Vokera linea 24 .. DHW goes hot and cold

[spannor]

Hi matey,
thanks for the reply. done the test again and yes 92c at cut out... just to add. i was watching the digital temp gauge on the boiler and the temp goes up pretty quick to approx 62c then cuts out ....but the water coming out of the tap stays cool. the central heating is running fine. also when i drained the system i had to bleed the pump up now i cannot remember if the dust cap ontop of the pump should that be tight closed or left open?

thanks again

just to add could it be a thermistor thats gone ?? due to the temp going up fast but cold water at the tap??

 

[Andygasman2010]

Nope it's not the thermistor, i'm affraid you have a blocked plate heat exchanger again.

 

[spannor]

hi matey,

yep your right. i stripped it down and took the plate out and it is full of black flakes . i have flushed and banged it and flushed it and blown it through and its working again. but for how long is anyone guess.

i am thinking of fitting a magnaclean set up. will this prevent it.

thanks for the info mate

 

[jezsherwood]

On a similar note.

My linea 24 is doing the same but with the boiler switched off on the front panel but mains power still on I can hear the diverter valve cycling and clicking.

Is it just a bad diverter valve?

ta

Jez.

 

[Happyplumber]

flush the system and put a spirovent maganabooster on the system to stop any magnetite getting into the boiler

You have very dirty system and need a filter all that magnetite going around the boiler is damaging other componets as well the rubber o rings and you need to sort this properly,before more lasting damage happens to other critical parts

 

[jezsherwood]

Thanks Happyplumber

 

[martineire]

To be more helpful on this situation, and find out if your plate heat exchanger is needing cleaned or replaced, try the following.

Make sure hot water thermostat on the boiler is up as high as can be, then turn hot water on at whichever tap you seem to think it affects the worst.
Now under your boiler you have a lever to the right on your cold mains pipe, it should be facing vertically upwards at this point, keep your hand on it, DO NOT move it at this stage, now watch the burner and as soon as it cuts out, turn the valve your holding anti clockwise 90 degrees, that will shut your hot water off, which is fine. As soon as you have done that look back to the display l.e.d on your boiler and what temperature is it showing now?

I am guessing 93 .

don't forget to turn it back on again though XD. Good luck.

I was just having a read of this old post and was just wondering can anyone please tell me in more detail how this test tells you if the plate needs cleaning or replacing? Say if the temp just rised to 75 degrees

 

[Agile]

The display shows the water temperature during hot water useage but the flow temp when DHW demand stops.

Wrong words were used in this thread.

The plate HE and EITHER be cleaned or replaced.

Tony

 

[martineire]

So in other words when mains is turned off if there was a good flow through the plate (ie not blocked) the temp would not rise to 85+ degrees. The plate just needs a clean.

 

[Agile]

If the plate is not blocked the flow temp does not go much above 65 C.

 

[DP]

During HW delivery, even with blocked HW heat exchanger, the digi display will not show 85 degrees.

 

[timhut]

My linea 24 boiler is playing up.

Firstly, the hot water starts, and when the temp gets to 38° ish, the burners cut, the temp drops down to 27° ish, then the burners start again. Sometimes error code 04 flashes briefly, sometimes error code 03 flashes briefly. This happens irregularly, but it's rare to have a shower and it not do this at least once.

I have tried the test to see if the DHW heat exchanger is bloked by waiting for the boiler to cut before shutting off the hot water. The temperature reads about 70° when I do this. Does this mean the DHW heat exchanger is ok?

Secondly, the central heating regularly seems to have trouble starting. It starts (from cold), and the temperature begins to rise, before the boiler cuts, breifly showing error code 03, sometimes error code 04, before the boiler starts again and repeats the process. Eventually the boiler stays lit and the temperature climbs steadily setting at about 59° with eveything running smoothly.

I recently changed the pressure differential switch, to (hopefully) solve the problem I describe below, but the weather has not been cold enough yet to fully test. I post the following problem description just in case it's linked to the heating/hot water problems I describe above.

During the last winter, when starting from cold (on the timer) the boiler would often fail to start, and i'd find it flashing error code 04. Switching it off and on again, it would sometimes run the fan for a few seconds, never starting the burner before stopping and showing error code 04. Switching off and on again a few times, it would eventually start up ok!

Hope someone can help!