NEMA RATING
- Thread starter ktan
- Start date
- Status
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: NEMA RATING
If you ventilate the enclosure it is no longer rated NEMA 4. If you need to maintain the NEMA 4 rating you will have to use an air conditioner or a heat exchanger.
Some customers don't really need a true NEMA 4 so they will let you add ventilation with baffles, but if you do this in reality you will have a Gasketed NEMA 1 enclosure.
If you ventilate the enclosure it is no longer rated NEMA 4. If you need to maintain the NEMA 4 rating you will have to use an air conditioner or a heat exchanger.
Some customers don't really need a true NEMA 4 so they will let you add ventilation with baffles, but if you do this in reality you will have a Gasketed NEMA 1 enclosure.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: NEMA RATING
You have a common situation. I would urge before you start cutting holes in your panel that you download the Hoffman temperature softweare off their website and run the calcs to see if you really need ventilation at all.
I often find that its not needed since VFDs don't dissipate anywhere near as much heat as they used to.
If you find that you are close, but in worst case you will be a bit over temp, you might consider putting a small fan inside the enclosure blowing over the VFD heatsink. The air movement will help dissipate more heat than still air will. Its a good idea to put a tstat inside the enclosure to alarm or shut off power if it goes over the VFD temeprature limit if you do this though. Hoffman makes a nice DIN rail mounted tstat.
Its possible to get either an air to air or water to air heat exchanger to remove heat and still have the panel remained sealed to NEMA4 specs, but both are a nuisance and add cost.
An air conditioner is possible but to meet the NEMA4 requirements you'd have to get an expensive stainless steel unit. There is also some maint required with an A/C unit.
I would look closely to see if I really needed the NEMA4 requirements, or if someone just put the thing in a NEMA4 box regardless of necessity. I usually use NEMA4 boxes (Hoffman Concept) because they are convenient and cost no more than a NEMA1 box. I can keep fewer part numbers in my head that way. Its possible the guy that put it in the NEMA4 box did it for the same reason.
You have a common situation. I would urge before you start cutting holes in your panel that you download the Hoffman temperature softweare off their website and run the calcs to see if you really need ventilation at all.
I often find that its not needed since VFDs don't dissipate anywhere near as much heat as they used to.
If you find that you are close, but in worst case you will be a bit over temp, you might consider putting a small fan inside the enclosure blowing over the VFD heatsink. The air movement will help dissipate more heat than still air will. Its a good idea to put a tstat inside the enclosure to alarm or shut off power if it goes over the VFD temeprature limit if you do this though. Hoffman makes a nice DIN rail mounted tstat.
Its possible to get either an air to air or water to air heat exchanger to remove heat and still have the panel remained sealed to NEMA4 specs, but both are a nuisance and add cost.
An air conditioner is possible but to meet the NEMA4 requirements you'd have to get an expensive stainless steel unit. There is also some maint required with an A/C unit.
I would look closely to see if I really needed the NEMA4 requirements, or if someone just put the thing in a NEMA4 box regardless of necessity. I usually use NEMA4 boxes (Hoffman Concept) because they are convenient and cost no more than a NEMA1 box. I can keep fewer part numbers in my head that way. Its possible the guy that put it in the NEMA4 box did it for the same reason.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: NEMA RATING
NEMA 4 does not require stainless steel (NEMA 4X does).
NEMA 4 does not require stainless steel (NEMA 4X does).
tony_psuee
Senior Member
- Location
- PA/MD
Re: NEMA RATING
jim,
Most of the enclosure air-conditioner vendors I have dealt with make their NEMA 4 units with stainless steel and have a dual NEMA 4/4X rating.
Does the installed location of the VFD require a NEMA 4 rated enclosure? If not then perhaps using a NEMA 12 with fans would be better.
tony
jim,
Most of the enclosure air-conditioner vendors I have dealt with make their NEMA 4 units with stainless steel and have a dual NEMA 4/4X rating.
Does the installed location of the VFD require a NEMA 4 rated enclosure? If not then perhaps using a NEMA 12 with fans would be better.
tony
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: NEMA RATING
all the nema4 rated a/c units I am aware of have SS housings.
wirenut1980
Senior Member
- Location
- Plainfield, IN
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: NEMA RATING
Very true. I think the point you are missing is that the A/C makers have for whatever reason chosen not to make a NEMA4 A/C unit. If you want NEMA4 what you have to buy is NEMA4X.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: NEMA RATING
Not be too fussy, but it took 5 minutes on Google to find a NEMA 4 only solid state air conditioner. But I do agree, they are not common from the enclosure vendors.
Not be too fussy, but it took 5 minutes on Google to find a NEMA 4 only solid state air conditioner. But I do agree, they are not common from the enclosure vendors.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: NEMA RATING
But then again, I have not looked at them for a long time.
Agreed, but last time I looked at these things they are so pricey you might as well spring for the SS A/C.
But then again, I have not looked at them for a long time.
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