Power cuts and cooling

During the semester there have been a few unscheduled power cuts at night during which the telescope had to be shutdown as the cooling system can not be run on the UPS back-up system. In the current situation the TCS will detect the power-cut and allow for 5 minutes before shutting down the telescope to avoid problems with overheating of the equipment in the electronics rack which can have serious affects on the functioning of the telescope, potentially damaging things. However, it was noted that likely the more modern equipment we have now is less sensitive than the old equipment.

Currently the TCS actually does not have any direct information about the temperature in the electronics rack and a system is being designed such that the TCS knows the temperature at all times. With this system it will be possible to let the telescope continue operating as long as the temperature is not too high and give timely warnings in case the temperature gets close to the limit. The TCS should also be aware if the power generator of the UPS is functioning, as the batteries alone do not allow for the telescope to operate for any extended period.

Looking in this issue in more detail it was noted that often we are actively cooling when only ventilation would be sufficient. Currently we are looking at modifying the cooling system including a by-pass system where we only cool the water in a passive way to provide for the ventilation (including the electronics rack). Especially at night, this should always provide sufficient cooling and allow to continue observing during a power cut. Also during normal operations there are many days that the outside temperature is so low that the passive cooling system would be sufficient which should provide significant savings on our power consumption.

As part of maintenance, 5 out of the 10 cooling fans in the service loft were replaced. Out of the 5, 3 were complete dead and 2 were moving only very slowly.