I need a user manual for the Fagor hot water boiler Model FEP 110 plus B Butano

I suggest getting in touch with your boiler company. They'll come out and check your thermostat, check your pipe's aren't freezing and that your boiler is igniting at least. P.s. I had this problem recently down to user error, been cold recently so had the heating on often then wondered why my water was chilly :S

Can you get the manual online? You have the Manufacturer info so you probably have the model number too. I found a manual on Manuals.com for my boiler so they may have yours too which will hopefully have some information on filling boiler although I realize each installation is somewhat different but that's why it's difficult to answer you question. Usually there is a manual pressure valve that regulates the water pressure in the boiler which is usually pretty low...like less than 20 lbs. The manual should tell you the pressure as well. But this pressure valve has a flip handle that comes off the cold water line to the boiler to do just what you want to do...refill it with water. When refilling the boiler (if you find the valve, you may have to purge the air out of the lines which there is a whole other process for. But you shouldn't allow cold water into a hot boiler...it could crack it when the cold water hits the hot cast iron. So make sure the boiler is cool when filling it up.
Now go try to find that manual!

your boiler needs a minimum gas pressure of 16 mb to light successfully. if your gas pipe has been extended it has to be able to flow enough gas. it may need upgrading to 28mm for even as little as a metre from the gas meter. if your central heating works ok when the fire is off then this is your problem

Is this a water heater?
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Gene

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There is a flow sensor in the circuit and it is not sensing the lower flow from just the hot water. When you put it on heat though it does.

Check the pressure reading, should be about 1 bar when system is cold. Various models in the range of 24cdi. If you do not have a manual, go to,
http://www.centralheating.co.uk/Boiler-Manuals/worcester-bosch-boiler-manuals/worcester-bosch-discontinued-boiler-manuals.
Get the manual for your unit, to wards the end of install manual it has a fault finder, Also has a basic 1 in the user manual. Number of flashes how fast the light flashes which one flashing can all mean different, So get the manual and check, Some parts are easy to fix, as long as you do not touch the gas side the rest is plumbing. Come back if needed.

We have just had our old system boiler replaced with a vaillant ecotec plus 837 and sounds like a similar working operation to ours. At first I was a little concerned,but I was told by our installer that he was told by vaillant that these very latest boilers size the system on start up for about 10 mins, then take temperature to target flow which you set boiler at. So even by setting target flow temperature very high you still get the initial sizing cycle, which ours was about 30-35c temp. These boilers seem to run biased for efficiency as after a while they modulate the boiler burner down and the radiators run more on the side of warm than really hot like the old type boilers. You also get better efficiency as at lower temperature the boiler condenses better. You will also find you get a more constant temperature in your home rather than over shoots. I was concerned at first, shame there was no info/explanation in user manual as people do need to know that this is normal operation. We are used to ours now, took a month and by the way these boilers can make a creaking noise but was told this normal expansion/ contraction but annoying when sited in bedroom cupboard. Best of luck!

your condensation pipe may be frozen get a hairdryer on it or a hot kettle that should sort it thats the whit pipe on the left usualy plastic

refere to manual check for override switch loss of pressure no problem re-pressurise and check for leak top of rad valve good place to start

sounds like the diaphragm