Portable generator cable ground wire dilemma

Users who are viewing this thread

nxnw

New Member
Messages
2
Reaction score
0
Points
1
Location
Alaska
Hello, all. First post here, and thanks in advance for your help.

My home was set up for emergency power when I moved in. A 3-wire cable ran from a double-pole, double-throw manual transfer switch to an L-14 20 120/240 plug on a Generac 5000-watt portable generator. The "non-hot" (you'll see why I use that term) wire passes intact through the transfer switch box and connects to the neutral/ground bus in the main CB box. The system appears to have been installed around the time the house was built in 1998 and has gotten us through a number of power outages over the past several years without issue. The only real downsides to the setup were the generator's balky, hard-pull cord starting and its ungodly noise level, which finally prompted me to pick up a used-but-newer Honda EM5000SX, a major improvement in both those areas.

In place of the 20 amp 120/240 outlet, though, the Honda has a 30 amp L-14 outlet, so I had to change the plug on the cable. In disassembling the original plug, I failed to notice whether the 3rd wire was connected to the ground prong or neutral prong. I had thought it was connected to ground, and some online research pointed me in that direction as well (neutral prong unwired). Everything worked fine when I started a trial run on generator power, but then fairly quickly it didn't. I had started with breakers for the larger draws turned off -- fridge, freezer, boiler, well pump. Boiler seemed to be working fine when I added the garage circuit with the freezer, but after the fridge went live, the boiler started cycling on/off, as did garage lights. My multimeter showed 150 voltage on a garage outlet. I quickly got the genny disconnected and everything was back to normal when returned to grid power.

L-L voltage on the generator outlet is 247, same at the transfer switch poles. L-N on the outlet 120 each for each leg.

I'm guessing I made the wrong call on the third wire, that it should have been connected to the neutral prong. Aside from wondering if that's right, I want to ask if it's legit to run this system without a ground wire between the generator (where outlets are grounded to the frame) and the house (itself grounded, of course). The Honda's manual says its ground and neutral are not connected; I don't know whether they were on the old Generac. Is the 4th wire a must-have? Could the power fluctuation have been due to something other than miswiring, a problem with the generator?
 

drick

In the Trades
Messages
455
Reaction score
15
Points
18
Your house has what is called single split phase power. Its 240 volts split by a center tap on the transformer at the street (this is where your neutral wire is derived from) . In your electrical panel is every other breaker is connected to one side of the split or the other. Loads connected to a single pole breaker and the neutral give you 120 volts. Loads connected to a two pole breaker and no neutral give you 240 volts.

When you left the neutral floating you provided 240 volts power that was unequally divided between the connected loads. Anything you had connected while the generator was on was potentially subjected to over/under voltage. Not good would be an understatement.

So to answer your question yes the "third" wire is the neutral not the ground.

>>I want to ask if it's legit to run this system without a ground wire between the generator (where outlets are grounded to the frame) and the house (itself grounded, of course).
The short answer is no its not legit by today's electrical code, but it may have been when your transfer switch was originally installed. Ideally you should replace the 3 wire cable with 4 wire. This will ground the generator through the home's electrical panel.

>>I'm guessing I made the wrong call on the third wire.
Don't guess! Obviously you have a meter and know how to use it so check the voltage between the two hot legs (+/- 240V ) and between each hot leg and the neutral (+/- 120V ) at your panel BEFORE connecting any loads.

-rick
 

nxnw

New Member
Messages
2
Reaction score
0
Points
1
Location
Alaska
Rick, thanks very much for the reply. I thought at the time I'd based my connection choice on good info, but clearly I was missing some. I switched the 3rd wire from ground to neutral and everything worked as it should, with good, steady. proper voltage. I'll look at adding the 4th wire to bring the connection up to code.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks