Under normal circumstances, in forced circulation hot water system should be used at least two units of circulating water pumps, especially in small and medium heating system, two units of the same type of pump units, a run, a spare. Reserve coefficient is 100%. Obviously there are drawbacks to this approach. Heating system must be at any time full load operation, in part load flow regulation, in order to save electric energy. For pump unit system, it is best to install two different pump units, a supply of water flow, the other can provide 75% of the calculation of water flow. The latter for the outdoor temperature is high use.
In the large regional hot water system, the ladder like water flow should not be less than three: 60%, 80% and 100%, the corresponding energy supply of water pump units such as 22%, 51%, and 100%. All pump units can be replaced with each other to a certain extent, so there is no need to install a spare pump unit.
Multiple units in parallel operation, covers an area of large, cost is also higher. The specific conditions of the project should be considered, and the method of parallel connection of multiple pump units can not be used blindly.
