PXI overheating

[Ennio]

I must put a PXI chasis in to a litle NEMA 4 cabinet (no air flow or fan installed to the exterior).
Max exterior temperature 35ºC, no direct sun.
What kind of considerations I must consider to know if I will have temperature problems?
Thanks in advance.

[Claudia]

Ennio,

The PXI-1000b, PXI-1006, PXI-1010 and PXI-1011 chassis are designed to operate on a bench or in an instrument rack. They can operate at temperatures up to 50ºC, but we recommend to install them in places where there is air flow for the cooling system of the PXI chassis to work well.

Unfortunately I cannot tell you what could go wrong if you operate your PXI chassis under conditions that are not recommended. Any component of the chassis, or even a board the chassis, could get damaged under this conditions.

The following is a paragraph that I extracted from the PXI-1000B manual.
It applies to the chassis mentioned above, but I recommend you to consu
lt the manual for your specific chassis.

"Apertures in the rear and along both sides of the mainframe facilitate power supply and module cooling. Air enters through filters and fan inlets located
in the lower rear of the mainframe and exits through the upper sections on both sides and through the rear.
Place your PXI-1000B on a bench top or in an instrument rack so that the fans (air inlets) and the air outlet apertures along both sides of the mainframe
have adequate ventilation. Keep other equipment a minimum of 3.0 in. (76.2 mm) away from the air inlets and outlets.
Install your mainframe so that you can easily access the rear panel. This simplifies the replacement of the air filters or power supply/fan assembly, if necessary."

Hope this helps,

Claudia Lorente
Applications Engineer
National Instruments

[Ennio]

Thanks Claudia.
I still having questions. Do you have information of heat disipation in a PXI-1002 with a PXI-8175 controller and NI-4472 board? That can help me to calculate the necessary heat transfer of the nema 4 cabinet.

Regards,

Ennio Perelli
Chief Engineer on Electrical Power Systems
Laboratory of Power Quality
Santa Maria University

[Greg Caesar]

You can estimate worse-case heat disipation by summing the power required for all modules, and assuming all that power is converted to heat. Power use is on the spec sheets for all the individual modules. For example, the 8175 pulls 28 watts in typical use, with 36 watts maximum (that's straight from the spec). The 4472 pulls approximately 15 watts (my memory). I don't believe we spec the 1002 chassis that way, (we spec available power), but I believe that power draw is around 15 watts for the 1002 (again, my memory). Therefore, you should be able to handle approximately 15 (1002) + 15 (4472) + 36 (8175) watts, which is 66 watts - similar to a standard 60-watt light-bulb. The spec is that your enclosure would have to handle that heat source
without the temperature inside the enclosure increasing above 50C.

A simple, practical test would be to setup the PXI chassis inside the enclosure and use a thermocouple or other means to monitor the temperature inside the enclosure. The temperature inside the enclosure is "ambient" temperature from the point-of-view of the PXI chassis. If the temperature cannot be held below 50C, then you would have to investigate adding ventilation or active cooling.

Greg Caesar
PXI Marketing Engineer
National Instruments

[Ennio]

Thanks Greg.
I hope your hints can help me a lot.

Regards,

Ennio