Before you rush and say: Call an engineer!
I only have the dreaded error F75 from an old vaillant boiler in winter and when it's very cold and at night time. I have to push the reset button about 10 times before it finally switches on.
Now, before even investigating and troubleshooting, can it simply be that it spits that error because it's simply too cold inside?
Flat is crap and badly insulated but I don't want to leave the heating on all day for obvious financial reasons.
Presumably a frost-stat to make it less likely to burst frozen water pipes via the condenser fan
Sorry, what is a frost-stat?
A secondary thermostat which is used when the heating is "turned off" to maintain the temperature above freezing to prevent burst pipes and such.
I think he is indicating in effect that although you don't want it on when out, some heat will be needed to stop it from freezing.
You almost want some form of electric blanket to keep the really cold air from the part that complains when its too cold. NOt sure if anyone makes such a thing. Brian
A quick search finds some useful info here:
A low temperature indoors with the radiators similarly very cold will result in the lowest pressure in the system. (When pressure was low to start with and house got very cold, I did have my Keston lock out because the system pressure dropped below ¼bar.) What does the static pressure read, and does it change when the pump starts?
Andrew
In the old days with simple boilers , that function for middle England weather anway, was done by the pilot light which gave enough local warmth to avoid water freezing in the boiler pipes.
Fine as far as it goes, but that does not protect other parts of the primary system from freezing at a distance from the boiler. A frost stat will also cause the pump to run the the rads to heat a little - thus protecting them as well.
The trouble with boilers is they have a direct metallic connection to the cold weather outside, unlike radiators and internal pipework.
It is basically saying it can't sense a pressure change when the pump spins up. So there are three likely causes:
System pressure is too low generally - check the pressure gauge is showing at least 1.2 bar. Top up if not.
Pump is not spinning - If you take off the front panel [1], check to see if you can feel / hear the pump spin. If you can't tell for sure, then make sure the boiler is not running, take the silver plug out of the front of the pump (have a cloth handy it will weep a bit), you should be able to put a screwdriver into the end of the impeller (it is a phillips head on mine), and it should turn freely. Replace pump if not working.
Another possibility is that the digital pressure gauge sensor is faulty and not reading the pressure correctly. Check that it matches the reading on the internal gauge[2]. Try adding some water and then bleeding some water - you should see it rise and fall.
There is a video on changing the sensor if required (fairly easy):
Not if they are modern condensing boilers with plastic flues, surely ?
The worst type of boiler is the old non-fan-assisted balanced flue type with a huge metal balanced flue sticking out of the wall. Fit that on a north or east wall and the heatloss through that metal must be quite significant.
What connection? Modern condensing boilers have such low exhaust temperatures that the flue is often plastic, as is the condensate drain.
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