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Discuss Vaillant boiler issues F28 on ecotec 430 not the normal culprit in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Hi there,

I’m hoping someone can help the last 9 months of intermittent issues we’re having.

We live in a large house which is heated by 2 Vaillant ecotec plus 430 system boilers. They’re wired up together so will work at the same time.

They are used to supply underfloor heating downstairs, 300l megaflo and radiators upstairs.

There are valves controlling the flow to each one and one large pump that circulates the water.

The house is controlled by Honeywell’s evohome system, 2 controllers to be precise.

The issue we’re having is sometimes the boilers don’t fire up. F28 fault code. The gas company over a period of months came and checked, they were adamant there wasn’t a gas issue but the pressure was on the low side of normal, 16-19mb and fluctuated.

After months they upgraded the gas pipe from the main road to the house to a 63mm pipe and the gas pressure is now 20mb.

The issue has always been intermittent from Day 1. Sometimes daily sometimes once a week. There is a G6 gas meter and a 28mm pipe from there to the boiler which splits in s t junction and goes to each boiler right under them, in 15mm.

I’ve still got the problem!! Can anyone else help.

One thing I have noticed is when the boiler switch on the the flame symbol comes up with the boiler output gauge display for a few seconds, switches off and then comes back. I presume this is a failed ignition attempt? It seems to do this regularly.

As I have 2 boilers that fire up at the same time and they’re both under 2 years of age I’ve presumed they both can’t be faulty.

Can someone please help as getting up in the morning to run downstairs to reset these things is annoying beyond words now!

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Gas pipework is possibly undersized to the boilers and you are borderline on what's allowed to be fitted to that meter, if you have any other gas appliances then your in trouble and will need a upgrade you need a GSI to attend and measure the gas rate on full load I suggest you turn off one boiler off reset and try running on one if that operates ok do the same with the next boiler with only one on at a time. Kop
 
Yes mate. You need a gas safe registered engineer to look at the boilers for you.

We have one 4 hob in the house and that’s it.

We had a gd1 or gp1 survey or whatever they do to calculate the load of the meter by Cadent gas and they said we’re on the upper capacity of it but they wouldn’t change it to an U16 as they said it wasn’t required.

One boiler switched off and still have the same issue.
 
We have one 4 job in the house and that’s it.

We had a gd1 or gp1 survey or whatever they do to calculate the load of the meter by Cadent gas and they said we’re on the upper capacity of it but they wouldn’t change it to an U16 as they said it wasn’t required.

One boiler switched off and still have the same issue.
So it sounds like a boiler issue and as I said you need a gas safe registered engineer to look at it for you.
 
If they're under two years old I'd contact valliant as they'll be under warranty. Just out if curiosity how big is your system, how many rads do you have and how much area is heated by the underfloor?
 
Gas pipework is possibly undersized to the boilers and you are borderline on what's allowed to be fitted to that meter, if you have any other gas appliances then your in trouble and will need a upgrade you need a GSI to attend and measure the gas rate on full load I suggest you turn off one boiler off reset and try running on one if that operates ok do the same with the next boiler with only one on at a time. Kop


We did initially think this but the problem is the boilers won’t fire up on full load before they switch off.

They ignite on a low flame level and then switch off straight away, reignite with a grumbling noise and then fire up. Ive been told they must do this 3 times before the F28 kicks in.

On max load I’m getting 21 mb into the meter and 19-20 on the exit pipe.
 
If they're under two years old I'd contact valliant as they'll be under warranty. Just out if curiosity how big is your system, how many rads do you have and how much area is heated by the underfloor?

150sqm downstairs, upstairs is 13 rads and 4 towel rads.

I will give Vaillant a call but then every plumber says it’s practically impossible that both boilers stop at the same time to be faulty.
 
So it sounds like a boiler issue and as I said you need a gas safe registered engineer to look at it for you.


I’m based in Northwood Middlesex. Is there any recommendations that someone can make?

The boilers have been checked and serviced a few months back by a gas safe engineer who said they were fine. I did mention the issue to him but said nothing obvious there.

He mentioned something about checking the earthing and electrics next.
 
As @Craig Watson says. If they are under two years of age then they are definitely within warranty. I would suggest you get the installer to come back and deal with this or book a visit from Vaillant.
If you choose the latter, there is a charge if the fault is not Vaillant product related.
 
As @Craig Watson says. If they are under two years of age then they are definitely within warranty. I would suggest you get the installer to come back and deal with this or book a visit from Vaillant.
If you choose the latter, there is a charge if the fault is not Vaillant product related.
This is of course assuming they have been fitted by a registered engineer and have had the warranty set up.
 
Not withstanding the F28, it would appear you have a you have 2 oversized boilers on a poorly designed system, I take it from the single large pump that there is no low loss header installed? (60kW through 28mm what were they thinking !!!)

Why haven't you gone back to the installer / manufacturer before now?

When you go down to reset, is it both that show the F28 ??
 
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Fair point I hadn’t seen that if that’s the case
 
Potentially blockage in the pipe?
Could be, if excessive flux was used it could be causing a restriction. Both boilers having the same fault are unlikely to be manufacturer related so either there's an issue with the gas supply or the boilers aren't earthed correctly.
 
What else throws up F28 in the depths of winter !!!
Could be if it is both or either, worth a check wouldn't you say?
Doubtful, he said he's been having intermittent issues for the last 9 months. Although there could be other reasons for that to be causing issues that don't relate to the cold weather.
 
Doubtful, he said he's been having intermittent issues for the last 9 months. Although there could be other reasons for that to be causing issues that don't relate to the cold weather.
I know it is not cold all year round but still produces, where does that pipe end up? Just a thought but would need to be on site.

One thing for sure 60kW's through 28mm ain't to clever & on U/F, rad mix, with no separation, another great design.
 
Not withstanding the F28, it would appear you have a you have 2 oversized boilers on a poorly designed system, I take it from the single large pump that there is no low loss header installed? (60kW through 28mm what were they thinking !!!)

Why haven't you gone back to the installer / manufacturer before now?

When you go down to reset, is it both that show the F28 ??

The issue was the installer had said it was due to the low main gas pressure. cadent gas tookmonths of coming out and checking before they agreed we had spikes in pressure hence the reason the F28 was coming up.

They rectified the issue by installing a 63mm pipe to the house.

I’m not in the trade and hence had presumed that it was a pressure issue and left it at that.

Now the issue isn’t the gas pressure as they fixed this in December and in all honesty for a month it worked faultlessly.

As the weather has got better the issue has become more apparent again and is daily.

I’ve switched off one boiler and and currently searching for a recommendation for someone to come rectify this for us.
 
I’m based in Northwood Middlesex. Is there any recommendations that someone can make?

There's a superb engineer and troubleshooter in your area called Andrew Millward of https://www.homecomfortassured.co.uk/ive

Just do what he recommends, as said already sounds like the boilers are well oversized so could possibly be a poorly designed system with no LLH.
 
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Why do you need two boilers for such a system with 30 kw each running in the same time? As mentioned above to all the others well oversized and get a reliable engineer or perhaps donit via warranty
 

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