The TurPol Cooler Manual
Comments to Carlos Perez El Freonero
The TURPOL cooler is the box which is
connected to the polarimeter head with black flexible hoses.
During observations it is placed on the telescope floor on a foam rubber
piece. It has to be plugged to the mains and then turned on (both switches,
which will light red). A display will show the temperature in red numbers.
When started after a long time, it can take 5 hours to get the right
working temperature between -18 to -24 degrees, which are the fixed values
for starting and stopping the compressor.
Trouble shooting guide
If after several hours the cooler can't reach the above working temperature,
or if, after getting there, it is "going bananas" (which is more positive),
then try to locate Mr Carlos Perez, the official cooling superexpert! If you
can not get him, then start the following procedure:
- Find the cooling gas R12, a grey coloured bottle, located by the rear of
the staircase on the observing floor and should have a red hose attached.
- Now open the cooler compressor filling tube cup. Don't worry -
it has a safety valve. Hold the end of the red hose and open the bottle
slowly using a suitable spanner, and only a bit. Leave it flowing for
about 30 seconds to clean the circuit.
- After that, minimize the flow and now connect this end to the cooler
while R12 is flowing from the tube. After having connected it,
close the bottle valve. (The purpose of this is to avoid letting air
enter into the cooler.)
- Power-on the cooler box. Something should be moving now in the cooler
gauge, the arrow should be going down, counter-clockwise. There are 2
scales to check: the one marked as R12 where you will see the
evaporation temperature and the other marked BARS where you will see the
pressure. The idea is to get, after some time running (5 min.), an
evaporation temperature of about -30 deg in the R12 scale which will
correspond to a pressure of almost zero, but about one line higher than
zero in the pressure scale. If the reading is 0 bars or lower, the
cooler needs freon (R12). Open the bottle valve for only 5 seconds (!)
and close it again. If you put too much gas the evaporation temperature
will be too high for our needs. Check for a few minutes and inject more
if needed, but in steps of 5 seconds, until you see that the meter gets
stable for minutes around the -30 deg region on the R12 scale. The
display will go down very slowly.
- If, after injecting gas, the pressure, which goes for a moment up, does
not come down close to 0 again, the circuit is blocked. Take the hotair
blower from one of the cabinets and heat up the spiral capillar copper
tube, which located on the polarimeter head near the freon tubes inlet.
NB! Take care not
to burn wires or plastics! Heat until it gets a temperature high
enough that you cant't touch it. And repeat until the pressure in the
gauge is going down.
When you have a stable pressure in the gauge for at least 15 minutes, i.e. at
just above zero, everything is ok and the display temperature will come down
slowly to the working temperature.
NOTE: Use gloves! Safety is up to you. Freon is not dangerous if you
handle it with care.
Put everything back as you found it!.