Sudden pressure loss Baxi boiler

[michaelconroy]

Hi

I have a Baxi Combi Instant 105e.

Originally it was providing DHW to 3 areas, central heating & underfloor heating (UFH).

For years it has shown a gradual loss of pressure from 2 – 0.5 over a 2 – 3 week period.

Now the system only provides DHW to 2 areas and to the UFH in 2 rooms and I am trying to solve this pressure loss problem.

I have undertaken the following repairs:-

1. Dismantled & tightened various mildly leaking joints in the boiler.
2. Replaced PRV
3. Replaced AAV and pump O rings
4. Fixed leak on UFH manifold

No leaks are visible now but the pressure situation is actually worse. I have to re-charge the system (with small quantities) every 2 – 3 days now. The pressure appears to stay constant for most of that period then to suddenly drop to 0.5.

Any suggestions please?

Mike

 

[bengasman]

gauge is full of carp and does not work properly is 1 option. from the history I would give you90% chance there is sludge in the system

 

[gas_man_gaz]

have ya checked the expansion vessel?

 

[michaelconroy]

Thanks for the advice.

I've seen what happens today before the loss of pressure.

The indicator lights on the boiler were showing the water temperature at 60° but no hot water came out of the tap. Nor did the boiler fire up. I let the hot tap run a while but only got cold water.

I left it a while & tried again, this time watching the boiler. This time when I turned on the hot tap the DHW sensor warning light flashed on then off, the boiler fired up and the water pressure dropped from 2.5 to 1.0 (it now stands at 0.5).

My plumber has already looked at the primary heat exchanger and found no external signs of a leak.

Looking at the manual I see an item described as a DHW plate heat exchanger which I have not inspected.

Could there be some way that the water in the primary circuit is leeching into the DHW and causing the loss of pressure?

Thanks

Mike