COMMERCIAL HEATING MAX FLOW Direct-fired condensing gas water heater with peak flows of 1,018 - 3,620 (L/60 at 40C) NEW WaterMaster Evo 6 models available - 25-120kW High performance 2022 Part L compliant Space and cost saving | PUMP SPECIFICATION the resistance of the pipework and fittings, and that of the plate exchanger itself. You will need to check what boilers you are specifying and if they already come with integral pumps. We sell correctly sized boiler shunt pumps as part of the boiler pipework kits on our Stratton mk2 wall-hung boiler and Upton boiler. Which method should I choose? As stated earlier, there is no correct method, as long as minimum flow is always maintained. However, there are some pros and cons to each (see panel below). Ultimately, both options allow you to maintain flowrate across your primary circuit with multiple boilers running in cascade. The decision will be based on criticality of building usage and the balance of cost against system reliability, and redundancy requirements. For example, a building such as an office block that while inconvenient and possibly financially disruptive could be offline for hours or potentially days, may choose a single primary circuit pump with the possibility of twinhead pump or duty/standby. However, a system that simply cannot risk any downtime, such as in a hospital or prison, may choose to install individual boiler shunt pumps. The installation and maintenance costs could negate the cost and disruption, and the potential human suffering, that could result if the system is out of action for any length of time. CJ IAN ROE is director and general manager at Hamworthy 5-year warranty* Proven reliability supported by 100 years of experience acv.com/gb 01383 820 100 A A L XXL *Terms and conditions apply. 58 February 2023 www.cibsejournal.com PROS AND CONS Single primary circuit pump n You only need to purchase one pump, making it simpler to install, maintain, and potentially more cost-effective. However, the physical size of the pump will be much larger. This can create installation and maintenance challenges, as often it will require a three-phase power supply n A single pump could create a single point of failure in the system. But this can be negated by installing a twin motor pump or two pumps as duty standby n Pipework can be more complex, as you need to configure a reverse return. However, as mentioned previously, this is often built into manufacturers pipework kits n You may get potential heat losses through non-firing boilers. Multiple boiler shunt pumps n By installing multiple pumps, you have an increased system redundancy should one pump fail, you still have other pumps running on other boilers to maintain heating n The pumps will be physically smaller and simpler to install n Modern boiler controls can often control the relevant boiler shunt pump, which takes the important pump overrun time away from the external controls n Reverse return configuration is not required in this case n Flow is isolated through non-firing boilers n Cost will be increased as there are more pumps to purchase and this may result in additional maintenance because of the number of pumps n There could be additional system complexity as there is an increased requirement for electrical supplies and controls wiring to each pump.