It is, but eric's voice-recognition software probably can't tell the difference.
Kind Regards, John
House fully rewired in trunking
- Thread starter jazzbhatia
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Kind Regards, John
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It's not the block that'll get hot, the metal screw would heat up first.
I've been trying to remember where I saw something (relating to fire protection) that said in tests between screwing into wood or rawlplug into masonry, the rawlplug failed really quickly and negated the protection of whatever it was.
The detail escaped me though.
All but the last bit of that may well be true but, as I said, in the context of a fixing to a (vertical) wall, there would normally be no forces trying to pull the screw out even if the plug had become totally liquid!
Kind Regards, John
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My point is simply we don't know. I do not have amendment 3 but from the lectures I attended the problem was where firemen entered a property to look for trapped people, so one assumes the fire has already been ranging for some time, this is very different from some one escaping a fire. The limit would be what a fireman's protective clothing will stand, he will be wearing BA set. So we are looking at a fair amount of heat which has had time to heat up walls and ceiling.
The standard method it seems is to use metal clips inside the plastic trunking
as shown so the cables even if melted do not obstruct the fireman's progress.
The clips however need to remain in place even when all that is left of the cables is copper wire. They are normally used every so often not every screw goes through one, when I was working on a gas terminal we used steel tie wraps every 5th the other 4 would be plastic, so the weight is increased to what is normal.
The steel tray work would clearly survive quite a raging fire, it was all steel construction, but a house is not the same, in the old days we had a packet of white flaky material which you spat on rolled in your fingers and shoved in the hole using the tool provided then turned the tool around and used the spike to make a start for your screw, it did not matter if the hole was over size it still worked, but then they decided that it was hazardous to health and all asbestos was banned. There are a range of products to replace it, the aluminium screw with matching steel screw used in plaster board, the spring loaded leaves which release behind plaster board, the metal leaves which expand normally used for very heavy loads, and the epoxy resin which glues in the bolt, again normally for very heavy loads, not sure about the epoxy resin type but most would stand really high heat. However the most common is the red plastic rawl plug in a 5.5 mm hole, there are also other colours for higher or lower loads, and some designed for plaster board, these work well, but there is simply no data about what heat they will work with and the main problem is it depends on what they are used with. Even with cable we have 70°C and 90°C according to what plastic is used. But with the simple red rawl plug no one knows what plastic is used, and we also don't know what temperature the wall will hit. If the other side of the wall is a lift shaft for example the chimney effect could cause the wall to be hotter than the room.
Likely in most houses trunking across the top of door ways will not fail before the fire crew have evacuated the house, but we are not privy to the information required to make that judgement. So the only way to be safe is to use the plaster board which forms the ceiling as the medium to prevent the trunking and cables from falling down onto firemen. So trunking down the wall is OK and trunking horizontal is OK but you can't cross any door ways without going into the ceiling space. I have in the past followed the frame of the door way and filled with caulk it made it look like a very heavy door frame but was near enough for an office wiring, but today doing that would likely not comply.
In the same way as I would not fit a 5 foot fluorescent fitting in a living room even if it was the best way to light it, I would only use trunking in the corners of a living room, however there is nothing to stop one using either if you so wished. The caulk takes over when the sticky back fails, the sticky back holds the trunking in place while the caulk dries.
The question is who does the reinstatement? When mothers house was re-wired I did the reinstatement so I put the plaster, and caulk on the back boxes and conduit and trunking where required. I also painted, and likely will in the fullness of time paper walls. Many of the back boxes were slightly loose and without the plaster, or caulk would likely get worse over time.
So what one needs to know is what agreement was reached and if the home owner has not asked the electrician to reinstate the plaster and paint and then failed to DIY the reinstatement he can hardly blame the electrician. In an ideal world we have first and second fix and the electrician sees how well the plaster etc has firmed up boxes and other items before he signs off the work, but with mothers house most of the finishing work was done after the electrician who signed the paperwork had left.
The standard method it seems is to use metal clips inside the plastic trunking
The clips however need to remain in place even when all that is left of the cables is copper wire. They are normally used every so often not every screw goes through one, when I was working on a gas terminal we used steel tie wraps every 5th the other 4 would be plastic, so the weight is increased to what is normal.
The steel tray work would clearly survive quite a raging fire, it was all steel construction, but a house is not the same, in the old days we had a packet of white flaky material which you spat on rolled in your fingers and shoved in the hole using the tool provided then turned the tool around and used the spike to make a start for your screw, it did not matter if the hole was over size it still worked, but then they decided that it was hazardous to health and all asbestos was banned. There are a range of products to replace it, the aluminium screw with matching steel screw used in plaster board, the spring loaded leaves which release behind plaster board, the metal leaves which expand normally used for very heavy loads, and the epoxy resin which glues in the bolt, again normally for very heavy loads, not sure about the epoxy resin type but most would stand really high heat. However the most common is the red plastic rawl plug in a 5.5 mm hole, there are also other colours for higher or lower loads, and some designed for plaster board, these work well, but there is simply no data about what heat they will work with and the main problem is it depends on what they are used with. Even with cable we have 70°C and 90°C according to what plastic is used. But with the simple red rawl plug no one knows what plastic is used, and we also don't know what temperature the wall will hit. If the other side of the wall is a lift shaft for example the chimney effect could cause the wall to be hotter than the room.
Likely in most houses trunking across the top of door ways will not fail before the fire crew have evacuated the house, but we are not privy to the information required to make that judgement. So the only way to be safe is to use the plaster board which forms the ceiling as the medium to prevent the trunking and cables from falling down onto firemen. So trunking down the wall is OK and trunking horizontal is OK but you can't cross any door ways without going into the ceiling space. I have in the past followed the frame of the door way and filled with caulk it made it look like a very heavy door frame but was near enough for an office wiring, but today doing that would likely not comply.
In the same way as I would not fit a 5 foot fluorescent fitting in a living room even if it was the best way to light it, I would only use trunking in the corners of a living room, however there is nothing to stop one using either if you so wished. The caulk takes over when the sticky back fails, the sticky back holds the trunking in place while the caulk dries.
The question is who does the reinstatement? When mothers house was re-wired I did the reinstatement so I put the plaster, and caulk on the back boxes and conduit and trunking where required. I also painted, and likely will in the fullness of time paper walls. Many of the back boxes were slightly loose and without the plaster, or caulk would likely get worse over time.
So what one needs to know is what agreement was reached and if the home owner has not asked the electrician to reinstate the plaster and paint and then failed to DIY the reinstatement he can hardly blame the electrician. In an ideal world we have first and second fix and the electrician sees how well the plaster etc has firmed up boxes and other items before he signs off the work, but with mothers house most of the finishing work was done after the electrician who signed the paperwork had left.
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