When to Use Circulating Pump Manufacturer？

If you’ve ever worked with a closed-loop system (think HVAC, hydronic heating, or certain industrial process loops) you’ve probably come across a circulating pump. These compact pumps are quite essential for keeping things moving behind the scenes.

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First Things First: What is a Circulating Pump?

A circulating pump (sometimes called a circulator pump) is a type of pump used to move fluid within a closed system. The key here is closed system – you’re not pulling in outside water or sending fluid to a drain. Instead, the pump helps recirculate the same liquid to maintain consistent flow, pressure, and temperature.

In HVAC systems, this could mean circulating hot water from a boiler to radiators or chilled water in a cooling loop. In industrial setups, a circulating pump might be keeping process fluid at a stable temperature or moving it through a filtration system.

It’s not about volume like you’d see with a high-flow dewatering pump. It’s about keeping the loop moving efficiently and reliably.

How Does a Circulating Pump Work?

At a basic level, a circulator pump is a type of centrifugal pump. It uses a spinning impeller to create pressure and move fluid through the system. Because the system is closed (meaning the same fluid is reused), these pumps don’t need to lift water or draw from a supply. They’re focused on keeping things moving.

Here’s the general idea:

1. The pump pulls fluid in through an inlet.
2. The impeller adds kinetic energy to the fluid.
3. That energy is converted to pressure, forcing the fluid through the discharge side and into the system.

Since it’s a loop, the fluid returns to the pump, and the cycle continues.

TIP: Circulating pumps aren’t made for higher pressures. If your system needs to move fluid across long distances or large vertical changes, you’ll want a different kind of pump.

Where Are Circulator Pumps Used?

You’ll find circulators in a variety of places…some more obvious than others:

• Hydronic heating systems – Moving hot water from a boiler to radiators or underfloor heating
• Chilled water systems – Recirculating water in cooling loops for AC or industrial chillers
• Solar thermal systems – Keeping heated water or glycol moving from solar collectors to storage tanks
• Process systems – In industrial settings, circulators help maintain temperature or move fluid between system components
• Domestic hot water recirculation – Preventing long waits at the tap by keeping hot water circulating near fixtures

Circulating Pumps vs. Booster Pumps

It’s easy to confuse circulator pumps with booster pumps, but they serve different purposes. Circulating pumps keep fluid moving in a closed system. Booster pumps increase pressure in an open system (like municipal water supply lines).

What Makes a Good Circulating Pump?

It’s not all about horsepower or flow rate. With circulating pumps, efficiency and reliability are usually more important than brute strength. A good pump runs quietly, resists corrosion, and stays consistent even after thousands of hours of operation.

Key Factors to Look At:

• Flow Rate – How much fluid is moving through the loop?
• Head Pressure – How much resistance does the system have?
• Material Compatibility – Is the fluid corrosive or high-temp?
• Pump Type – Inline, end suction, close-coupled… the design affects footprint and maintenance.
• Motor Efficiency – ECM motors are common for their energy savings in smaller systems.

Tips from Pump Experts

Here’s some quick advice we’ve picked up after years in the pump business:

• Don’t oversize the pump. Bigger isn’t better, and too much flow can be just as problematic as too little, especially in closed systems.
• Always check system head before specifying. A loop that seems simple can hide a lot of friction loss.
• Pay attention to noise. Circulators are usually quiet, so if it’s buzzing or knocking, something’s off.
• Match materials to the fluid. Corrosion or scale buildup can quietly kill a circulator pump over time.

Circulator pumps are generally low-maintenance, but they’re not maintenance-free. Over time, seals can wear out, bearings can go bad, and buildup from poor water quality can gum things up.

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Work With a Pump Partner Who Gets It

Circulating pumps may be small, but they’re a big part of many systems running reliably day after day. If you’re unsure which pump fits your system or just want to upgrade for better efficiency, PumpWorks is here to help.

We’re more than just a pump manufacturer or supplier. We work with you to understand your system’s flow demands, operating conditions, and control needs to recommend a solution that performs well without overcomplicating things. At PumpWorks, we help customers spec the right pump for the right job…not just whatever’s on the shelf.

Pump for circulating fluid around a closed circuit for hydronic purposes

A circulator pump or circulating pump is a specific type of pump used to circulate gases, liquids, or slurries in a closed circuit with small elevation changes. They are commonly found circulating water in a hydronic heating or cooling system. They are specialized in providing a large flow rate rather than providing much head, as they are supposed to only overcome the friction of a piping system, as opposed to a regular centrifugal pump which may need to lift a fluid significantly.

Circulator pumps as used in hydronic systems are usually electrically powered centrifugal pumps. As used in homes, they are often small, sealed, and rated at a fraction of a horsepower, but in commercial applications they range in size up to many horsepower and the electric motor is usually separated from the pump body by some form of mechanical coupling. The sealed units used in home applications often have the motor rotor, pump impeller, and support bearings combined and sealed within the water circuit. This avoids one of the principal challenges faced by the larger, two-part pumps: maintaining a water-tight seal at the point where the pump drive shaft enters the pump body.

Small- to medium-sized circulator pumps are usually supported entirely by the pipe flanges that join them to the rest of the hydronic plumbing. Large pumps are usually pad-mounted.

Pumps that are used solely for closed hydronic systems can be made with cast iron components as the water in the loop will either become de-oxygenated or be treated with chemicals to inhibit corrosion. But pumps that have a steady stream of oxygenated, potable water flowing through them must be made of more expensive materials such as bronze.

Circulating pumps are often used to circulate domestic hot water so that a faucet will provide hot water instantly upon demand, or (more conserving of energy) a short time after a user's request for hot water. In regions where water conservation issues are rising in importance with rapidly expanding and urbanizing populations local water authorities offer rebates to homeowners and builders that install a circulator pump to save water. In typical one-way plumbing without a circulation pump, water is simply piped from the water heater through the pipes to the tap. Once the tap is shut off, the water remaining in the pipes cools producing the familiar wait for hot water the next time the tap is opened. By adding a circulator pump and constantly circulating a small amount of hot water through the pipes from the heater to the farthest fixture and back to the heater, the water in the pipes is always hot, and no water is wasted during the wait. The tradeoff is the energy wasted in operating the pump and the additional demand on the water heater to make up for the heat lost from the constantly hot pipes.

While the majority of these pumps mount nearest to the hot water heater and have no adjustable temperature capabilities, a significant reduction in energy can be achieved by using a temperature adjustable thermostatically controlled circulation pump mounted at the last fixture on the loop. Thermostatically controlled circulation pumps allow owners to choose the desired temperature of hot water to be maintained within the hot water pipes since most homes do not require 120 °F (49 °C) degree water instantly out of their taps. Thermostatically controlled circulation pumps cycle on and off to maintain a user's chosen temperature and consume less energy than a continuously operating pump. By installing a thermostatically controlled pump just after the farthest fixture on the loop, cyclic pumping maintains ready hot water up to the last fixture on the loop instead of wasting energy heating the piping from the last fixture to the water heater. Installing a circulation pump at the farthest fixture on a hot water circulation loop is often not feasible due to limited available space, cosmetics, noise restrictions or lack of available power. Recent advancements in hot water circulation technology allow for benefiting from temperature controlled pumping without having to install the pump at the last fixture on the hot water loop. These advanced hot water circulation systems utilize a water contacting temperature probe strategically installed at the last fixture on the loop to minimize the energy wasted heating lengthy return pipes. Thermal insulation applied to the pipes helps mitigate this second loss and minimize the amount of water that must be pumped to keep hot water constantly available.

The traditional hot water recirculation system uses the existing cold water line as return line from the point of use located farthest from the hot water tank back to the hot water tank. The first of two system types has a pump mounted at the hot water heater while a "normally open" thermostatic control valve gets installed at the farthest fixture from the water heater and closes once hot water contacts the valve to control crossover flow between the hot and cold lines. A second type of system uses a thermostatically controlled pump which gets installed at the farthest fixture from the water heater. These thermostatically controlled pumps often have a built-in "normally closed" check-valve which prevents water in the cold water line from entering into the hot water line. Compared to a dedicated return line, using the cold water line as a return has the disadvantage of heating the cold water pipe (and the contained water). Accurate temperature monitoring and active flow control can minimize loss of cold water within the cold water line.

Technological advancements within the industry allow for incorporating timers to limit the operations during specific hours of the day to reduce energy waste by only operating when occupants are likely to use hot water. Additional advancements in technology include pumps which cycle on and off to maintain hot water temperature versus a continuously operating pump which consumes more electrical energy. Reduced energy waste and discomfort is possible by preventing occurrences of hot water line siphoning in open-loop hot water circulation systems which utilize the cold water line to return water back to the water heater. Hot Water Line Siphoning occurs when water from within the hot water line siphons or is forced into the cold water line due to differences in water pressure between the hot and cold water lines. Utilizing "normally closed" solenoid valve significantly reduces energy consumption by preventing siphoning of non-hot water out of hot water lines during cold water use. Using cold water instantly lowers the water pressure in the cold water lines, the higher water pressure in the hot water lines force water through "normally open" thermostatic crossover valves and backflow check valves (which only prevent cold water from flowing into hot water line), increasing the energy demand on the water heater.

It is important to take note of the increased heat in the piping system, which in turn increases system pressure. Piping that is sensitive to the water condition (i.e., copper, and soft water) will be adversely affected by the continual flow.[citation needed] Although water is conserved, the parasitic heat loss through the piping will be greater as a result of the increased heat passing through it.

During the pump operation, there is a drop of the liquid flow in the center of the rotor, causing the inflow of the liquid through the suction port. In the event of an excessive pressure decrease, in some parts of the rotor, the pressure can be lower than the saturation pressure corresponding to the temperature of the pumped liquid, causing the so-called cavitation, i.e. liquid evaporation. To prevent this, the pressure in the suction port (at the inlet of the pump) should be higher than the saturation pressure corresponding to the liquid temperature by the net positive suction head (NPSH).

The following parameters are characteristic for the circulating pumps: capacity Q, pump pressure ∆p (delivery head ∆H), energy consumption P with pump unit efficiency η, impeller rotational speed n, NPSH and sound level L. In practice, the graphical relationship between the values Q, ∆ p(∆H), P and η is used. These are called the pump curves. They are determined by studies, whose methodology is standardized. These curves are specified when water is pumped with a density of  kg/m3 and kinematic viscosity of 1 mm2/s. When the circulating pump is used for liquids of different density and viscosity, the pump curves have to be recalculated. These curves are provided in catalogues and in operation and maintenance manuals, however their stroke is the subject of pump manufacturers warranty.

As from 1 January , circulators must comply with European regulation 641/.[1][2] This regulation is part of the ecodesign policy of the European Union.

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