Plastic anchors, like any other anchor, have specified pull-out and shear strengths. While it would have a much greater shear strength than pull-out, plastic anchors have been used for years to hold light weight fixtures to ceilings. If weight is a problem, switch to lead anchors or some other metal shield. As to melting under fire conditions, it would have to first heat up the concrete to melt the plastic. At those temperatures, I don't think it would matter.
Re: plastic anchors in ceilings?#34832 02/24/0403:25 PM02/24/0403:25 PM
Well, after finding out that the zinc alloy nail-in anchors are not supposed to be used for anchoring to ceilings (because of the low fusing tmeperature), it just made sense to me to have the same prohibition for plastic anchors. Yet, I haven't found any literature to that effect. Recently I removed some stem hung 2 tube 8 ft fixtures, and they were fastened to the concrete with plastic anchors, and it just seemed too flimsy, especially because of the increased dynamic load due to the 3 ft long stems.
Re: plastic anchors in ceilings?#34833 02/24/0404:06 PM02/24/0404:06 PM
Lead anchors are illegal in my area now for years, they've been replaced with steal. There's gripple, they make several different types of hanging systems for fixtures. They have a website. www.gripple.com check them out.
Re: plastic anchors in ceilings?#34835 02/24/0409:59 PM02/24/0409:59 PM
I've been told by different inspectors they can't be used as well as lead can't be used for those same reasons. In case of fire for the protection of victims as well as fire fighters. I would think that with enough convection, but I'm thinking moreso enough radiant heat that it would conduct rather easily through whatever was being fastened, down the shank of the screw, and turn it to liquid.
I like tapcons myself.
Re: plastic anchors in ceilings?#34837 02/24/0411:12 PM02/24/0411:12 PM
Has anyone actually done tests on these different fasteners in a controlled (fire)environment before passing judgement? I would tend towards Earl's opinion that if the concrete has got that hot then no-one is passing underneath.