Repressurising sealed system

[Mark]

Hi,

I need to repressurise a sealed system after a leak (leak is fixed) and I would like to know if this has to be done when the system is cold since SWMBO does not want the CH switched off at all today! It's down to 0.8 bar ATM.

TIA, Mark

[John Rumm]

It ought to be done cold. However you can usually get away with topping it up a little when hot if you take it slowly. Working out what to pressurise it to is harder though since you probably don't know the normal "hot" operating pressure is, or for that matter how hot the system actually is at the time you add water. If the system is good and hot, I would be tempted to take it to about 1.5 bar.

[The Natural Philosopher]

TBH its not critical. I generally go to about 1.5 bar cold. Probably too much, but it seems to take it.

[Mark]

Thanks for the replies. I'll let it cool a little to avoid burning myself and then do it slowly. IIRC the pressure does not change a lot when hot vs cold.