C/H Pressure incresing on a Baxi 105e

[hatstand69]

Hi,

Up until a week ago my C/H on my Baxi 105e was stable at 1.3. The boiler hasn’t been touched, but has started to increase the pressure until it vents outside at about 3.2. if I turn the boiler off and switch it on the next day, it takes about ½ hour before venting again.

Before I call in the experts, is there anything I can do? I have previously used this site to cure my lack of hat water woe’s, thank you very much. So am pretty competent with a screw driver. But don’t want to risk doing something out of my league.

 

[hammerswinger]

Hi,
it sounds like the expansion vessel (pressure vessel) has lost it's air or is knackered.

Take a look at the 2nd post at the link below:

//www.diynot.com/forums/viewtopic.php?p=251090#251090


Cheers.

 

[hatstand69]

Thanks hammerswinger, I will check the pressure tomorrow night and follow the guidance given (working away from home). I'll post back the outcome.

Thanks.

 

[hatstand69]

hi, i followed the instructions to test the pressure of the Pessure Vessel. Dropped the pressure to zero and the reading was 5.5 psi. i charged the vessel to 10 psi. refilled to 1.2 and started the C/h up. The pressure increased to 2.5 and rising before i switched off.

I tested the pressure vessel when I switched off and it read 29 psi. is this right?

Is there anything else I can do before calling in the experts?

 

[hammerswinger]

Did any water come out of the expansion vessel valve?

It is important to follow those instructions to the letter when recharging the air.

I can't see any reason why your CH system would suddenly start to increase pressure other than the expansion vessel having no air in it or being knackered.



Cheers.

 

[petit_pablo]

If the expansion vessel is pumped up to around 1 bar and the problem persists you potentially have a blockage within the boiler leading to the expansion vessel

 

[baxpoti]

Another possibility, If filling loop is disconnected you may need a new plate heat exchanger

 

[hammerswinger]

If the expansion vessel is pumped up to around 1 bar and the problem persists you potentially have a blockage within the boiler leading to the expansion vessel

I thought about that, but as the pressure in the expansion vessel seems to be increasing as the system pressure rises I thought it must be ok?

If filling loop is disconnected you need a new plate heat exchanger

Would you explain the reasoning behind this please as I don't follow but am willing to learn.


Cheers.

 

[hatstand69]

thanks very much for taking the time to reply. it is much appreciated.

No water came out of valve, just air. I bled a radiator near the boiler to get the pressure to zero, but didn't take out 10 ltrs as the instructions say. I will repeat and take 10 ltrs out. Then make sure the vessel is at 14psi (1 bar).

If that fails is it time to get someone in, or is changing the heat plate the nxt step.

 

[hammerswinger]

If no water came out of the air side of the expansion vessel that's a good sign as it means that the diaphragm isn't punctured.

It is possible that there is a blockage in the tube that connects the vessel to the boiler pipework, but as you noted a change in the pressure reading of the vessel before I'm assuming it's not blocked.

i charged the vessel to 10 psi. refilled to 1.2 and started the C/h up. The pressure increased to 2.5 and rising before i switched off.
I tested the pressure vessel when I switched off and it read 29 psi...

It may be easier to re-pressurise the vessel this way:

Close the service valves on the Flow & Return pipes to the boiler.
Drain the boiler at the boiler drain point, leave this open whilst you pump up the vessel.
Once you are happy that the vessel is at the correct pressure close the boiler drain point & open the service valves.
Top up the system with the filling loop to whatever you have it at, approx 1.25 bar.

Note:
Even when pumped up there isn't much air in the vessel so when you disconnect the pump you can loose quite a bit, so remove and refit the pump to see how much the pressure drops when you remove it, you can now put a bit extra air in to compensate for the air you will loose when you disconnect the pump!

I think baxpoti is thinking along the lines that the plate heat exchanger could be pin holed so could be letting mains pressure water into the CH circuit causing it to over pressure.

Cheers.

 

[hatstand69]

It worked. I did as you said, refilled and hey presto. It hasn't gone above 1.6. Brilliant.

Thank you very much for your help, it is very much appreciated.

 

[hammerswinger]

Glad you're sorted


Cheers.