Worcester Greenstar high pressure / PR pipe droplets

[FourCandles]

Hello

I have noticed water droplets from the pressure relief pipe recently which has also changed colour at the end ( blue ).

I have kept an eye on the water pressure which on heating is always in the red / 3 bar. It then drops to 2 bar when water temp around 50 during the day / when no call for heat.

After reading the FAQ's I turned off the boiler, vented the rads ( which had lots of air in ) which dropped the pressure to zero and then checked the expansion vessel. the reading I get is 35 psi which is 2.4 bar. The FAQ's and the Worcester manual mention 0.75 bar. I then filled the system to 1 bar and run on max. The pressure now goes to to 2.5 bar when 80 degree temp.

- Is the 2.5 bar expansion vessel reading someone to be concerned with ??
- I take it the PRP droplets was due to the high pressure ?

Any comments will be very gratefully received. Thanks in advance.

 

[lightning]

How did you check the expansion vessel ???

 

[FourCandles]

Using a tyre gauge.

 

[boilerdoktor]

you have probably tested the system pressure!

If you press the scraeder valve does water or air come out??

If its water replace vessel. If its air you can re pressurize it!

See FAQ

 

[GasNewb]

Most boilers when set to max temp will work to the 2.5 bar pressure. If it gets to that and stays there then i'm told its fine. Should it keep on rising past 2.5, and then the PRV opens, then the expansion vessel is the issue. As stated above, check to see if you have air or water coming out when the pin is pushed in.

 

[bengasman]

Most boilers when set to max temp will work to the 2.5 bar pressure.

It shouldn't. A properly installed and maintained system will be around 1 cold, and 1.5 hot



In most cases like this the ev is either flat or dead, with obvious remedies.


Which model greenstar is this, 24i junior?

 

[FourCandles]

Thanks for all the replies.

@ boilerdoktor

- I tested the internal expansion vessel using a tyre gauge, isn't the system pressure the bar gauge from 0 - 4 bar on the front of the unit?

- When EV scraeder pressed only air comes out. After using the tyre pressure gauge on the EV the reading was 35 psi.

- See FAQ - As original post, FAQ read and followed.

@ GasNewb

Now 1 - 1.5 bar on cold / 33 degree system temp. 2.5 bar 82 degree system temp.

@ bengasman

- Greenstar 30 cdi. Is 2.5 bar system pressure at 82 degrees too high ? The gauge has a black line on 2 bar but the manual has no reference to what the mark is referring to. I assumed ' normal hot system pressure indicator ' ?


Follow up q's

1. Why is the expansion vessel pressure so high? The manual says 0.75 bar ( 11 psi ) and mine is 35 psi !!

2. Should I let out air on the EV ?

3. Am I worrying over nothing ? The system works fine and the droplets out of the prv have now stopped,now the system pressure is not going above 2.5 bar.


Thanks in advance again and I really appreciate all input.

 

[bengasman]

EV must be charged with system pressure at virtually 0. Somewhere around 1 bar should do the trick, it doesn't have to be that accurate.

Flow temperature at 82 is way too high. Not a problem for the boiler, but your gas use will be about 10% more than necessary.

CDI is quite a good boiler, and as they are not cheap, they are usually installed quite well.

The blue indicates the system water is not clean, and the open ls valves show it was not balanced.

It's worth spending some money to get all done to spec, after which you should have a reliable, durable system.

 

[GasNewb]

I'm told that if the boiler manages to hold the pressure at 2.5 bar, rises no more over when set to max temp then it is working as is intended. Operating to its maximum ch pressure which would appear to be 2.5 bar whilst containing the expansion. But i'm not anywhere close to as experienced as bengasman and i haven't got a clue about the blue he's mentioned.

I'm sure I stand to be corrected though.

 

[bengasman]

I'm told that if the boiler manages to hold the pressure at 2.5 bar, rises no more over when set to max temp then it is working as is intended.

Working at 2.5 bar in itself is not a problem, but close to the limit. If the 2.5 was reached from a cold at 2 bar, it wouldn't be a problem. It is the rise of 1.5 to get there that is too close to the limit. It only takes a little bit more and the prv will operate with the risk of continued leaking.

 

[GasNewb]

I see what you mean Ben, so it should only be rising 0.5 bar from its cold pressure. What would be causing it to rise soo far? His expansion vessel has plenty pressure in it, thus my mind seems to think it is capable of containing the expansion. Could it be undersized?

Cheers.

 

[bengasman]

I see what you mean Ben, so it should only be rising 0.5 bar from its cold pressure.

It's more art than science;0.5 is an arbitrary figure.


What would be causing it to rise soo far? His expansion vessel has plenty pressure in it, thus my mind seems to think it is capable of containing the expansion. Could it be undersized?

Could be any of the theoretical causes, it's the engineer's job to find out which one.
Don't fall into the trap of the "in my mind" routine; always test your theory.

 

[GasNewb]

I see, i'll question me brain matter a bit more. But sundays a day of rest so i'm gonna do just that!