Install New 120v Circuit and Outlet

[dbj216]

I need an electrician's help please. I want to install a new circuit in my 1966 Trade Wind to power my microwave. I need the outlet below the galley counter.

The circuit breaker box has two breakers downstream of the main 30 amp breaker. There is no room to add a third breaker. There are three circuits running from the box, one is the AC, the other two are "general purpose" circuits powering the outlets around the trailer. It appears the AC circuit was added later as there is a separate old fashioned screw in fuse and the wire is run along the floor, over the wheel well, and then between the skins up to the AC.

Interestingly, Airstream provided an "extra wire" to the circuit box but not connected. I think this is the "pre-wire" for a future AC. I have not found where this wire terminates, but I bet it is near the AC on the roof.

A microwave is a relative high power appliance. My 86 Limited has the famous switch that routes power either to the AC or the microwave outlet, but not both at the same time. A hair dryer or electric heater pulls 1500 watts, more than the microwave. It is easy to see why some old trailer owners see "burn marks" on the wiring around the outlets.

How should I run a new circuit to power the microwave?

David

PS I didn't know the right category to make this post. Maybe "General Repair"?

[dbj216]

You folks that have rewired Airstream 115v circuits may have some ideas for me.


David

[Jammer]

The best thing to do is replace the existing breaker box with a larger one. I recommend the Square D "QO" type 6-breaker box, which Airstream has used in many newer production trailers.

The Square D "QO" box is smaller than similar products from other sources because it uses a slightly smaller breaker. You would also need the ground bar kit.

You would want to choose the placement of the box carefully so that the existing wires will reach.

[GeocamperAS]

Originally Posted by dbj216

I need the outlet below the galley counter.

If there is one already there you could just use that. Just keep in mind you will take a chance of tripping that breaker when using the M/W if something larger than a 5amp draw is running on the circuit at the same time. Adding a new one and running a new line (12 gauge wire) from the breaker box in cabinets or under things so it is not exposed, would be easier.

Originally Posted by dbj216

It appears the AC circuit was added later as there is a separate old fashioned screw in fuse and the wire is run along the floor, over the wheel well, and then between the skins up to the AC.

Keep in mind that Romex cable was not meant to be exposed to anything that could cut through it. like sharp edges of pot and pans.

Originally Posted by dbj216

The circuit breaker box has two breakers downstream of the main 30 amp breaker. There is no room to add a third breaker. There are three circuits running from the box, one is the AC, the other two are "general purpose" circuits powering the outlets around the trailer. It appears the AC circuit was added later as there is a separate old fashioned screw in fuse and the wire is run along the floor, over the wheel well, and then between the skins up to the AC.

One option is to replace your current breaker box with one that has room for more circuits. Another is to add your outlet to one of the 3 circuits after the 30amp main. If you add it to the A/C line you will blow the fuse if you ran the
A/C and M/W at the same time. If you add it to one of the 20amp breakers you will also take a chance of tripping that breaker when using the M/W if something larger than a 5amp draw is running on the circuit at the same time.
You still may not be able to run the A/C and M/W at the same time without tripping the 30amp main. Each of them draw close to 15amps. That is why your 86 Limited has that switch.
As far as attaching the wires (make sure the trailer is not plugged it) when you open the breaker box you will see where the black, white, and ground wire go. Connect your new ones in the same manner. Black to any of the circuits except the main breaker of course. On the outlet, black goes to the brass colored screw, white to the silver and ground to the green.

Originally Posted by dbj216

Interestingly, Airstream provided an "extra wire" to the circuit box but not connected. I think this is the "pre-wire" for a future AC. I have not found where this wire terminates, but I bet it is near the AC on the roof.

You would be correct. But no need to mess with that now unless you want to get rid of the wire going along the floor so nothing sharp pokes it. I would just cover that wire with something. I have taken a length of PVC and with a Drumel tool cut a slice length wise. Slipped it over the Romex and clamped the PVC to the floor so the slice was not showing.

[dbj216]

Jammer, thanks for the tip on the Square D QO 6 breaker box. The smallest at my local big box store was a rather large 8 breaker box. I don't need, or have the room for such a big breaker box hanging on my bathroom wall.


And thanks Geocamper for your help. I don't have an outlet close to my proposed microwave location. My old Trade Wind is wired with the less than desirable aluminum wiring. I limit the existing circuits to 15 amp max for safety reasons. A new, copper circuit with a 20 amp breaker would allow a microwave or electric heater to safely run. The AC circuit is run in copper. I will get it in conduit as you suggest.


And any wire I run will be protected with conduit. Thanks for the heads up.


I think I need a new box so I can run a new circuit to run the microwave and not the AC at the same time like my 86. 30 amp input is all I got and I understand that. And I prefer to limit my aluminum wiring to 15 amps.


David

[Minno]

Since you have aluminum wiring, make sure you buy circuit breakers that are rated to connect to both aluminum and copper. Not all are rated for aluminum wiring.

Chris

[dbj216]

Thanks Minno. I will double check the breakers. If I go with Square D QO and their breakers, I may be in trouble with the aluminum wire consideration. I'll double check to insure I'm okay.


I've come to the conclusion I need a new box with a 20 amp breaker for the new microwave circuit. I could also run another outlet on this circuit for a 115v heater. And I will protect the old aluminum wired outlets (two circuits) with 15 amp breakers, which is adequate for "normal" household loads.


I will need to wire the "A/C or Microwave" switch as 30 amp input has about 2000 watt power limitations. I think my AC consumes about 1800 watts when running on high.


David

[dbj216]

I mounted two new outlets under the "stove" cabinet. One will power the microwave, and the other will power an electric heater for chilly mornings. Both of these outlets are served by 12 ga copper wire and protected by a 20 amp breaker.


I have decided to install a new Square D QO six breaker box. It is bigger, and heaver, but still fits in the area close to the existing box. I will power the two existing aluminum circuits with 15 amp breakers, and power the AC and microwave copper circuits with 20 amp breakers.


I have a question again! Since the 30 amp shore power always has a 30 amp breaker on the pole at the campground, why would I need to install another one in my new breaker box? The existing box has one, but why? Secondly I was planning on the famous "either AC or Microwave" power routing switch, but again why would I need this switch if I protect both circuits with 20 amp breakers, and the power inlet is protected with the 30 amp breaker on the shore power pole?


I'm thinking I should let the campground 30 amp breaker do its job and not duplicate the effort.


David

[nvestysly]

Originally Posted by dbj216

I have a question again! Since the 30 amp shore power always has a 30 amp breaker on the pole at the campground, why would I need to install another one in my new breaker box? The existing box has one, but why? Secondly I was planning on the famous "either AC or Microwave" power routing switch, but again why would I need this switch if I protect both circuits with 20 amp breakers, and the power inlet is protected with the 30 amp breaker on the shore power pole?


I'm thinking I should let the campground 30 amp breaker do its job and not duplicate the effort.


David

I'm not certain why there is a 30 A breaker inside the trailer but I would leave it there. It seems like a good idea to be able to quickly turn off the AC power to all circuits with one switch.

[Minno]

David,

The 30 amp inlet breaker is required by the RV code. Do NOT solely rely on the campground post breaker. They get a ton of use, and are exposed to the weather. If it fails to trip, you run the risk of overloading your shore power line. Overloaded electrical lines lead to melted insulation and in extreme cases, a fire.

Also, suppose you run into this situation. The 30 amp outlet on the post doesn't work, but there's a 50 amp outlet on the post that does work (I've run into this before). So, you use an adapter to plug your trailer into the 50 amp outlet. Without the 30 amp breaker, your only protection for your shore power cord is a 50 amp breaker. You can run the a/c, microwave, and heater without tripping the 50 amp breaker, but you have drastically overloaded the 30 amp rated shore power cord. Again, leading to melted insulation and a fire.

It's fairly easy to keep an eye on the shore power cord to see if there are problems. But, there's that short length of shore power line inside the wall that you cannot see. Do everything you can to protect it.

Regarding the microwave or a/c switch, I did not include one in Little Girl. The a/c is on a dedicated 20 amp circuit as is the microwave. If both are running, and the total draw exceeds 30 amps, the main breaker will trip. But, we rarely use the microwave, and know not to use it while the a/c is running.

Chris

[dbj216]

Thank you Chris. Now I know why the 30 amp breaker is there. The RV code is important, but when I think about it, I have adapted up to the 50 amp plug at the campgrounds because the 30 amp wouldn't work. That is reason enough to protect my trailer and people with the on board 30 amp breaker.


I do think I will save the trouble of the "either AC / or microwave" switch. It is rare to run both at once, and after one overload trip, I will remember.


Thanks again for your help. 8" of snow Friday, 60F Sunday! Instant spring!


David

[Minno]

Ya, now if the rest of the snow would only melt...

[dbj216]

I installed the new Square D QO breaker box and two new 20 amp outlets, one for the microwave and one for an electric heater. I tested the new breakers and all the outlets with my "outlet tester". All is good.

Thanks for your help. The new circuits are the yellow romex. Both are 20 amp. One to the AC, and one to the microwave.


David

[Minno]

That looks a lot nicer. I would add a grommet to the hole where the bare copper wire leaves the box. That will prevent the wire from being worn or cut in half by the raw edge of the hole while traveling.

Chris

[dbj216]

Thanks Minno


Yes, that ground wire needs a clamp where it exits the box. It's on my list. The original copper ground wire was cut by the PO for some reason. I will splice it with a connecting lug for a solid connection. I simply connected new to old for my test until I get the correct box clamp.


David