20A Wire, 15A receptacle

[babzog]

I am planning to add some 120V wiring to my encl utility trailer so I can fire up the genny and have some heat and light and power in the trailer during the upcoming race season. I was going to add an external 20A duplex with individualized spring loaded covers. Feed 20A wire to a small sub panel with two slots for breakers, which I can use tandem breakers to give me 4 circuits. Overkill but that's the smallest panel I could find and it's also the cheapest ($42 at HD plus $16 or $18 for the breakers).

Then I spotted this. Now, I'm wondering, would I be safe using this 15A receptacle with 20A wire feeding that panel? Is it really a big issue using a 15A receptacle? What could happen, other than the deadly plagues returning to Egypt?

 

[pattenp]

15A outlets are okay on a 20A circuit as long as there is more than one outlet on the circuit. If it was just one oulet then it would need to be a 20A rated outlet. Now all this applies to residential wiring. I don't know about a generator supplied outlet circuit in a utility trailer.

 

[Charles (in GA)]

Just so the OP understands what "more than one outlet" is...........

ARTICLE 100—DEFINITIONS

Receptacle. A receptacle is a contact device installed at the
outlet for the connection of an attachment plug. A single
receptacle is a single contact device with no other contact
device on the same yoke. A multiple receptacle is two or
more contact devices on the same yoke.


The typical duplex receptacle we are all used to seeing, is TWO receptacles according to the code.

EDIT: after re-reading the OP's post, I think he is wanting to use a receptacle on the OUTSIDE of the trailer as an INLET, which would mean using an extension cord with MALE ends on both ends............ PLEASE do not do this, as someone will get electrocuted when they unplug it from the trailer while the generator is still running.......... bad plan.

Your second plan, to use the 15 amp inlet connector is a much better choice. You actually would be better off to use a 30 amp RV twist lock inlet, as it won't easily become disconnected.

Charles

 

[pattenp]

Charles, good catch on the OP's post. I totally misunderstood what was being asked. I agree on the twist lock inlet.

 

[babzog]

Charles, yes, thank you for that catch! Holy cow, I had not considered that (shock possibility) and that could certainly be a problem waiting to happen, esp since my 7yr old will be around all of this equipment and probably wanting (doing) to hook it all up.

I had considered the twist lock route in addition to the standard blade plug - what is a good (cheap) source for such supplies? I see there is a 20A version of the plug I originally posted for a few dollars more.. still comes to nearly $30 shipped from amazon or ebay.

I'll probably still use 20A romex to connect from the external feed plug to the panel (since that's what I have). I'll probably look for a 20-30A plug to feed it, but am still curious about what might happen if I used a 15A plug instead? Is the thing going to melt if I pump 20A through it? Looking at a standard 15A receptacle vs a 20A one, the latter doesn't look a whole lot beefier, just has the funny + plug terminal.

 

[2ManyProjects]

I am planning to add some 120V wiring to my encl utility trailer so I can fire up the genny and have some heat and light and power in the trailer during the upcoming race season.

Charles, yes, thank you for that catch! Holy cow, I had not considered that (shock possibility) and that could certainly be a problem waiting to happen, esp since my 7yr old will be around all of this equipment and probably wanting (doing) to hook it all up.

I had considered the twist lock route in addition to the standard blade plug - what is a good (cheap) source for such supplies? I see there is a 20A version of the plug I originally posted for a few dollars more.. still comes to nearly $30 shipped from amazon or ebay.

Personally, I would suggest that you go with a quality marine-grade 30A twist-lock inlet, which is designed for just such purposes. After all, the application is essentially the same, as are the conditions it will see in use (except for the salt, perhaps; but if you use the trailer in the Winter, it will see some of that, too). This one:

http://www.defender.com/product3.jsp?path=-1|328|2290035|2290039&id=139844

would be a particularly good choice, as it also provides some protection of the wiring connections inside the trailer from accidental contact.

If you want "bling", you can go with full polished stainless steel:

http://www.defender.com/product3.jsp?path=-1|328|2290035|2290039&id=52601

I'll probably still use 20A romex to connect from the external feed plug to the panel (since that's what I have). I'll probably look for a 20-30A plug to feed it, but am still curious about what might happen if I used a 15A plug instead? Is the thing going to melt if I pump 20A through it? Looking at a standard 15A receptacle vs a 20A one, the latter doesn't look a whole lot beefier, just has the funny + plug terminal.

Don't "Rube Goldberg" this; you'll regret it in the long run.

 

[Speedy Petey]

Since it hasn't been noticed, the OP Is in Canada. I know they have different rules with regard to15 & 20A receptacles than the US.

I'll probably still use 20A romex to connect from the external feed plug to the panel (since that's what I have). I'll probably look for a 20-30A plug to feed it, but am still curious about what might happen if I used a 15A plug instead? Is the thing going to melt if I pump 20A through it? Looking at a standard 15A receptacle vs a 20A one, the latter doesn't look a whole lot beefier, just has the funny + plug terminal.

Just so you know, wire is rated in size, NOT amperage. So there is technically not "20A wire". Several factors determine a conductor's ampacity, size being the most important one.
With regard to 15 and 20A receptacles; typically they are both the same internally with just the face being different. In fact, you ask if a 15A will melt? A 15A duplex receptacle is TWO 15A receptacles on a single yoke. It IS rated for 20A feed-thru.
For a trailer inlet I'd definitely go with a 15A since you'll have much more access to a 15A extension cord. And I would not bother with a twist lock. All you are doing is adding cost and hassle. I have a marine grade cover on a 15A flanged male plug on the side of my enclosed trailer. It works perfectly and has for years.
I also have a double-throw switch inside that chooses between the 120V flanged inlet (for shore power or generator) or a mounted 2500W inverter. This way there cannot be a backfeed or exposed live parts.

 

[trainer]

I am planning to add some 120V wiring to my encl utility trailer so I can fire up the genny and have some heat and light and power in the trailer during the upcoming race season. I was going to add an external 20A duplex with individualized spring loaded covers. Feed 20A wire to a small sub panel with two slots for breakers, which I can use tandem breakers to give me 4 circuits. Overkill but that's the smallest panel I could find and it's also the cheapest ($42 at HD plus $16 or $18 for the breakers).

Then I spotted this. Now, I'm wondering, would I be safe using this 15A receptacle with 20A wire feeding that panel? Is it really a big issue using a 15A receptacle? What could happen, other than the deadly plagues returning to Egypt?

That inlet would work perfectly and it would be perfectly safe!. Since it's a male inlet(not a female outlet) there is no need for a double-male cable that could cause a shock hazard.

I would take your panel and use one slot as a feed, with a 15amp "main"" breaker and then use tandem breakers to run two 15a circuits. YOu could also use #14 wire and save a bit there too.

Should give you lots of power and you can plug into land power easily with an extension cord.

 

[RickP]

I am planning to add some 120V wiring to my encl utility trailer so I can fire up the genny and have some heat and light and power in the trailer during the upcoming race season. I was going to add an external 20A duplex with individualized spring loaded covers. Feed 20A wire to a small sub panel with two slots for breakers, which I can use tandem breakers to give me 4 circuits. Overkill but that's the smallest panel I could find and it's also the cheapest ($42 at HD plus $16 or $18 for the breakers).

Does your genny have breakers on it? Do you need a subpanel in the trailer? If the genny has a 30A breaker, could you just oversize the wire and outlets in the trailer? That seems a lot easier/cheaper than adding a subpanel.

 

[babzog]

For a trailer inlet I'd definitely go with a 15A since you'll have much more access to a 15A extension cord. And I would not bother with a twist lock. All you are doing is adding cost and hassle. I have a marine grade cover on a 15A flanged male plug on the side of my enclosed trailer. It works perfectly and has for years.
I also have a double-throw switch inside that chooses between the 120V flanged inlet (for shore power or generator) or a mounted 2500W inverter. This way there cannot be a backfeed or exposed live parts.

That sounds like what I want to do and good point about the availability of extension cords. I had planned to make my own since most of the COTS cords are lightweight. Figure I could buy 6' of heavy cord and a couple ends and make a good connection.

What switch are you using? I plan to add an inverter, probably next year, just to have the capability to run a few things without having to fire up genny.

 

[babzog]

I would take your panel and use one slot as a feed, with a 15amp "main"" breaker and then use tandem breakers to run two 15a circuits. YOu could also use #14 wire and save a bit there too.

I was going to use #12 for the shore power feed wire and #14 throughout the trailer. Two outlets each side, two up front, another up front in the cabinetry to plug in a battery charger, likely one external plug on the man door side and two 8' florescent lights, one on each side, with the switch by the man door. Also going to add 12v rear floods, externally, above the ramp, to light that area up if needed (backing up, working, celebrating, etc), which means I'll either need a battery (planned) or a 12V power supply (ie: PC power supply).

I had thought about using one slot as a "main" breaker of sorts. If the genny has a breaker, is that overkill?

What breakdown of circuit layout do you think would be best? Going to tote some kitchen appliances (coffee maker, nuker, toaster oven) and will have an electric (max 1500watt) heater to make it comfortable. I imagine I'll have the heater plugged into the left-hand side as the sled will likely be parked on the right.

 

[babzog]

Does your genny have breakers on it? Do you need a subpanel in the trailer? If the genny has a 30A breaker, could you just oversize the wire and outlets in the trailer? That seems a lot easier/cheaper than adding a subpanel.

Looking at a smaller genny... probably will have 20A max. 3000-4000 watt. Easier to store and manoever plus cheaper.

You're thinking, rely on the genny's breaker and branch all circuits from a junction box somewhere? Is that safe/wise?

 

[Speedy Petey]

What switch are you using? I plan to add an inverter, probably next year, just to have the capability to run a few things without having to fire up genny.

Since I did not need or want a center off I just used a 20A 3-way wall switch. Luckily it's what I normally use on jobs so I had plenty on hand.
I just wired a cord lead with a male plug to plug into the inverter inside the trailer under the workbench. This way I can also remove the inverter and use it elsewhere if I want.

 

[trainer]

I've got a cabin running off a 3000w Champion Generator... the ones CTC has on sale quite often.
I wired it with a 4-place sub panel, using one slot for a 20amp "main" and two 15 amp tandems with one slot still open. The feed is #12 from the 120v twist lock on the generator.

One breaker feeds two kitchen plugs, one feeds all the lights, and the other two feed outside lights and a few other plugs.


I put the lights on a separate circuit so if I blow a breaker, I'm not in the dark. A coffee maker and toaster on at the same time will pop a 15a breaker.

 

[babzog]

Since I did not need or want a center off I just used a 20A 3-way wall switch.

That's brilliant!

 

[RickP]

Looking at a smaller genny... probably will have 20A max. 3000-4000 watt. Easier to store and manoever plus cheaper.

You're thinking, rely on the genny's breaker and branch all circuits from a junction box somewhere? Is that safe/wise?

If you're only using a 20A genny, you could just wire the whole trailer with 12 ga. wire and rely on the breaker on the genset panel.

I guess it depends on your overall plan -- are you going to be plugging the trailer into an an external power source other than the genny? If you do plug the trailer into a 30A outlet (or larger) than you'd need a breaker to protect the wires in the trailer. But it sounds like your power needs are relatively light, so if you use a 20A outlet for the trailer at home, the wires in the trailer would be protected by the home's breaker panel. Are you only going to use the genny at the track? or is there a chance you'd want to plug into an outlet there? If so, it might be safer to have your own built-in panel.

 

[babzog]

Rick: I might plug in at home, but the outlet would only be 15A. At the track, it would be genset only.

 

[2ManyProjects]

Rick: I might plug in at home, but the outlet would only be 15A. At the track, it would be genset only.

As the saying goes, never say "never".

If your trailer is set up for 30A service, (such as by using one of the power inlet devices I referenced earlier, along with proper circuit protection), you can still run it off a lower-rated service (such as that 15A outlet at home, or your portable generator) when that is all you have to choose from. Adapters (such as http://www.hodgesmarine.com/Hubbell-Hbl31cm28-Adapter-30a-Female-To-15a-Male-p/hubhbl31cm28.htm, among others) are widely available to accommodate just this sort of application. Of course, you'll still be limited to 15A of total draw when running off such a service (which will presumably be enforced by the breaker protecting that outlet circuit). But the point is, you preserve the possibility of safely utilizing a 30A "shore power" outlet if/when such is available.

 

[babzog]

As the saying goes, never say "never".

If your trailer is set up for 30A service, (such as by using one of the power inlet devices I referenced earlier, along with proper circuit protection), you can still run it off a lower-rated service (such as that 15A outlet at home, or your portable generator) when that is all you have to choose from. Adapters (such as http://www.hodgesmarine.com/Hubbell-Hbl31cm28-Adapter-30a-Female-To-15a-Male-p/hubhbl31cm28.htm, among others) are widely available to accommodate just this sort of application. Of course, you'll still be limited to 15A of total draw when running off such a service (which will presumably be enforced by the breaker protecting that outlet circuit). But the point is, you preserve the possibility of safely utilizing a 30A "shore power" outlet if/when such is available.

If I used the 15A marine inlet (the one I posted initially, which I picked up, BTW) and 12-2 romex to a 20A breaker in a panel being used as a "main", would that not give me all the protection I'd require? I'd be limited to 20A total draw, which should be lots for a utility trailer. When plugging into the house, the house wires should be protected by the breaker on the house circuit? Or, am I better off with a 15A main in the trailer?

The biggest draw I'd anticipate would be running a heater on max (1500W) and a coffee maker or microwave or toaster oven (1500W max, but probably closer to 1300W) while the two flourescent lights (8' T8, actually tandem 4' in one fixture) are on and the battery charger is doing its thing (Battery Tender Plus).

 

[2ManyProjects]

If I used the 15A marine inlet (the one I posted initially, which I picked up, BTW) and 12-2 romex to a 20A breaker in a panel being used as a "main", would that not give me all the protection I'd require?

That setup would protect anything downstream of that breaker, but not the shore power cord itself, the inlet, that chunk of 12/2 Romex, etc.; and if you ever were to use a 30A-->20A adapter (i.e., basically the reverse of the type I pointed you at earlier) to run that off a 30A service outlet (which, AFAIK, are the most commonly found types in RV parks, marinas etc.), the "shore side" breaker would not even think of tripping until at least 30-35 amps are flowing through it. Is this a huge problem in practice? Probably not. But it's still not what I would call "ideal".

I'd be limited to 20A total draw, which should be lots for a utility trailer. When plugging into the house, the house wires should be protected by the breaker on the house circuit? Or, am I better off with a 15A main in the trailer?

The thing to understand is, a breaker can only protect those things which lie "downstream" of it. Further, breakers installed in service panels and such are neither designed nor intended to protect whatever is ultimately plugged into the power outlet; their SOLE job is to protect the WIRE between that breaker and the outlet. And so, presuming proper wiring practices, any place you see a 30A power outlet, you can count on the wire feeding it (from the shore side breaker panel) will be sized to accommodate at least that much load, as will the breaker. That does nothing to "protect" your 20A gear further downstream.

The biggest draw I'd anticipate would be running a heater on max (1500W) and a coffee maker or microwave or toaster oven (1500W max, but probably closer to 1300W) while the two flourescent lights (8' T8, actually tandem 4' in one fixture) are on and the battery charger is doing its thing (Battery Tender Plus).

It's not that I think you will necessarily need more than 20A service to do what you want to do; you probably won't, even if you run some of those devices simultaneously. The point was to maintain your flexibility in terms of what power sources you can safely and conveniently use, regardless of where you might travel.