San Yuan vs San He 三元／三合 Glossary
The two great lineage families of compass feng shui: San Yuan reads buildings through time-cycled star charts; San He reads sites through three-harmony water and dragon methods.
Sānyuán / Sānhé · 三元／三合 (simplified and traditional identical)
Source credibility (S/A/B/C/X): S Rule computability (A/B/C): A for each lineage's procedures; the choice between them is a school configuration, not a computable question
What it is
Compass-based feng shui （理氣） splits into two family trees. San He （三合） organises a site around the twelve-stage life cycle of the dragon's element: sitting mountain, incoming dragon and water exit must fall into matching growth, peak and grave stages — the "four great water exits" （四大水口）. Its classic vehicle is the Yuchi Jing （玉尺經）, which the Four Treasures catalogue judged a Ming forgery — while noting that "since this book flourished, the geomancy of Jiangnan has regarded San He as the orthodox". San Yuan （三元） instead times the site: the Xuan Kong Flying Star chart and the period cycle, transmitted through Jiang Dahong's Dili Bianzheng line.
The disagreement is substantive, not cosmetic. San He first determines the dragon's five-element phase and requires the sitting mountain to match it; San Yuan permits other sitting elements provided the water method agrees. There is no academic adjudication between the two — they are different traditions, each internally coherent, each with its own classical corpus.
School differences
This entry is itself a school difference. Concretely, the split shows up in hardware (San He needs the full three-needle luopan with dragon and fenjin rings; San Yuan needs only the correct needle — see Luopan), in the year and period boundaries, and in which directional spirits matter (San He practice leans on Sansha and the year-spirit system in date selection). The project's dispute register records such disagreements side by side rather than voting: School Dispute Register.
How this engine computes it
- San Yuan and San He are separate rule-set packages (
ruleset_id), not flags sprinkled through one algorithm; a chart records which package produced it. - Both lineages' procedures are implemented as A-grade computable rules where the source tables are closed: the San He four-exit framework and the Xuan Kong chart algorithm alike.
- Luopan ring requirements are scoped per module: the Xuan Kong module uses only the correct-needle 24-mountain ring and 360° scale; three-needle and dragon-ring logic live in the San He module.
- Where a rule inside either lineage is disputed (replacement stars, day-boundary conventions), the register's convention applies: parallel output and a recorded choice, never a silent pick.
Related entries
Xuan Kong Flying Star · Luopan · Yun Period · Sansha
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