baxi 105e boiler

[mitsubishiman]

ihave a baxi 105e economy boiler and it needs presureising every time i use the central heating. What it does when i turn central heating on is presure goes round to 3.5 bar and drips water out of the overflow. nowwhen i turn central heating off overnight it loses all presure and needs re presureising in the morning for hot water.It blows a pint or so of water from over presure safety pipe into jar and consequently when it cools overnight has no presure in the morning even for hot water. Domestic hot water only keeps presure and is fine but as soon as i put heating on it winds round to 3.5 bar or more and is ok while working but when turned off it loses all presure because i think it has lost about a pint of water because of over presure. Any ideas

mitsubishiman.

 

[45yearsagasman]

1st thing is to check the expansion vessel for charge pressure.Depressurise the system via drain cock and locate exp vessel valve (top rear of boiler).Remove dust cap and check pressure,should be approx 0.75-1.0bar.If no pressure then pump it up using tyre pump.If water comes out of valve then exp vessel has failed.

 

[bengasman]

Chances are your safety valve is leaking too now.