Info

1 UP 26-116 F; 2 UP 26-99 F; S UP 43-75 F/UP 5C-75 F; 4 UP 26-96 F; 5 UP 26-64 F; B UP 15-42 F BRUTE II; 7 UPS 15-58F/FC (Spd 3); S UP 15-1C F/FR; S UP 15-1CC F; 10 UP 26-12C U

1 UP 26-116 F; 2 UP 26-99 F; S UP 43-75 F/UP 5C-75 F; 4 UP 26-96 F; 5 UP 26-64 F; B UP 15-42 F BRUTE II; 7 UPS 15-58F/FC (Spd 3); S UP 15-1C F/FR; S UP 15-1CC F; 10 UP 26-12C U

the system will not function. Pumps in a plumbing circuit that always remains full of liquid do not need to overcome any atmospheric head. These kinds of loops include closed-loop antifreeze and direct-pump open systems.

Friction-head loss is the resistance to flow due to the circulating fluid's contact with the pipe walls. Frictional head increases with smaller pipe diameter, increased length, changes in direction (like elbows, etc.), and increased flow. Given the details of those factors, frictional head loss can be accurately calculated. But normally, those factors are not significant enough to bother calculating in small solar

Installation Notes

✓ You can put two pumps in series to double the total head pumped. But beware: Using series or stacked pumps to achieve the head required in some drainback systems can cause big problems. If one pump quits during colder months (and they all quit eventually), and the other keeps pumping, it could lift the water just high enough to where it can sit and freeze. The frozen pipe can burst, and then the system could pump all the water in its drainback tank into the attic. This is one reason for the less-than-stellar reputation of drainback systems in some parts of the United States. The solutions to this head problem are to raise the drainback tank to a level that will accommodate the head of the chosen pump (see how James Dontje solved this in his article in HP120) or to select a higher-head pump if available.

✓ Many new pump installations will need a flange set or union set to connect the pump to the piping system. Make sure you have the additional parts you need before you start work on the system.

✓ Installing two pumps in a parallel piping arrangement will increase the flow of the circulating fluid, but will not increase the total head.

✓ All the SHW pumps mentioned in this article are classified as "fractional horsepower" and don't require a separate electrical circuit. However, fractional hp pumps do require a disconnect—an appropriately rated switch or breaker or a UL-approved cord and plug connection.

heating systems—except in rare circumstances such as very long piping runs (100 feet or more) with small tubing.

The flow rate through solar collectors should meet the manufacturers' specifications, but there is a good deal of fudge

Medium-Head Pumps

A Grundfos 15-42 iron pump suitable for most small-and medium-sized antifreeze-type solar water heaters (shown with pump flange set).

The March 809-HS magnetic drive, bronze DC pump needs a 50-watt module to pump to its rated 15-foot head. The magnetic drive tends to be noisier than other types of pumps.

A Grundfos 15-42 iron pump suitable for most small-and medium-sized antifreeze-type solar water heaters (shown with pump flange set).

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