calorifier pressure relief valve operation

[marchhare]

On checking my calorifier today, looking at ease of draining as a precaution against freezing, I recognised the PRV rated at 3.5 bar on a red plastic knob which I tried to turn, thought it might be a tap to be able to drain, but it clicked once so I stopped.
I would like to know if the click has any implications, is the cap just a cover or have I disturbed something critical to the valve operation?

 

[Ceejay]

It's designed like that. You can keep turning and it lifts the seal off its seat and then the spring bangs it back down on its seat again. You're supposed to do it now and again to keep dirt off the seal and keep it properly seated, I think.
CJ

 

[jwilson]

It's designed like that. You can keep turning and it lifts the seal off its seat and then the spring bangs it back down on its seat again. You're supposed to do it now and again to keep dirt off the seal and keep it properly seated, I think.
CJ

You are meant to click it round about once a month. Found this out when after 4 years untouched mine started leaking. Needed a new one.

 

[marchhare]

Thanks for the replies, reassuring to know that when after fiddling with stuff you know nothing about the result may not be as bad as it might have been. This is the firat time the red knob on this PRV has been turned since I have had the boat, 5 years, and no idea since new in 2000. Need to dig out some operating instructions if I can.