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Unitronics VFD Mounting


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Has anyone mounted a 2HP Unitronics VFD in a NEMA 4 Enclosure? Most of our applications require a VFD with a NEMA 4 rating. In the past, we have used a VFD that was rated for a NEMA 4 environment and so we had no need to have an enclosure. With the new Unitronics VFD, we would like to use it instead but to meet the area classification, we would need to mount it in a NEMA 4 enclosure and we would like to keep the enclosure size to a minimum. Can anyone tell me what the smallest enclosure size can be if the ambient temperature is about 105 deg. max and there is no cooling fan? The only think inside the enclosure will be the VFD. The VFD I am looking at is UMI-0015BU-B1 with a 2HP Rating

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  • MVP 2023


You must use data from  this table from unitronics support


and make some investigation with this  document


Then you can see - is it possible to use UMI-0015BU-B1 in NEMA 4 Enclosure with predefined box dimention.

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  • MVP 2023

@kratmel - I do like your Rockwell library. 

I was thinking about this problem as a 2 HP (1.5kW) drive running full load at 90% efficiency that needs to dump 150W of heat continuously.  The part number mentioned above is not in the table but if we swag all the part numbers that include -0015xx to 150W we should be OK.

Typically if I put VFDs in panels I add a fan and a thermostat and just call it good.  But it's not NEMA 4.  If it's going outside you can get the little rain blocking hoods that go over the fan grilles so you can get NEMA 3R.

I've sized heaters for outdoor enclosures before and was going to track down those equations and work them backwards to get panel surface area and therefore enclosure size, but your Rockwell document makes it much easier. 

So, @YINGD, what enclosure size will you use?

Joe T.


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  • MVP 2023
13 minutes ago, Joe Tauser said:

part number mentioned above is not in the table

It is little copy paste  mistake in table   :)  0007 is not 1.5kW drive (row#6).

I use the rule 1 to 8, respectively, 1 volume of the frequency converter should correspond to 8 volumes of air in the box where the VFD is placed in a closed cabinet. It works on an elevator that moves over chemical baths. However, there the ratio of operating time to the total time of the VFD cycle there does not exceed 40%.

P.S. I cannot upload picture of this installation (my profile attachment limit if full) :(

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This is foto  of installation for elevator -  NEMA 4 cabinet with two VFD inside working now on 3 production lines. The first of them was installed 2 years ago.


The customer had problems with the wires. Shielded remote control wires and cables to two motors are damaged very quickly (galvanic chemical production).

And this often led to the failure of VFDs that were mounted in a large control cabinet at the beginning of the line.

We changed the scheme - put two VFD in the NEMA 4 cabinet and installed it directly on the elevator. Currently, only a flexible mobile unshielded power line is used to supply power to the cabinet. If the power line breaks down - this is not a problem.

Relay galvanic isolation with separate power supplies was also used to control the VFD discrete inputs.
This protects the frequency converters in the event that the remote control accidentally enters to the bath with live electrolyte.

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