Vokera Linea 24.Intermittent on hot water

[fabio]

Working on voker linea 24 today.the boiler worked fine on the ch mode but when the hot water was turned on it would only run for about 1 minute then cut off and start again after about 20secs??i checked the dhw thermister,flowswitch and diverter valve...all working ok?? i have been told that there can sometimes be a blockage in the plate heat exchanger which can cause this fault?Any one had this problem before?.Thanks guys......

 

[Puddle]

As it is working ok on heating and problem only on hot water it does sound like the boiler is over heating due to insufficient circulation or no modulation, all plate heat exchangers can block up on a dirty system and it does not take a lot cause problems, double check thermistor resistance, then looks towards plate maybe

 

[aggis]

Easy test on the Linea, turn on hot water tap watch boiler, when burner goes off imediatelly turn the cold water valve under the boiler off. If the temparature guage reads @ 90 degrees c. it's the plate h exch.[guage reads water temp when tap running & boiler temp when off or heating in use.] More than likely the system will also req' flushing, note it on job sheet if customer doesn't want flush, as it prob' going to block again!!

 

[bringaling]

Hi, I realise this is an old thread, but I came across it on a google search, it seems relevant to my problem so I didn't want to start a new thread!

I have a Vokera Linea 24 with what seems to be a similar problem:

My central heating is working fine, but when I try and use a hot tap or shower the boiler fires up, the temp gauge creeps up, reaches 38degrees or so, then falls back to 18ish, While it does this, it sounds like water isnt flowing freely through it and the pressure gauge wobbles. It repeats this process until eventually cutting out and giving me error code '02' which the manual says is an overheating problem.

I tried the last posts suggestion of turning the cold water valve as soon as the burner stops firing and lo and behold - 94degrees, which presumably points to the plate heat exchange (as suggested in the post). My questions are:

If it is the plate heat exchange, what is causing it? and is it something I can tackle myself?

Having read the internet and obviously now knowing all there is to know about all boilers and there nuances I'm assuming that it's failing due to scale build up? If so, can I simply remove the part,e descale it and refit? And is there anything I can do to prevent it in the future? Is "Flushing" a process I could tackle aswell? I have seen kits online, and other forums have suggested they are hireable.

If you guys think it is definitely not something anyone other than a trained professional can do then obviously I'll get one in, but money as ever is tight so if I can do it myself I would prefer to!

Alternatively has anybody got any other suggestions as to why my boiler is behaving like this?!

Awesome forum by the way, virtually all my internet searches landed on this site so you guys are obviously doing a good job!

Cheers.

 

[Billy Bob Bob]

well it would point to 94 degrees if you turn the water off to it a instant overheat,a better test is to carefully touch the flow pipe to ch if ch off for a while and calling for dhw only if very hot its dumping down plate heat blocked or diverter jammed in either case you need a gas safe engineer to check it out

 

[pobsdad]

There should be at least 20 degree between primary and secondary water if the 'plate' is clean.Get an engineer in,you realy don't want to be trying to clean out a heat exchanger if you don't know what you're doing!