I contact them to dispute their 'diagnosis'.

Thank you in advance.

 

[garrythegasman]

Plate heat exchanger blocked due to debris in ch circuit

 

[dancinplumba]

cancel your contract save money and get a pro in imo

 

[GrahamM]

If thermistors changed that rules them out.
Switch off heating for while till cools down. Do not use hot water either.
Once boiler heating pipes bellow boiler cool, run hot tap. If heating pipes get warm it is a divertor issue. If not it is probable that the plate heat exchanger is furred up.

 

[wnjswozo]

intermittant faults are a nightmare to trace,as a engineer you want the applaince broken down,as these problems can be anything from a aps to faulty pcb to wiring harness,
they will only go so far,as throwing parts at it,will cost a small fortune,hence the uneconomical vaible,if you dont accept this they will,no longer want your business,to be fair they are a poor boiler,lifespan 5-10 years if that

 

[diamondgas]

Hwy PlumbPunter :welcome: to the forum.

Sounds like, as mentioned, your plate heatexcnanger is not working as expected? In all honesty it depends whether its a 24 or 28?
24,,,,,,,, well there ya go ... 28 ..hmmmmmmm needs more investigation ! IMHO

 

[Mbear]

Sounds like a choked plate or sticking div valve, either way there is only (usually) ome cause and that is sludge/iron oxide/limescale basically dirt and debris in the heating circuit

 

[JeffD]

You should no if its a sensor or plate heat its really a basic test

 

[aggis]

If it's the plate h/exch. turn on tap, run hot water till the burner shuts down, imediately turn off tap watching temp guage if it soars upto late 80's or over 90 c it's the plate h/exch.
Which is blocked due to dirty system, if you're going to get it changed, the system will require/must be chemically cleaning, talk to a GSR engineer.