Vaillant boiler issues F28 on ecotec 430 not the normal culprit

[Navi Bhander]

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!

 

[king of pipes]

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

 

[Harvest Fields]

Yes mate. You need a gas safe registered engineer to look at the boilers for you.

 

[Navi Bhander]

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.

 

[Harvest Fields]

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.

 

[Aire]

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?

 

[Navi Bhander]

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.

 

[Navi Bhander]

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.

 

[Navi Bhander]

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.

 

[Aire]

I would say your boilers are oversized and your gas is undersized.

 

[Harvest Fields]

I would say your boilers are oversized and your gas is undersized.

So they need a Gas safe engineer to go back do they not?

 

[Riley]

Also I hope op is not testing the mbar

 

[Last Plumber]

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.

 

[Harvest Fields]

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.

 

[Aire]

So they need a Gas safe engineer to go back do they not?

Definitely and thats the last advice I'm giving op on the subject

 

[chris watkins]

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 ??

 

[Riley]

I still reckon it’s a pipework isue

 

[chris watkins]

I still reckon it’s a pipework isue

Why if it still does it with just the one switched on ?

 

[Aire]

Why if it still does it with just the one switched on ?

Where does he say this still happens when only one is switched on?

 

[chris watkins]

Where does he say this still happens when only one is switched on?

Bottom of post 4

 

[Riley]

Fair point I hadn’t seen that if that’s the case

 

[Aire]

Bottom of post 4

I see, missed that one 😳

 

[Aire]

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.

 

[Harvest Fields]

Naughty boy @Riley 😛😛

 

[chris watkins]

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?