The Metlund D'MAND SYSTEMS are available in three models. The use of the D'MAND System for tankless water heaters is dependent on distance to the last hot water fixture. Tankless water heaters require a higher water pressure flow (measured in PSI or pounds per square inch) to activate the water heater. This requires one of our higher performance D'MAND System models. The following guide can be used for most conditions.

Tankless Water Heaters and DMAND Systems
	S-70T	S-02T
Standard Plumbing AND Distance between tankless water heater and fixture where DMAND system is installed	Under 60 feet	Over 60 feet
Re-Circulation Plumbing AND square footage of house	Under 2500 sq. ft.	Over 2500 sq. ft.

 
Note: Standard plumbing requires the D’MAND System to be installed between the hot and cold water line at the most distant hot water location.

Model S-70T Series

If the distance between the tankless water heater and the last hot water fixture where the D’MAND System is installed is less than 60 feet, the Metlund D''MAND System S-70T series will be acceptable.

Model S-02T Series

If the distance between the tankless water heater and the Metlund D''MAND System pump is more than 60 feet, the S-02T series is recommended. Generally the S-02T series will work on any residential home if the distance is under 300 feet between the water heater and last fixture where the D''MAND System is located. Depending on the distance, type of pipe, (copper, plastic, etc.) and pipe size (both hot and cold), there will be a difference on the pressure drop and ability to move the hot water quickly to the fixtures.

Re-circulation Plumbing: a dedicated hot water loop-line (return or re-circulation line) runs from the water heater through the home and back to the water heater.

Model S-70T Series

If the home is under 2,500 sq ft. and the Metlund D'MAND System is located at the water heater on the dedicated return line, the S-70T model is acceptable. If the home is two stories you should call the Metlund office at 800-638-5863 to discuss the plumbing layout as the S-70T may not have the flow factor needed to properly service your home.

Model S-02T Series

Homes over 2,500 sq. ft. should use the S-02T series. Again, the Metlund D'MAND System should be located at the water heater on the dedicated return line.

Important Note About Pipe Sizing
Both the S-70T and the S-02T Series operate more efficiently if the dedicated hot water return line is 3/4 inch pipe and not 1/2 inch. The object is to move the hot water quickly on demand, and 1/2 inch return lines will be restrictive. However, the D'MAND System will work on the 1/2 inch return line.

Activation

Activation of D'MAND Systems includes choices of hard wired buttons, wireless remote RF (radio frequency) buttons, motion sensors (wired or wireless), and in some cases flow switches. In most cases flow switches are only used in commercial or multi family operations.

Control of Activation

The Metlund D'MAND System electronics and sensors work on a very accurate Delta-T (rise of temperature) which will turn the D'MAND System off quickly and will not allow the pump to activate if hot water is in the line. Once activated by the user, everything is automatic.

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