Introduction

The Little Giant Circulation Pump MS320P-6B is a reliable and efficient solution for various water transfer applications, including aquariums, fountains, and evaporative coolers. Designed for continuous operation, this pump features a durable construction that ensures long-lasting performance. Ideal for both residential and light commercial use, the Little Giant MS320P-6B is priced at approximately $129.99. With a maximum flow rate of 320 gallons per hour and a compact design, it easily fits into tight spaces while delivering powerful circulation.

These stainless steel and bronze pumps come in four models and are intended to be used submerged or stacked with flooded suction. They are intended to circulate fresh or salt water through the heat exchanger coils of marine air conditioners. Each pump includes a sturdy mounting bracket to secure the pump in position and hold it in place.

Specifications

Model	Volts	HZ	Amps	Watts	Shut Off ft (m)
MS320P-6B	115	60	0.50	60	14.8 (4.51)
MS580P-6B	115	60	0.65	70	13.2 (4.02)
MS580P-6-2B	230	50/60	0.40	92	10.0 (3.05) / 13.2 (4.02)
MS900P-6B	115	60	0.75	85	15.6 (4.75)
MS1200P-6B	115	60	1.00	105	20 (6.10)

Model	Inlet Size		Discharge Size
	Thread	Hose I.D. in (cm)	Thread	Hose I.D. in (cm)
MS320P-6B	1/2 - 14 MNPT	3/4” (1.91)	1/4 - 18 MNPT	1/2” (1.27)
MS580P-6B	3/4 - 14 MNPT	1” (2.54)	1/2 - 14 MNPT	3/4” (1.91)
MS580P-6-2B
MS900P-6B
MS1200P-6B

Description

The Little Giant Circulation Pump MS320P-6B is built with a robust and durable design, ensuring long-lasting operation in demanding environments. The pump features a corrosion-resistant body and a stainless steel shaft, which enhances its durability and resistance to wear and tear. The 1/2 HP motor is powerful yet energy-efficient, making it an excellent choice for both residential and commercial applications.

The pump's compact size and lightweight design make it easy to install and maintain. It is compatible with a variety of heating systems and can be used in both open and closed-loop configurations.

SAFETY INSTRUCTIONS

This equipment should be installed and serviced by technically qualified personnel who are familiar with the proper selection and use of appropriate tools, equipment, and procedures. Failure to comply with national and local electrical and plumbing codes and Little Giant recommendations may result in electric shock or fire hazards, unsatisfactory performance, or equipment failure. Know the product's application, limitations and potential hazards.

Read and follow the instructions carefully to avoid injury and property damage. Do not disassemble or repair the unit unless described in this manual. Failure to follow installation or operating procedures and all applicable codes may result in the following hazards:

DANGER
Risk of death, personal injury or property damage due to explosion, fire or electric shock.

Do not use for pumping flammable, combustible or explosive liquids such as gasoline, fuel oil, kerosene, etc.
Do not use in explosive atmospheres or hazardous locations as classified by NEC, ANSI/NFPA70.
Do not operate the pump or pump motor with wet hands or when standing on a wet or damp surface, or in water.
When the pump is in use, do not touch the motor, pipes or water until the device is disconnected from the mains or electricity.
If the power switch is out of sight, lock it in the open position and tag it to prevent unexpected power applications.

WARNING
Risk of serious injury or death from electric shock.

To reduce the risk of electric shock, turn off the power before working on or around the system.
Wired pump system for correct volumetage.
Be sure this pump is connected to a circuit equipped with a ground fault circuit interrupter (GFCI) if required by code.
Check the electrical connections with a circuit analyzer to ensure that the power, neutral, and ground wires are properly connected.
Some pumps are supplied with a grounding conductor and a grounding type attachment plug. To reduce the risk of electric shock, ensure that it is connected only to a properly grounded grounding-type outlet. Do not remove the third prong from the plug. The third step is grounding the pump to prevent possible electrical shock hazard. Do not use an extension cord.
Some pumps are supplied with lead wires and are intended to be connected using a junction box or other approved enclosure. Pumps include a grounding plug. To reduce the risk of electric shock, make sure it is properly grounded.
Check local electrical and building codes before installation. Installation must comply with their regulations as well as the latest National Electrical Code (NEC) and Occupational Safety and Health Act (OSHA) and marine electrical codes.
Do not use the power cord to lift the pump.
The pump should only be used with fluids that are compatible with the materials of the pump components. If the pump is used with fluids incompatible with the pump components, the fluid may cause failure of the electrical insulation system resulting in electric shock.

ATTENTION
Risk of personal injury, electric shock, or equipment damage.

This equipment must not be used by children or persons with reduced physical, sensory or mental capabilities or lack of experience and expertise, unless they have been given supervision or instruction. Children must not use the equipment or play with the unit or in the immediate vicinity.
The equipment can start automatically. Always disconnect the pump power cord and disconnect the electrical supply before servicing the pump or switch.
The pump is rated for use with water only.
Operation of this equipment requires detailed installation and operating instructions provided in this manual. Read the entire manual before starting installation and operation. The end user should obtain and retain the manual for future reference.

NOTICE
Risk of damage to the pump or other equipment.

If the pump is dried out, it can damage the pump and void the warranty.
Inspect pump and system components periodically. Check hoses regularly for weakness or wear, making sure all connections are secure.
Schedule and perform routine maintenance as needed and in accordance with “Maintenance” on page 6 of this manual.

Installation

Typical Installation

Physical installation

NOTE: This pump can be used indoors or submerged. It is not self-priming and must be located below the waterline. Seawater enters low and exits high.

Connect the strainer to the pump inlet. See "Specifications" on page 1.
Ensure accessibility for future maintenance.
Both the pump and strainer must be mounted 2 feet from the hull.
IMPORTANT: Do not connect the pump to the engine's water cooling supply as this may cause the engine to dry out.
Connect the sea cock and the colander. Refer to "Specifications" on page 1.
Secure each connection with stainless steel clamps.
NOTE: Through hull and marine cover must be installed at least 8-12" below the water line.
Connect the pump discharge to the air conditioner. Refer to “Specifications” on page 1.
This pump is ignition protected and must be within 10 feet of the air conditioner.
IMPORTANT: Do not cut the hose until it is in its final location.
Attach the pump bracket and mount the assembly horizontally on a stable, level spot in the section.
For powered boats: Make sure the pump always sits below the waterline, even when hydroplaning.
For sailboats: mount the pump close to the centerline to avoid loss of water supply when backing up.
NOTE: The outlet must always sit above the inlet.
NOTE: Always orient the screw so that the inlet is closest to the strainer and the discharge is closest to the air conditioner.
Run the water return line through the hull as close to the pump as possible and 4-8” above the water.

Electrical connections

Hire an electrician to do the wiring.
Connect the power cord to a constant power source that matches the pump nameplate voltage.
The pump should be wired or connected to its own circuit, with no other equipment in the circuit.
Do not connect to a fan or any alternating current device.
The fuses or circuit breaker should be of amp capacity.
Connect to a circuit equipped with a ground fault circuit interrupter (GFCI) if required by code.
Do not splice into the pump's power cord. If additional cable length needs to be added, use a sealed junction box to splice the marine grade cable to the existing pump cable.
Do not remove the existing cable supplied with the pump.

IMPORTANT: If the power cord is damaged, the entire device must be replaced.

MAINTENANCE

Periodic maintenance
Periodically observe the operation of the pump. If a decrease in flow is observed, clean the pump as follows:

Unplug the pump and remove it from the water source.
Unscrew the pump housing from the pump body.
IMPORTANT: Do not open the motor housing.
Carefully clean all debris from the impeller and pump housing.
IMPORTANT: Do not remove the impeller from the motor shaft.
Replace the pump housing, making sure to also replace the O-ring in the groove on the pump body.

Storage

Refer to "Periodic Maintenance" on page 6 for cleaning.
Coat the pump housing, impeller, shaft, and seal with general-purpose oil.
Reinstall the pump.
To keep in a dry place.

Setup Guide

To operate the Little Giant Circulation Pump MS320P-6B, follow these steps:

Ensure the pump is properly connected to the heating system using the 1" NPT female threads.
Check that all electrical connections are secure and meet local electrical codes.
Fill the system with water and bleed any air from the lines to prevent cavitation.
Turn on the pump and adjust the flow rate as necessary using the built-in control or an external controller.
Regularly inspect and maintain the pump to ensure optimal performance and longevity.

Troubleshooting

Problem	Probable Causes	Corrective Action
No water flow from pump	There is no power to pump	Connect the pump to power.
No water flow from pump	The pump is not priming	Ensure that the inlet of the pump is below the water sur- face.
Low water flow from the pump	The pump intake is blocked	Remove debris blocking the intake or impeller.
	The pump is not large enough	Select a larger capacity pump.
	The seacock is partially or completely closed	Open seacock to allow for full flow.
Pump runs intermittently	The pump is too hot	Check to see that no debris is clogging the suction port.

Replacement parts

Item(s)	Model(s)	Description	Order Number
1	MS320P-6B	Overhaul Kit	305626005
	MS580P-6B; MS580P-6-2B		305626006
	MS900P-6B		305626007
	MS1200P-6B		305626008
2	MS320P-6B	Mounting Plate Kit (Includes: 1 Mounting Plate, 4 Bushings, 1 Hose Cap)	305626011
3	MS580P-6B; MS580P-6-2B; MS900P-6B; MS1200P-6B	Bracket Kit (Includes: 2 Bracket Sets with upper and lower parts, 8 Bushings, 4 Screws, 4 Nuts)	305626012

Warranty

This product is covered by a Limited Warranty for a period of 2 years from the date of original purchase by the consumer. For complete warranty information, please visit http://www.littlegiant.com./

Troubleshooting

Common issues with the Little Giant Circulation Pump MS320P-6B include:

No Flow: Check for blockages in the system, ensure proper electrical connections, and verify that the pump is primed.
Overheating: Ensure adequate clearance around the pump, check for blockages in the cooling system, and verify that the pump is not running continuously without rest periods.
Noisy Operation: Check for misalignment or loose connections, ensure the system is properly primed, and verify that the pump is installed on a level surface.

Little Giant Circulation Pump MS320P Pros & Cons

Pros

High flow rates and efficient energy consumption
Durable and corrosion-resistant construction
Compact and lightweight design for easy installation
Compatible with various heating systems and configurations
Easy to maintain and repair

Cons

Potentially higher initial cost compared to some competitors
May require professional installation for complex systems
Some users may find the noise level slightly higher than expected during operation

Customer Reviews

Customers have generally praised the Little Giant Circulation Pump MS320P-6B for its reliability and performance. Many users have noted its ease of installation and maintenance, as well as its efficient operation. However, some users have mentioned that the pump can be slightly noisy during operation and that the initial cost may be higher than some other options on the market.

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