Hello, what size RV plug, does a TWIN KING or MidBath need?

Log in

Log In | Register

Skip to main content

Topic: Hello, what size RV plug, does a TWIN KING or MidBath need? (Read 923 times) previous topic - next topic

0 Members and 1 Guest are viewing this topic.

Hello, what size RV plug, does a TWIN KING or MidBath need?

October 14, 2025, 09:47:50 am

Hoping for a quick answer, so my electrician doesn’t put in the wrong size receptacle

30amp or 50amp?
Thanks in advance 👍

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #1 – October 14, 2025, 10:29:32 am

30 AMP 120V. Electricians are used to 30 AMP 240v for dryers. They are not the same, so make sure you're getting the right thing.

NEMA TT-30 is what you want.

NEMA connector - Wikipedia

Rich

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #2 – October 14, 2025, 10:30:06 am

30 amp

Bob

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #3 – October 14, 2025, 10:59:51 am

I had the electrician install a panel like the ones used at RV parks. It has 50A, 30A and 20A outlets. I wanted the option of buying a 50A coach without having to change the wiring or hardware on the side of the garage. The panel is Connecticut Electric part number CESMPSC75GRHR (link to their Web page is here).

Current pricing on Internet sites appears to be $220. Given per-hour labor costs these days, the higher cost of the panel (relative to a 30A-only outlet) is not as hard to swallow.

The cover on the box listed above is quite deep and should accommodate "handled" shore cords.

Even though I've sold the coaches, I still use the 20A outlet often.

The warning about the correct outlet type (NEMA TT-30) and wiring (120V not 240V) must be heeded or damage to 120V devices inside the coach could occur. Do not assume a professional electrician can't make this mistake.

Mark H.

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #4 – October 15, 2025, 10:15:15 am

Yes as several have said, very important to note 30 amp RV (aka TT) is only 120v. Many years ago my Dad had an outlet installed by an electrician and he put in a 30 amp 220v "dryer" outlet. (which also had 3 prongs back then). Luckily RV would not plug directly into new outlet and the mistake was caught before any damage was done.

(50 amp RV is 220v which can add to the confusion)

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #5 – October 15, 2025, 05:04:03 pm

Hi MarkT; The 50Amp plug for larger powered motorhome electrical systems provides two 120AC circuits at 50 A each leg, for a total of 100A at 120VAC. While a particular motorhome could be wired for 220VAC, that isn't the common connection or usage. Your average 45' diesel pusher, still only has 120VAC circuits.
   Here is a google answer I got: big motorhome with 50 amp service details of voltage required - Google Search
   Previously this was covered in another thread: Installing Outlet for our RV - 30 or 50 amp?
   Another thing can happen; My father had an electrician install an RV plug TT-30 in his new house, to accommodate an RV in his back yard, with a section of sliding fence for access to a common alley in the back. I parked my T/K there once for two weeks, but I didn't use the plug. He never used it. Years later, I parked in the alley, and connected to the plug (for A/C), but tripped my main breaker. Checking the plug... Wired backwards from the original installer! Unbelievable!
   I corrected the outlets wiring. Pretty clear that the white wire goes to the silver screw head, and the black wire goes to the brass screw head! At least it wasn't 220VAC.    RonB

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #6 – October 15, 2025, 06:19:05 pm

Quote from: RonB - October 15, 2025, 05:04:03 pm

Hi MarkT; The 50Amp plug for larger powered motorhome electrical systems provides two 120AC circuits at 50 A each leg, for a total of 100A at 120VAC. While a particular motorhome could be wired for 220VAC, that isn't the common connection. Your average 45' diesel pusher, still only has 120VAC circuits.
   Here is a google answer I got: big motorhome with 50 amp service details of voltage required - Google Search
   Previously this was covered in another thread: Installing Outlet for our RV - 30 or 50 amp?
   .................................................. RonB

I'm going to disagree, RonB. Standard USA 220/240V residential service uses two 120v wires, one from each hot "buss bar" in the electrical panel. The NEMA 14-50 plug is commonly used for 240v electric stoves, charging EV's, 240v air compressors, 240v welders, etc. In addition to the two "hot" wires, the 14-50 has a neutral wire and ground wire.

While yes, a 50 amp RV is only 120v, it uses each 120v input from each side of the main panel separately and uses the neutral to complete each circuit for 120v. If you connected across both "hot" wires you'd have 240v.

With the exception of RV's, that's how a NEMA 14-50 is commonly used, both "hot" leads are used in the same circuit for a total of 240 volts. It is absolutely a 240v outlet.

In contrast, the TT-30 outlet only has one "hot" wire (120v), a neutral, and a ground. With only one hot wire, the 30amp outlet can only provide 120v.

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #7 – October 15, 2025, 10:14:45 pm

Quote from: MarkT - October 15, 2025, 06:19:05 pm

I'm going to disagree, RonB. Standard USA 220/240V residential service uses two 120v wires, one from each hot "buss bar" in the electrical panel. The NEMA 14-50 plug is commonly used for 240v electric stoves, charging EV's, 240v air compressors, 240v welders, etc. In addition to the two "hot" wires, the 14-50 has a neutral wire and ground wire.

MarkT is correct. We have a 50 amp RV. The 2 "hots" are definitely on 2 different legs, so it is not a 120V-only RV, although we have no 240V appliances. BUT - if we wanted to use one, we could if we had the circuit wired for 240V and were on 50 amp shore power (and in our case, the generator since ours is wired for 240V output.)

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #8 – October 16, 2025, 02:51:07 am

OK Michele; My comment was to specify that it is 220 AC at a 50A pedestal plug. It could be used as 220Vac, and run appliances at 220V. But that isn't how most large motorhomes are wired or used. I stand by that.
As motorhomes get larger, and appliances like air fryers, air conditioners, refrigerators(freezers) and electric water heaters are more mainstream, the resemblances to small mobile houses, makes 30A 120vAC not up to the task.
Installing a 30A only pedestal on a house, restricts the future hook up 'ability' for bigger motorhomes. Converting a Lazy Daze to 50A capability is certainly easy enough. Dual roof A/C, electric water heat, electric food preparation, are things that would be useful. RonB

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #9 – October 16, 2025, 08:39:41 pm

A 50 amp RV panel is not configured like a regular panel where the bus bar alternates between phases as it goes down. On a 50 amp RV panel one side is line one and the other side is line two. There is no place to put in a 2-pole breaker to get 240.

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #10 – October 16, 2025, 09:44:13 pm

We used to own a Tiffin Diesel Pusher that used a 50 Amp service. While most electrical devices were wired to one or the other of the two 120 Volt leads, 240 Volt service was available. We had a Wolf induction cooktop that required 240 Volt service and knew folks that had 240 Volt clothes dryers. On occasion we had to use a 30 Amp pedestal (using a cord adapter) and could not use the Wolf unless we started the 10KW diesel generator. For those times we kept a portable 120 Volt single burner induction cooktop. The main breaker panel in the motorhome had a double 50A circuit breaker for incoming power (either shore or generator power via a transfer switch). The wiring was not that much different than house breaker panels.

Art

Re: Hello, what size RV plug, does a TWIN KING or MidBath need?

Reply #11 – October 18, 2025, 04:50:09 pm

Quote from: Older_Fossil - October 16, 2025, 09:44:13 pm

The main breaker panel in the motorhome had a double 50A circuit breaker for incoming power (either shore or generator power via a transfer switch). The wiring was not that much different than house breaker panels.

Art

As does ours, in a 2000 class A (and our 2003 did as well). While both of these have/had an LP cooktop, a 240V electric cooktop was an option in those model years.

Ours has a typical residential GE breaker panel with the double 50A mains breaker at the top.

Affiliate Notice

LDOF is user-supported. When you purchase through some links on our site, we may earn an affiliate commission at no cost to you. As an Amazon Associate I earn from qualifying purchases.