high and low pressure

[boilerslave]

I have a heatslave 20-25 thats driving me nuts, HELP PLEASE. Origional problem was a slow loss of pressure overnight. Re-pressurised every morning for 7 days, then auto air pressure valve dumped water all over floor, replaced valve. pressure still seeps away overnight (have tried reseating prv). Now when boiler is running pressure rises from .75bar to 3+bar and i keep having to shut the boiler off manualy. Have checked pv is ok (let air out, no water) and repressurised to .6 bar. Dont know what to do next. Any suggestion?????

 

[GPlumb]

The pipe connecting vessel to the boiler may be blocked. check that.

 

[boilerslave]

Have checked pipe and its clear, any other thoughts?

 

[snb]

if when the system is cold and you have 1 bar pressure and then turn the heat on if it rises more than 0.5 bar then either your expansion vessel has no precharge or it is knackered. On these boilers it is common for them to need replacing every 4 or 5 years

 

[boilerslave]

As ive said already pressure vessel has no water in it and it holds the .6 bar i put in. Could this have anything to do with the heat exchanger, and if so how would i check it?

 

[Agile]

As ive said already pressure vessel has no water in it and it holds the .6 bar i put in. quote]

It is quite possible to have all that but still not be communicating with the rest of the system or set up correctly!

I suspect that you have just not followed the instructions in the FAQ.

Please would you open a drain cock and then pressurise the EXV to 0.9 bar. This should take about 10-20 strokes of a foot pump operated by hand. Then repressurise the system to 1.5 Bar WITH the foot pump still connected and tell us what the gauge reads. Then remove it and replace the cap. Problem solved! ( But only if you follow what I have told you rather than thinking anyone who works on boilers is stupid! )

Tony

 

[boilerslave]

Agile, have followed your instructions. the pv reading is still .9bar. Does this mean a blockage in feed to pvessel.? or is the reading supposed to stay the same ?. Thanks for your help.

 

[Agile]

Have checked pipe and its clear, any other thoughts?

Thanks for properly following my instructions!

You have now proved ( to me ) that the connecting pipe is indeed blocked as we suspected but contrary to the statement you posted above.

Obviously, when you increase the system pressure to 1.5 if there is no blockage then the air pressure will increase to the same value.

It should be fairly easy to remove the connecting pipe and probably find the blockage at the boiler side and perhaps poke it free!

I must apologise to everyone for some deficiencies in the FAQ on this topic but unfortunatly I am not allowed to edit it.

Tony Glazier

 

[boilerslave]

Some say he has fernox coursing through his veins,
others say his plumbing has gone a bit saggy,
we just know him as agile.
Thank you agile, have just performed arterial surgery on the pipe from boiler to pressure vessel and removed a very large clot from aforementioned tube. I had already checked this before but wrongly!. I undid the nut on the pv end of the pipe just a fraction and water spurted out at some pressure. I stupidly presumed water had come from boiler end, but of course it was backpressure from pv, still i was in the right area, not bad for a chippy. As soon as you said to leave the pump on the pv i realised my mistake. thanks again agile. Hopefully the losing pressure aspect was just the prv venting or dripping. Will put tin under overflow and check in morning.

 

[Agile]

Dont bother unless you have ongoing pressure loss.

Previously there was no where for the expansion to go so the pressure increased and opened the PRV.

Now the expansion is absorbed by the PRV and the presure will only rise about 0.3 Bar between hot and cold.

Simple repair when you know how!

Tony

 

[boilerslave]

Thanks again. The other problem my wife has been complaining about (apart from the obvious) has been a lack of domestic hot water for a shower first thing in the morning. timer set to heat water 3/4 hour before use, but just a limited amount of warm appearing. At other times of day dhw seems to work ok. Is this a knock on effect from the fault on the prv pipe as i cant get my head round why this would be. the small amount of time the boiler fies to heat water tank would not be long enough to pressure the system to 3bar+ thus venting the prv. please explain this to me if you think the problem will now disappear. Sorry agile, my mind wont let me rest unless i understand how and why things work.
As we speak house warming up nicely for the first time in two weeks, pressure has only risen .5bar in two hours