I am presently using a hermetically sealed enclosure for a single pushbutton unit in a Class I Div 2 area. The AB 3-position momentary pushbutton has 1 N.O. and 1 N.C. contacts rated for Class I Div 2.
I need a contact block of 1 N.C. and 1 N.C.L.B. for the pushbutton and AB does not offer such a contact block rated for Class I Div 2. I can achieve the same results of the needed type of contacts with the existing contact block and some relays in the non-rated control cabinet, however I would like to save some money and space.
So I have two questions:
First question: Do I need a rated contact block since the contact block is in a hermetically sealed enclosure?
Second question: For other applications, different from the above described issue, if I have a Class I Div 2 rated pushbutton unit, is it necessary to install it in a hermetically sealed enclosure? Or can a general purpose enclosure be used with the appropriate type of seal-offs at 18 in. from enclosure and +/- 10 ft from boundary?
BigDog, If the enclosure is an explosionproof enclosure, then you can use standard blocks, however I expect that you have sealed contacts and an enclosure that is not explosionproof. Can you post the part numbers, so that we can see what you have? If the contacts are sealed and you are in Class 1 Div 2 areas, the enclosure does not have to be explosionproof and conduit seals are not required at the enclosure. Don(resqcapt19)
The enclosure is not "explosionproof," but it is not a general purpose enclosure either. It is hermetically sealed for Class I Div 2, and the contact is rated for Class I Div 2.
The enclosure is a single push button unit hermetically sealed for Class I Div 2 hazardous locations, (AB Part #: 800R-1HZ4). The 3-position momentary push button (AB Part #: 800T-FXNP16RAR) contains a logic reed contact block with 1 N.O. and 1 N.C. contacts (AB Part #: 800T-XAR) for Class I Div 2.
The standard contact block I would like to use contains 1 N.C. and 1 N.C.L.B. contacts (AB Part #: 800T-XA7).
My interpretation of the code, is that I should be able to use a standard contact block in a hermetically sealed enclosure for Class I Div 2. If the area was rated for Class I Div 1, then I would agree either the contact would need to be sealed in a general purpose enclosure or vice versa.
BigDog, That is not a hermetically sealed enclosure. The sealed contact can be use in any enclosure. The sealing of the contact itself it what makes it suitable for the area, not the enclosure that it is installed in. The contacts I use are the 800T-XAP because they have a higher current rating than the logic reed contacts, but they aren't available in the style that you need either. You could look at 800H-FPXNP16RA7 with a 800H-NP31 cover and 800H-1HZX7 enclosure. I think that you will find that this option will be more expensive than the relays. Also you can't use 800T devices in 800R-1HZ4R enclosures. There is no wa to ground the exposed metal parts of the 800T operator and 250-2(b) requires the exposed metal parts of the operator to be grounded. You should be using 800H devices which have no exposed metal parts.