Over the last few weeks I have been involved with installing some extraction fans in the local Intermediate School classrooms, to allow air circulation within the said clasrooms.
These are pre-fab rooms, added on bit by bit over the 1970's.
Here is a shot of some of the fans that I installed:


Also here is a shot of the conduit runs for one of the rooms:


Finally, here is a shot of one of the fans.
Shown is the 6" (150mm) dia ducting protruding through the roofing iron and through a Dek-tite rubber sealing Membrane.


And here is all what the kiddies will see from below:





[This message has been edited by Trumpy (edited 01-24-2004).]

Paul, sorry to stretch the thing out but I'll be blowed if I can find my Photobase software at the moment!.
BTW folks, there are 12 0f these fans, 3 per classroom, in 4 classrooms.
Just as a note, I ended up installing speed controllers on the whole lot, after I used a 7Core multi cable to supply them, mainly because the fans were too noisy!.
I knew that before the things were even installed, but hey, I do the work, I get paid!.

You had modular classrooms in the 1970s as well?

We had these "Huts" as they were often called in schools everywhere in the 1970s as schools ran out of room, alt5hough your modular buildings look a little more substantial.

Paul,
Yes these rooms are called Pre-fabs here, because they are built, wired plumbed and so forth before they are fitted into place here.
Just try and install wiring in the darned things, the fellow that originally drilled the holes in the dwangs (noggings), made the holes big enough for his wires, didn't he, but no one else!.

Gotcha covered Mate!

I was able to make them smaller and faster loading for you. Nice to see that Camera is back in action.


Bill

Very neat and clean work Mike!

In Canada, they are called "Portables". They aren't actually attached tot he school building, but are standalone. Depending on their location on the school lot, they would get their power form the main school building, or their own service. Communications and fire alarm wire would connect to the main school. They would have no plumbing whatsoever, but would have electric heat and airconditioning.

Mike,

What kind of conduit is that?

Bill,
It's 20mm PVC Conduit.

It looks pretty much the same as the 20mm PVC conduit used here.

Mike,

I was going to say it looked like PVC, but then it seemed way too straight.

Bill

Bill,
Yes I know what you mean there!.
It was really hot up on the roof over the time that I was up there installing all the conduit work and cabling.
Had to really work hard to keep the PVC from getting a permanent bend in it, due to the heat.
But it all turned out OK in the end.
The only thing I hated about the conduit in this job, was the fact that I had nowhere to put the jar of conduit solvent, while I was using the brush to apply glue to the joints, there wasn't a level place anywhere!.

i like the 'boots' there Trumpy

~S~

Mike,

I have found a thousand and one uses for this device. It may not have worked as well on a metal roof like you were on, but works wonders on most others. You also might not find them in your area. I'm in a large city and have only seen them in one place. It's extremely strong, but it was expensive (like $85US).

http://www.provisiontools.com/prod1.htm

Bill,
Thanks for re-sizing my pictures!.
There's not many things more annoying than having to scroll sideways and up and down to see the whole picture.
Sparky,
I find the Dek-tite's really annoying to install, lots of rivets and RTV Silicone Sealant is used when I install one.
After installing the 12 in this job, I was just about seeing stars.
BTW, is there a similar thing on the market in other countries?.
We use these things for water-proofing protrusions through roofs and walls, what do you guys use?.
Gene,
Thanks for the compliment, , mind you, I really hate seeing shoddy work, especially with exterior conduit, even though mine is up on the roof, that's no reason to do a messy job.
But, even though I was under a bit of pressure to get this job done before the kids started back at school,this is the result of sitting down for a few moments and just thinking about how the wiring/conduit is going to be done and what gear will be needed.
Paul,
I realise that you guys use PVC conduit in the UK, but do you guys still use Conduit wires inside them?.
The reason I ask this, is because, we gave up doing this a few years ago, apart from in Industrial installations.
In most cases, it's a lot easier to pull TPS through the conduits, before it's assembled, that's how I did this job.
Just means that you need a size larger than normal.

Yes, we still pull individual cables through conduit. I use PVC conduit mostly in light commercial applications, such as shops. For domestic work, about the only places it gets used is somewhere like a garage or home workshop, where something a little better than surface run twin-&-earth is a good idea.

Paul,
Do you mean wires, as in Conduit wires?.
How much is 16mm conduit used in the UK?.
We usually start at 20mm and work up from there.
Only with Flexible Non-Metallic (PVC) Conduit is it used in this size (16mm) and this is only where Flex requires mechanical protection, under a Hot Water Cylinder.

Residential work here means for flush work either NYM (round cable with solid conductors, el cheapo style) or non-metallic flex conduit from 16mm up with individual wires. Surface-mount work in garages, basements and other exposed locations means NYM in rigid non-metallic conduit, usually just straight runs with the cable being exposed in the bends and near fittings. Otherwise surface-mount work just means NYM stapled to the wall surface. I've also seen electricians nail up 3x0.75mm2 flex to supply an additional kitchen receptacle.
@ Andy: Is it really true that the Germans just recntly went to metric conduit sizes? I remember hearing something like that. here in Austria conduit has been metric for ages, probaly since after WWI when the monarchy died and along with that metric units were introduced. The nails I've been pulling out here from our floors are still pre-metric.

You can buy 16 mm flex conduit complete with wires in some European countries, including Sweden. 16 mm conduit is the norm here as the boxes are designed for this size. Boxes that accept 20 mm conduit are less common.

Our boxes usually have concentric knockouts for 16 and 20mm or 4-section-knockouts. 1/4 for round cable, 2 sections out for flat cable and all 4 for whatever kind of conduit. Since most wires are solidly buried in plaster all the way strain relief doesn't seem to be much of an issue here, so most people use whatever they get. And it's sometimes near impossible to get out the inner part of the very flimsy concentric knockouts, so you usually end up using the 20mm one anyway. With thel old-style metal boxes I've seen holes punched in everywhere to allow for some more wires or wires from angles the orignal designer never even dreamed of... (long long ago there was a smaller kind of box with a different support for the device, small tabs to the left and right that would be gripped by 2 pieces of metal that were pulled together with screws. Those boxes only had one knockout. In our stairway they daisy-chained the pushbuttons, running the wires up from the basement. To do this they hacked tiny holes into the boxes and pulled the wires. The makeshift knockouts had very sharp edges and I had to replace the wire because the insulation was almost chewed down to the bare copper. I think the boxes disappeared after WWII when modern style devices with screws or claws were introduced.

20mm is the smallest size generally used for normal electrical work, then 25mm and upwards.

The IEE and electrical industry in the U.K. changed to metric specifications about 1970.

Paul,
I just wondered if 16mm was used over in the UK?.
Like yourselves, we use 20mm and up!.

No, 20mm is the smallest, and also the size of knock-outs provided on fixture boxes. Heavy gauge steel conduit also starts in 20mm as the smallest size.

20mm was also the smallest size used in South Africa. I am not sure though whether the RSA white PVC was UV rated for outside use - I can't seem to find any old off-cuts right now.

Hutch,
Both types we use here (grey and orange) are UV-stabilised.
Although we had some Orange flexible conduit a few years back that just fell to pieces after a few months in the sunlight.
But the plastics people must have got thier act together, because I've never seen anything like it since!.
BTW, does anyone ever use Black HFT conduit?.


[This message has been edited by Trumpy (edited 02-06-2004).]

I was told there was a call-back to this job last week.
The handyman on site, decided to install a water pipe thru one of my Dek-tites.
Not only did his coupling leak, he never bothered to seal around the cut in my Dek-tite.
When I get a hold of......

In the US this would not be permitted; under NEC 310.18(A) you must install the complete raceway between 'pull-points' and then pull the wires in.

I'd always understood this to protect the conductors from getting damaged during the installation process, but I know the actual reasoning. I would be quite concerned about the welding solvent for non-metallic conduit softening the conductor insulation.

-Jon

One summer here and conduit runs like that on a tin roof would be looking very sad. I guess that's not so much a problem in NZ

16mm conduit is available in Australia but you rarely see it used. With the limited application where you could use it for the only slight savings in cost it's not worth the trouble of carrying it around with all it's associated fittings.
For the same reason I often use 6mm² where 4mm² would be allowed.
You have to weigh up what's worth stocking so you can get by in a van rather than having to drive around in a pantech.

Is there a reason for that. Orange conduit in Australia is not UV-stabilised. If it is run where it's exposed to the sun it has to be painted.

There's one reason why I used to love 16mm flex conduit before I had a Hilti... old construction plaster is usually thick enough to take 16mm conduit without touching the bricks. It doesn't really take more than 4 1,5mm2 wires. I once fitted 6, but it was a stright run and I had to use copious amounts of liquid soap.

Briselec,
You are absolutely right mate.
The Grey stuff is u-PVC (UV-stabilised PVC).
The Orange stuff is Chemically resistant PVC.
I have never ever seen Orange PVC conduit being painted and I mean there is HEAPS of it used over here, a lot of it by Power Companies.
I just read in AS/NZS 3000, it is supposed to be painted if not UV stabilised.
You learn something new every day.