Vokera Linea 28 - Hot Water Problem

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Hi
in the last 5 months, my Linea 28 has been driving me mad. The CH works fine, but HW [sometimes] fluctuates between normal temperature and freezing cold. The problem is worse (although not exclusively) when the cold tap is running too.

I\\\'ve also noticed that the temperature on the boiler gets to 54 degrees before cutting off the heat, and then kicks in again once the temperate reaches cold.

I\\\'m not an engineer and dont know much about boilers, but I\\\'ve had a BG Engineer out twice now, and the 2nd time he suggested it might be something to do with the pressure in my house being too low. I assume the pressure hasnt changed during the last 5 months, but dont really know what to suggest/illustrate to counter argue.

Can anyone suggest a list of ideas/possible solutions that I can suggest to the engineer the next time he comes out, which will be very soon?

Eternally grateful for any suggestions.

Many thanks
 
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Well you would tend to think thermistors but I would imagine that has already been tried.
 
I once had a somewhat similar problem which was down to the Air Pressure Swich In that case a bang with the screwdriver handle followed by a few blows/sucks on the tubes and it was working once again -permanently too. Now that cure was one that did not immediately come to mind!

I assume you have a contract with BG and you are not paying BG for every callout!!
 
There is a well know large heating service company that does not hire a lot (if any) experienced engineers but in stead unskilled people who then get trained on the job. The easy way out in a lot of cases is to blame it on lack of pressure in the mains. Personally I have never, no never, seen a boiler fail due to lack of pressure. Lets face it, most boilers work fine on 0.5 bar that equals 5 metres of static column. If you don’t have this, chances are it won’t be enough to reach the tank.
If the hot water goes from hot to cold and back again it is usually a blocked secondary heat exchanger.
 
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the problem you have is very common,the secondary heat exchanger is partially blocked.remove the unit this takes about five mins.flush out by alternating the flow i use an old washing machine tap hose witch fits on to the heat exchanger.after flushing put the heat exchanger in the oven on medium heat this cause the metal to expand and the rest of the dirt to come away from the unit. repeat flushing can take upto half an hour .you might want to do this to the primary exchanger.before refitting top up with a cleaner/'restorer witch can be left in for a week.reflush the whole system.then fill with an inhibitor in all ittakes about 2-3 hours
 
may first be worth replacing / cleaning the non return valve in the flow to the hw heat exchanger.
 
Many thanks to everyone for your help! Much appreciated.
:D
 
If your pressure is very low then the HW will collapse when you turn a cold tap on.
Scale in heat exchanger(s) sure, leads to hot/cold/hot. Much quicker to clean if you use a descaling chemical.
Like Oilski said that temp is low - does it go higher on CH? It would be worth checking the sensor(s) (= thermistors).
 
Hi guys

I've had a Vokera Linea 28 for 5 years.
The last few months I've had problems with hot water. It would keep cutting out at 51.c.

After doing a search and finding this thread, I set about cleaning the heat exchanger. It was removed after partly draining system, and removing the two pozi screws. (crutial info for me).

After descaling and refitting my boiler works great!.. it's like new.. :LOL:

Big thanks to thoose who created, and contributed to this thread.

Prag..
 

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