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Convert NEMA 14-50 60 amp line to Hard Wiring Wall Connector

Rocky_H

Well-Known Member
Feb 19, 2015
8,597
11,172
Boise, ID
Something is weird there. I don't think you're actually finding the same wire in those different places, because the labeling doesn't make sense. Wires bundled together in a rubber sheath would be NM-B, not THHN, and it would only have printed labeling on the outside of the sheath. They don't print labeling on the individual wires inside. THHN are always separate wires with labeling on them, but they would NOT be bundled together in a sheath.

So the pictures you show that have THHN are not the same physical piece as the pictures you show that appear to be a multi-wire cable. Now it's possible that there is some junction or splice somewhere in it, where maybe they are both part of the same total path in one circuit. But if that is the case, the rating of the circuit has to go by the lowest rated. So if you can find the gauge of each of those (the NM-B and the THHN), then you can see whichever has the lower current rating to see what the circuit should be.

And yeah, my opinion/guess is that the NM-B cable looks like 6--doesn't appear to be fat enough to be 4 gauge.
 

Genie

Member
Supporting Member
Something is weird there. I don't think you're actually finding the same wire in those different places, because the labeling doesn't make sense. Wires bundled together in a rubber sheath would be NM-B, not THHN, and it would only have printed labeling on the outside of the sheath. They don't print labeling on the individual wires inside. THHN are always separate wires with labeling on them, but they would NOT be bundled together in a sheath.

So the pictures you show that have THHN are not the same physical piece as the pictures you show that appear to be a multi-wire cable. Now it's possible that there is some junction or splice somewhere in it, where maybe they are both part of the same total path in one circuit. But if that is the case, the rating of the circuit has to go by the lowest rated. So if you can find the gauge of each of those (the NM-B and the THHN), then you can see whichever has the lower current rating to see what the circuit should be.

And yeah, my opinion/guess is that the NM-B cable looks like 6--doesn't appear to be fat enough to be 4 gauge.
Right, after looking again at the newer pics I see the THHN coming from conduit center bottom. The red and white wires appear to be from the black sheathed cable
 

RTPEV

Active Member
Mar 21, 2016
1,845
2,494
Durham, NC
Given the questions raised my advice is to hire an electrician to install the Wall Connector and to get a definitive answer as to what that wire actually is. Just remember 55-amp wire is not acceptable for a 60-amp circuit. Otherwise, DIY and assume you have a 50-amp circuit.
Right...you can still set the wall connector to run at 40A max, and then if and when you decide you need 48A, THEN you can pay an electrician to come in and re-wire (or validate).
 
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ATPMSD

Active Member
Mar 12, 2021
1,769
1,712
Atlanta, GA
Right...you can still set the wall connector to run at 40A max, and then if and when you decide you need 48A, THEN you can pay an electrician to come in and re-wire (or validate).
And just to avoid confusion for our OP, the wall connector will be set to a 50-amp circuit and will deliver a charge rate of 40-amps.
 
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Great advice y’all.

Yes, the THHN are the cables in the conduit after the junction box to the nema 14-50. We are probably talking less than 30 feet of wire for that part and then under 10 for the other part.

I’ve asked my solar installer to confirm the cables used. They’re willing to install my wall connector, but want 200-300 more than other certified installers to do it. So expensive for such an easy job…assuming the existing wires can handle the full 60amps.
 

Rocky_H

Well-Known Member
Feb 19, 2015
8,597
11,172
Boise, ID
assuming the existing wires can handle the full 60amps.
Yeah, that's going to be the tough one. Make sure you find out the gauge of both of those separate sections involved in the circuit. This is why someone just saying, "It's 6 gauge" isn't fully informative enough. The same wire gauge will have different amp ratings for those two different installation methods. See this chart for reference:


The multi-wire cable is the first column under 60 degrees C, and the wires in conduit is going to be the second column under 75 degrees C. So whatever combination of those you have needs to meet at least 60A for both to be used for a 60A circuit.
 
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