Home » Viessmann F1 Fault Code – Central Heating – Combi Boiler
Viessmann Vitodens 100 F1 Fault Code. Today we’re going to look at the F1 fault on the Viessmann boiler. This is Viessmann Vitodens 100, this is a 35 kilowatt Combi boiler, but it’s the same fault on all of them. I’m going to go through, I’ll go through a few of the different faults that could cause an F1 fault. If you’ve got any tips, or if you’ve got any F1 faults that I haven’t covered, please add them in the comments below, and then hopefully it will help other people as well. But yeah, let’s have a look at the boiler now.

One of the first things to check with an F1 fault is the pressure. If this pressure has dropped, if it’s down here to zero, then you might just need to top the pressure up, which is just on these taps underneath. All you need to do to top the pressure up is open them taps, so that one, you’d open that tap there down and then this one, if you open that tap you would hear the pressure going up. You can see there it’s going up. Obviously, that’s too high now. We’d only normally want this around 1 bar when the system is cold. The F1 fault is a circulation fault, so that could mean it could mean the pump is faulty, it could also mean that there’s air in the system. What I’ll do is I’ll take the case off now. Always remember, if you’re going to take the case off a boiler, you must be Gas Safe registered. We’ll take the case off now.

As I say, always remember, if you’re going to take the case off a boiler, you must be Gas Safe registered. This is part of the seal for the combustion. On this one, we’ve got some pipes here, and there’s a bleed point at the top here. You can connect a hose pipe on here and you can bleed some of the air out of here. Sometimes this heat exchanger gets air in the coil, and as I say, you can bleed it from there. The most likely cause of, when I’ve been out to people, the most popular F1 fault has been low water pressure. That’s the normal cause. The other cause, pump, if the pump was faulty. On this particular boiler, what I’ve done, so that I can get the F1 fault, I’ve actually just disconnected the pump there. Obviously on this one, it’s the pump that’s faulty. What I’ll do now is I’ll plug that back in, I’ll turn the power off, plug that back in, and then we’ll have a look and make sure that that F1 fault goes.

I’ve plugged the pump back in now, so I’m just going to reset the boiler. Just see that temperature now going down, that’s getting the heat away from the boiler. Obviously because the pump wasn’t working and the boiler tried to fire up, inside the boiler was very hot. I’ll just turn that up, and now the boiler will fire up. As I say, on this, F1 was the pump. But F1 is a circulation issue, so it could just be that it just needs topping up, and it could be that it’s the pump, or it could need air bleeding out of the system. So yeah, hope that was of some use. Thanks for watching.

Allen Hart

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