Water pressure for block of flats

[CarlJa]

Hi,

I will try to explain best I can, please bare in mind I am currently in a learning stage so just trying to understand the process behind things.

A building with three floors and 69 rooms. How do you work out the pressure needed on the hot water system? I’m sure there is a calculation to work out the flow rate and pressure. Sometimes the top floor experience low pressure on the hot water, I believe it is currently supplied at 2.5 bar.

I would like to try and do the calculations to work out the correct pressure setting.

appreciate any help or advice given.

Thank you.

 

[Deleted member 120897]

There’s a difference between pressure and flow rate, and there’s a calculation used for working out which each floor needs by a way of working out what is needed to be fed on those floors. More experienced engineers than me might say an accumulator could be used?

 

[ShaunCorbs]

Chances are the booster system isn’t designed for total load or is starting to fail eg pump seals etc

 

[CarlJa]

There’s a difference between pressure and flow rate, and there’s a calculation used for working out which each floor needs by a way of working out what is needed to be fed on those floors. More experienced engineers than me might say an accumulator could

Thank you for the reply. Do you know the formula for the calculation please? I would quite like to work out the pressure per floor. A hot water expansion vessel is used on the system which is set at 2.5 bar unsure if this is correct or how to work out the correct pressure.

 

[ShaunCorbs]

Thank you for the reply. Do you know the formula for the calculation please? I would quite like to work out the pressure per floor. A hot water expansion vessel is used on the system which is set at 2.5 bar unsure if this is correct or how to work out the correct pressure.

2.5 bar cold so let’s say 3 bar per flat and 20lpm how many floors ?

 

[CarlJa]

2.5 bar cold so let’s say 3 bar per flat and 20lpm how many floors ?

3 floors

 

[ShaunCorbs]

3 floors

So let’s take 2.6m to allow for dropped ceilings etc that gives you 10.4m need to pump so adds 1.04 bar ontop of your outlet pressure requirement so 4.04 bar required to give you 3 bar 4 floors up

Working on the 70% rule that’s 50 flats needing water at the same time so that’s 1000lpm eg 20lpm for each flat

So 4.1 bar and 1000lpm is your duty cycle