Vaillant ecotech pressure failure

[Winnieweg]

Seven year old boiler, no problems at all, regular service. Sudden F75 fails, replaced sensor, still failing, replaced pump, still failing but now no fail codes, just overnight pressure drops resulting in non start. Cold boiler display .5, two second fill jumped to 1.8, system started and dropped to 1.5.
PCB next? Any ideas? Tia

 

[ianmcd]

unlikely to be the PCB check the expansion vessel and pressure releif valve

 

[Winnieweg]

Thanks, I'm just waiting on the engineer to come, from what I'm reading I don't think PCB had anything to do with this but he says he's ordered one. I have checked house for leaks and nothing so thinking prv as you suggest.

 

[CBW]

I've had an f75 on a pcb once, but only the once. If it's losing pressure I agree with @ianmcd, probably going to be expansion vessel or prv. Also could be a leak on system, and get engineer to check for rubber hoses inside boiler (prone to leaking) and in earlier models of ecotec.

 

[SpecialK]

Top it up and turn it off. Isolate the heating loop. Does it still drop pressure?

 

[Winnieweg]

I'll check that.
Trying to decide if it's an actual leak that causes the drop, or if it's lying to me/boiler about the pressure as it goes up and down like a yo-yo.

 

[Winnieweg]

Prv checked and dry. Boiler drained and expansion vessel repressurised. Analogue and digital gauges showing same pressure. F22 fail on fail history so PCB not at fault. Leaving overnight to see if pressure maintains. Visual check to see if any system leaks, tied all joints with paper butterflies. Waiting game.......

 

[CBW]

One method I like to try is take pressure up to approx 2.8 - 2.9 bar and check for leaks that way, if it’s going to show, a good amount of pressure should help.

 

[ianmcd]

https://www.ebay.co.uk/p/Genuine-Va...fpWzn0KdC-vPS92DICR2BHivbPLbb53saAiNWEALw_wcB

 

[dilalio]

And, worth noting... Heat exchanger can leak straight down into the condense sump and not be evident to other indicators on the sealed system.

 

[ScottishGasMan]

Prv checked and dry. Boiler drained and expansion vessel repressurised. Analogue and digital gauges showing same pressure. F22 fail on fail history so PCB not at fault. Leaving overnight to see if pressure maintains. Visual check to see if any system leaks, tied all joints with paper butterflies. Waiting game.......

Was the vessel pressure low?

 

[Winnieweg]

Vessel pressure wasn't low, not hot to touch under operation either. Recently serviced so engineer decided to repressurise in event air may have gone into system and caught in auto air vent. ( I'm just repeating what he said).

 

[John D v2.0]

If the pressure is going from 0.5 to 1.8 with 2 second fill then your expansion vessel isn't allowing expansion. Either the initial pressure in it is at least 1.8 bar, the vessel is full of water, or the pipe connecting it to the boiler is blocked.

 

[Winnieweg]

Engineer checked air was coming out. He then repressurised suggesting it was possibly his error. It was fine the next morning. I'm away from home so he asked me to now time and pressure and turn system off. We shall see what it's doing on Friday when I get back
I appreciate your information, it's helped enormously.

 

[Winnieweg]

So, after a week away. System was off, boiler was on. Pressure was 1.6 when we left.
Pressure 0.1 on return. Filled to 1.6, switched on and rose to 2.
Worked fine that evening and all next day.
Today, back to 0.1
This has to be the boiler surely?
No leaks in the house, I keep checking.
If system was off, valves would be closed? So pressure drop has to be the boiler?
Starting to get annoying.....