Heat Line VISO 24 DHW Issue

[MACE1]

I have inherited the boiler with the property. Heating comes on OK with timer or manually and gives good heat. The Domestic Hot water is however a problem as when the tap is on full bore it only then starts to heat and is very cool.
My first instinct is the Flow Sensor as I have had a previous boiler with a similar issue however this boiler is considerably different to anything I have had before and there looks to be only one sensor of this type in the Viso 24.
If it was a thermistor issue I think we would have no hot anything or too hot so need urgent advice to get this working before the cold weather bites !
Suggestions please.
http://www.heatline.co.uk/boilers/assets/products/manuals/Vizo 24 and 28 manual.pdf

 

[kevplumb]

what is the flow rate

 

[MACE1]

The mains water pressure is quite high so on full bore it will fill a bucket very quickly but with barely warm water.
Have to take care to point down plug hole or risk of soaking everything in area.
At a rate that is useable to say wash your hands I don't hear the boiler start up.

 

[Agile]

Turn heating off.

Set hot tap to give 9 litres per minute and measure temperature.

Tony

 

[StevenJames125]

Is this to check the plate heat exchanger is partially blocked up Agile? ...

 

[Agile]

Its for me to help the OP.

 

[StevenJames125]

Its for me to help the OP.

was just trying to work out what that'd prove

 

[kevplumb]

9lpm@35 rise

 

[StevenJames125]

sorry of course - I see.... so obviously if not then a partially blocked plate heat ex possibly

 

[Agile]

A simple test like that can identify the presence of several different faults, either singly or together.

The most obvious is wrong gas settings, a blocked secondary or a scaled primary.

Or the most likely perhaps that the owner has too high a DHW flow rate!

Tony

 

[Slugbabydotcom]

After checking the flow rate isn't too high as mentioned, the next most common fault I find when theres a Hot water problem on these is the HW thermistor.

It's very difficult/ impossible to get to without removing the left hand casing.

This involves exposing the combustion chamber so its an RGI job.

 

[kevplumb]

ye god's it's alive

must be dark

 

[Beerlover]

Most likley a sticking aquasensor p/n 0020061630; however this boiler will only provide sufficient DHW at 9.5 l/min - both need checking.

 

[ColinJac]

Most likley a sticking aquasensor p/n 0020061630; however this boiler will only provide sufficient DHW at 9.5 l/min - both need checking.

Are Heatline good boilers? Some on here say they are not. I have heard they are good and cheap.

The problem at hand. In this case is it worth putting in a 10 litres per minute flow regulator before the combi so the tap cannot be turned up beyond the capacity of the combi?

 

[Paul Barker]

Its for me to help the OP.

was just trying to work out what that'd prove

It proves you know very little, I would ask less questions and listen fully to what is being said instead until you have some wisdom on the matter.