At one point in time, this schematic appeared in a manufacturer's installation manual.

The Glitch


The Glitch

Overview: At one point in time, the schematic shown at right appeared in a manufacturer’s installation manual. It represented their recommendations on installing a two-zone system.

Exercise: Can you identify at least five things that should be changed to improve this system?

The Fix

The Fix

What’s wrong?

1. The zone valves should be located on the supply side of the zone circuits to eliminate heat migration into inactive zone circuits.

2. The tee shown below the zone valves is a “bullhead” tee. When both zones are on, return flows slam directly into each other. This creates turbulence and noise. It also wastes circulator head.

3. There should be at least 12 diameters of straight pipe leading into the circulator. Placing it close to the side port of the bullhead tee allows turbulent flow into the circulator. This decreases circulator performance and creates noise.

4. The circulator in The Glitch drawing is pumping toward rather than away from the expansion tank. This causes a decrease in pressure within the zone circuits when their circulators operate.

5. There is no provision for differential pressure control in the original system.

6. There are no purging valves in the original system.

These glitches have been corrected in the fix drawing.

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