bionichamster wrote:Boiler has been working fine today, then at 9pm I go to have bath and there's no hot water! I check the heating and it's out too. House is warm so it can't have packed up too long ago.
It's an Alpha CB28 in the attic, red and yellow lights flashing together in synchronised harmony, so not the normal low pressure (pressure is fine, I check). I look in the manual and it lseems it might mean a flue or fan fault. Then it clicks, is it the snow?
It's been snowing much of the day, could be eight to ten inches on the shallow sloped roof. The boiler flue exits the roof horizontally and only protrudes a short distance so it is potentially below the snow line but I go outside and at first glance from atop the ladders it appears to be fairly clear. The flue is about eight foot up the roof slope fro the gutter and it's too dangerous to try and climb up the slates to it in these conditions (although maybe the snow would soften the impact if I fell off the roof!
). I use a long section of 15mm plastic pipe to clear snow from around the flue and then ducttape a brush to it and clear the grill on the end. But all this is to no avail, the boiler still won't heat up and persists with its error flashy lights.
Any ideas? Is it possible that snow has gone inside the flue, or even been sucked deep inside and blocked it? (I'm assuming it's a balanced in/out pipe of course). The flue pipe was very cold inside the attic and I tried warming the end of it gently but that did nothing either. I've e-mailed my usual boiler servicing company and will call them first thing too, but interested to know if I'm barking up the wrong tree with possible cause.
Not the best day for this to happen, -7 predicted tonight and lots of compacted snow on the roads, so as well as being cold, if there is snow in the flue it likely won't thaw and I'm wondering if the gas engineer will even be able to get to us depending on road conditions....
BH
Right, for what it's worth commenting at this time of night, it always surprises me how often people in the stress of a broken boiler, don't think of having a gander in the instruction book. Yours can be downloaded here if you don't have a paper copy.
https://www.freeboilermanuals.com/asset ... b24-28.pdfTurn to the fault-finding flow chart on Pages 29 and 31 and you'll see the fault code you describe of both lights flashing in unison, and AiY is bang on the money with his comment about checking the flue fan. The twin flashing lights is the PCB saying the safety device that checks the fan is running (the air pressure switch) before lighting the gas, is failing to detect the fan running, hence the fault code.
The APS looks (loosely speaking) for a difference in air pressure between the inlet and outlet of the fan, and on your boiler the control board believes it is not detecting any. This can have a variety of causes as follows:
1) The fan has actually packed up. Can you hear it running?
2) The fan is running and the APS is failing to detect it. This could be because the flue itself is blocked with something e.g. snow (as you already suspect). You might get lucky and find a fan heater or hair dryer aimed at the boiler for an hour or so will warm it up enough to melt the blockage and it all bursts into life, or you might be dead unlucky and the snow (if there is any) melts and the water wrecks the fan or the control board. Or both. Are you up for turning the electricity off, taking the front off the boiler and having a gander inside? You *might* find it is indeed full of snow. If it is, try to get it out without melting it.
3) The APS itself has failed. An amazing coincidence if this is the case, but not uncommon.
4) One or both of the little thin hoses connecting the APS to the fan are blocked with something, e.g. a snowflake.....
5) The fan is running, the flue is not blocked, the APS is operating, but the control board (PCB) has a fault and incorrectly thinks the APS has not operated, and is therefore refusing to light the gas. Again quite common but in this case would be quite a coincidence. One trick that surprisingly often brings a faulty PCB back to life is to warm it up with a hair dryer. If you are happy the fan is running and the boiler is not actually have any snow inside, try this. PCBs have a lot of capacitors on them which degrade with both age and heat and letting a PCB get cold and/or damp can stop it working. A blast with a hair dryer will sometimes raise the dead!
So apart from the above, I've no idea what might be wrong with your boiler....
Hope that helps, if only a bit. Just knowing what is wrong sometimes helps too, even if you can't actually fix it.
P.S. To everyone reading this, don't have your next boiler fitted in the loft, it is usually such an utter ball-ache I wrote a long web page ranting about it!
My bad 
