Hi could someone please offer some advice....recently added an extra rad in the loft conversion..after topping up rad system and bled all the air from rad whilst filling..the pressure in the system rises to 3 bar and lifts the safety valve . I have drained some excess pressure from the system from the new rad back down to 1.5 bar when the system is hot ...however the next day it will rise to between 2-3 bar when hot...should i lower the pressure again and check the expansion vessel and top up with some more air to lessen the amount of water expansion...Thanks ...Chris
worcester/bosch 24cdi pressure keeps rising
- Thread starter milkybarkid01
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does it rise to 3bar wen the ch is on then drop back down to 1.5bar wen turned off or does it just rise to 3bar and stay there?
No the system starts of at 1.5bar when cold and rises to 2.5-3bar whilst hot but drops back down to between 1.5-2bar when cold...I`ve just checked the PV to see if it was hot indicating a high water level, anyway it was cool so i am assuming the water to air ratio is about right...Thanks Chris
sounds like ya need to pump the exspansion vessel up 
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I`ve tried adding some air through the valve on the pressure vessel but the symptoms are still the same...do i need to keep adding more air and draining excess pressure off by releasing fluid....
you can only repressurize the expansion vessel by turning off the heating flow and return valves depressurize the boiler then pump up the vessel to around 0.7 bar, then undo the valves and then refill as normal then if the diaphram is ok it will hold the pressure overnight and when the boiler is operating at ,max
How can i depressurise the boiler if the heating feed and return are closed....Thanks
I thought the 24Cdi had a drain off built in.
open the 3 bar prv valve to release the boiler pressure then leave it open while you put air in the vessle otherwise you will pehaps notice the main gauge moving up after you pressurerize it close off the prv valve and open the flow and return valves and repressurize to 1 bar on the main front pressure guage
I would never recommend anyone using the prv on any boiler to drain it down, unless they had a spare with them to replace it when some carp gets on the valve seat and won't let it close properly afterwards.
If i close both feed and return valves and depressurise the system ,do i also bleed off the air from the pressure vessel.so there is no pressure either side of the diaphragm and then add air to 0.7 bar open both valves and top up the heating system to 1 bar through the filling loop...also thanks for all the reply`s guys i do appreciate it,,,
Do NOT take any notice of what is said above. The CDi has a white plastic drain off underneath, use that to drain, keep it open when you repressure.
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it has two drainoffs, both are prone to blocking and are unlikely to work.
The prv and drain off valves are both working...were fortunate in cornwall to have soft water and do not suffer from the affects of limescale
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