Baxi 80e Pressure problem

[LegionOfBrad]

Hi there,

We have a Baxi 80e (with instant hot water) in our loft. On occasion i go up there and notice that the pressure has gone down to almost 0. Much less than 0.5 that is its minimum operation specs. We had the expansion vessel replaced about 2 years ago when we were having pressure issues with it before.

I fired the heating up to 30 degrees (so i could make sure the heating stayed on) this morning to watch what it was doing.

Once the heating goes on the pressure gradually rises up to 3.0. At that point the flame light goes off and the pressure then over a few minutes goes back down to 2.5 at which point the flame goes on and the pressure rises to 3.0. Rinse and repeat. I couldn't get it to dump the pressure down to zero after about an hour (at which point the wife was boiling so i had to turn it off)

Does the regulating pressure between 3 and 2.5 sound like the expansion vessel is working correctly? And thus i need to look else where for whether there is a slow leak somewhere dropping the pressure? Unfortunately with it being in the loft i don't go past it that often but today i'll be checking it every couple of hours to see what happens.

There don't seem to be any leaks at the boiler or at any of the radiators.

Can anyone give me any thoughts on what the pressure dropping to zero could be?

 

[jackthom]

If it's rising to 3 bar it's got to be the expansion vessel again. Above 3 bar the pressure release valve will let out water, so when things cool down and the water contracts again you'll find the pressure falls close to zero.

Has the vessel been checked since it was replaced. It may just need repressurising.

//www.diynot.com/wiki/Plumbing:faq7

 

[MeldrewsMate]

Has the vessel been checked since it was replaced. It may just need repressurising.

To clarify, that's repressurising the air side of the expansion vessel.

 

[LegionOfBrad]

Thanks guys. Pressure on the expansion vessel is virtually 0. I have ordered and extension for my foot pump and will drain the system and pump to 0.8 bar tomorrow. If it's still going to 3Bar after that i wall get a plumber in.

 

[LegionOfBrad]

No water on the valve on the vessel.

System drained and vessel recharged to 0.8 bar this morning. Pressurised the boiler to 1 bar the bled the radiators and pressurised again. All tip top except one radiator where the key just spins on the nipple so will need to see if I can find a less worn down key.

Will keep and eye on it over the next few days to see how it goes. If it starts to lose pressure maybe it's a leaky valve?

 

[jackthom]

Yes, you will need to keep an eye on the Pressure Release Valve because once they have passed water they often don't fully close again.

If you suspect it is leaking look for the outlet pipe (should be copper pipe to outside, NOT the plastic one which is the condensate drain) and tie a plastic bag around the end to see if you catch any water coming from it.

 

[LegionOfBrad]

I can see the pipe by unfortunately we live on a terrace 2 ft higher than our neighbours and it releases into the gap in between our roofs. So no chance to see whether it is venting out.

Have been sat here for 45 minutes with the heating set to 30degrees and the pressure hasn't gone over about 1.8. I will do another blast of it later on.