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Combi Boiler With Expansion Vessel

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dillon | 11:36 Thu 23rd May 2024 | Technology
11 Answers

 Should the two black levers be on or off?



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If you mean the two valves used to top up the pressure, then they should be off when not used for that purpose. If they are left on, they are likely to overfill the system and open the pressure release valve.

Question Author

Ah yes the two black pressure levers / valves..... They should both be off and in the horizontal position then? i.e. at 90 degrees to pipe

Yes. Except for topping up the system. Topping up should not be necessary - if it needs doing often it suggests a problem such as a leak on the system, or a faulty pressure relief valve letting by at a low pressure, or the system is overfilled anyway, or the expansion vessel has a fault or needs some air to be pumped in.

Question Author

Thanks for your answer.... I've only ever used the two levers for increasing the pressure to 1.5 bar.  When you say topping up, is that something different?

One increases the pressure by topping up with more water.

OG has said it. 1.5 bars should be fine.

Question Author

Thanks for all the replies.  Pressure is nearly at 3 bar. How do I reduce?   Both valves are closed I think (both at 90 degrees to pipe)

3 bar is high. That's about where the Pressure Relief Valve operates to relieve excess pressure.

Find the outlet from the PRV (outside the house) and stick a glass bottle over it. Carry on as you are and monitor the bottle to see if it fills up.

can bleed a rad worked for me

You can reduce the pressure by bleeding water from one of the radiators.

(my pressure relief valve bleeds into the condensate run-off pipe & operates at about 4 bar)

You say the pressure is nearly 3 bars. Is that with a hot system? (i.e. are the radiators hot?). When the heating is off and all is cool, does the pressure drop back to about 1.5bar?

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