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ericp
I have a problem with a Worcester Greenstar Heatslave 18/25. I've read all the related threads but need some clarification on the PRV/Expansion Tank issue.
If I leave the sytem running contiuously, pressure stays up at 1.5 to 2.0 bars for a week no problem. If however, I run it on the timer, I have to get up at 6.00 am every morning to repressurise the system which by then is down to zero. It then runs fine all day at around 1.5 to 2.0 bars. (I pressurise to about 1.0 bar when cold). If I don't fill it up, the system starts up, air seems to get into the pump (how?) and after a while the overheat cut out operates. In the past I was releasing steam from the end screw on the pump but have stopped that by re-pressurising before it occurs.
There is some evidence of a leak in the prv - I put a freezer bag over the outlet and when working normally I can get about a cupful of water in 24 hours. When switched off however, a pint or so collects in the bag.
The boiler is relatively new (2-3 years?) and been regularly serviced. The guy who serviced it a couple of weeks ago reckons it may need a secondary expansion tank since the house is quite large, but since the pressure does not go above 2.5 bars when hot (that's what the handbook says), I'm not sure this is the root of the problem. The other parameter in the book is if the system is bigger than 180 litres which I don't think it is.
I have tried letting off the pressure using the prv to try and flush out any dirt, but looking at previous posts, this may have made matters worse with dirt getting stuck.
If someone can help me understand why the loss of pressure is happening when cold and why air gets in when the system cools down that would be a step forward.
There are no leaks visible in the rads or pipework (microbore - horrible I know but that what the guy installed and it seems to work).
The engineer checked the expansion tank simply by pressing the valve to check air came out and not water. He didn't check the actual pressure so I am going to try that next. However I'm not sure what to pump it up to. The installation manual quotes initial charge pressure of 0.5bar for a 180 or 107 litre system (initial system pressure of 0.5 and 1.0 bar respectively) but 1.0 bar for both system and charge pressure for a 138 litre system.
I don't know the capacity of my system but there are 12 rads plus a towel rail fitted.
Regds
EricP
If I leave the sytem running contiuously, pressure stays up at 1.5 to 2.0 bars for a week no problem. If however, I run it on the timer, I have to get up at 6.00 am every morning to repressurise the system which by then is down to zero. It then runs fine all day at around 1.5 to 2.0 bars. (I pressurise to about 1.0 bar when cold). If I don't fill it up, the system starts up, air seems to get into the pump (how?) and after a while the overheat cut out operates. In the past I was releasing steam from the end screw on the pump but have stopped that by re-pressurising before it occurs.
There is some evidence of a leak in the prv - I put a freezer bag over the outlet and when working normally I can get about a cupful of water in 24 hours. When switched off however, a pint or so collects in the bag.
The boiler is relatively new (2-3 years?) and been regularly serviced. The guy who serviced it a couple of weeks ago reckons it may need a secondary expansion tank since the house is quite large, but since the pressure does not go above 2.5 bars when hot (that's what the handbook says), I'm not sure this is the root of the problem. The other parameter in the book is if the system is bigger than 180 litres which I don't think it is.
I have tried letting off the pressure using the prv to try and flush out any dirt, but looking at previous posts, this may have made matters worse with dirt getting stuck.
If someone can help me understand why the loss of pressure is happening when cold and why air gets in when the system cools down that would be a step forward.
There are no leaks visible in the rads or pipework (microbore - horrible I know but that what the guy installed and it seems to work).
The engineer checked the expansion tank simply by pressing the valve to check air came out and not water. He didn't check the actual pressure so I am going to try that next. However I'm not sure what to pump it up to. The installation manual quotes initial charge pressure of 0.5bar for a 180 or 107 litre system (initial system pressure of 0.5 and 1.0 bar respectively) but 1.0 bar for both system and charge pressure for a 138 litre system.
I don't know the capacity of my system but there are 12 rads plus a towel rail fitted.
Regds
EricP
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