wil-design
New User
- Location
- Florida
- Occupation
- Electrician
We have a concrete contractor requiring that our piping prior to a concrete pour not be strapped directly to rebar via usual methods consisting of use of wrapped twisted tie wire.
To comply, we are suspending the conduit and fittings away from the rebar using tie wiring in different directions to keep the encased conduit and fittings including Rob Roy stub ups "floating" thus keeping them from physically touching the rebar ( even if it is just a fraction of an inch )-- no minimum gap distance is specified. The job site is at a industrial location.
This verbal requirement by the contractor includes installation of RobRoy ( Plasti-Bond PVC Coated Aluminum ) conduit and PVC plastic conduit in smaller sizes such as 1 inch, 4 inch, and 2 inch. There is no written specification that he can specify in his prints or that we can find in our documentation. Voltages are 480 Volts maximum.
Is this a common industry practice by a concrete contractor imposed on our trade for industrial installations ( paper mills, water reclamation plants, powerhouses, etc.?
I do not have many contacts in my industrial electrical trade nor structural engineering trades, etc. We are trying to comply with the contractors wishes and I do not have the contacts or resources for professional advice.
I have thought about contacting the manufacturer of the Rob Roy conduit to find out if they show that contact of their coated conduit with standard steel rebar resists corrosion and weakening of the structural rebar which is the reason we have been given by the contractor. The same for manufacturer of the PVC conduit.
One workaround is to use tie wire fashioned to create a small gap between the conduit and the rebar since obviously tie wie contact with rebar is Ok. The concrete contractor has rejected this idea.
The concrete contractor has also rejected the use of thin cut 1/4" or 1/2" slices of scrap PVC to be strapped via tie wire between the piping and rebar. I do see his side of the issue that if the PVC is allowed to be strapped parallel to the rebar for more than a few inches that unequal rates of expansion and contraction of the concrete and rebar vs. the hollow plastic and plastic coated piping could cause a crush zone and allow the rebar to shift and comprimize its structural purpose.
Keeping the electrical piping away from parallel lengths of rebar via some minimum distance such as using sections of cut PVC spacers cut to say, half an inch in spacing, to be sufficient to keep the piping lengths from getting too close as it distorts and flexes before permanently being encased after the pour.
Their requirement seems both rare and unreasonable for our electrical installation but would in fact be reasonable if we, for example, improperly used bare metal piping, fittings, etc. contacting rebar for this encased in concrete application I will admit. The increased labor and manpower costs are a part of compliance which we are doing. We are looking for alternative solutions that can be shown / proven will not compromise the structure.
Any advice in this matter would be greatly appreciated.
Bryan
To comply, we are suspending the conduit and fittings away from the rebar using tie wiring in different directions to keep the encased conduit and fittings including Rob Roy stub ups "floating" thus keeping them from physically touching the rebar ( even if it is just a fraction of an inch )-- no minimum gap distance is specified. The job site is at a industrial location.
This verbal requirement by the contractor includes installation of RobRoy ( Plasti-Bond PVC Coated Aluminum ) conduit and PVC plastic conduit in smaller sizes such as 1 inch, 4 inch, and 2 inch. There is no written specification that he can specify in his prints or that we can find in our documentation. Voltages are 480 Volts maximum.
Is this a common industry practice by a concrete contractor imposed on our trade for industrial installations ( paper mills, water reclamation plants, powerhouses, etc.?
I do not have many contacts in my industrial electrical trade nor structural engineering trades, etc. We are trying to comply with the contractors wishes and I do not have the contacts or resources for professional advice.
I have thought about contacting the manufacturer of the Rob Roy conduit to find out if they show that contact of their coated conduit with standard steel rebar resists corrosion and weakening of the structural rebar which is the reason we have been given by the contractor. The same for manufacturer of the PVC conduit.
One workaround is to use tie wire fashioned to create a small gap between the conduit and the rebar since obviously tie wie contact with rebar is Ok. The concrete contractor has rejected this idea.
The concrete contractor has also rejected the use of thin cut 1/4" or 1/2" slices of scrap PVC to be strapped via tie wire between the piping and rebar. I do see his side of the issue that if the PVC is allowed to be strapped parallel to the rebar for more than a few inches that unequal rates of expansion and contraction of the concrete and rebar vs. the hollow plastic and plastic coated piping could cause a crush zone and allow the rebar to shift and comprimize its structural purpose.
Keeping the electrical piping away from parallel lengths of rebar via some minimum distance such as using sections of cut PVC spacers cut to say, half an inch in spacing, to be sufficient to keep the piping lengths from getting too close as it distorts and flexes before permanently being encased after the pour.
Their requirement seems both rare and unreasonable for our electrical installation but would in fact be reasonable if we, for example, improperly used bare metal piping, fittings, etc. contacting rebar for this encased in concrete application I will admit. The increased labor and manpower costs are a part of compliance which we are doing. We are looking for alternative solutions that can be shown / proven will not compromise the structure.
Any advice in this matter would be greatly appreciated.
Bryan
