No hot water after brief power cut

ItsADryHeat

Hello,

I wonder if anyone can help me?

We've just had a brief power outage, I flipped the fuse in the fusebox and the electricity came back on no problem. However our boiler now refuses to produce hot water, and won't heat the radiators (not that that's necessary in this weather). The boiler is on, making the same noises it always did, and the correct lights come on when you turn on a hot tap. But the water is cold.

I've tried resetting it using the red reset button, but that hasn't done anything. Held it down for 10 seconds, waited, but no luck.

I've tried increasing the water pressure using the correct valve underneath but the gague didn't move. It's currently resting below 1 but has always been at that level and worked fine.

It's an old Vailant combi that worked perfectly until the power outage. I don't have the manual, unfortunately.

Am I missing something? It seems like it can't actually be broken, surely? It must have just reset itself somehow due to the power outage.

One possible complication is that it is hooked up to an ancient Randall timer box. But that has never had any effect on it previously. We never use it or touch it.

I was just hoping someone might have an idea before I call an engineer over and they perform a 30 second fix that I could have done myself.

Thanks in advance!

Homer_home

does the pilot light light come on when you turn on the hot tap?

can you hear a whoosh inside the combi as the gas is ignited?

Rosa_Damascena

The green light tells us that its not the power that's the problem, so as alluded to above consider the gas ignition in your diagnostics.

You're right not to want to shell out on an engineer. I would guess that you're boiler is not covered (which is a MSE option) but often a call to the helpline can resolve the issue without a call out. In lieu of this I would get googling the boiler model, there's a good chance someone out there has posted a video.

tacpot12

It is possible that the powercut has damaged the boiler's control board. You will probably need an engineer to diagnose this, although if you have the manual for the boiler and there is a troubleshooting flow chart in it, you might be able to diagnose the fault yourself. 

Rosa_Damascena

tacpot12 said:

It is possible that the powercut has damaged the boiler's control board. You will probably need an engineer to diagnose this, although if you have the manual for the boiler and there is a troubleshooting flow chart in it, you might be able to diagnose the fault yourself. 

Lots of manuals can be found online these days, even for obsolete models. Worth a try.

J_B

With our (non Vailant) boiler, simply switching it off for a few minutes seems to reset it.

However, the power outage may have caused a voltage spike (?) and fried some of the circuitry perhaps??

ItsADryHeat

Thanks for the help everyone, I do appreciate it.

I found a maual online and went through its fault checklist. Seems like either the fan or electronics board is faulty. Which is a shame, I'll have to get someone out to look at it.

Le_Kirk

It is unlikely that just a power cut (outage to use the American expression) would cause the boiler to become faulty; if this was the case, then every time the controller turns off the power, the boiler would pack up.  Much more likely a spike as suggested by @J_B has damaged the circuit board; however, on these boards there is often a little fuse which is designed to protect the board.  If you are competent and confident and you can see the board without having to dismantle too much of the boiler casing, you might be able to see it and with the power OFF see if the fuse is intact.  They are normally glass so easy to see a black mark.
What is the exact model number please?
ETA.  On reflection, you did mention that you could hear the boiler making "all the usual noises" so possibly the spike/fuse argument is a red herring.

ItsADryHeat

I got an engineer out and he was sure it would be a faulty circuit board. But it turns out that was fine, and it was a dead fan that was the problem. The power cut was indeed a red herring, the fan just died of natural causes (being almost 17 years old).

Rosa_Damascena

ItsADryHeat said:

I got an engineer out and he was sure it would be a faulty circuit board. But it turns out that was fine, and it was a dead fan that was the problem. The power cut was indeed a red herring, the fan just died of natural causes (being almost 17 years old).

How much did that cost you?

Le_Kirk

ItsADryHeat said:

I got an engineer out and he was sure it would be a faulty circuit board. But it turns out that was fine, and it was a dead fan that was the problem. The power cut was indeed a red herring, the fan just died of natural causes (being almost 17 years old).

Don't you just hate coincidences?  Still, doesn't owe you anything after 17 years.  I've just had to change a thermostat in our oven and a solenoid valve in the power shower.  When I checked on the original paperwork, one was 13 years and one was 15 years old!