Baxi 105he Instant pressure loss

[Brompton]

New member here! Had pressure loss problems on Baxi 105he instant for months now. Boiler approx 2 1/2 years old. Have checked CH system and no leaks. Have repressurised pressure vessel and still getting pressure loss - down from 1 bar to under 0.5 bar in 3 weeks.

Looked at forums and seems I have a pressure vessel/ prv problem. Will need to get a CORGI guy out.

Is it best to replace the pressure vessel and the pressure relief valve at same time, or just the prv and see what happens?

Any ideas of part numbers and costs of vessel (with auto air vent if possible) and prv?

Thanks

 

[corgiman]

is the pressure rising whilst the boiler is in operation?

 

[Brompton]

Yes - for HW and for CH. With CH, pressure drops back pretty quickly once room thermostat switches off. I also get a bit of a noise as the divertor valve switches from HW to CH, though the seals were replaced last year.

 

[corgiman]

how high does the pressure get?

 

[Brompton]

On CH, it gets up to around 2 bar (starting at 0.5 bar). On HW, looking at it, it decreases to 0 Bar as soon as I run a hot tap, and goes back to 0.5 bar when the overrun cuts out. It has always dropped temporarily on HW, but I thought that was normal! Appreciate your help.

 

[Vic Spanner]

I`ll ask the bleeding obvious is the discharge pipe dripping outside.

What do i know

 

[Brompton]

Been outside to check. No drips on HW. On CH, pipe drips between 0.5 bar and 1.0 bar, then drips seem to slow down above 1.0 bar

 

[JPC]

so its is dripping on the outside then ?

 

[Brompton]

Yes, from the discharge pipe at certain pressures. New Pressure relief valve needed?

 

[corgiman]

what are these "certain" pressures

 

[Brompton]

On CH, pipe drips between 0.5 bar and 1.0 bar, then drips seem to slow down above 1.0 bar

See above post

 

[corgiman]

but they dont make any sense?

The pressure relief valve should open at 3 bar, and if its dripping at .5 why would it stop at 1 bar.

is the dripping defo coming from a pipe that is outside??

 

[Brompton]

I didn't think it made any sense either. Defo drips from a pipe outside that is connected to the PRV on the boiler and then goes outside. Have just run it again on CH - drips start at 0.7bar. Replace PRV and see what happens?

 

[corgiman]

Sounds like a start

Sorry mate but I aint got a clue wots going on

 

[Brompton]

Done some more checks. Drips outside are NOT from PRV (have isolated pipework). Drips are from condensate drain, which joins with PRV pipework outside. PRV is fine at 2 bar - NO drips. Should have noticed, sorry

Does this mean its a pressure vessel problem?