AHU 2 Cooling Coil 3's strainer cleaning has had minimal impact on LVEA temperature value, nor fluctuations. Excellent!
(Note, we've been calling these Fans, but I found out in talking with Bubba and Tyler today that this is a liquid strainer that filters the line that feeds the cooling coils. The *numbering* is still legit, they cleaned AHU2 Cooling Coil 4 strainer on May 30 2023 and today they cleaned AHU2 Coiling Coil 3 strainer)

Separately, the change to have AHU 1 Damper at 60% is OK (Bubba had adjusted from 70% he mentions in his above aLOG to 60% shortly after posting; comments on its effect in the timeline below). 

After unplugging the drain of the air handler, and holding the damper open at 60% in "manual" mode (as opposed to servo controlled "auto" mode), the AHU 1 cooling coils 1 and 2 have now restored to much better/cooler, normal temperatures (~47 deg F) that we had lost by May 30th 2023 (the fateful fire-alarm chaos day; see timeline in LHO:70284). Excellent!

LVEA temperature excursions in Zones 1A (this BSC2 / Beam Splitter), Zone 4 (Output Arm), and Zone 5 (Input Arm) never exceeded 0.4 deg F outside of 67 deg F range, and restored to normal ~67 deg F temperatures with small diurnal fluctuations within 7 hours. Excellent!

Slowly but surely, I think these maintenance activities are good, and not only restoring expected system behavior, but making it better. We now have a much tighter collection of temperatures in the LVEA, cooling coils are operating at a nice low temperature, and more zone heaters are coming alive such that we have the expected "constant heat, constant cool in order to keep the LVEA temperature nice and controlled" behavior.

I now have much more confidence that we can continue to do this kind of maintenance and not have it impact the IFO.

Timeline of today's work all within today's Tuesday Maintenance:
See Today's trend compared against a 7 day and 21 day trend.

Jun 13 2023 08:26 PDT 
    Bubba and Tyler start work, bringing down Air Handler 2, valving out AHU2's cooling coil 3's strainer and clean it.
    Understandably, all zones temperatures start to rise from 67 +/- 0.1 deg F but only max out 67.4 +/- 0.1 deg F.

    Also while out there, this is when they find that air handler 1 AHU 1 is flooded "again."

Jun 13 2023 09:03 PDT 
    Within a half hour, they're done with AHU2 strainer cleaning, AHU1 drain de-clogging, turn AHU2 back on, and temperatures begin to drop accordingly.
    
    Upon restoration, though, and back at the control room work station -- they still see AHU 1's cooling coil temperatures high (~ 61 deg F), as its been since May 30 2023.
    Indeed, also, the damper for AHU 1 is closed at 0%, as it has been doing diurnally since May 30 2023 -- the HVAC servo opens up AHU 1's damper each day (around when outside temperatures exceed 70 deg F), and then gradually ramps closed again by nightfall's temperature drop.
    Prior to May 30 2023, AHU 1 damper stayed around ~35% open throughout the day and night.

Jun 13 2023 09:03 PDT
    Bubba intuits that there's too much condensation gathering in AHU 1 because its damper is closed too often, and that condensation doesn't get drained out because its drain is clogged. As a mitigation attempt, instead of having the HVAC servo drive the damper open percentage, he switches over to Manual mode and holds it at 70% as described in his aLOG.

    This drops both cooling coil's 1 and 2's temperature down from 61 to ~47 deg F. Awesome.
    But, this starts to scare the wimpy scientists (me) who are paying too close attention too quickly, because they see the temperatures in the LVEA drop below the 67 deg F set point.

Jun 13 2023 10:02 PDT
    Zone 4 (input arm) zone heater turns on, and begins to bring the Zone 4 temperature back in line.

Jun 13 2023 11:00 PDT
    Bubba makes a further adjustment of the AHU 1 damper percent open from 70% to 60% open to try to decrease the cooling in the LVEA.

Jun 13 2023 12:07 PDT
    Zone 1A's zone heater collection turns on (human controlled? servo controlled?) for the first time, much like Zones 4 and 5 heaters came on for the first time after AHU2's cooling coil 4's strainer was cleaned, ramping up to ~70% in 5 minutes by 12:15 PDT.

    This really starts to turn around the LVEA temperatures for the better; the temperatures bottom out turn back up, overshoot a bit, and settle to yesterday's mid-day value. 

Jun 13 2023 17:00 PDT
   Temperatures are all restored within to ~67 +/- 0.2 deg F, and again, they never exceeded +/- 0.4 deg F.
   The "natural experiment" reveals the impulse response of the Zone 1A is about 5 hours, as long at the zone heater for that zone comes on!