Heat dissipation in IP 67 Enclosure

[structure59]

Hi,
I have a 750mmDx600mmWx450mmH IP 67 enclosure of SS 304 and it has one 5KVA online UPS plus 4SMPS inside.Total power input is 3000Watts.Willthe heat dissipation be a problem? The enclosure will be used in open air.

 

[che12345]

Dear Mr. structure59 (Structural)
1. Thank you for coming back and clarified that the ambient may be as high as 40 degree Celsius on some summer days.
2. Based on ambient 40^oC, IP 67 ; installing heatsinks on 4 sides would not be able to achieve the internal temperature to < 40^oC. Most UPS and SMPS are tested at 40^oC. A de-rating factor would have to be applied with surrounding cooling air temperature >40^oC.
3. A 5kVA UPS with say 90% efficiency would generate say 500W, with SMPS excluded. Alternatively, a 3000W input with say 90% efficiency would generate say 300W of heat.
4. If based on say temperature rise of 50-40 ^oC = 10K, with the power generated of 300W, the enclosure would have to be six times bigger.. Adding heatsink with area equal to 2 times the enclosure surface area would still need an enclosure two times the size.
5. BTY In general, avoid operating any electronic devices with ambient temperature >50^oC. The device has to be de-rated and the [insulation life] would be reduced by 50% for every temperature rise of 10K.
Che Kuan Yau (Singapore)

 

[7anoter4]

I found the attached article interesting:

https://www.heatsinkcalculator.com/blog/how-to-calculate-the-temperature-rise-in-a-sealed-enclosure/

 

[che12345]

Dear Mr. structure59 (Structural)

1. If based on equipment [heat generated taken to be 500W? ] , permissible [temperature rise 10K]; the present enclosure size is by far too small. Adding heatsink on all sides is a good proposal but would need much more surfaces.
2. I would like to propose [force cooling] instead, for consideration.
Build an another housing* to act as a "chimney" covering the existing enclosure. The housing* may be of lower quality material instead of SS 304 and with IP say X1. The size shall be at least [100mm clearance] from all sides but with say [300mm clearances at the bottom and 400mm clearance at the top]. The bottom IP X1 and the bottom skirting (all sides) up to 200mm with openings IP X1. The top and top down (all sides) 300mm with opening IPX1. Install (an extractor fan) of about [20W with IP54] covering the fan motor only.
3. Install a thermostat (set to switch on the fan automatically at 30^oC). The fan is [off] when the ambient temperature < 30^oC. When ambient is at say at 31^oC, The fan will maintain the internal temperature <42^oC. When ambient may be as high as 40 degree Celsius on some summer days, the fan will maintain the internal temperature to < 51^oC....
4. Attention: on summer days with ambient temperature of 40^oC, the internal temperature may reach 50^oC with the fan on. A [de-rating factor] should be seriously taken into consideration for the electronic devices.
Che Kuan Yau (Singapore)