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12-21-2014 11:00 AM - edited 08-07-2015 07:43 AM
I have been adding HP PWM 4-wire case fans to my xw workstation builds when we use higher powered dual video cards, to get added air flow through the case, directed initially down by the video cards. Those have a brownish special 4-pin plug on their ends to mesh with the standard HP PMW case fan headers on the motherboards. There is a dedicated header for the front cooling fan at the bottom front corner of most workstations, and the black plastic housings originally meant to hold those fans are rare and expensive. I figured out how to mount these fans directly to the front grill for the xw6400 and xw6600 workstations, and here is how it works for the xw4600 and Z400 workstations. More details are present in my initial post regarding exactly what size machine screws to use..... you need to use exactly those because the tolerances will be tight and you can not go up one size for the screws. Search for that post under Ghetto in the "Search HP Forum" box above (which only searches inside this forum).
The HP 92x92x25 mm case fans I use are the NMB-MAT 3610RL-04W-B56 HP 453473-001 and the ADDA AD0912UX-A7BGL HP 372651-001. These have the brown plugs, and those plugs are a different shape than the standard white PMW plugs that HP uses on their 92mm memory fans. The ADDA fan blades are recessed just a bit more than the NMB-MAT ones, so you may need to add a spacer between the fan and the inside of the case for the NMB-MAT type. Here's the parts you'll want, and you generally can find the #6-32 x 1.5" screws/nylock 6-32 nuts/#10 small and #10 fender washers at Ace Hardware:
First, remove the front cover and mark the front of the case as shown below.... the intersect points are where the screws will pass through.
The ADDA fans run faster than the NMB-MAT ones. I have a 4-wire resister in line adapter to drop the fan speed some, but really don't need that..... it is running at about 900 RPM with that in place, and they are quiet enough without it. Note on this next image the arrows..... the inside of the front case cover has a plastic projection that runs through that to the point that its "shoulders" bottom out against the front of the metal where the arrows are. You want to clip off about half of the length of the narrower projection so that it does not go too far in and hit the fan blades. It starts at about 1/4" and you want it to be about 1/8". The shoulders will still bottom out as before, providing the same degree of support.
Finally, a picture of the fan in place from the inside. I use a grill there for protection. Gentle hand tighten the parts together...... they don't need to be cranked down, and they have never vibrated when done this way. The ambient air sensor is zip tied to the metal grill of the case originally, and here it had been unclipped during the install, and then reattached just above the top edge of the fan almost exactly where it had been originally.
The nice thing about using these fans is that they were designed by HP to have their RPMs supressed by the motherboard's PWM control originally (so they don't make a lot of noise), and they can respond as needed if you choose to boost your fan speeds in BIOS during intensive processing jobs, and also respond to the needs of the motherboard in unusual circumstances such as high ambient temperature situations.