This article should help you understand the two main Booster pump pressure settings and how to calculate the right values. There may be other considerations so please contact our team for advice at firstname.lastname@example.org.
All variable speed booster sets (VSBS) will have a pressure vessel that must be charged at the correct pressure for the unit and system to run without problems. Normally these vessels are much smaller than those on fixed speed sets as the VSBS only hold pressure in its vessel slightly higher than the setpoint pressure. On a VSBS the vessel should be charged 1 Bar below the running set point. This gives some cushion for the pumps to ramp against and over the ramp at low demand.
If at a low demand the inverters over ramp slightly above the setpoint, the vessel will hold the pressure and the inverter will ramp down and go into sleep mode.
The pumps will start in a cascade if the flow rate of the lead pump reaches 50HZ, this will trigger the next pump to start to keep up with the flow requirements.
Also, you should check that the set point of the VSBS is greater than the static head of the building. As a rule, you can count the floors and times them by 3m per floor, adding 1Bar on top so that the upper floors are always pressurised. For example:
- 10 Floor building + 1 basement = (11 x 3m) / 10 = 3.3 Bar Vessel Pre-Charge
- 10 Floor building + 1 basement = (11 x 3m) / 10 = 3.3 Bar + 1 Bar = 4.3 Bar Cut-in Pressure Setting
It is critical that the air charge is correct or the pumps will hunt or will never sleep which will cause them to overheat and if the setpoint is too low the top floors will suffer from pressure fluctuations.
A vessel should be pre-charged using nitrogen and not standard air. If normal air is used then when the vessel expands and contracts the air will condense on the inside of the vessel and cause corrosion/rust to form. Eventually, this will damage the bladder/diaphragm and cause a failure of the vessel completely.
It is advisable to ensure your vessels are regularly checked in compliance with the ‘Pressure Systems Regulation 2000‘ Act. This consists of a thorough check using special equipment to ensure your vessel walls have not corroded internally over time and are structurally sound/safe. Book an inspection here.