Grundfos Bronze and Stainless Steel circulating pumps are used for hot water recirculation and open systems because these materials are not effected by air and oxygen released into these types of systems through the constant introduction of fresh water. They’re made for whisper quiet operation for sound sensitive conditions. These pumps are of the canned-rotor type, i.e. pump and motor form an integral unit without shaft seal and with only two gaskets for sealing which helps to extend pump life by keeping foreign debris out. The bearings are lubricated by the pumped liquid.
The maximum temperature of liquids to be used with these pumps will vary by pump and the maximum liquid temperature will be directly affected by the ambient or surrounding air temperature around the pump. If a UP pump is equipped with a timer, then the maximum allowable liquid temperature is 150°F (66°C). The Grundfos UP and UPS pump types 25, 26, 43, and 50, can be used with chilled water because their motor construction is suitable for temperatures as low as 32°F (0°C) as long as the pump housings are compatible with the pumped liquids.
3-speed pumps are adjusted manually by the user to the preferred speed as needed offering more flow rate flexibility than single speed pumps. Speed adjustment should not be done while pumps are in operation.
Variable speed and mixing-reset control pumps are used to customize heating systems to increase user comfort. Variable speed pumps can be set for variable speed operation or can be set manually to operate at one speed. The motor output can be set to run at a variable speed by either voltage or current. The motor output is set by adjusting 4 switches (called “dip switches”) located on the pump, in a predetermined sequence by the manufacturer, to control by Voltage: 0-10V(DC) or 2-10V(DC); Current: 0-20mA or 4-20 mA.
These pumps are excellent for open solar heating systems, domestic hot water recirculation, and circulation of liquid in cooling and air conditioning systems. Grundfos bronze and stainless steel pumps are manufactured for use with potable or non-potable water, softened water or with a 50/50 mixture of water and propylene glycol. These pumps can be installed in both horizontal or vertical piping installations.
For a new recirculation system setup, you will need a flange or union adapter set, which are sold, to properly install your pump. If you are replacing an old Grundfos recirculating pump, you may not need new adapters.