britony combi 80 boiler

[antony]

hello new to this so hopefully have done this right.

Got a britony combi 80 boiler which looses it pressure down to 0 bar when you run the hot water for a shower or bath, then when the heating comes back on it goes back up to 1.5 bar????? anybody got any ideas

 

[wnjswozo]

expansion vessal,needs recharging,or replacing

 

[LIFES A GAS]

expansion vessal,needs recharging,or replacing

I don’t see how the expansion vessel could cause this to happen, if it's lost its pressure (air) then as the boiler reaches high temp when heating is running I would expect the pressure (system water) to rise and when it reached 3 bars the PRV would open resulting in loss of system pressure. I can’t understand how a boiler can re-pressurise itself without opening the filling loop unless the plate heat exchanger had failed but that would not explain the system pressure dropping to zero??
Martin

 

[oldplumber]

if the plate heat exchanger is holes and you run the tap pressure can drop to zero as water flows out of system, turn off hw tap and system pressure will rise as cold water now repressurises the heating system and then the heating of water in the heating will pressurise as it warms omho but check expn vssl first as its easy to do and see if its ok, and repressurise it is needed when sytem pressure is zero,

 

[LIFES A GAS]

if the plate heat exchanger is holes and you run the tap pressure can drop to zero as water flows out of system, turn off hw tap and system pressure will rise as cold water now repressurises the heating system and then the heating of water in the heating will pressurise as it warms omho but check expn vssl first as its easy to do and see if its ok, and repressurise it is needed when sytem pressure is zero,

I guess that would be possible but only if the mains cold water was 1.5 bar
Martin

 

[wnjswozo]

surely if cross plate heat exchanger goes,then water out of hot tap would be dirty

 

[oldplumber]

I guess that would be possible but only if the mains cold water was 1.5 bar
Martin

ok , whats your opinion then as to the cause of the problem, you have only commented on other peoples ideas not given an opinion as to the cause of the problem!

 

[antony]

kinda confused now guys

 

[Billy Bob Bob]

hello new to this so hopefully have done this right.

Got a britony combi 80 boiler which looses it pressure down to 0 bar when you run the hot water for a shower or bath, then when the heating comes back on it goes back up to 1.5 bar????? anybody got any ideas

its french and strange lol????

 

[LIFES A GAS]

ok , whats your opinion then as to the cause of the problem, you have only commented on other peoples ideas not given an opinion as to the cause of the problem!

I thought I was agreeing with you on my last post, not saying you were wrong, it’s one of those faults that with the limited info we have we can only rule out what it cannot be! I bet it’s not the PCB but I’ve come across so called engineers who would have changed it to try and cure the problem.
Martin

 

[stevetheplumber]

simplest explanation would be the filling loop is open and either theres no non return valve of its stuck open then water preasure drops when hot runs as mains presure drops
turn of loop and remove hose to see whats happening

 

[Billy Bob Bob]

this could well be a plate heat another reason it may do this knackered expansion vessel and prv taken out,loop passing and low incoming mains pressure when the hot is run the pressure drops because of a faulty e/vessel leaking out of prv when tap/shower turned of pressure increases loop passing these symptoms

simplest explanation would be the filling loop is open and either theres no non return valve of its stuck open then water preasure drops when hot runs as mains presure drops
turn of loop and remove hose to see whats happening

beat me to it Steve!!!!

 

[antony]

okay will give as much detail as i can. the boiler is charged to 1.5 bar, if i dont run hot water or heating and go out for the day when i come back it will be down to 0bar. If i recharge to 1.5 bar and turn the heating on it will go up to about 2.5 maybe 3 bar. but gradually drop down but not always. If i run the hot water for a bath or shower it will drop to 0bar by the time you get out of the shower. and 9 times out of 10 if you just leave it and the heating kicks in it will go up to 1.5 bar. few months back the pressure kept going right up and it turned out to be the pipe from the boiler to the exapnsion vessel bloked. the gas man also said that the prv would probably need replacing at some point so dont know if related. Think that is about all.

 

[LIFES A GAS]

The very small bore flexi hose that connects the expansion vessel to the boiler is a well known problem, it becoming blocked with sediment rendering the expansion vessel inefective even if the air pressure in it is correct. I have cleared a few of them by disconnecting the hose where it is attached the the PRV block and feeding my roll of solder up the hose and removing the blockage. As your pressure is rising to 3 bar when boiler is hot I would think the hose has blocked again or the air pressure has been lost.
Martin.

 

[antony]

martin would that make the pressure drop to zero as well??

 

[LIFES A GAS]

martin would that make the pressure drop to zero as well??

Yes, after rising to 3 bars, then the PRV would be forced open, and water would be lost until the pressure dropped when the PRV would close again, after a few time of it doing this all system pressure would be lost.
Martin.

 

[oldplumber]

I thought I was agreeing with you on my last post, not saying you were wrong, it’s one of those faults that with the limited info we have we can only rule out what it cannot be! I bet it’s not the PCB but I’ve come across so called engineers who would have changed it to try and cure the problem.
Martin

yup , sorry,was feeling tired after a sh*tty day full of leaks, like your latest theory, works for me.