- suspected PSL's HVAC might not be in Science Mode configuration, and went out to check.
- makeup air was set to 100%
- set the makeup air to the 20% we use for Science Mode
- this seems a likely reason for the 2degF temperature drops
- talked to PeterK before and after heading out to the LVEA
That's interesting. When I checked the make-up air on Wednesday (after Travis first witnessed this temp drop) it was definitely running at 20%. Did you check the make-up air fan in the acoustic closet (East of the PSL enclosure) to confirm it was running at 100% (it's very loud and drowns out the power supply in the closet when at 100%)? There have been times when the PSL environmental controls indicate the fan is 100%, but when the make-up air fan itself is checked it is running at 20%. There seems to be some odd link in the evironmental controls software where it shows 100% on all fans if one set of fans (i.e. the anteroom or laser room HEPA fans) was set to 100%. This also works the other way, where the HEPA fans will sometimes show 20% (they are either 100% or off) after the make-up air has been set to 20%. Essentially, the environmental controls appear to hold the last user set fan speed that then follows from fan screen to fan screen, but appears to not be applied until the user does so. I don't know if this is how the system is supposed to behave, but I have seen this behavior on more than one occasion.
Received alerts on PSL AC/Temp at 21:29 & 21:59 UTC. Spoke with Jason. Dropped out of Observing (LLO down) to go into the LVEA and check Makeup Air fans and AC controls. (1). Makeup Air fan is running at LOW SPEED. It is NOT running at 100%. (2). The AC Controls - Makeup Air fan speed at 100%. I reset it to 20%. Verified that the Makeup Air fan was still at low speed. Trended the five temperature sensors located in the PSL Laser enclosure for the past 30 days. Results are posted below. There were 8 low temperature event starting on 03/01 at around 20:02 UTC. These events are consistent across the five sensors. The Dust Monitor looks a bit odd but this is due to the 1 minute sample taken every 10 minutes. There is some time lag but reasonably good coherence none the less. There is less coherence between the temperatures in the PSL and in the LVEA.
(John W, Gerardo M)
There appears to be something that is turning on, then off, maybe something triggered by a thermostat. Noise can be observed on the accelerometers on the PSL table. See attachments, all plots are 5 days long. On first plot the signal for the accelerometer (color blue) was modified to match the temperature signal. Other plot no mods done.
