how many breakers and circuits?

[StandUpGuy]

Square D is what I was looking to purchase. My brother is a union electrician and that is what he buys. The price is also fair on the products. Glad to know that the extension cord idea is not problematic. That saves me some cash. I have been looking at the plugs in the big box stores and of course there are many types. I have seen the images of the RV plugs online and they are the two slanted blades and the post right

[StandUpGuy]

I have a tiny travel trailer not a teardrop.

[GuitarPhotog]

no breakers and just 2 or 3 circuits.

teardrop is to simple to require sofistication.

slow

But not too simple to require safety.

<Chas>

[StandUpGuy]

I went to buy my main service box and breakers today but I saw a load center that I did not before. This one was smaller and was marked 30 amps. The one I was going to buy was 70 amps. They both have two positions for breakers. My intention is to put two tandem 15 amp breakers in my box. Is this 30 amp box too small for two tandem 15 amp breakers? The two boxes are almost the same price but the 30 amp one is physically small which is good for me.

[Engineer Guy]

The Tandem Breakers I've been referring to are 1/2 width. 2 of them are as wide as 1 'conventional'-size Breaker. So, 2 Tandem Breakers of this type should fit fine in the 30 Amp Box; a Box I've looked at in the past to perhaps upgrade to in my lil TTT.

There are 'full size' Tandem Breakers where 1 Breaker Handle trips both Breakers. They are used mainly for 230 VAC Dryers; Stoves; Welders; etc..

The Square D Box Packaging should clearly identify which Series of Breakers are compatible with it. For these scenarios, I always have a Tape Measure with me, and I just measure length x width to be extra-sure of compatibility.

[StandUpGuy]

That is not what I was asking about. I understand the tandem vs the double breakers. My question was about the load center. there is a load center that is marked 30 amp and has postions for two breakers. Is this OK for me to use with two tandem 15 amp breakers? They will fit. I was just wondering if the rating of 30 amp on the load center meant that the resistance in the internal components could not handle the capacity of two 15 amp breakers.

[dh]

That is not what I was asking about. I understand the tandem vs the double breakers. My question was about the load center. there is a load center that is marked 30 amp and has postions for two breakers. Is this OK for me to use with two tandem 15 amp breakers? They will fit. I was just wondering if the rating of 30 amp on the load center meant that the resistance in the internal components could not handle the capacity of two 15 amp breakers.

If you have two 15 amp tandem breakers, you really have four 15 amp breakers, totaling 60 amps. This is not an issue, you should have a 30amp main breaker.

[StandUpGuy]

That is not what I was asking about. I understand the tandem vs the double breakers. My question was about the load center. there is a load center that is marked 30 amp and has postions for two breakers. Is this OK for me to use with two tandem 15 amp breakers? They will fit. I was just wondering if the rating of 30 amp on the load center meant that the resistance in the internal components could not handle the capacity of two 15 amp breakers.

If you have two 15 amp tandem breakers, you really have four 15 amp breakers, totaling 60 amps. This is not an issue, you should have a 30amp main breaker.

I am glad to hear that because the 30 amp load center isa nice and small and will fit well. Thanks.

[Engineer Guy]

There isn't any internal resistance in a Box worth noting, and none that varies from 2 - 30 Amp Breakers to 4 - Breakers total that will fit the form factor of the Box [physical Panel space for the Breakers, and compatible Breakers that 'snap into' the Box under consideration].

In a 200 Amp Panel Box for a House, the individual Breakers add up to more than 200 Amps. This is also convention. The Main Breaker rating 'saves you', so to speak, from excess/dangerous current draw from the local Step Down Transformer wiring -> House Panel.

This same 'saving factor' will be at work in your Box. Any proper Plug that plugs in at an RV Park Pedestal will be 30 Amp rated. 50 Amp Plugs, for example, are different and larger. Unless someone really screwed up at the RV Park [or elsewhere], a 30 Amp Plug will be/should be breakered at 30 Amps.

That 30 Amp 'Main' Breaker will be exactly analogous to the 200 Amp Breaker in the House Panel scenario. Your 4 x 15 Amp 'half size' Tandem Breakers add up to more than the 30 Amp Main Breaker. And, that's OK. The 30 Amp Main Breaker will 'save' you.

These assumptions are why I focused on the physical fit and form factor. That 30 Amp Box is sweet for this application; that's why it caught my attention too... The Bus Bars in this, and any Breaker Box that the Breakers snap onto, will carry more current than they're rated for; a convention in electrical safety practices.

[StandUpGuy]

Thank you very much for the info. That is exactly what I wanted to hear.I will buy the little 30amp box tomorrow. It will fit perfectly where I need it to.

[StandUpGuy]

...Your 4 x 15 Amp 'half size' Tandem Breakers add up to more than the 30 Amp Main Breaker. And, that's OK. The 30 Amp Main Breaker will 'save' you.
....

What main breaker are you refering to here in this sentence?

[Engineer Guy]

I'm referring to the 30 Amp Breaker in an RV Park Pedestal whether you actually ever plug into one or not. By whether you actually ever plug into one or not I mean 'The World' ought to be breakering a 30 Amp Outlet at 30 Amps, even it's something someone added to supply an RV parked in their Driveway, etc.. RV Park convention now is to supply 50 Amps for RV Big Rigs.

Any proper Plug that plugs in at an RV Park Pedestal will be 30 Amp rated. 50 Amp Plugs, for example, are different and larger. Unless someone really screwed up at the RV Park [or elsewhere], a 30 Amp Plug will be/should be breakered at 30 Amps.

For whatever historical reason, many older and 'not huge' Commercial Trailers and RVs are wired for 30 Amp Service. This convention starts at the RV Park Pedestal, which will typically also have a Duplex Receptacle, much like in your House [except 20 Amp and always GFI'ed]. Once that became convention, breakering [and wiring] that Service at 30 Amp was part of the implicit standard or convention. The Wire/Cable size mentioned/recommended above running from the Pedestal to the Trailer also became part of that convention, as did a 30 Amp-capable Plug.

Continuing on down the electrical chain, Power and Charge Centers in Commercial Trailers and RVs typically handle 30 Amps minimum because the implicit expectation is that a Power Center will be plugged into 30 Amp Service versus, say, 10 Amp Service.

RV Park Pedestal

[Kharn]

Somewhat related, but has anyone set up their TD to accept both 15 and 30amp power (obviously you would not use both at the same time, idiot-proofing would be a good idea, but how would you accomplish it?)? It would result in greatly reduced capability if running off 15 amp power, but it would at least allow you to run the AC at night without needing a hook-up almost unavailable outside of RV parks.

I assume you would just wire 30amp to the main breaker, and then back-feed the 15amp to a dedicated breaker?

[Engineer Guy]

If I fully understand your question, the 'usual' way of accomplishing this is to use a 30 Amp -> 15 Amp Adapter like this:

30 Amp Adapter

Breakers properly deployed in a Trailer should protect loads in it such that the 30 Amp Mains Breaker cannot overload Trailer Wiring. That is, AC is on a separate Breaker in the Trailer, etc.. Wiring to the Trailer is the typical AWG 10, and so on... If the Trailer is plugged into a House 15 or 20 Amp Breaker, then that Breaker is the protection necessary, and assumed in my answer.

As an aside, without a 'Soft Start' Capacitor integral to the A/C, or added on later, many 13.5k BTU A/Cs will trip a 15 Amp Breaker [mine w/'Soft Start' doesn't].

In terms of safely, 20 Amp Receptacles and Plugs turn the left Neutral Leg 90 degrees to the left to distinguish they're breakered at 20 Amps [among other reasons]. However, the Blade surface area is the same as on 15 Amp Receptacles and Plugs. So, there's not some additional risk from overheating at full amperage draw. The surface area Resistance is the same. I keep my Connectors shined up 'just because'.

[Kharn]

I meant going the other direction, having a trailer designed to fully run on 30 amps, but with the capability to plug into 15 amps if that is all that is available.