GG Dehumidification Coil Condensation

Prep - Overview
- Email request from Tom Brennan to investigate as follows:
  - "We have a need for the Labs group to make a recommendation for how to deal with the condensation coming off the bottom of the dehumidification coil.
  - The issue is there is condensation coming off the drain pan on the dehumidification coil when the outdoor humidity gets very high.
  - We're looking for an effective, low cost answer. A complete redesign is not possible.
  - Would like to address this in June before the humid weather gets here."
- J Gallagher observations from past summers also recorded below.

Hands-On
- Visual observation for signs of past moisture
  - Rust on outside of coil/drain pan section
  - Some white residue on wood from water on floor in Annex
- Activated dehumidification mode
  - Dehumidification activated, but Altherma not coming on
  - Communication to Altherma failed, low water alarm indicator communication failed
  - Traced back and found GFI in bathroom was tripped; power to Jace controller is from connected outlet in Janitor's Closet
  - Reset breaker and power came back on; Altherma functioning
  - Time clock on Jace scheduling was another 2 hours off; set ERV schedule two hours later so ventilation on during occupied hours
- Screenshot of system taken during thermal imaging of coil, noting Outside Air T/RH and Annex T/RH
- Thermal imaged coil / duct area to check for extent of colder areas
- Checked duct joints / coil drain pan for moisture leakage - indoor conditions not humid enough to cause condensation yet
  - Rust at border between drain pan and coil near bottom of section
  - Listened for air leakage; does not appear to be an issue

Brain Work
- Analyzed thermal imaging
  - No extreme cold spots shown
- Observations
  - Water on floor in Annex observed mid-July to end of August, generally
  - Condensation is worst during weekend recirculation dehumidification cycle
  - Coil pan was not originally sloped to drain correctly; improved by adjusting hangers for better slope, but still an issue
  - Condensation only observed in bottom area of coil drain pan where cold water collects, not around air duct area
- Ideas Discussed
  - Secondary drain pan under coil drain pan with more definite slope
  - Fabricate new coil drain pan with better slope and dimensional control to manage condensation collection
  - Externally insulate drain pan where condensation occurs (recommended option)
- Recommendations
  - Insulate sections where condensation occurs with self-adhesive elastomeric insulation, minimum of 1/2" thick
  - Add note about GFI in bathroom if no power to that outlet again in building operating notes and with local sign
  - Future Improvement: Could revise wiring so Janitor's Closet power for controls is on separate GFI from bathroom

Conclusions - Suggestions
- Provide access panel upstream / downstream of coil for cleaning coil and drain pan and for observing duct, coil, and air conditions
- Repeat thermal imaging and take dewpoint readings on hot, humid day to check results

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