Another Vaillant boiler problem

[mtecally]

Hi.Hope some nice person can help with this

I have a vaillant turbomax 828e boiler around 5 years old.The CH works fine however the HW is only slighty better than luke warm.

I have checked the divertor valve and it appears to be working ok.I also did a test wherby i switched the heating off and let it cool down then checked to see if the HW was was leaking past the valve.The pipe stayed cold so iu have eliminated the valve i think.

My next port of call is the heat exchanger which i plan to remove a flush through.I live in an area which does not suffer from hard water so i was unsure if there would be a build up in the exchanger.

The Boiler will produce reasonably hot water provided the flow rate from the taps is kept low however when the tap is turned on more the boiler cuts of and then refires.This cycle will then continue and the water will become cold.

My theory is that the heat exchanger is partially blocked and the over heat sensor is cutting the boiler off( due to a lack of available water).

Is this theory/solution possible or i am i talking non sense.

Any Help much appreciated.

 

[bellairaphon]

whats the temp showing on the display when you have the tap on full. another possible cause could be the ntcs

Nath

 

[petit_pablo]

Your on the right track but the hw heat exchanger will be blocked with system debris not scale on the mains side.

If its bad it might be worth your while investing in a system filter like a magnaclean or spirovent

 

[mtecally]

whats the temp showing on the display when you have the tap on full. another possible cause could be the ntcs

Nath

Hi

Just put the tap on full the temp rises to 86 then boiler cuts and the temp drops back

 

[petit_pablo]

Still points to it being blocked

 

[mtecally]

Your on the right track but the hw heat exchanger will be blocked with system debris not scale on the mains side.

If its bad it might be worth your while investing in a system filter like a magnaclean or spirovent

Hi

Yeah i had considered a magna clean.Is this more or less an in line filter for the mains water to prevent rubbish entering the boiler.

 

[mtecally]

Still points to it being blocked

Once i have removed the exchanger will flushing it through with water disolve any build up or would a descaler product help with this

Thanks

 

[petit_pablo]

Its a filter for the CH system. Goes on the heating return pipe and stops alot of debris getting into the boiler and blocking the HW heat exchanger.

 

[bellairaphon]

and is it the same when you select central heating only too and very quick rise in temp? there is a black hose on the left hand side that can become blocked.

Nath

 

[mtecally]

Thanks.

looks like i will do this tomorrow night.

Ps I assume that i will have to drain down the full system for this.

 

[petit_pablo]

OK stop with the scaling idea!

Its most likely iron oxide blocking the system side of the heat exchanger. Ive never seen one blocked with scale and ive worked in hard water areas before.

You should be able to clean it with mains water and some tapping. You want to get the bits out the same way they came in. The heat exchanger will have arrows on it like this >>>>>>>>. Flush through the opposite way.

 

[petit_pablo]

and is it the same when you select central heating only too and very quick rise in temp? there is a black hose on the left hand side that can become blocked.

Nath

Not on a turbomax there isnt, thats the newer ecomax

 

[petit_pablo]

Thanks.

looks like i will do this tomorrow night.

Ps I assume that i will have to drain down the full system for this.

Turn off mains under boiler and open hot tap. Shut off isolation valves under boiler and drain boiler. Vailliant valves dont tend to leak.

 

[mtecally]

and is it the same when you select central heating only too and very quick rise in temp? there is a black hose on the left hand side that can become blocked.

Nath

Switched the heating off for 5 mins then back on the temp rises steadily up to about 68

 

[mtecally]

OK stop with the scaling idea!

Its most likely iron oxide blocking the system side of the heat exchanger. Ive never seen one blocked with scale and ive worked in hard water areas before.

You should be able to clean it with mains water and some tapping. You want to get the bits out the same way they came in. The heat exchanger will have arrows on it like this >>>>>>>>. Flush through the opposite way.

Sorry... by scaling i really just meant foreign material lol.
Great i was hoping that i didnt nead to drain down the system.

Thanks