c&m overheat after vessel check....please help.

[ukes]

Hi guys, yet another issue with my combi boiler.....please help, pregnant missus and the moods not good!!!

Okay, so my boilers been running fine since new pump was fitted (different story) for months.......apart from the fact that every morning it needs topping up after the low pressure switch craps out......top back up until the next morning, no problem.

So today i set about investigation the issue and suspected either a knakketed vessel or dodgy pressure release valve.


1) Switch off
2) Drained water pressure to zero at radiator.
3) Released pressure on shreader valve on expansion vessel, no water, seems pressured
4) Attach guage, currently at about 0.8bar
5) Add a little pressure up to 0.9 to allow for any loss when removing pump.

Assuming thats okay I now assume im losing pressure through the release valve, so attach bag ready for tonights drop out.

Turn boiler back on and its is running hot/cold in 10 second periods, eventually getting ridiculously hot. Happens to central heating as well, can feel the nearest rad start to warm then cool continously. Taps do it with both ch on and off! Pressure on the water guage is rising and dropping continously (only about 0.3bar).

So without getting to the initial problem i now have another, and her in doors aint best pleased.

Does anyone have any idea why all of a sudden i now have this hot/cold issue?

Please!!!!!

 

[ukes]

I forgot to add that the pipe from the prv was wet when i attached the bag, and theres condensation/water droplets in the flexi hose.

 

[AngelesPlumbing]

Fill the system about 1.5 bar and open manually the PRV for 30 seconds to get rid rubbing in the system. If it still leaking, look filling loop is letting by? Or expansion vessel ruptured and finally have you radiator in you home might be too much volume in your system, if it does you need extra 12 litre expansion vessel

 

[ukes]

Fill the system about 1.5 bar and open manually the PRV for 30 seconds to get rid rubbing in the system. If it still leaking, look filling loop is letting by? Or expansion vessel ruptured and finally have you radiator in you home might be too much volume in your system, if it does you need extra 12 litre expansion vessel

Hi, thanks for the reply

Im a bit confused though, i thought opening the prv was a no no because it sticks?

Are you suggesting i open the prv and then top back up?

There is indeed a rubbing noise in the system like trapped air, and despite the fact the water temp on boiler is pn the lowest setting its running almost boiling, then freezing, then boiling etc

Anyone else got any ideas?

 

[ukes]

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• ukes
• 28 Mar 2014
• 1

[/list]

 

[twgas]

does your system pressure remain below 2bar when the radiators heat up (from 1 bar cold)?
the heating/cooling problem might be due to a circulation, temp sensor or combustion/setting problem. I would suggest getting the pressure sorted first and advise against opening the prv unless it is already passing, in which case it may well need to be replaced.

 

[Agile]

Set the pressure to 1.0 bar when cold and watch the pressure as it warms up the rads and see how much it increases.

Should only be about 0.3 bar !

Tony

 

[ukes]

Thanks guys

Yeah the pressure remains at about 1bar irrespective.

I forgot to add that it does it on both ch and taps!!! can feel the rad warm up then cool off ala the taps!

Seems to me it could one of about 20 things, think ill get someone out from the insurance company and have a shower at the mother in laws all weekend again....