I need some help finding the right boxes for supporting ceiling fixtures in a ceiling that is made from plaster and wire mesh( old commercial building) this ceiling is supported on the metal I beams that are separated at least 3 feet from each other.We are putting some 3 bulb surface mounted lights and some pendants no more than 30 lb. Any ideas?
Luminaries Boxes for weird ceiling
- Thread starter mtn_elec
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al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Luminaries Boxes for weird ceiling
If you lay two pieces of 3/4" EMT across the I beams, will you have enough thickness of plaster & lathe to hang a box using clamps like this?
If you lay two pieces of 3/4" EMT across the I beams, will you have enough thickness of plaster & lathe to hang a box using clamps like this?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Luminaries Boxes for weird ceiling
Since when have you been allowed to use emt for hanging things?
Since when have you been allowed to use emt for hanging things?
- Location
- Massachusetts
Re: Luminaries Boxes for weird ceiling
Forever, as long as your not using it to run conductors in at the same time.
Re: Luminaries Boxes for weird ceiling
the information I gave before was not accurate at all. It is even worst. This is a second floor ceiling, the material is plaster maybe 3/8" or more,then the wire mesh which is secured to parallels runs(every 12" or so)or steel "c" channels (1/2"X3/4")and this channels supported by steel strips that are attached to the roof which is a concrete bed; this concrete bed is supported by I beams that are spaced every 8 feet or so. So the ceiling that I have to work on is actually floating like 16" off down of these beams.The distance between roof and floating ceiling 36"or so.Does anybody have ever work on any of these ceiling before?
the information I gave before was not accurate at all. It is even worst. This is a second floor ceiling, the material is plaster maybe 3/8" or more,then the wire mesh which is secured to parallels runs(every 12" or so)or steel "c" channels (1/2"X3/4")and this channels supported by steel strips that are attached to the roof which is a concrete bed; this concrete bed is supported by I beams that are spaced every 8 feet or so. So the ceiling that I have to work on is actually floating like 16" off down of these beams.The distance between roof and floating ceiling 36"or so.Does anybody have ever work on any of these ceiling before?
davedottcom
Senior Member
Re: Luminaries Boxes for weird ceiling
mtn_elec, if you cut a 4" hole in the plaster ceiling for a ceiling box how high is the solid concrete above that? 16" ?
mtn_elec, if you cut a 4" hole in the plaster ceiling for a ceiling box how high is the solid concrete above that? 16" ?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Re: Luminaries Boxes for weird ceiling
For the surface mounted fixtures I would buy a 7/8" carbide hole saw to drill the plaster and lathe and hang the fixtures with toggle bolts. If the ceiling is accessible from above I would mount a "mud" box with steel bars acrossed the support channel for the plaster ceiling. You could also drill this hole (4") with a carbide hole saw although it may run you about $75. Still saves a lot of time and leaves a nice neat cutout.
For the surface mounted fixtures I would buy a 7/8" carbide hole saw to drill the plaster and lathe and hang the fixtures with toggle bolts. If the ceiling is accessible from above I would mount a "mud" box with steel bars acrossed the support channel for the plaster ceiling. You could also drill this hole (4") with a carbide hole saw although it may run you about $75. Still saves a lot of time and leaves a nice neat cutout.
Re: Luminaries Boxes for weird ceiling
With mud you mean the metal pancake boxes?
Because I need to put several of this lights and I would need to put more than 2 cables per box and I thinkk it would exceed the capac. There is no access for the above but we could break some ceiling GC will repair it.
With mud you mean the metal pancake boxes?
Because I need to put several of this lights and I would need to put more than 2 cables per box and I thinkk it would exceed the capac. There is no access for the above but we could break some ceiling GC will repair it.
frankft2000
Senior Member
- Location
- Maine
Re: Luminaries Boxes for weird ceiling
Instead of a pan box you could use a 4 inch square box with a round mud ring. They make those mud rings I beleive up to 2" deep.
Instead of a pan box you could use a 4 inch square box with a round mud ring. They make those mud rings I beleive up to 2" deep.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Luminaries Boxes for weird ceiling
mtn,
Here's another variation of the EMT-as-bracket idea that I posted above. </font>
mtn,
Here's another variation of the EMT-as-bracket idea that I posted above. </font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Use two tek screws to attach the j-box to the EMT, instead of the hanger I pictured.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Use 1/2" EMT with a saddle bend just deep enough for the irregular surface on top of this ceiling surface; and cut the EMT just long enough to extend over the adjacent U channel or rail.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">The tek screws will keep the saddle from rolling.</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">Pick a cable connector that will clear the side of the EMT.</font>
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Re: Luminaries Boxes for weird ceiling
This is the box that I meant. It should accept many cables due to it's large size. The link appears below for more info:
http://www.hubbellcatalog.com/raco/RACO_datasheet.asp?PN=280&FAM=RacoBoxes
This is the box that I meant. It should accept many cables due to it's large size. The link appears below for more info:
http://www.hubbellcatalog.com/raco/RACO_datasheet.asp?PN=280&FAM=RacoBoxes
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: Luminaries Boxes for weird ceiling
Nice box! Is the mounting of the hanger bars adjustable for depth of the ring below the bars? I can't quite tell from the product literature at the link.
Nice box! Is the mounting of the hanger bars adjustable for depth of the ring below the bars? I can't quite tell from the product literature at the link.
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