I get to talk to a lot of churches now. Being involved with a number of church renovation projects each year, I hear some interesting strategies. One of those strategies is to not run conduit for AVL wiring, but to plan on doing what we call “free air” wiring instead. Free air is just what it sounds like; the cable is running through free air. There may be ceiling trusses or beams to attach to, but for the most part, the cable is just running up there in the air, outside of conduit.
Now, I get the premise behind this; conduit is expensive! Those pesky electrical contractors (ECs) charge a pretty penny to install and terminate conduit. And when you talk to an AVL integrator, they are going to want a lot of conduit! So it seems like a great way to save money is to skip the whole conduit thing and just have the AV company free air all the wire. Or at least a lot of it. That should save a ton of cash, which lowers the overall cost of the project. Win-win!
Not So Fast
That’s the big problem with running wire free air; it’s not so fast. Let’s take the example of pulling speaker wire up to a stack of speakers. There will likely be several runs of individual cable going up to each speaker cluster. If there is a conduit that starts at the rack room, and ends at the speakers, it’s a simple matter of laying out the cable and pulling it through the conduit. It doesn’t take long at all. However, if that speaker wire has to be threaded through the ceiling trusses, across and over, down and around, all from a lift, it’s going to take a while. A good long while.
Now you might think that installing conduit will also take a while, since it has to traverse the path as well. That’s true. However, conduit comes in 10’ rigid pieces, and it only has to be attached in a few points. It’s a lot faster and easier to make that look good than it is to pull cable through the same space. Moreover, if the conduit runs are laid out wisely, the EC can start pulling multiple conduit through the same path, which makes if even faster for the cable pull.
Another cost imbalance is that most of the time, the AV installer is charging a higher labor rate than the EC is for the conduit installer. So if you skimp on conduit (which can be installed by a lower labor rate worker), and make the wire pull harder for the higher labor rate AV installer, you’re not saving anything.
But wait, there’s more! Did you know that code requires you to use what is called plenum-rated cable if you don’t pull it through conduit? And did you know that plenum-rated cable is 2-3 times as expensive as the non-plenum-rated version? That’s because in case of a fire, codes want to minimize the amount of poisonous gasses that fill the air. Normal cable has a PVC jacket on it that will burn and give off highly toxic gasses. Those gasses can incapacitate or kill people before the fire does. So that’s bad.
Thus, if you’re going to free air cable through what is known as a plenum space (a space where air moves through that you might breathe), you have to use plenum-rated cable. So sure, you may have saved a little money on conduit, but if your cable bill is 3 times what it should be, have you saved anything?
Run Extra Conduit
One more tip; if you’re running conduit—or rather if you’re paying your EC to run conduit—have them run an extra tube here and there. Now, it may not be necessary to run a spare conduit to each TV in the lobby, but it wouldn’t be a bad idea to have an extra, empty conduit between FOH and the amp room. Or between FOH booths in a building. Or maybe even a spare tube between the amp room and the ceiling (for later TBD use).
This is especially true if you’re going to cut the floor in a major remodel. If you’re cutting the floor, the biggest cost of that job is the concrete work. Adding a few extra unused pieces of PVC conduit underground costs almost nothing, and may well save you a lot of headaches down the road.
Do yourself and your church a favor…don’t skimp on the conduit budget.