I just built a DC system using 4″ PVC pipe, with ABS blast gates. I was mulling over different options for grounding. I saw the recent FWW article where the main premise was that grounding a small home system was not necessary. However, I thought I would still ground the outside of the unit.
Rather than wrapping the unit with bare copper wire, I picked up a roll of ‘U-Fix-It’ metal repair tape at an auto supply store. It was in the body repair section. It’s 1.5″ wide, has a peel-off adhesive on one side, and I verified its conductivity with an ohmmeter. I thought I’d apply the tape on the main ‘run’ of the pipe, and have circles of tape around the pipe every couple of feet that overlap the main straight run. Then I figured I’d ground one end of the tape via a length of copper wire to the ground at one of my electrical outlets. I can’t ground it to a water pipe, as all the water pipes in the house are made of PEX, a plastic-like material.
Any thoughts on the tape idea, anyone else done it already?
Dan
Replies
The main purpose for wrapping wire around the outside of the PVC duct is to reduce the electrical build up in the system and prevent getting "zapped" when you touch the duct. Therefore if the tape coducts electricity I would think that it would carry the current to the grounding point. My only question is will the current transfer through the adhesive side of the tape? Have you checked the conductivity of both sides of the tape? In theory, if it is conductive I do not see why it would not work. Keep us posted.
rrwood
What matter if the back of the tape doesn't conduct...the PVC it's applied to doesn't either! The thousands of volts that build up to cause static discharge aren't gonna be stopped by a couple mils of adhesive. It'll likely work fine--though cost more than garden-variety copper wire (i like twisted copper antenna wire--Radio SHack)
To me, very clearly, the grounding medium should be inside the pipe/conduit. This would end any potential for campacitance from the insulating PVC.
Any reduction of potential on the outside should also reduce potential on the inside. The question of whether it's important to reduce the static on the inside has been beat to death here & elsewhere. Many are just wrapping the pipes to lessen the discomfort of getting a static zap. Grounding the inside of the pipe is best but bare wire just snags long shavings (jointer, planer). Applying the tape to the inside would be a chore but very effective at cancelling the voltage at the source. My read on the original post was that the tape was to be applied to the outside, though.
Thanks to all who have respondedl
Yes my plan is to attach it to the outside of the pipe, to reduce the chances of me getting a shock rather than in an attempt to prevent explosions. Attaching it inside might be useful, but I have already glued all the pipes together, plus I was worried about the long term durability of the tape adhesive when inside.
I don't want to gound it to the DC itself since I actually have the DC outside via some flex tubing to reduce noise in the shop.
Good news is I found some metallic tape at the local hardware store. It appears to be the identical material to what I found at the automotive shop, but at a fraction of the price.
I also agree with the point that the whether the adhesive is conductive or not shouldn't matter, since the pipe is not conductive either. FYI I tested the adhesive with the ohmmeter and it is not conductive.
Thanks,
Dan
I recall reading somewhere to use the foil tape that is applied to windows in security systems. It's copper & can be soldered, if desired. There are various connectors available for attaching wire. If the hdw. store tape is cheaper then go with it. On the outside of the pipe shouldn't be too demanding of the tape & adhesive. How are you attaching wires & bridging joints?
I have been using a PVC duct on my DC system for 5 years & have never been zapped. But then my system sets on the floor along 1 wall because of the low overhead. I believe this has the same effect as grounding with wire. It also has is's other benifits the DC pulls the chips down from the machines & only has to pull the chips from floor level up to the opening in the impeller housing.
I have heard that it doesn't make any difference whether the DC system pulls up or horizontal but I think it does because I have a friend with the same DC & his system was set up where everything was pulled up & across the ceiling to the DC. Both systems used 4" duct & my system worked much better. I think both of us would benefit from changing out 2 hp DC's over to a 6" inlet & running everything from start to finish through 6" duct.
Why not just spiral wrap it, and then wire it to the DC frame, since that's already grounded?
Be seeing you...
This forum post is now archived. Commenting has been disabled