Baxi Boiler (Megaflow)

matjay

Hello,

Im wondering could anyone shed any light on an issue Ive recently been having with my Baxi Megaflo boiler?

Recently its been losing pressure, but heres the thing it only seems to do so when the heating is put on. Ive re pressurized the last few mornings and gone out to work and come back and pressure is still fine. The water comes on at 4pm and no pressure drop so the water cant be the issue. But when the heating goes on and finishes the pressure drops slowly until its gone and the boiler shows the error for no pressure and wont run until I put pressure back in by letting water back in through the valve in the hot press (fitting with a screw turn in it)

Ive watched the boiler closely over the last few runs on the heating and the pressure does rise above 2 bars crossing over into the red when heating the rads. Ive checked all rads and joints I can find in the hot-press and attic and no leaks can be found ( I was thinking that maybe a fitting had started to leak when the heat comes on.

Can anyone shed any light on this please?

Thank you,

J

Wearb

Your expansion vessel needs checking.
You most likely have water coming out of the safety pipe as the boiler starts to heat up. This pipe might be close to the flue exit in an outside wall, but wouldn't have to be there.

Would be best to have a registered gas technition look at it. Maybe book a service at same time.

matjay

Thanks for the info 👠I will look for the water coming out from the back when I'm home later.

Weird how the pressure doesn't drop when the water comes in but does after the heating??

Will book a service and get it looked at proper ðŸ‘👌

Wearb

matjay wrote: »

Thanks for the info 👠I will look for the water coming out from the back when I'm home later.

Weird how the pressure doesn't drop when the water comes in but does after the heating??

Will book a service and get it looked at proper ��

Heating expands the water. The expansion tank absorbs this expansion, when working properly.

matjay

Just an update after coming home I have run the heating and pressure is steady at 2 bars. I've turned the temp down on the boiler to 65 degrees rather then 80.

The pressure hasn't dropped since I've done this. Is there a chance the boiler was running too high for too long and this was the cause of the pressure build up, hence causing the PRV to kick in?

Cheers again for the input.

Wearb

Higher temperature causes more expansion. I've no idea why your system is ok now. Fingers crossed.

John.G

If the exp vessel is OK and has been set up properly, ie a pre charge pressure of 1.0 bar and a filling pressure of 1.5 bar when cold then if 65C results in 2.0 bar pressure, running at 80C should result in ~ 2.4 bar, suggest checking pressure when system is cold. The PRV lifts at 3.0 bar.