Flood through conduits
Flood through conduits
(OP)
Working on a case where transformer pit flooded and water entered underground conduit and entered homeowners basement where electrical service enters the house. Caused major flooding damage because house was downhill from transformer. Beginning of conduit in transformer pit was resting on the ground and wide open (unsealed). Question is, is there anything in NEC or other code or standard procedure requiring opening of conduit to be above surface of bottom of transformer pit to prevent water from entering it when pit gets flooded? Thanks so much in advance for any help on this.





RE: Flood through conduits
"(G) Raceway Seals. Conduits or raceways through which
moisture may contact energized live parts shall be sealed or
plugged at either or both ends." This should have been caught by the inspector (assuming it was inspected), when the home was built. It may be that the home predates the transformer installation, so the utility that installed the transformer would bear responsibility.
However, no conduit can be thought of as completely watertight, condensation forms even if sealed. That is why you must use water resistant cable inside. In reality, the installation at the house should have addressed this issue IMHO. The underground feed should have come up the outside wall and entered the building up high with a weather head. That way any water in the feed conduit would just stay there and eventaully drain out when the weather dries up, or worst case, overflow the top of the conduit and not eneter the building. Every basement electrical service entrance I have seen is designed that way, overhead or underground feed.
"Venditori de oleum-vipera non vigere excordis populi"
RE: Flood through conduits
RE: Flood through conduits
Now a follow-up question (or two). Is it standard to raise the opening of the conduit up off of the bottom surface of the transformer pit or use something drainable such as crushed stone at the bottom of the transformer pit? It just seems that leaving the conduit laying at the bottom of the pit unsealed is inviting bulk water into the conduit.
Also would an inflatable cable seal be sufficient at the customer's service box for resisting water pressure with about ten feet of head? That's what they've added since the incident, but it seems to me that they should raise the elevation of the next conduit that actually enters the customer's basement so that any floodwater that happens to pass that seal will just drain out of the meter box insead of entering the basement. The opening of the conduit entering the CT box is at the bottom of the box, and the conduit exiting the CT box and entering the basement is also at the bottom of the box. It would seem to me that this second conduit opening should be raised.
RE: Flood through conduits
Conduit installed through a building wall shall have internal and external seals intended to limit
the likelihood of the entrance of gas into the building. The use of seals may be supplemented by
gas-venting devices in order to minimize building up of positive gas pressures in the conduit.
If it's gas proof, it's water proof too I think. NESC covers the utility side of the installation.
RE: Flood through conduits
RE: Flood through conduits
ht
"Venditori de oleum-vipera non vigere excordis populi"
RE: Flood through conduits
They use rubber seals with stainless steel compression fittings. They are expensive and have to ordered to fit the conduit and cabel size. Worth the time and money if you have water with a head on it.
RE: Flood through conduits
"Venditori de oleum-vipera non vigere excordis populi"
RE: Flood through conduits