Vaillant EcoTec Pro 28 Combi

[KemikalAli]

Hey Guys!

I'm newly registered to the forum but have been an avid reader of all advice regarding my central heating boiler.

It is a Vaillant Ecotec Pro 28 and was fitted about 3 years ago, it has been great until last year (around this time of winter) when the outside condensation pipe froze up, it backed up and started dripping water from the trap, it could not be defrosted with boliling water so I severed the 32mm outside and removed the rod of ice that had built up.

Unfortunately it is fitted on the most exposed wall of the downstairs kitchen where the wind blows the hardest.

Anyway, to cut a long story short it recently started to show the common F75 fault, I checked and repressurized the EV to 0.9bar, bled all of the CH heating system twice, checking for dead legs but the whole thing is fine and red hot when working.

The trouble is when the system gets to up to temperature or there is demand for hot water when the boiler tries to restart the CH system, it goes through the S1-S4 startup and then F75's, the only way I can get the system to fire is to add a little more water via the fixed filling loop and restart the boiler, the display also shows a S91 code (pressure over 2.9 bar) which is not suprising as the visual gauge is always in the red for the boiler to work. Water is constantly coming from the blow off pipe outside due to the excess pressure.

I have a new pressure sensor switch on its way which I should hopefully receive tomorrow all being well, I will fit this as soon as I get it as a matter or course.

So I'm my summing up before any of you kind gents can advise me, I believe the pressure sensor switch is knackered telling the system I need more water pressure, when the system expands when working at temperature the excess water is being driven out via the blow off pipe. the system water then cools pressure drops causing the F75, The frozen condensor pipe I believe is a seperate issue due to the weather!?

I took the condensor bottle out yesterday to find it was full of some kind of metal sediment, I cleaned and refilled this to 10mm from the top as per the manual.

I need to keep this boiler running as I have a severely disabled 9 year old daughter who needs to be kept warm.

All and any advice appreciated, thanks in advance

Kind regards

Steve.

 

[mickyg]

its more likely from your description that the canoe filter is blocked. Possible the switch is blocked as well. Probably doesnt need replacing. Why have you filled it so far? It should only be 1-1.5 bar. Release some water from a drain point. The "-" button should give you the exact pressure.

 

[KemikalAli]

Hi Mick,

Thanks for your quick reply.....

The reason for the high pressure is that the boiler shows a F75 fault and fails to fire if the pressure is anywhere less than near or in the red zone.

The pressure is taken from the LCD display using the method you advise.

This is my reason for suspecting that the pressure sensor is faulty!

Steve.

 

[Agile]

I would suggest you depressurise the boiler and refill the expansion vessel to 0.9 Bar but that must be done with the system pressure kept at zero. See FAQ for fullinstructions.

Last week I went to one of those and the pressure gauge was reading about two or three times the actual pressure.

Set the pressure to 1.5 Bar on the digital display and see what the pressure gauge shows.

The tube into the pressure sensor may be blocked and the pink ones are less reliable than the later black ones.

Tony

 

[KemikalAli]

Thanks Tony,

I will do that in the morning, the sensor is the later type black one btw!

Regards

Steve.

 

[mickyg]

while you've got the boiler drained i would take out the sensor and see if its blocked. and use a torch to check the condition of the filter that sits behind it.

 

[KemikalAli]

The boiler went off around 2am, the house was freezing so I went to do some tinkering!

I isolated the CH system as well as the mains eletcricity, drained down the boiler and checked the pressure on the EV.... okay, depressed the valve and it dumped its entire contents into a bowl, around 10 litres, re-pressured the EV to 0.9bar, took out the pressure switch to find it was clogged with black muck, cleaned it, replaced and refilled the system, ran the PO purge programme..... PERFECT!

I bled the pump and lots ofc black gunge spilled out! .... time for a flush and treat after xmas!!

Thanks guys, you're the best!

Merry xmas to all

Regards

Steve.

 

[Yukster]

I accidently overfilled the boiler. Initially the gage went up half way but when the boiler fired up the pressure gage showed 3 bar! I switched the boiler off and bled the radiator. The pressure went down BUT the boiler doesn't switch on and there's nothing showing on digital display, as if it's power is off.

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• Yukster
• 4 Jan 2014
• 2

I checked the fusebox and all fuses are on! Any advice on how i could resolve this?!?!