Baxi 105HE high C/heating pressure and low DHW pressure?


26 Sep 2012
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West Glamorgan
United Kingdom
Hi guys. I have a baxi 105he which was losing pressure regularly. There were no evident leaks but I then noticed the PRV discharge pipework was hot. The Prv was continually open.
As the system had drained on its own I changed the prv.

I recharged the system but still seem to be losing a little pressure. When I repressurise the system to 1 bar the central heating pressure becomes high (3 bar) but when i open hot water tap the system then becomes lower?

Any suggestions?[/quote]
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I will try to expand on the previous.
You need to in this order turn of your boiler electrically,isolate the flow and return iso valves,drain the boiler by opening the drain off small white valve behind condensate trap [bit awkward to access],while that drain is open attach a foot pump to the valve on the expansion vessel and pump it up this will blow the excess water out of the vessel,when most of the water has been discharged close the drain valve make sure there is about 1.5 bar charge in the vessel and iso valves and re-pressurise system to 1.5bar.
Hope this helps
Thanks I'll give it a go and report back. Really pleased with your quick responses. Can't fault you both
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Thanks for your help guys. Drained system blew out remaining water with foot pump recharged vessel and re- pressurised the system.
Initially when I turned the unit back on the pressure dropped off but I think that was due to any releasing any residual air in the system?
Recharged 0.5 bar again and now the ch and she seem to be holding at around 1.8 bar.
I'll monitor over the weekend.
Thanks again
With the system open you need to pressure the air to about 0.9 bar and then pressurise the system to about 1.5 Bar cold.

When hot the system pressure should only increase by about 0.3 Bar.

Its best to let all the air out of the EXV BEFORE you depressurise the system. That will force any water out of the air side and enable you to see if there is any water in it.

Make sure you remove the filling loop to be sure it not letting by.

You say that the pressure creep up to 3 bars then you turn on hot tap and the pressure drop down? Sound like pinhole in water to water heat exchanger.


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