notes on mvd installation

How to tune the cooling air flows

Also see the cooling system schematic

ps version

Insert the anemometers
From the heat exchange box, two hoses go up to the MVD. One hose is for the plenum air, the other for the 'volume' air. The volume air path is the one with the big valve (V1) in it. Starting at the box, there is first an elbow, then a short flexible section. This is where the anemometers A1 and A2 are (temporarily) inserted. The readout should be set to m/s. Turn them off when not in use - the batteries run out fast (3 AAA).
Turn on the fan
- Turn down the LV supply that controls the fan speed.
- Power up the fan with the software - this provides 110V power to the fan motor.
Next turn up the fan with the LV supply. Read the velocities on the anemometers. It should be 13.2 for the plenum, and 4.1 for the 'volume' air.
Balance the flows by manipulating the fan speed and the valve (V1) in the volume supply line.
Neutralize the MVD pressure The supply side of the air path (between the fan and the MVD) has more impedance in it than the return side, between the MVD and the fan. Therefore the pressure in the MVD tends to be a little negative. There are 2 big valves (V2 and V3) in the lines coming out of the MVD, and by partially closing them, you can increase the return-path impedance, until the pressure inside the MVD is neutral.
- Get the pressure meter (P) and a section of hose, long enough so that you can look at the meter while manipulating the valves. Insert the hose into the MVD through a small hole in the outer enclosure.
- With the air running, slowly close both valves until the pressure reads zero.
- Close up the hole with a piece of rohacell, aluminum foil and tape.
Remove the anemometers
The anemometers are not designed for long-term use, since the bearings will wear out. When you're done and everything is set up and written down, take out the anemometers and replace them with the same-length inserts that are made for this.
Same for the other half
Repeat steps 1-5 for the other half of the MVD. This is another reason you need to remove the anemometers.

Last update 12 April 2001 - HvH
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