thermal

THERMAL ISSUES (hot stuff...)

Last updated June 15th, 2000

TEMPERATURE SENSORS LOCATION AND LIST

See drawing CH2917.C001

On February 9th, we have replaced the old temp4m PC with the new Labview-based system. The data is accessed by typing 'temp4m' from any machine. That will show you the important fields logged in /ut02/seeing/temper/newtemp.log which are described below:

1	2	3 = A	4 = B	5 = C	6 = D	7 = E	8 = F	9 = G	10 = H
UT time	UT date	Lo tru NW	Lo tru NE	Lo tru E	Lo tru W	Up tru N	Up tru E	Up tru S	Up tru W
11 = I	12 = J	13 = K	14 = L	15 = M	16 = N	17 = O	18 = P	19 = Q	20 = R
unused	Mirror glycol	Mc air out	Oil pump	Low dome	Oil bef pad	Oil aft pad	High dome	PF cage	Cass cage out
21 = S	22 = T	23 = U	24 = V	25 = W	26 = X	27 = Y	28 = Z	29 = a	30 = b
Mirror W	Chimney	Mirror N	Mirror E	Mirror S	outside	Dome floor	Oil glycol	Dome RH	Oil volt read
31 = c	32 = d	33 = e	34 = f	35 = g	36 = h	37	38	39	40
MC volt read	Oil pump status	Cass cage in	air M1 cell	air above M1	guider air	dew point	oil volt calc	mc volt calc

Notes:

- the letters are the addresses of the DGHs

- Mc stands for "mirror cooler"

- 35 and 36 added on 31Aug00

- Since 04/nov/99, both temperature logs (the old one 'temp.log' and the new one) read UT time (instead of local time before).

SOME QUICK CHECKS THAT THE THERMAL SYSTEM IS WORKING!!

Typing "temp4m" on a Sun machine gives a list of temperature:

See drawing CH2890-A001 for mirror cooler details.

MIRROR COOLER:

In day time: "mc glycol" should be negative typically between -5° and 0°(if the cooler works)
At night time: "mc glycol" gently comes back to ambient temperature
In day time: "Valve voltage" should read between 0 and 5 volts.
At night time (cooling off): a voltage is still calculated by the PC and logged but there is a pressure gauge in the air duct (just after the cooler) which, after the sucker mode is being selected at the start of the night, detects 0 pressure in the lower air duct and will override the PC voltage and send 0 to the Mamac so that the valve is closed. The glycol stops flowing and warms up slowly to ambient during the night (#5 in temp.log).

OIL:

Day and night: "Glycol" should be negative typically between -5° and 0°. If this is not the case, think about an eventual problem in the glycol room (tank + pumps) located in the building next to Las Tacas. When glycol doesn't flow to cool the oil, "Before Pad" and "Glycol" will say typically +30° (oil warms up to ambient temperature and a bit higher at night when the telescope moves). During day time the oil valve is closed and the "oil glycol" sensor will be a good indicator of the glycol temperature sent by the plant and getting to the mirror cooler system (which comes second in the system after the oil loop).
At night time: "Valve voltage" should be >0 and "Pump On/Off" should say 1 (if telescope is active)
In day time: "Valve voltage" should be =0 and "Pump On/Off" should 0

DOME and TEL:

Day and night, "Low dome", "High dome", "Serr truss", "Primary North", South" and "West" should always be within 1-2° from each other (and closer at night time), the mirror temperatures being hopefully slightly lower than the dome ones.
Cass cage is always a few degrees hotter than the previous set of sensors.

GLYCOL SYSTEM

There are 2 separate circuits starting from the Glycol room: one for the building air conditioning and the other for the 4m telescope of : oil + mirror air cooler + M/C floors.

Notes about the old 'temp.log':

a- On 04/Nov/99, we found out errors in field labels in temp.log:

#3: previously saying south, was actually east
#4: previously saying west, was actually south
#6: previously saying north, was actually west

b- On 04/nov/99, we modified the labels on the old temp4m PC display and swap connectors at the multiplexer input in order to have the PC algorithm use the correct sensors and log a trustful temp.log as indicated in the table above.

c- the old grey relay box in the Cass cage has the following inputs for the mirror sensors: #1 with cable labeled north, #2 with east, #3 with south and #4 with west. DO NOT change that!

- the values displayed by the multiplexer in Tolnet show small variations (+/- 1°) from the reality (due to sensor calibration, effects of the cables,...) and serves only for debugging. The old PC algorithm uses a correction table for each sensor (file "tcoef").