The commoners guide to plug and receptacle designations used on portable generators
Which plug or receptacle does my generator come with? The jargon for portable generators can be confusing to the novice user and especially when the manufactures start throwing out the array of acronyms associated with the electrical industry.
This article covers the North American electrical market where the terms duplex and NEMA plugs are used.
NEMA is the North American National Electrical Manufactures Association which labels the plug types. So every plug will start with this abbreviation.
The common plugs are rated for 125V to 600V and 15 amps to 60 amps.
In addition they are grouped by single phase or three phase. And in the common portable generator market we are most concerned with single phase which limits just how much we really have to know about receptacles and plugs.
To see a complete list and description of the NEMA AC power plug Connectors you can review them here: NEMA Connectors. However, it’s fairly easy to understand the designations. Let’s take a look.
- NEMA as defined above for the association
- 5 = the type of blade arrangement
- L = locking blade, no L is a straight blade and plugs can be pulled out easily. TT in this case means travel trailer and is used for RVs
- -15 or -30 = after the hyphen it is the rating in amperes (current)
- R or P = Receptacle or Plug respectively
Below we look at the common plug types individually that you will run across when looking at the portable generator configurations.
Typically, portable generators provide the 20 and 30 amp ratings and will (in the larger wattage sizes) use at least one locking plug typically a L5, L10, or L14 with a couple for standard duplex plugs. Some provide the TT-30 for RV or Travel Trailer use.
When buying cords and other receptacles or plugs make sure you match up the type and rating. This will be important as a 20 amp receptacle and a 30 amp receptacle will not have the exact same prong configuration for any NEMA L type.
In single phase (household and small appliance and at the 120V/125V and 240V/250V ranges you’ll be looking at the NEMA 1 for 2 prong and NEMA 5, 6, and 10, for 3 prongs and 14 for four prong.
First up the duplex plug is your standard 2 or 3 prong plug used in your house; these are NEMA 1 (15 amp only) and NEMA 5 respectively. It is a grounded connector where you have a hot and neutral wire and for a 3 prong an added ground wire.
in most cases you will typically find the 3 prong plug unless you have a structure built before 1960 or have specifically built a plug for two prong. Some small appliance still come in a two prong configuration and are usable in 3 prong outlets.
In AC electrical supply there is not a need for small appliances to have a specific hot and neutral lead, however, the widths many 2 prong plugs/receptacles will have a wider width on one prong to keep phase and hot wires consistent and is also true with 3 prongs.
The NEMA 5-15R is the designation used for these outlets. In the majority of cases your extension cords and appliance use 5-15P.
The NEMA 5-20R provides for a perpendicular prong which looks like a T on the larger prong. The plug will have the perpendicular prong. The receptacle can be used with both a 5-15 and 5-20 plug. Most portable generators will provide the MEMA 5-20 T slot to allow you to use 15 and 20 amp plugs.
Although you can get 30 and 50 amp NEMA 5 Receptacles and plugs they are not common.
Different L series receptacles are used for different voltages and phases. The twist lock provides for a what to prevent plug pull out due to normal vibration and pull on the cord.
Note that the following is for single phase only, if you are considering 3 phase power that is a different discussion and use.
In the 125V range the typical L types are:
L1-15 is only at this 15 amp rating.
For all the following lock plugs they are typically available in 15, 20, and 30 amp ratings although some specialty plug and receptacle types can be obtained for higher amp ratings. In most general portable generator styles you can expect that 30 amp ratings to be the typical maximum size.
The plugs and receptacles have different slot configuration for each of the amp ratings..
L6 types are for 250V rating having similar configurations to the L5. Both L5 and L6.
Dual 125V / 250V:
L10 and L14 are used for both voltages..
Note that TT (aka RV30) and 10 plugs are often confused and you need to be careful that you are using the right one.
Most Plugs and Receptacles used on the various portable generators int the under 10,000 watt range will be duplex 5-20, with an addition of L14 in either a 20 or 30 amp. With some of the more feature added ones you can also get the TT-30 for RV hookups.