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Thread: Vaillant Ecotec combi boiler problem

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    Default Vaillant Ecotec combi boiler problem

    Any brains I can pick before calling in the trade please?



    One of these about 5 year old and been faultless up to now (no service contract ) Wireless stat/programmer for c/h cycles.

    When it's running it's fine but it shuts down at night and the pressure drops so it won't fire up in the morning - no heat or hot water. Dial gauge shows little or no pressure but pressing the button (left of ladder symbol) shows around 2 Bar. Red led lit showing error code F75.

    So I open the taps on the filling loop for a few seconds till the dial gauge goes up, shut the loop off, led goes out so I press the 'flame' button and away she goes till next time it shuts down. Repeat ad nauseum.

    Why does the dial gauge appear to disagree with the digital readout? Is one the system pressure and the other the boiler internal pressure?

    No obvious leaks on the pipework or radiators - no puddles/drips evident anyway. The emergency overflow/pressure release pipe is plumbed into my washing machine waste pipe so it's not obvious whether water is escaping from the boiler that way.


    Obv I'm not Corgi but I don't mind firtling with water or electric connections and the problem doesn't seem to be gas supply related anyway. Duff pressure sensor or something?

    Cheers.


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    Default Re: Vaillant Ecotec combi boiler problem

    Quote Originally Posted by fastfitter View Post
    Any brains I can pick before calling in the trade please?



    One of these about 5 year old and been faultless up to now (no service contract ) Wireless stat/programmer for c/h cycles.

    When it's running it's fine but it shuts down at night and the pressure drops so it won't fire up in the morning - no heat or hot water. Dial gauge shows little or no pressure but pressing the button (left of ladder symbol) shows around 2 Bar. Red led lit showing error code F75.

    So I open the taps on the filling loop for a few seconds till the dial gauge goes up, shut the loop off, led goes out so I press the 'flame' button and away she goes till next time it shuts down. Repeat ad nauseum.

    Why does the dial gauge appear to disagree with the digital readout? Is one the system pressure and the other the boiler internal pressure?

    No obvious leaks on the pipework or radiators - no puddles/drips evident anyway. The emergency overflow/pressure release pipe is plumbed into my washing machine waste pipe so it's not obvious whether water is escaping from the boiler that way.


    Obv I'm not Corgi but I don't mind firtling with water or electric connections and the problem doesn't seem to be gas supply related anyway. Duff pressure sensor or something?

    Cheers.
    I'm no expert but that doesn't sound like a sensor problem.

    It's obvioulsly leaking water from the loop system somewhere because you keep adding water to it each day. How do you drain the system down? Could it be that valve which is slightly open?

    If it only loses water when the system is cold, it could be a slow leak in a pipe joint somewhere. When hot, the leak may seal up.

    Edit - this post is very similar to yours and suggests it could be the expansion vessel which needs charging up with a foot pump. The OP got the code wrong and corrects it to F75 later on.

    Vaillant Combi condesing boiler losing pressure daily no sign of leak - MoneySavingExpert.com Forums

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    Default Re: Vaillant Ecotec combi boiler problem

    Cheers for that, a blob (when/if I can suss that out)

    I've done a bit of Googling but most replies from 'the trade' are a bit technical and quickly resort to 'walk away and don't be a cnut'

    Checked the expansion vessel - no water from the schraeder valve and around 1.5 Bar on my tyre pressure gauge.

    The filling loop is normally removed, I've just been leaving it on since it started playing up so I'm confident the taps for it seal ok.

    An idea from that thread though - why didn't I think of it? - tonight I'll shut all the taps to/from the system. That should indicate tomorrow whether it's a boiler of system problem I think.

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    Default Re: Vaillant Ecotec combi boiler problem

    Bollocks. Had the boiler valves closed for two hours now and the gauge and digital pressure read-outs haven't budged. I'll give it a bit longer and then restore to normal. In which case I suspect the gauge will plummet.

    I've got a leak in my heating system somewhere haven't I? I'll have to wait for the plasterboard to start drooping

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    Default Re: Vaillant Ecotec combi boiler problem

    That water must be going somewhere. Could you disconnect the drain pipe that goes to your washing machine drain? If the water is escaping that way, at least you know your heating and hot water pipes are sound.

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    Default Re: Vaillant Ecotec combi boiler problem

    If it ain't leaking from the pipes or rads then I would think it was via the PRV or the heat exchanger is holed losing boiler/CH water to the HW supply.

    Trust me I'm not a plumber.

    or it's fucked Brucie.
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    Default Re: Vaillant Ecotec combi boiler problem

    Cheers chaps. Three hours or so and the gauges on the boiler didn't budge. I opened the flow and return taps to the system and there was a whoosh and the dial dropped like a stone. Boiler wouldn't fire up (F75) until I put the loop back on and boosted to get a reading on the gauge. Now working normally again.

    All pipes are under the upstairs floorboards except where they come down to the downstairs rads (concrete raft floor) so I might be pulling floorboards soon.

    I'll have to cobble up a bit of pipe so I can remove the overflow and direct it into a receptacle to check for water there.

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    Default Re: Vaillant Ecotec combi boiler problem

    How much water are you putting into the system? Is it just a boost or is it filling for a long time?

    Vaillant Boiler F.75 error code... - Advice - Digital Spy Forums

    Shows it as either a stuck pump, blasting water in would free up a sticky pump as would it running continuously during the day, with it sticking again overnight or a U/S pressure sensor

    See the last post on page one

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    Default Re: Vaillant Ecotec combi boiler problem

    Just a squirt basically. I left it off for a couple of hours tonight with the expansion tube? disconnected - nothing in the bowl under the tube but pressure dropped and F75 again. Boosted via the filling loop for a few seconds and away we go.

    I'll read through that thread tomorrow when I'm focussing better cheers for the link.

    I'll switch it off and leave it in half an hour and see what we have in the morning - I fear no radiator socks

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    Default Re: Vaillant Ecotec combi boiler problem

    Update-ish - I had a trawl through those links (thanks again) and they're all a bit inconclusive to me. Trouble is the OPs don't come back when (if) they've had the problem solved.

    If it gets no worse than needing a squirt every morning I'll live with it till the new year and then drain the system and clean any filters I can find and put some of that magic fluid in. If that don't fix it I'll call the trade in.

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    Default Re: Vaillant Ecotec combi boiler problem

    Once the pressure check valve opens it tends to fail, bits of manky corrosion get in it and stick it slightly open. You then have a constant drip when the boiler is operating.

    It doesn't sound like that though tbh. The other problem is, if it has opened then there was a reason, ergo fitting a new PRV will just start the cycle again...

    Good luck, sounds like a system leak somewhere.

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    Default Re: Vaillant Ecotec combi boiler problem

    Got a similar one myself, the guy who fitted it said they are very good boilers (he also fitted the previous one, said it was crap, and it was). Had mine about 5 or 6 years, it is heating tap water like it should and heating the house when its in the mood. Ho hum!
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    Default Re: Vaillant Ecotec combi boiler problem

    I think (seat of the pants engineering) that shutting the boiler valves and getting no pressure drop on the gauges seems to point at the pipework/rads rather than the boiler itself. I'm constantly checking the ceiling plasterboards for sag

    When it's running it's fine, all rads are bled with no sign of air though and get hot right to the top

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    Default Re: Vaillant Ecotec combi boiler problem

    How many seconds does it take to fill the system enough to get the system to trigger?


    If it is only a few, it ain't a leak, it is a switch, sensor or the pump and I reckon any surplus from the boost is getting shoved out of the Pressure Relief Valve oonce the system gets to temperature.
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    Default Re: Vaillant Ecotec combi boiler problem

    Only takes a few seconds to boost it back up but ....... I think I've found it

    Just been out the back to fetch the bin round (staff's day off) and the drain-off cock sticking out the wall has a very slight but steady drip.




    So I'll get another and try a live change of the insert.

    If I end up having to change the lot can anyone recommend what inhibitor/magic fluid I should put in when I re-fill the system? Three-bed terrace with 8 rads in total.

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