1. The five pumping systems in Brazilian buildings
Separate the duties before comparing pumps. The table sets out five functions that may exist in a building; whether each one is present, and how it is sized, depends on the design. Standards referenced for the system are not certificates for every model in the series.
| System | Fluid/Condition | Design reference | What to check on the pump |
|---|---|---|---|
| Chilled water loop (CHW) | Specified temperatures and additives | HVAC design and adopted edition | Thermal flow, losses and fill pressure |
| Condenser water (CW) | Tower water and treatment | Chiller and tower data | Materials, suction and open-circuit head |
| Cold water supply | Potable, reservoir | NBR 5626 | Levels, flow and potable-water requirements |
| Pressurization (booster) | Potable, floors | Building design and adopted NBR 5626 | Demand range, pressure and control sequence |
| Fire fighting | Hydrants + sprinklers | NBR 13714, NBR 10897, NFPA 20 | Assembly and fire-system design records |
2. Chilled water loop: hydraulic selection and control
Supply and return temperatures are chiller and terminal design inputs; 7/12 °C is not a universal ASHRAE or NBR 16401 requirement. Flow must carry the thermal load at the specified ΔT and fluid properties. In a closed loop, friction losses in piping and equipment are the predominant pump load, and static head only comes in where there are vented tanks at different elevations (Improving Pumping System Performance, the US DOE and Hydraulic Institute sourcebook, p. 8).
Illustrative example: for water at assumed ρ = 1,000 kg/m³ and cp = 4.18 kJ/(kg·K), Q = 3,600 × P/(ρ × cp × ΔT), with P in kW and Q in m³/h. NIST converts 1 refrigeration ton to 3.516853 kW. Therefore 300 TR and ΔT = 5 K give approximately 182 m³/h. This does not select an FBCN 80-200 or its motor: system curve, suction and efficiency are still needed.
Primary-secondary and variable-flow arrangements must respect chiller, valve and pump limits. Define minimum flows, differential control, part-load operation and transients. The same sourcebook names pump speed adjustment as the most efficient means of controlling flow, especially in friction-dominated systems such as this one (pp. 8 and 51). The FBCN speed range with a variable-frequency drive must be confirmed for pump, motor and coupling.
In a tall building, a basement pump receives at suction the pressure of the whole loop column, and discharge adds the pressure the pump develops. Table 1 of the MTEC-03/00 manual limits FBCN suction pressure to 10 bar, about 102 m of water column at 20 °C. At discharge, limits come from Figures 1 to 4 (casing and flanges, as a function of temperature) and, with a mechanical seal, from Table 3, which gives 10 bar up to 90 °C.
Q (m³/h) ≈ 3,03 × TR / ΔT(K) → 300 TR, 5 K → Q ≈ 182 m³/hWater example: convert thermal load before calculating flow
3. Condenser water: open tower and aggressive chemistry
Condenser-water flow follows rejected heat, ΔT and equipment data. Check whether the arrangement uses an open tower or a closed-loop heat exchanger: hydraulic conditions differ. Do not derive flow by simply adding 25% to chilled-water flow or assume 30/35 °C without the thermal design.
In an open tower, evaporation concentrates dissolved solids, and makeup water replaces evaporation, blowdown and drift. According to FEMP Best Management Practice #10 (US DOE), many systems operate at two to four cycles of concentration, and six or more may be possible; the actual number depends on makeup-water quality and the treatment regimen, which typically includes corrosion, scaling and biological fouling inhibitors. Provide makeup and circulating-water analyses to assess materials and seals.
MTEC-03/00 documents FBCN materials such as cast iron, WCB and CF8M. Choose the configuration against water composition, temperature and treatment. Bronze B62 is not presented as standard, and no service life in years or guaranteed saving is attributed to a change of material.
4. Building water transfer pump (NBR 5626): from lower to upper reservoir
The building water transfer pump lifts water from the cistern to the upper reservoir. To select it, record minimum and maximum levels, the elevation difference, losses and pressure at the end points. NBR 5626:2020 covers building cold- and hot-water systems; check the adopted edition and the design requirements, including water quality and protection against contamination.
Flow depends on expected demand, the volume to be transferred and the available operating time. Record simultaneity, reserve and replenishment strategy. A generic range by building category does not replace calculation or determine the pump model.
Assess pressures at the lowest and highest points, at rest, during operation and during transients. Zoning, pressure reduction and pumping must be coordinated with network components and requirements. Floor count alone does not establish when a specific solution is mandatory.
Unlike the chilled-water loop, transfer pumping is an open system: besides losses, the pump overcomes the elevation difference between the cistern and the upper reservoir (DOE, p. 8). Where that static head is a large portion of total head, the sourcebook advises caution when slowing the pump, which could induce vibration and problems similar to operating against shutoff head (p. 51).
5. Boosting: demand, pumps and controls
A booster set serves a range of demand flows and pressures. The number of pumps, parallel operation, standby and controls should result from that profile. Compare pump curves with the network in the planned combinations, including minimum demand.
Parallel pumps suit systems with high static head and provide redundancy: one can be taken off line for maintenance while the others support operation. With identical pumps, the DOE sourcebook recommends equal operating hours and reconditioning them all at the same time, so the curves stay matched (p. 9).
At low demand, assess the specified control strategy and auxiliaries; a jockey pump is not universally required in every building booster. Table 1 of MTEC-03/00 sets FBCN minimum and maximum flow at 0.1 Qot and 1.1 Qot for bearing frames 30 and 40, and at 0.15 Qot and 1.1 Qot from frame 50 upwards. Define a solution that avoids operation outside that range and unsuitable cycling.
The design must record the measurement point, the reference pressure, the pump staging sequence and the response to faults. Ramp and stop settings must take the network and the drive into account. Use these data to assess pressure stability during commissioning.
Compare options using measured or modelled consumption over the same hours and demand ranges. Include pump, motor and drive efficiency and maintenance cost. Savings, stability and payback require building data rather than fixed percentages.
Note
Domestic boosting and fire protection serve different functions. Keep their specification, power supply and controls under their respective designs; do not use a domestic pump as a presumed substitute for a fire pump assembly.
6. Integration with building fire-fighting system
The fire design identifies the standards for the systems served and for the pump assembly, together with local regulations. NBR 13714, NBR 10897, NBR 16704 and NFPA 20 have different scopes; record the editions actually adopted.
Water reserve, pump quantity, alternative power and pressure maintenance depend on the installation and on state regulation. In Goiás, under Fire Department Technical Standard NT 22, the hydrant-system fire pump is used for that purpose only (C.1.2). A booster fire pump requires a main pump with a backup power source; a fixed pump also requires a standby pump with the backup source and may require a jockey (C.1.3).
In low-risk buildings (fire load up to 300 MJ/m²), a fixed pump is exempt from the standby pump, and the main pump then carries the backup power source (Note 1).
Define water-supply, control, testing and maintenance interfaces with the responsible engineer. Test frequencies come from the adopted references and manuals; no universal weekly routine is attributed to NBR 16704. Permitting documentation depends on the authority and the design, with no automatic approval from purchasing the equipment.
7. Cistern suction: minimum level and NPSH
Assess suction at the minimum cistern level and at the verification flow. Fittings, entrance, strainer, valves and piping all contribute losses. Suction lift and length must go into the calculation; on their own, they are not criteria to approve or reject the installation.
Obtain NPSHr from the pump curve at the selected speed and flow. On the published FBCN 50-200 curve at 1,750 rpm (CC-117.07, 219 mm impeller, clean water at 20 °C), NPSHr stays near 1.8 m up to 30 m³/h and rises to about 2.4 m at 50 m³/h.
The curve runs to 70 m³/h, but Table 1 of the manual sets maximum flow at 1.1 Qot; the example below uses 50 m³/h, close to the curve best efficiency point of about 48 m³/h.
Hypothetical example: absolute Patm = 101 kPa, Pv = 3.2 kPa, ρ = 1,000 kg/m³, g = 9.81 m/s², level 3 m below the shaft and suction losses of 1.5 m. NPSHa = (101,000 − 3,200)/(1,000 × 9.81) − 3 − 1.5 ≈ 5.47 m. Do not subtract the margin from NPSHa; obtain it by comparison with the pump requirement.
Keeping the other assumptions and lowering the level to 5 m below the shaft reduces NPSHa to about 3.47 m. For the 50-200 at 50 m³/h, which requires about 2.4 m, the margin falls from about 3.1 m to about 1.1 m. The example shows the weight of the level; it does not prove performance or cavitation-free operation of any model.
Compare internal diameter, routing, fittings and pump position using loss and NPSH calculations. Check submergence, air ingress and priming for the arrangement. A vertical in-line pump does not automatically resolve insufficient NPSH; alternatives need their own hydraulic and mechanical assessment.