Vaillant Combi Boiler Problems

Hi, we moved into a house last year which has a 2 (now almost 3) year old Vaillant Combi Boiler (think it is the TurboMax). The water takes an absolute age to get hot - anything upwards of five minutes and even then it is never 'scalding' enough to get pans soaked etc! I have had two corgi engineers out who both reckon there is nothing wrong with it!

Anyway, my latest problem is that it has today shut itself down with error code F28 - boiler block out due to insufficient gas supply or faulty valve etc. It would appear that the boiler has done this before as the previous owners have made a note of this error code on the front cover of the manual.

Has anyone any ideas what this is and what is going on with this boiler. The heating side seems to work fine (obviously not today because it is totally off!)

So far I aint very impressed with Vaillant!

Fault code F28 covers a variety of faults, but most likely in your case is a problem with ignition, i.e. defective igniter, ignition lead or ignition probe. It's unlikely that your gas supply has been lost, but just check that no one's turned it off! Anyway these things are Corgi territory, so you need a competent engineer.

As for the 5 minute delay before hot water comes through, this can't be right unless you've got a run of maybe 500 metres of pipe from boiler to hot tap! Might be best to get Vaillant's own engineers to look, since it seems you haven't been able to find anyone competent locally.

Thanks Chris. I did check the meter just in case but everything looks okay and the lever for the supply is still on - it was working earlier today but by the evening it stopped.

I have a corgi engineer coming tomorrow first thing, hopefully they will sort it.

I will consider paying for a Vaillant engineer to come out, as you say it can't be right waiting that long for the hot water to get thru.

Consistent with the gas valve sticking. RRP is about £100 inc vat. It would be interesting to know what it is, especially if the problem's something else!

pcb's are known to go faulty on these boilers causing lockout f28, to check ignition turn off gas supply and run through 4 or 5 ignition sequences checking for good strong blue spark at electrode with no missfires.

hw fault may be diverter valve may not be operating correctly(rads get warm when running hw for 5 mins), dwh heat exchanger blocked(hw not very hot but burner cycles on /off and flow from main h/e to dhw h/e hot but return cold to main h/e, undersized gas pipe ie only 15mm or gas meter set under pressure, aqua sensor may be sticking(when running hot tap green led flashes to show this is working).
all corgi job only

Thanks for you help guys. Engineer replaced gas control valve and now back to normal. He agrees that the water takes too long to get warm but states that this is due to boilers location (in an 'outbuilding' that has now been attached to the house) and the length of pipes etc!! I give up for now!

Just checking - are you aware of the "keep a bit of water hot on standby" feature, which Vaillant call something more elegant? You turn it on by putting the water temp knob to max, so the green(?) light comes on permanently. Repeating turns the mode off.

This will reduce your waiting time.

Thanks Chris, I'm sure we've tried this in the past, I think its called warmstart or something, and it didn't seem to make much difference. I guess we are just cursed or something! We're moving house anyway but was just trying to get an idea if Vaillant were a good make or not as we may have to put central heating into the house we are moving into. I heard Worcester and Bosch were the best boilers around (different topic I realise now!!)