Odd question from imist

[Adsibob]

Due to the open plan layout of our ground floor, BCO insisted on getting a fire engineering report which recommended a sprinkler system. We went with imist who initially said all I needed to do was ensure there was a power supply and water supply to the area where the tank and pump would be installed and they would do everything else. This turned out to be a bit misleading with them actually sending through a list of much more detailed requirements for my plumber and electrician to sort out. They have now done that and I had to supply photographs of what had been done to imist prior to the final fix of the sprinkler system.

A These photos have prompted imist to raise the following question: I can see you have installed a pressure reducing valve, is this due to having a booster on site and the pressure being above 4 bar?I find this question a little surprising because I thought PRVs were fairly standard operating practice and required to balance the system. Our pressure on the the below gauge is showing 3.3bar. This was take at 845am on a weekday, so I assume though not quite at peak demand time, it was close to peak demand time.

 

 

My questions are:

 

1. Why do imist care given they state their requirements are a minimum of 1 bar and I clearly have more than this?
2. Does the red hand point to where the PRV has been restricted to? i.e. my pressure won't exceed 4.8 bar?

[Nickfromwales]

1. imist should be connecting to their own stopcock rising off the main, eg you should have the mains cold coming in and going to everything you have there atm, plus you should then also have a tee connection immediately PRIOR TO the existing stopcock feeding a lockable isolation tap, that then becomes the dedicated non-interruptible supply the mist system.
2. No. It should be set to represent the pressure that the PRV restricts at, so basically it is a visual indicator that shows if the PRV has started 'passing' and needs servicing. If, for eg, it's a 3 bar PRV then move the red pointer to 3 bar and leave there. If the black pointer ever goes past the red, there is a problem.

[Adsibob]

16 minutes ago, Nickfromwales said:

1. imist should be connecting to their own stopcock rising off the main, eg you should have the mains cold coming in and going to everything you have there atm, plus you should then also have a tee connection immediately PRIOR TO the existing stopcock feeding a lockable isolation tap, that then becomes the dedicated non-interruptible supply the mist system.
2. No. It should be set to represent the pressure that the PRV restricts at, so basically it is a visual indicator that shows if the PRV has started 'passing' and needs servicing. If, for eg, it's a 3 bar PRV then move the red pointer to 3 bar and leave there. If the black pointer ever goes past the red, there is a problem.

Thanks @Nickfromwales. On your response to Q2, i probably wasn't being clear. My question was whether the fact the red hand is pointing to 4.8 means that it is set to restrict to 4.8 and so the reading of 3.3 is just the unrestricted reading at that time of the day. i.e. is it best practice that when you set it up you leave the red hand pointing to where you've restricted it to? Sorry, no idea how a PRV works.

[Nickfromwales]

40 minutes ago, Adsibob said:

Thanks @Nickfromwales. On your response to Q2, i probably wasn't being clear. My question was whether the fact the red hand is pointing to 4.8 means that it is set to restrict to 4.8 and so the reading of 3.3 is just the unrestricted reading at that time of the day

Unless you know what value that PRedV was commissioned / factory supplied at, I cannot comment on where the red pointer should reside.

46 minutes ago, Adsibob said:

i.e. is it best practice that when you set it up you leave the red hand pointing to where you've restricted it to? Sorry, no idea how a PRV works.

Pretty much what I said above  so yes.