Vaillant Boiler losing pressure

[kopper99]

Hi
I have a Vaillant EcoFit 830 boiler that had suddenly keeps losing pressure to 0 Bar with a F22 error. So there is no hot water or heating.

After re-pressurising it, it starts working again for 2 hours before the same thing happens again. I had a Boiler Engineer through breakdown insurance attend and he checked a few things but could not see any obvious issues with the boiler. He said the most likely cause is a leak in the pipes somewhere under the floors and I would need to find a plumber to do a test and trace.
Is this correct and does anyone have any experience of this issue?
The boiler is under warranty with Vaillant but there is no point calling them if the issue is an external fault rather than the boiler.
Any advice?
Thanks

 

[MeldrewsMate]

Isolate the heating pipework when the heating is cold, and have it tested to 3 bar with a pressure pump. Any drop in boiler pressure shows it as a boiler problem, a drop in system pressure indicates a pipework leak. Don't ignore the hot water cylinder though, a leak in the cylinder's heating coil is not visible, and it may be worth pressure testing just the cylinder.

However..... If you have an unvented cylinder the boiler pressure will rise on a cylinder leak.
If you have the boiler downstairs and a vented cylinder with loft tank the pressure should not fall below about 0.3 bar, unless you have a bungalow!
Try to isolate the problem to a specific area to keep your professional help costs to a minimum.

 

[kopper99]

Isolate the heating pipework when the heating is cold, and have it tested to 3 bar with a pressure pump. Any drop in boiler pressure shows it as a boiler problem, a drop in system pressure indicates a pipework leak. Don't ignore the hot water cylinder though, a leak in the cylinder's heating coil is not visible, and it may be worth pressure testing just the cylinder.

However..... If you have an unvented cylinder the boiler pressure will rise on a cylinder leak.
If you have the boiler downstairs and a vented cylinder with loft tank the pressure should not fall below about 0.3 bar, unless you have a bungalow!
Try to isolate the problem to a specific area to keep your professional help costs to a minimum.

Thanks. It's a Combi boiler in the kitchen with no external cylinders.

 

[MeldrewsMate]

Then simply get it up to temperature, turn it off, and isolate

Thanks. It's a Combi boiler in the kitchen with no external cylinders.

That info would have prevented the waste of more than 50% of my last post.

Simply get it up to temperature, turn it off, and isolate at both heating valves.
Note the boiler pressure, and wait.
What is the boiler pressure after 1 hour?
What is the boiler pressure after 8 hours?
Does the boiler pressure go up or go down when you re-open the heating valves?

 

[kopper99]

I called another engineer and he suggested turning off the isolation valve after re-pressurising it for a few hours. He said if the pressure then drops it could be a Boiler fault.

I've checked underneath but cannot work out which is the isolation valve:

 

[kopper99]

Then simply get it up to temperature, turn it off, and isolate

That info would have prevented the waste of more than 50% of my last post.

Simply get it up to temperature, turn it off, and isolate at both heating valves.
Note the boiler pressure, and wait.
What is the boiler pressure after 1 hour?
What is the boiler pressure after 8 hours?
Does the boiler pressure go up or go down when you re-open the heating valves?

Sorry I thought by stating the model number would be sufficient.

I have just been told what you have suggested but any chance you can tell me how to isolate it? Also, does turning it off mean turning it off at the mains?

Thanks

 

[kopper99]

Update
A Vaillant engineer came out as it was under warranty and confirmed the boiler is fine and the issue is caused by a leak somewhere in the system. As there are no damp patches anywhere in the upstairs ceilings he said it will most likely be under the floor boards downstairs.
He also suggested to try and get a plumber to pour in CT1 Miracle Seal into the towel radiator upstairs but not sure how effective that would be.
Has anyone used this Sealant before?

 

[Johntheo5]

What is the pressure rising to while system is heating up??, it shouldn't rise above 2.7bar, but generally will rise to ~ 1.7/2.0bar.
The boiler will have a PRV (pressure relief valve), opens at 3.0bar, with the vent pipe normally exiting out the wall at the back of the boiler, can you locate this and ensure no leakage.

 

[kopper99]

What is the pressure rising to while system is heating up??, it shouldn't rise above 2.7bar, but generally will rise to ~ 1.7/2.0bar.
The boiler will have a PRV (pressure relief valve), opens at 3.0bar, with the vent pipe normally exiting out the wall at the back of the boiler, can you locate this and ensure no leakage.

If I fill it to 1.5 and put the heating it rises to 1.6 and stays. Once the heating is off, it drops all the way to 0.0 within 2 hours

 

[Johntheo5]

Unlikely to be the PRV then but no harm checking it.

 

[kopper99]

Unlikely to be the PRV then but no harm checking it.

That was replaced by the Vaillant engineer on case. He also isolated the boiler from the system and confirmed afterwards there is a leak somewhere under the floorboards.
I am also considering calling professional leak detection company but not sure how reliable they are in detecting leaks like this. All the flooring in the house is laminate.

 

[ianmcd]

Check your house insurance policy, many include trace and repair these days for your scenario