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Beopt Heat/Cool Unmet Hours

asked 2022-01-05 17:00:12 -0600

edquinlan's avatar

updated 2022-02-07 14:09:39 -0600

If BEopt is autosizing the HVAC system, why is the output reporting 50-100 unmet hours? This is a very simple new, 2-story house being modelled. How many unmet hours should trigger a deeper dive (e.g. when more than xx unmet hours)?

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answered 2022-01-07 11:41:59 -0600

Some unmet hours is to be expected. BEopt autosizes HVAC systems based on ACCA Manual J, which uses 1%/99% design temperatures. In other words, the HVAC is intentionally sized not to meet 1% of all hours of the year, or 87.6 hours. Since the Manual J calculation is a simplification relative to an hourly energy simulation, the actual hours not met will vary somewhat from that. If you look at the hourly output for temperatures in the living space, you'll probably find that the temperature deviates very little from the setpoint during these 50-100 hours.

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Asked: 2022-01-05 17:00:12 -0600

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Last updated: Jan 07 '22