Generator Transfer Conversion

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Old 08-26-11, 12:31 PM
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Generator Transfer Conversion

Hi Everyone,
Nearly 20 years ago, I had a generator transfer switch (manual) installed in my house with 4 circuits...one of them a 240 volt circuit for my well. So what's the problem? My old coleman generator had a NEMA 6-20 outlet (not an L6-20, btw). When the transfer switch was installed, the electrician installed a NEMA 6-20 inlet to the transfer switch subpanel and made up a NEMA 6-20 generator cable to use with the coleman generator. The old coleman gave up the ghost a year or so ago, so I purchased a Troy Built 5,000 watt. The new generator has a NEMA L14-20 twist lock outlet which, of course, properly requires 4 wire to connect it rather than the old 3 wire cable. Now I understand that I should have already converted the transfer switch inlet to NEMA L14 (and had 4 wire properly installed, but procrastinator that I am, it isn't done yet and here comes Irene. So, is there and easy, (and SAFE) way to convert a NEMA L14-20 to insert into a NEMA 6-30 inlet? Could I simply cut the NEMA 6-20 plug on my existing 3 wire generator cable used to plug into the old generator and connect the 2 hots and the ground to provide 240 leaving the neutral unconnected. It seems like I could since I am feeding 240 directly and will not be using the a 120 circuit (naturally the circuit is split in my transfer switch sub-panel for the 120 circuits). Is this safe? I wonder because I have seen a NEMA L14-20to NEMA 6-20 converter cable advertised on the Internet so I presume that must be the case for that particular cable. If I have to, and power goes out, I can simply run extension cords through windows from the 120 outlets on the generator. However, it would be nice to be able run the well which is why the transfer switch was initially added. Also, making a change to my old 3 wire cable should be quick and easy. If this is do-able (and safe!), anything else I need to know?...like make sure to ground the generator (I could do that quickly with a stake and copper wire). Thanks in advance for your responses.
 
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Old 08-26-11, 12:46 PM
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Originally Posted by BeqauW View Post
Could I simply cut the NEMA 6-20 plug on my existing 3 wire generator cable used to plug into the old generator and connect the 2 hots and the ground to provide 240 leaving the neutral unconnected.
Yes you can. Remove the old 6-20 male from the generator side of the cord. Replace it with a L14-20 male and leave the neutral pin unconnected.

The generator does not need to be earth-grounded, that happens through the hookup to the transfer panel.
 
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Old 08-26-11, 12:52 PM
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You will not be able to run any 120 loads with that setup.
 
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Old 08-26-11, 02:17 PM
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Without knowing just how the transfer panel is wired I am somewhat hesitant to write this but...

I think that your original generator must have had the neutral and equipment ground bonded together at the generator and the electrician simply used the three-conductor cable to the transfer panel connecting the combined neutral/equipment ground conductor to the neutral in the transfer panel. The proper method would be to have the generator neutral and equipment ground isolated at the generator because in most cases the neutral-equipment ground BOND is made in the SERVICE panel and there is an unbroken connection from that bond to the transfer panel neutral.

IF this is how things are wired in your service and transfer panels AND the new generator has the equipment ground isolated from the neutral then I would simply use the existing three-conductor generator-transfer panel interconnect cable by cutting off the original generator-side plug and connecting the L14-20 plug to the two "hot" conductors and the NEUTRAL (not ground) connections of the plug. This is relatively safe although the interconnect cable is now without hot-to-ground fault protection. Make darn sure that the interconnect cable is in excellent physical condition and place it where it is safe from any physical damage. This will allow both 240 and 120 volt circuits in the transfer panel to be used.

Some pictures of the wiring of the transfer panel circuits would be helpful.
 

Last edited by Furd; 08-26-11 at 03:18 PM.
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Old 08-27-11, 10:50 AM
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Thanks HEfor the info, guys.

Just to clarify, the old transfer switch was basically setup to work with a 20 yr old generator that had a NEMA 6-20 outlet. I guess for consistency purposes, the electrician simply installed a 6-20 inlet to the transfer panel. The feed was NOT a 240/120 connect, but an actually 240 connect. I am well aware of how 120 is fed froma NEMA L 14, for example, but the old generator had the 240 volt circuit isolated from 2-120 volt circuits. It always worked fine and since I just usued it on occasion for a couple days at a time, I got a lot of longevity from it. The really nice thing about the transfer panel in addition to protecting linemen and being proper code, is that the other circuits in the main panel actually become my indicator as to when power is restored. It's kinda funny how almost every light in the house comes on (except those on the transfer switch circuits which may be either on or off) when power is restored because the tendency is to flip switches as you go room to room even though we know the power is out!
Just to clarify, however: I do believe I need to connect the 2 'hots' in the old 3 wire gen cable and the GROUND...not the neutral (which I understand to be used for a 120 circuit). Am I correct? Already bought an L14-20 male connector to plug into the generator outlet...I just wanted to verify what I wanted to do was OK. After this is over, I'm going to replace the transfer inlet with a NEMA L14 so I can just use a proper, standard NEMA L14 gen cable. I presume the 4th wire has to be somehow connected into the panel, but I'll leave that up to an electrician since I have no desire to work inside a breaker panel.
 
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Old 08-27-11, 11:10 AM
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Actually, I have been running 2 120 appliance circuits off the NEMA 6 setup for years. There is NOT a 240/120 supply from the old generator...Just a straight 240 supply. The new generator having the separated neutral and ground (and thus requiring 4 wire for conventional setup) throws me a curve, however, as to how exactly I get the 240 only supply from the NEMA L14-20. It seems there is disagreement as to whether I have to attach the generator ground or neutral to NEMA L14 to get the 240 only setup. FYI, this old transfer switch isn't like most newer ones. While it has the 'toggle' that prevents house feed and generator feed at the same time, it did not come with a built in inlet. The electrician installed an inlet and ran three wire through the wall and connected to the 'generator breaker' side of the transfer switch. I am pretty sure of this because he created my cable from the same 3 wire he used to install the inlet and also to connect the mainpanel to the switch.
 
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Old 08-29-11, 12:33 PM
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Originally Posted by BeqauW View Post
how exactly I get the 240 only supply from the NEMA L14-20. It seems there is disagreement as to whether I have to attach the generator ground or neutral to NEMA L14 to get the 240 only setup.
On many small generators it doesn't really matter (except in a technical code sense perhaps). The neutral and ground are bonded to each other inside the generator and inside the main panel, so the neutral and ground are effectively the same conductor. If you have a multimeter, set it to the continuity or ohms scale and measure between a neutral slot on the generator receptacle and the frame while the generator is off and all cords disconnected from it. This should tell you if the neutral and ground are connected inside the generator.

If you are only interested in the 240V hookup, then use the two hots and the ground pin; ignore the neutral. If you're looking to do both 120V and 240V circuits, let us know the results of the multimeter test and we can advise you better how to proceed.
 
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Old 09-07-11, 09:59 AM
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Smile Thanks, everyone...

...For your inputs. Power was out with Irene for 3 days. I didn't start the generator until about 12 hours after the power outage because I didn't want / need it running during the height of the storm and the generator had to sit out unprotected while running. The freezer and fridge are usually good for that long as long as you leave 'em closed anyway. I did a multimeter test of the generator neutral and ground showed continuity between them. BTW, the 2 NEMA 6 connectors were actually NEMA 6-30's. The old gen (5500 watts, 6500 surge) I guess could put out a full 30 amps. That caused me some trepidation because I was afraid the new Gen wouldn't run everything (It's a 3550 watt with 5550 surge), but that didn't seem to be an issue. Anyway, I simply removed the NEMA 6-30 male plug that connected to the old generator and replaced it with a NEMA L14 -20P that fit the new generator wiring the 2 hots and the ground....which you verified for me should be do-able. I had both circuits for the fridge and freezer working plus I could run my well as well (pardon the pun!) Ran the generator 12 -14 hours for a couple of stints...only used about 3 -4 gallons of gas and saved my food plus had running water available.

Worked great! thanks, again!
 
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