Pressure problems after fix

25 Jan 2016
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United Kingdom

Hope that this is the right place for me question.
I had a problem with a high pressure and noticed that my prv is leaking after pressure going up to 3bar, also expansion vessel was dead. To solve this the Prv was replaced, pressure sensor as it was reading to high and expansion vessel as well.
Boiler pressure was set for 1bar and EV was precharged to 1.5 according to the sticker on EV.
The engineer did not check the actual pressure in EV before and after fitting.
The problem is when system is cold and boiler will read 1bar but when heating is on 2.3 or 2.4 when heating up at the early stage and then when is settling to desire temp which is 53C is on 2 or 2.1 bar. When heating stop the pressure will drop from 2.1 to 1.8 in 20 min and then it will drop down to 1bar after cooling down for few hours.
To get this info I did watch the boiler very often (my wife think I went crazy watching boiler for hours ;)) Also I did turn off the cold water feed coming to the boiler as filling loop is possibly leaking but I did isolated this by turning off main cold supply valve to the boiler as we cannot use hot water ATM anyway (read below).

We have luke worm water as well so he will come back and replace plate heat exchanger this week.

I will be grateful for any advice as I did find a lot of helpful info on this site.

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Bit confused by your post... Not sure what the actual problem is that you have now!

Its normal for pressure to go up when system gets hot... Hotter = more pressure.

As long as it doesn't reach 3bar when fully on then the PRV won't activate and all is fine.
Sorry for that....

When system is cold the pressure is 1bar, and when CH is on and set up to 53C it will go up to 2.4bar for 10 min and after that it will drop to 2.1bar for some time until will have to work hard again to heat up water (2.4bar).

I know the pressure should go up but not by 1.4bar? From 1 to 2.4?
I did read boiler manual and it says that EV should be (or it is when boiler is new) at 0.75bar. My system is 1bar when cold and new EV which was fitted was delivered with precharge of 1.5 bar according to the sticker on EV but engineer havent check the pressure of new EV.

Should the pressure of EV be the same as boiler pressure?
Was the Expansion Vessel (EV)replaced like for like? Almost sounds as if your EV is close to being not large enough for your system.
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Yes, I did order it for my glow worm ultracom 30cxi which is 8L EV. Is it something to do with the EV pressure? As I believe it was 1.5bar precharge ( engineer haven’t check it) Is it to much?

The EV should be set to what the boiler needs it to be, not what is says on the EV.

Not sure where you are reading but as far as the Ultracom 30cxi's (G.C. No. 47-019-02) MI is concerned then the EV pre-charge should be set to 0.5bar on an open system.

The EV needs setup again .... properly.
Hmmm I just ordered a new EV for my boiler and plumber did the rest. He just fit a new EV and that was it. He will be back tomorrow so I will tell him about that. The new EV was precharged at 1.5bar and according to boiler manual this 8L Ev should be at 0.75 bar :/
Should I tell him to change it to 0.75 bar or it should be the same as system pressure? Boiler is filled to 1bar when cold. Should we do the same with EV? Thanks
Thank you. I did looked again and it should be 0.5bar.
I will set boiler for 1.2 and EV as it should be (0.5)
Will this sort high pressure problem?

I dont have to drain the boiler? I will have to drain the boiler before changing pressure? I will wait for my plumber so he will do that as I need new plate heat exchanger so boiler will have to be drained anyway so we’ll do EV at the same time:)

thanks for your help!
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Yes, the boiler needs to be de-pressurised and the system open to air to allow the EV to be pre-charged properly.

Maybe you need a boiler engineer rather than a plumber. Whoever installed the EV should have been a GSR, as the EV in that boiler is inside the room sealed section of the case and they should have performed some safety checks. They should also have known that an EV pre-charge always needs checked and set properly with a new EV.
He is a gsr engineer. He was a bit in a hurry that day but he is a top bloke :)
I will tell him tomorrow and it should be easy to do as he will have to put new plate heat exchanger Due to luke warm water :/
Pressure should be ok until he pop in as I was watching it all day and on high heating stage it was reaching 2.4bar and then it was stable at 2.1 bar, so hopefuly it will be lower after bringing pressure down a bit.

thank again :)

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