Vaillant Turbomax Plus 828e - no hot water, CH OK

[Faisal]

Had a problem with our boiler today - managed to fix it.

FYI

Problem:
1. No Hot Water - on Demand (When Tap is opened), water pressure higher than normal.
2. If pre-heat is on - water is heated automatically whilst tap is closed, when tap is open there is hot water for about 10 seconds and then freezing cold water.
3. Central Heating Working.
4. Can't advise if boiler was firing up or not.
5. Tried all combinations CH+DHW no Hot water.

Panic - Tried: New Diverter Valve = £91.00 inc. - problem not fixed,
bought a diaphragm kit - £5.00, but did not know where it required to be fitted.

Stopped - Tried figuring out how the boiler worked!!! - good starting point.

Cause:
1. When tap opened - Noticed no demand lights (Green & yellow lights both off).
2. Managed to borrow manuals from family friends who have the same boiler/manuals. Checked diagnostics info, i & + = d.22 = 0 when hot tap open (should be 1 to confirm water demand)

Action:
1. On water incoming to boiler (after water service valve) there is an aqua sensor assembly, which was not detecting water flowing through boiler when hot tap is opened, hence no hot water, boiler = demand not present. So the cold mains water passed straight through boiler and out of hot water tap.
2. Isolated power, Closed all service valves, depressurised system.
3. Removed circlip on aqua sensor
4. Removed propeller and cleaned - contained a bit of grit.
5. Removed the breather nut on top of aqua sensor housing, which was blocked - cleaned and blew through it to ensure it was open.
6. Refitted in reverse order.
7. Refilled boiler.
8. Opened service valves
9. Power ON - Opened Hot water tap, green light flashing & yellow on = Hot water!!!!!!


Aqua sensor is in two parts,

The operational principle I understood as follows:

- the reciever (RX) the sensor (fitted on outside of housing and has three wires)
- propellar - the transmitter - as water flows through the housing the propeller spins, and produces an oscillating signal which is picked-up by the RX, the faster the propellor spins the higher the frequency and the greater the demand for hot water.

As the propellor was not spinning before, there was no demand, hence the cold water.

Regards

Faisal

 

[ChrisR]

You'll have fun fitting the diaphragm!

 

[Slugbabydotcom]

Well done! Heres your Blue Peter badge

Don't cry too much about the £91 you spent on the DV. I dont play with many of these but I am aware they are a weak spot so hopefully you have averted the next problem and will now have a spare which could come in handy in a few years time.

 

[Faisal]

What does the diaphragm kit fit into?

What does it do?

Thanks

Faisal

 

[Slugbabydotcom]

What does the diaphragm kit fit into?

Its packaging

What does it do?

Sits in its packaging!

Who cares? You don't need it anyway

 

[afzaals]

Had a problem with our boiler today - managed to fix it.

FYI

Problem:
1. No Hot Water - on Demand (When Tap is opened), water pressure higher than normal.
2. If pre-heat is on - water is heated automatically whilst tap is closed, when tap is open there is hot water for about 10 seconds and then freezing cold water.
3. Central Heating Working.
4. Can't advise if boiler was firing up or not.
5. Tried all combinations CH+DHW no Hot water.

Panic - Tried: New Diverter Valve = £91.00 inc. - problem not fixed,
bought a diaphragm kit - £5.00, but did not know where it required to be fitted.

Stopped - Tried figuring out how the boiler worked!!! - good starting point.

Cause:
1. When tap opened - Noticed no demand lights (Green & yellow lights both off).
2. Managed to borrow manuals from family friends who have the same boiler/manuals. Checked diagnostics info, i & + = d.22 = 0 when hot tap open (should be 1 to confirm water demand)

Action:
1. On water incoming to boiler (after water service valve) there is an aqua sensor assembly, which was not detecting water flowing through boiler when hot tap is opened, hence no hot water, boiler = demand not present. So the cold mains water passed straight through boiler and out of hot water tap.
2. Isolated power, Closed all service valves, depressurised system.
3. Removed circlip on aqua sensor
4. Removed propeller and cleaned - contained a bit of grit.
5. Removed the breather nut on top of aqua sensor housing, which was blocked - cleaned and blew through it to ensure it was open.
6. Refitted in reverse order.
7. Refilled boiler.
8. Opened service valves
9. Power ON - Opened Hot water tap, green light flashing & yellow on = Hot water!!!!!!


Aqua sensor is in two parts,

The operational principle I understood as follows:

- the reciever (RX) the sensor (fitted on outside of housing and has three wires)
- propellar - the transmitter - as water flows through the housing the propeller spins, and produces an oscillating signal which is picked-up by the RX, the faster the propellor spins the higher the frequency and the greater the demand for hot water.

As the propellor was not spinning before, there was no demand, hence the cold water.

Regards

Faisal

Hi Faisal, would you be able to let me have a copy of manuals? i am having similar problams with mine! kindly let me know. Thanks

 

[stokieshinobi]

Sorry to revive an old topic.

I have the exact same symptoms as you describe EXCEPT when no hot water runs the green and orange lights are indeed active. Therefore I am guessing it is the diverter valve, not the aqua sensor - would you agree?

Also, during summer months when we were running the bath, the radiators would get hot even tho stat was off. This says diverter valve to me. Am I correct?

 

[Agile]

Probably, but searching this forum would give you more help.

We are reluctant to keep writing the same old stuff when its saved so many times in old postings.

Tony

 

[twgas]

I'm amazed that you have the exact same problem yet you have different lights showing to op.

 

[Agile]

To be fair he did say the same symptoms and not the same problem.

But then boiler users often confuse symptoms with problems!

Tony

 

[poor1]

Similar problem but the fault lay with the Aqua Sensor valve fitted complete with sensor, but also fitted new actuator to be on the safe side. Actuator a five minute job and the Aqua Sensor valve about an hour.
Symptoms were that the hot water would only work occasionally.
Complete cure.

 

[Bunnyman]

Hope you clamped the aqua sensor on when you fitted the clip they can be a pig and blow off an flood the place days later

 

[ianmcd]

Hope you clamped the aqua sensor on when you fitted the clip they can be a pig and blow off an flood the place days later

My first ever aqua sensor fault bunnyman brand new flat no HW turned off the cold water inlet opened hot tap no water running, open aqua sensor circlip , yep flooded the bloody place, hot and cold piped up wrong way round , havent made that mistake again

 

[Agile]

Reminds me of a fully refurbished flat where I had repaired the faulty boiler installation under guaranty but as chargeable as it was an installation error.

A week later the foreman phoned me and said the boiler was not working again!

I just told him to turn on the cold tap!

Could hear him running water and then some swearing!

His Polish plumbers had connected the taps wrongly.

He asked me how I knew that was the problem. I just replied that Biasi boilers were very reliable and that was all it could be!

 

[poor1]

Thanks for the heads up regarding the circlip. I must have done it right because there has not been a problem with leaks..

One thing which might be of interest is that with a new Aqua Sensor valve comes a kit of '0' rings, circlips and a small round brass piece which I was unable to reconcile with the existing valve. I was informed by a reliable source that part (small brass piece) is not required in the UK. Don't ask me why. Anyway I took the advice and it was not used.

Incidentally the Aqua sensor valve is only about £50.00 so it's a lot cheaper than the Diverter Valve. The Aqua Sensor valve was quite grotty and I prefer to fit new parts in the knowledge that the existing one had lasted for about ten years.