Grundfos variable speed heating zone circulator pump UPS 15-58FC (C) Grundfos InspectApediaVariable-Speed Zone Circulators
Brands & features of heating circulators that can vary circulating speed

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Variable speed heating zone circulators:

This article describes brands & models of forced hot water heating system circulator pumps whose motor speed or circulating speed can be set to varying rates.

We describe both older obsolete variable speed circulator pumps and modern currently-available models including manufacturer brand, model, and circulator pump sources.

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Variable Speed Hot Water Heating Circulator Pumps, Motors & Controls

B&G UpStart circulator with variable speed motor (C) Daniel FriedmanVariable speed heating zone circulators provide an additional level of heating zone control and can be used to solve heating problems amenable to either an increase in circulating water speed (get more heat in a zone) or a decrease in heating zone circulator speed (less heat or continuous, more even heat).

Older Variable Speed Heating Circulator Pumps

At left is a Bell & Gossett UpStart hot water heating zone circulator pump produced - a B&G product no longer distributed. This circulator pump included a variable-speed circulator motor (see that gold knob on the electrical box atop the motor?).

This hot water heating zone circulator used a four-speed motor whose output rate could be set by the consumer or heating service technician.

By changing the circulator motor speed on this pump or on the next model shown below, we could slow or speed the flow rate of hot water through the zone managed by this circulator. The result: this control provided another way to balance heat flow among multiple zones (and circulators) in a building.

This circulator, the Bell & Gossett SLC-25 Upstart Circulator was sold during the 1980's and is not currently available. But B&G offered similar replacements (such as the NRF-22).

At below is a newer but also obsolete product, the B&G NRF-VS variable speed circulator is shown.

B&G NRF-VS variable speed control with circuator pump - InspectApedia Bell&Gossett Xylem

Currently-Available Variable-Speed Heating Circulator Pumps & Controls: Taco BumbleBee & Grundfos Alpha Series & MixiMiser™

Other variable speed circulators include the Taco BumbleBee High-Efficiency Variable-Speed Circulator HEC-2 and Variable speed circulators from Grundfos.

Quoting from the company's product literature:

The Taco Bumble Bee (model HEC-2) represents the very latest in variable speed wet rotor circulator technology. Its high efficiency ECM motor uses up to 85% less electricity than a standard circulator, and its out-of-the-box settings and 360 ̊ swivel flange makes it a breeze to install. Most importantly, the Bumble Bee’s Delta-T variable speed technology maximizes the overall efficiency of your heating system. - Taco Catalog q#100-101 retrieved 1/24/2014 [on file] see References at the end of this article

Taco BumbleBee HEC-2 variable speed heating circulator pump (C) Taco InspectApedia

Alpha Series pumps by Grundfos also provide variable speed hydronic heating water circulation control. Quoting [with minor adaptations] from product literature from Grundfos, including the UPS15-58FC and the Grundfos Alpha series.

Grundfos variable speed heating zone circulator pump UPS 15-58FC (C) Grundfos InspectApedia Grundfos Alpha variable speed heating zone circulator pump (C) Grundfos InspectApedia

The Alpha Series pumps [above right] (e.g. ALPHA 15-55F - ALPHA 15-55SF/LC) have permanent magnet motors designed for circulating water through domestic hot water systems, heating systems, or cooling and air conditioning systems.

The Alpha pumps can be used in systems with either constant or varying water flow rates. example of a Grundfos ALPHA pump The Alpha pumps incorporate a frequency converter, an integrated differential pressure control, and an electronic processor to automatically adjust pump speed based on the system demand and flow rates.

The AUTOADAPT™ software recognizes changes in the system like opening and closing valves or faucets that can cause a change in the head-flow requirements of the system. AUTOADAPT™ monitors the motor current versus the pump hydraulic or pressure conditions and automatically adjusts the motor speed to minimize the pumps energy consumption and at the same time maximize your system needs for your comfort level.

The Grundfos MixiMiser™ is the only pump and controller system of its kind. The mixing-reset control automatically calculates and controls water temperatures according to outdoor temperatures in primary and secondary heating systems.

The MixiMizer™ can be installed into a thermostatic or zoning control system for maximum design flexibility.

A fully serviceable check valve is installed into the pump housing to eliminate unwanted, uncontrolled, flow when the pump is not on and will not inhibit water flow when the pump is on. LED indicators located on the terminal box indicate pump performance and help diagnose possible faults without the use of tools.


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