Infrastructure - Keck Lab
Air Supply
The air supplied to the lab-space is conditioned by multiple steps
between the air intake and the supply ducts in the room. Here is a
general description of how the air is treated and how it can be
monitored.
I] Conditioning steps:
| Location |
Conditioning
steps |
Monitored status |
| 1) Air intake |
100% Outside air is drawn into the air handler
(there is no air recycling for the Keck Lab) |
Outside air temperature Outside air humidity |
| 2) Air handler intake |
Air is filtered through prefilters and
HEPA filters |
Magnehelic gauge on air handler indicates how
clogged filters are. New filters should read <0.5 inch pressure
drop. When drop is 1.0 inches then it is time to replace the
prefilters. HLPA filters are replaced once every 6 months. VFD 1
and 2 Speed (there is one variable frequency drive (VFD) that runs
the air handler fans and a second one that serves as a backup
should the first one fail. Their status can be monitored. At all
times one of them should indicate that it is not active.) |
| 3) Air handler |
a) Air is cooled to the cooling coil temperature
in order to remove excess moisture. The setpoint for this is
usually 46°f in the monsoon season, and 53°f in the dry season.
Note that too low a cooling point can result in insufficient
humidification of the instrument lab. |
Cooling Coil Setpoint Cooling Coil Temperature |
| b) Air is heated to the setpoint for the air
handler discharge. (55°f) |
Discharge Air Temperature Cooling Setpoint
Cooling-heating-setpoint
Cooling Output (monitors how much the cooling valve is open)
Heating Output (monitors how much the heating valve is open) |
| c) Air is humidified to set level (70%) |
Discharge Air Humidity Discharge Air Humidity
Setpoint |
| d) Air handler fan speed is adjusted to maintain
the static pressure setpoint in the main duct in the corridor.
(current setpoint is 2.00 inches of water) |
Supply Fan Output (gives fan speed in %. Note that
100% corresponds to 90 Hz) Discharge Air Static Pressure
Discharge Air Static Setpoint (this value has changed over the
life of the lab when we had air handler problems. Value as of May
2007 is 2.00 in wc) |
| 4) Corridors |
Chilled air runs to the various lab supply ducts.
Herckes Lab (PSF-7) as well as the Keck Lab (minus metallomics and
the conference room) are supplied by this air. |
The status of this air can only be monitored by
the main duct pressure (Discharge Air Static Pressure) and the
discharge air temperature and humidity monitored at the air
handler. |
| Air is split through the different Phoenix Valves
to the different lab spaces. NOTE THAT ALL AIR SUPPLY PHOENIX
VALVES ARE MANUALLY CONTROLLED ONLY. NONE OF THEM ARE MONITORED
ELECTRONICALLY. |
Pressure drops across the phoenix valves can be
measured with the department meter. |
| 5) Lab space above ceilings |
Air is heated to maintain the room temperature
setpoint |
Monitor the Reheats on the metasys server. Reheats
indicate local discharge air temperature as well as how open the
heating coil is. |
| 6) Air supply ducts |
Air passes through HEPA filters to the instrument
lab areas, and through ULPA filters to the clean lab space. There
is no additional filtration for the general lab. |
Pressure drops across the filters can be monitored
to determine the status of the filter. A clogged filter will have
a drop of > 1 in wc. |
| 7) Exhaust ducts |
a) Air passes through exhaust grids or ducts in
the various rooms. |
a) Dampers: many of the ducts have dampers which
offer coarse control of the air flow out of a room (or
instrument). b) Phoenix valves: some systems have manually
controlled Phoenix Valves to obtain a fixed room exhaust.
c) Phoenix valves: several rooms have electronically monitored
and controlled Phoenix Valves which can be reset by Building
Automations on campus (Call FACMAN at 5-3633 and ask to be put
through to building automations). These all provide a fixed
exhaust flow and may have several ducts leading to them. For
example, exhaust valve 29 (in room F-10) controls the exhaust for
a Neptune, future Element-2, several standalone hoods, the
X-series ICP, and the gIRMS exhausts. Closing the damper for one
of these items will result in an increased exhaust in the other
ducts so as to maintain the same total exhaust through the valve.
|
| 8) Instrument lab prep room (PSF-10C) |
The exhaust air from half of the clean lab and the
Herckes lab joins up with exhaust air from the clean lab, general
lab, metallomics, and the instrument lab right above the ceiling
in this room. It used to be an elevator shaft. |
|
| 9) Building roof |
There are two main exhaust fans on the building
roof top. They are set to a constant speed by Building
Automations. They do not automatically change speed to
maintain a constant static pressure in the main exhaust rise in
the elevator shaft. |
Exhaust static pressure Exhaust fan (1 and 2)
speed
Go to the top of the building and have a look at these huge
fans with Chris. Note that there are dampers on these exhaust fans
and they have occasionally closed partially or failed during the
hot summer months (mainly the ones on the east fan). If there are
exhaust issues in the lab in the summer, this is a place to look. |
II] Monitoring the laboratory climate control
system:
It is possible to monitor the lab status from a PC on or off
campus, however, one will first need to gain access to the metasys
server which is done via the lab manager. Once on the metasys server,
here is what you will see:
Double click on the first "AHU-1" heading and here is what you will
see:
In the image above, the "value" is either a setpoint or a readback.
These numbers update every 30 seconds or so. What's more important to
see here is the description given on the left. We frequently prefer to
look at trends over the last week or longer. To do so, it is necessary
to open the appropriate folder on the left and then find the correct
item. For example, if we would like to see the instrument lab room
temperature over the last week, then we'll need to find the
appropriate tab for it.
In the screen shot above, the current readback values and their
description are listed on the right. However, to access the trending
data we need to doubleclick on the appropriate tab in the left window.
For the room temperature it will be the file ending in ZN-T (short for
zone temperature). Double clicking on that gives the following screen:
To access the weekly trend data, click on the "trend" tab. Here is
the result:
If you click on the chart box (just under the "delete" button on
the screenshot above) then you can access a table of values for the
temperature. Highlight the top line and press CNTRL-A to highlight all
of the content of the table. Now click on the "copy to clipboard"
button and you can paste all of this into notepad and transfer it to
excel.
There are many, many parameters of the laboratory climate control
system that are accessible on the metasys server. The only way to find
out about them is really to play with it for some time and try to
understand what each item is. After looking through the system for
some time, the parameter names will start to make some sense.
Page last updated: May 20, 2007
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