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RV Park Wiring Issue

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 Drew
(@Drew)
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Joined: 1 year ago
Posts: 5
Topic starter  

This post may not make much sense unless you have some knowledge as to how electrical distribution systems are wired, at least here in the US.
Here’s what I came across:
From the main service a three conductor direct burial type cable was used to feed the RV type power pedestals. So, two ‘hot’ conductors and a neutral.
Each RV pedestal had a ground rod driven which was connected to the ground bar in the pedestal.
Although the (US) National Electrical Code now requires that a grounding conductor be installed along with the feeders it wasn’t required when this park was originally wired so long as each pedestal was considered its own ‘service’. That requires that neutral and ground are bonded together. Or in other words electrically connected with either a screw or bonding jumper from the neutral bar to the cabinet or ground bar.
None of the bonding jumpers had been installed in any of park RV pedestals. Curiously enough, the factory-supplied jumpers and screws were still in their packages, neatly tucked under the neutral bars.
So what happens in this case if there is a short between hot and ground in an RV where the circuit isn’t protected by GFCI? Answer: Nothing. The trailer frame becomes energized. – No breakers trip.
I took some ohm readings between ground and neutral at various points around the park and was getting anywhere between 12 Ω and 75 Ω.
If we do the math: 120V / 12 Ω = 10 Amps. So a 20 Amp breaker just sees a 10 Amp load – Not a short circuit.
Interesting to note that RV voltage testers/protectors aren’t looking for resistance/impedance issues.

 

Mike:  Isn't this pretty common in many older parks?


   
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 Arn Chamberlain
(@Arn Chamberlain)
Active Member
Joined: 1 year ago
Posts: 7
 

Hi Drew,

While I  am not an electrician, your post does not make a lot of sense to me.  Shouldn't the neutral wire be connected to ground at its point of origin at the distribution center?  In which case, any short between a live wire and the neutral in the RV would have an electrical pathway from the neutral, back to the dstribution center and then to ground thus tripping the breaker.  If there was no ground rod at the distribution center, what would be the point on providing a neutral third wire to the pedestal in the first place?  As I see it, providing a connection to ground at the pedestal is merely a safety redundancy.

The only way the frame of the camper could get energized from a short between the neutral and a live wire in the RV and not trip a breaker is if the neutral wire in the pedestal did not provide an electrical pathway to ground.  This would happen if the neutral wire coming into tne pedestal from the distribution center was not connected to the buss bar in the pedestal and the buss bar in the pedestal was not connected to an external ground rod at the pedestal.  The other scenario on which the RV frame could become energized was if the grounding lug in the receptacle in the pedestal was not actually connected to ground (through connection to the buss bar) or was connected to the buss bar with a wire with corroded connections.  In this case, a connection between a live wire and the neutral in the RV would result in an incomplete pathway for electrons to the ground and would energize the frame of the RV in that it is common practice to use the frame of the RV as a return pathway for the neutral wire.  In suchba situation, if one were to touch the energized RV frame and be grounded, that person would then complete the electrical pathway to the ground and would get a very big surprise!


   
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 Drew
(@Drew)
Active Member
Joined: 1 year ago
Posts: 5
Topic starter  

Arn,

 

I copied and pasted that post from another forum hoping to get clarification- it's not mine.  Your answer makes sense.  Rv's however don't bond the neutral and ground together.  I am still waiting for mike Sokol to respond also.

 

Thanks,

 

Drew


   
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