Worcester Green Star 35cdi high pressure

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1 Feb 2009
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Location
Fife
Country
United Kingdom
Hi all, little advice please. I have a Worcester Green Star 35cdi which has always had a small leak some where and although never found it was so small only had to top up the system a few times in the summer and a little more frequent in the winter however I have recently developed another problem.

The pressure gauge has been rising to 3.5bar resulting in the PRV discharging water this only occurs when the central heating system is on and does not happen when using hot water.

I need to turn the boiler thermostat down to number 4 in order to ensure that the pressure doesn,t rise to 3.0bar however it is still pretty close. I have checked the expansion vessel and I get air out of the shredder valve and not water, I have checked all the radiators and they did not need bleeding. Some forums have stated check inlet pie to EV is not blocked don,t know how to do this.

Main concern is the Heat Exchanger has a hole and needs replacing question is would this result in high pressure readings ?? How to I check for this. or what other potential problems would cause this high pressure.

Any advice greatly appreciated also I not to got with boiler technology so any response appreciated but please keep it simple for an idiot like me

Thanks Alan
 
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Most likely cause is expansion vessel lost it's charge pressure or pipe blocked. Check the Wiki for details of how to check this. if you're not comfortable doing this you'll need to get someone in.
 
Hi thanks for the reply, as for the expansion vessel I,ve already checked this and air is expelled rather than water no expert but I believe this is what is regarded as normal, as for blocked pipe perhaps not sure how to check which is one of the main reasons for posting on forum rather than getting some out to check however it may well come to this

thanks
 
Hi
You need to check expansion vessell is charged to about 1 bar with no pressure in system!
 
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Thanks will do, is there a quick way to release the pressure in the system or do I have to drain the whole system as I would prefer not to if at all possible
Cheers
 
Just put a hose or a bucket on a drain valve, and leave this open as you repressurise the expansion vessell!
 
So hose or bucket open drain valve I,m assuming the I would have to wait until the whole central heating system is empty to ensure no pressure before pressurising EV. As I previously stated is there another option other than draining the whole system ie can I drain the boiler ONLY, there a drain valve in the boiler and if so how where and how


Cheers
 
Hi
There's a black plastic drain point on the boiler under the pump, opens by twisting it!
 
Hi just to confirm, I can only locate what looks like 1 black drain point not sure if it's is the correct one because if I open this open all the water will run out and below is where all the electrics are, not sure if this is the correct one as I,m not sure if above is the puump or HX
 
The drain plug is under the pump. It's black plastic. Just twist anti clockwise with a hose connected.
 

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