Have a ecotec 824 plus boiler the bar goes upto 2.7 and stays round 1.5 when not operating,what is causing this?

you might have a small cold water leak

Pressure inside the tank will rise along with the water temperature. As the water inside cools the pressure will wane until the heating element turns on and reheats the water with a subsequent rise in pressure. Running the hot water at the same time will draw heat energy from the boiler and lower the internal temp and pressure as well.

USE A ELECTRIC METER AND CHECK FOR 120 VOLTS AT CIRCUIT BOARD AT LINE IN AND COMMON , IF YOU DO HAVE 12 0 VOLTS THE LOOK FOR TAPPINGS FOR 24 VOLT OUT PUT MAYBE A BAD TRANSFORMER OR CIRCUIT BOARD

The Symbols should be there whenever the boiler is in use, it confirms the pump is running and the gas valve is open...i.e firing.
the pump overrun may come on after a firing to dissipate excess heat and is what it says, i.e the pump continues to run to keep the hot water moving to prevent the boiler from getting noisey. Sometimes you may see a radiator symbol which means the boiler is doing a 'heating' cycle as against hot water.

wrong category. If you post to correct category you will get a faster response.

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!

you should have a filling loop turn the vavles to get the pressuer back up to 1.5bar

You either have a bad circulating pump or you have air in the system. A little bit of air can completely stop water flow in a boiler system. Your problem is more than likely air though. Each radiator should have an air bleed on it. Turn your boiler completely off. Go to each radiator and open the air bleed. It will be located towards the top of the radiator. After air is bled out, close the air bleed and go to the next one until all have been done. If you have a two story house, start at the lowest level of radiators. When you are finished start the boiler back up and let it run for about 2 to 3 minutes and shut it back down and bleed all the radiators again. If you are making progress and getting more to heat up but not all of them yet, keep repeating process until all of them heat up.

F.22 Dry fire Too little water in the appliance, water pressure sensor defective,
cable to pump or water sensor defective, pump blocked or defective,
pump output too low

try to enter here all informations and you can find the manual: http://instructions-manuals.com/search.php?cmarque=VALLIANT%20&modele=ECOTEC%20PLUS%20824