Using VFD in a Class 1, Div 2 area

Status
Not open for further replies.

Gonen

Member
Location
Israel
Are there any restrictions regarding usage of VFD (Variable-Frequency Drive) for regulating motor speed, in a Class 1, Div 2 area?
From my least knowledge, it is only refered with respect to the motor it regulating and its AIT.

A note: It seems that Class 1, Div 2 is the most complicated classified area. On one hand it is not really considered hazardous zone, so most of the standard equipment can be used. On the other hand the equipment might require certifications, and not all of them clearly stated, so you might stumble over few bumps before characterize the suitable equipment...
Fortunately, I found this forum that helps me a lot!
 

nhee2

Senior Member
Location
NH
I was going to reply that the drive would need to be listed for use in Cl I Div 2 locations (and I don't think there are drives with this listing) or that the drive would need to be installed in a Type Z enclosure. However (2014) 501.115(B)(1)(4) seems to say it could be installed if its AIT is less than 80% of the gas/vapor.

We have never pursued locating a VFD in a classified area.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Are there any restrictions regarding usage of VFD (Variable-Frequency Drive) for regulating motor speed, in a Class 1, Div 2 area?
From my least knowledge, it is only refered with respect to the motor it regulating and its AIT.
I'll generally endorse nhee2's response with a few caveats assuming this is still a Canadian installation; i.e., the NEC is not actually the appropriate application standard. The CEC will first require the entire assembly to be listed to CSA standards. I believe you will find it difficult to find a VFD with an overall "T code" suitable for most Division 2 applications. Remember the internal components' "T-codes" must also be considered since an internal ignition would still be possible.

A note: It seems that Class 1, Div 2 is the most complicated classified area. On one hand it is not really considered hazardous zone, so most of the standard equipment can be used. On the other hand the equipment might require certifications, and not all of them clearly stated, so you might stumble over few bumps before characterize the suitable equipment...
Fortunately, I found this forum that helps me a lot!
Welcome to the world of classified locations. While other "protection techniques" exist, Class I, Division 1 basically requires all enclosures to be specifically recognized for Division 1. Division 2 doesn't but expects you to know why they aren't required to be specifically recognized.

One other thing to note. The CSA technical committee in charge of classified locations generally prefers CEC Zone classification and installations. Canadians (the public) still generally prefer Divisions which the CEC still allows. Many here will tell you the general public has little influence on the NEC. The general public has even less on the CEC.
 

John.Blue

New member
Location
Houston, Texas
Classs 1 Div 2 drive

Classs 1 Div 2 drive

Actually a Class 1 Div 2 drive was recently developed by SAI Drives out of Tomball, Texas. The units range from 20 to 100 HP in a 480 Volt configuration and are also rated NEMA Type 4x. The website for SAI Drives is saidrives.com

The only other alternative is to use either a purged enclosures or package the VFD in an explosionproof (NEMA Type 7) enclosure. The thermal issues related to the NEMA Type 7 enclosure can be formidable and one ends up with a very large, heavy and expensive package. The purged system will require a constant supply of purging air to void the enclosure of any explosive gasses.

The Div 2 rating indicates that a possibility exist that explosive gasses may be present in the rated area. in a Div 1 area you can be sure that under most operating conditions, explosive vapors will be present.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Actually a Class 1 Div 2 drive was recently developed by SAI Drives out of Tomball, Texas. The units range from 20 to 100 HP in a 480 Volt configuration and are also rated NEMA Type 4x. The website for SAI Drives is saidrives.com

The only other alternative is to use either a purged enclosures or package the VFD in an explosionproof (NEMA Type 7) enclosure. The thermal issues related to the NEMA Type 7 enclosure can be formidable and one ends up with a very large, heavy and expensive package. The purged system will require a constant supply of purging air to void the enclosure of any explosive gasses.

The Div 2 rating indicates that a possibility exist that explosive gasses may be present in the rated area. in a Div 1 area you can be sure that under most operating conditions, explosive vapors will be present.
Vacon (Finland) is the actual mfr of that drive, I think SAI is just the US company who took it through UL for use here, as opposed to the ATEX ratings it may have for use in other parts of the world. Being that you (OP) are in Israel, you would not likely care about UL or CSA issues, but it appears that Vacon offers this option themselves. Clever marketing, but I've never been impressed with the quality of Vacon drives, I've had a lot of trouble with them in the field. Vacon used to (maybe still does) brand label their drives to Cutler Hammer here in the US and most of my troubles were with those actually. But it's the same product.

One of the difficulties in using VFDs or other electronics in classified areas is if there are relays in it that can cause ignition. Small relays can be hermetically sealed which generally allows for Div. 2 listing, but on VFDs there is a capacitor pre-charge circuit that tends to have a relay that is too large to be offered that way. So it appears that the Vacon/SAI drives have somehow "sealed" the on-board relays in some way. But look at this from the manua pertaining to the Classified Area use of the drivesl;

Warning:
Exposure to some chemicals may degrade the sealing properties of materials used in the relays inside of the drive.

The types of chemicals often associated with degrading sealants tend to be the types of chemicals frequently found in petrochemical plants, especially in the classified areas. Yet they fail to specify exactly WHICH chemicals they are. I would be very very cautious with that and insist that they provide a detailed list of those specific chemicals so that you can determine your risk.
 
Last edited:
Status
Not open for further replies.
Top