Wiring for a Microwave

[jch511]

Greetings,

I'm finally getting around to wiring and was thankfully given a huge roll of very well insulated 12 gauge wire. I'd like to run the wiring inside the walls of the bus to wire just about everything, except I'm concerned about whether the 12 gauge that would run about 24 feet is enough to support my microwave or toaster oven (on separate lines). I've already wired the air conditioner/heater with 10 gauge, and that works fine at 1585 watts on a 20 amp breaker. Should I go for a larger gauge than 12 for the microwave and toaster oven? Should I use a 30 amp breaker instead of a 20 amp breaker? Obviously I'm a novice, but I AM trying to find an electrician who will advise, but so far they only do houses (for some reason). Sooner or later I'll find a certified electrician to check over everything, but I'd hate to have to re-string wiring through the ceiling (that was tough), so I'm trying to make it on the "definitely safe" side to start with. Any thoughts or guidance?

Thanks!
Jim (The Jazz Buzz)

[DeMac]

If it's120v 12/2, it's rated for 20A. Your micro is likely 12A or less. Dedicated 15A (or 20A) OCP, see nameplate rating on appliance. At 120v, 20A brkr @100 ft okay, longer if only 15A brkr on 12 wire.

What is the "well insulated wire" type? Romex, MC, UF, thhn/thwn....

[Rucker]

Residential standards for a microwave is a dedicated 20 amp circuit with 12 gauge wire. Even with a fairly long run you should be okay.

Toaster ovens don't have the same requirement but probably should.

For 'definitely safe' you need to determine if using solid core romex wire is acceptable in your situation (hot debate on this, with most people voting for stranded wire) and whether to bury the wire in the wall or use conduit.

You didn't mention what kind of wire it was, but if it's Romex (standard residential wiring with a plastic covering) and you plan on using it I recommend having zero wire nuts and the entire branch circuit accessible for periodic inspection. I also recommend you get an ohm reading for each complete circuit so you can monitor conductivity over the life of the system.

[HamSkoolie]

Originally Posted by Rucker

For 'definitely safe' you need to determine if using solid core romex wire is acceptable in your situation (hot debate on this, with most people voting for stranded wire) and whether to bury the wire in the wall or use conduit.

Solid core is perfectly fine so long as the nature of the installation (mobile and bouncing) is taken into consideration. Solid core is routinely used in RVIA trailers, 5th wheels, and motor homes..... which are built significantly less sound than our steel buses. And, properly installed, (i.e. not sticking nails through it) Romex is perfectly acceptable in most areas of skoolie construction.
YES, THHN would be better but it's like saying we shouldn't buy Chinese parking heaters and instead pay 1000% or more for a name brand Webasto.

Originally Posted by Rucker

I recommend having zero wire nuts and the entire branch circuit accessible for periodic inspection. I also recommend you get an ohm reading for each complete circuit so you can monitor conductivity over the life of the system.

NICE and I agree on the wire nuts because of the vibratory nature of a mobile installation but seriously overkill with the rest.

Definitely don't put any splices where you can't access them and make sure any you do have are in an appropriate box for containment in the event of failure.

Perhaps my idea of ""accessible" is different from yours but to me it means the entire length of wire can be accessed while still intact electrically and while that's nice, it's usually not practical (though I'm trying my damndest to have as much of mine as possible do just that. But running through conduit or some other channel is fine so long as wire ends can be accessed for continuity testing and new wires pulled if needed.


Perhaps my combination of motor vehicle, aircraft, helicopter (heliflopters are NOT aircraft they are merely machines that beat the air into submission while violently attempting to destroy themselves with vibratory moments in multiple vectors), and housing electrical maintenance and repair gives me a different view.

[jch511]

Thank you all so much! I learn a ton from you guys each time.

I found a neighbor who specifically works at marine and RV wiring, and this is what he emailed to me:

-----------------------
12 Gauge wire is Good for 20 AMPs for 100 feet

10 Gauge is Good for 30 AMPs to 100 feet

14 Gauge is good for 15 Amps for 100 feet

If the Distance is Shorter Then the More Amperage it can be Good For

------------------------

That sounds good enough for me, but I'm going to do some tests before I close everything up.

Thanks again!

[jch511]

Originally Posted by DeMac

If it's120v 12/2, it's rated for 20A. Your micro is likely 12A or less. Dedicated 15A (or 20A) OCP, see nameplate rating on appliance. At 120v, 20A brkr @100 ft okay, longer if only 15A brkr on 12 wire.

What is the "well insulated wire" type? Romex, MC, UF, thhn/thwn....

I took pictures of the wire so that I could answer your question about "well insulated", but it appears I can not attach pictures and would have to put them on a Web site.

[jch511]

Originally Posted by Rucker

Residential standards for a microwave is a dedicated 20 amp circuit with 12 gauge wire. Even with a fairly long run you should be okay.

Toaster ovens don't have the same requirement but probably should.

For 'definitely safe' you need to determine if using solid core romex wire is acceptable in your situation (hot debate on this, with most people voting for stranded wire) and whether to bury the wire in the wall or use conduit.

You didn't mention what kind of wire it was, but if it's Romex (standard residential wiring with a plastic covering) and you plan on using it I recommend having zero wire nuts and the entire branch circuit accessible for periodic inspection. I also recommend you get an ohm reading for each complete circuit so you can monitor conductivity over the life of the system.

Okay, I can't put images in my response of what kind of wire it is, or what the wire looks like, so I put them in a Google Doc, here:

https://docs.google.com/document/d/1...it?usp=sharing

If you are able to access this site (you should be able to if you have a Google account), it would definitely be instructive to know what you call this type of wire.

Thanks again!

[jch511]

Originally Posted by HamSkoolie

Solid core is perfectly fine so long as the nature of the installation (mobile and bouncing) is taken into consideration. Solid core is routinely used in RVIA trailers, 5th wheels, and motor homes..... which are built significantly less sound than our steel buses. And, properly installed, (i.e. not sticking nails through it) Romex is perfectly acceptable in most areas of skoolie construction.
YES, THHN would be better but it's like saying we shouldn't buy Chinese parking heaters and instead pay 1000% or more for a name brand Webasto.




NICE and I agree on the wire nuts because of the vibratory nature of a mobile installation but seriously overkill with the rest.

Definitely don't put any splices where you can't access them and make sure any you do have are in an appropriate box for containment in the event of failure.

Perhaps my idea of ""accessible" is different from yours but to me it means the entire length of wire can be accessed while still intact electrically and while that's nice, it's usually not practical (though I'm trying my damndest to have as much of mine as possible do just that. But running through conduit or some other channel is fine so long as wire ends can be accessed for continuity testing and new wires pulled if needed.


Perhaps my combination of motor vehicle, aircraft, helicopter (heliflopters are NOT aircraft they are merely machines that beat the air into submission while violently attempting to destroy themselves with vibratory moments in multiple vectors), and housing electrical maintenance and repair gives me a different view.

BTW, there are NO wire nuts along the entire length of all lines. Great recommendation, though, because I hadn't even thought about the effects of long term vibrations.

Thanks!

[jch511]

Originally Posted by Rucker

Residential standards for a microwave is a dedicated 20 amp circuit with 12 gauge wire. Even with a fairly long run you should be okay.

Toaster ovens don't have the same requirement but probably should.

For 'definitely safe' you need to determine if using solid core romex wire is acceptable in your situation (hot debate on this, with most people voting for stranded wire) and whether to bury the wire in the wall or use conduit.

You didn't mention what kind of wire it was, but if it's Romex (standard residential wiring with a plastic covering) and you plan on using it I recommend having zero wire nuts and the entire branch circuit accessible for periodic inspection. I also recommend you get an ohm reading for each complete circuit so you can monitor conductivity over the life of the system.

Why do you say, "Toaster ovens don't have the same requirement but probably should"? What's the special deal with toaster ovens? I'm guessing because they can draw more amps depending upon the oven temperature utilized.

[TheHubbardBus]

Originally Posted by jch511

Thank you all so much! I learn a ton from you guys each time.

I found a neighbor who specifically works at marine and RV wiring, and this is what he emailed to me:

-----------------------
12 Gauge wire is Good for 20 AMPs for 100 feet

10 Gauge is Good for 30 AMPs to 100 feet

14 Gauge is good for 15 Amps for 100 feet

If the Distance is Shorter Then the More Amperage it can be Good For

------------------------

That sounds good enough for me, but I'm going to do some tests before I close everything up.

Thanks again!

That's not good advice, IMO.
Those generalities don't take into account any derating factors, to include insulation temp rating, environmental temps, number of wires bundled together, whether they're run in conduit (or a conduit-like enclosure) or not, wire type (solid vs stranded, copper vs CCA vs aluminum), etc. Also, the one thing mentioned (distance) is the least-important factor in all of it since @ 120V AC within the run-lengths you'd see on a bus, any voltage drop would be negligible.
Even if he was talking DC circuits instead of AC, which it sounds like he might, they remain generalities that may or may not hold true once you factor in the things mentioned above, as well as allowable voltage drop.

[DeMac]

Originally Posted by jch511

Okay, I can't put images in my response of what kind of wire it is, or what the wire looks like, so I put them in a Google Doc, here:

https://docs.google.com/document/d/1...it?usp=sharing

If you are able to access this site (you should be able to if you have a Google account), it would definitely be instructive to know what you call this type of wire.

Thanks again!

‐--------------------

The pictures you provided, show the wire type as SJTW.

S = Service Grade
J = Hard Service
T = Thermoplastic
W = Outdoor

It's Extension Cord. Not as good as SO cord, which is Extra Hard Service with Oil Resistant jacket.

It is well protected, not "well insulated" nor is it listed to be perminantly installed. "S" Service grade is only to be used as "Cord Connected", as defined, meaning there ought to be a male or female plug on one end. Never concealed in walls or ceilings. To be used only in open air applications.

I cannot stress this enough.
DO Not Use Extension Cord
as part of your wirestructure. The insulation begins to breakdown immediately after production. Just like tires, it will expire. Wire is cheap, fire is not.

[Rucker]

Originally Posted by jch511

Okay, I can't put images in my response of what kind of wire it is, or what the wire looks like, so I put them in a Google Doc, here:

https://docs.google.com/document/d/1...it?usp=sharing

If you are able to access this site (you should be able to if you have a Google account), it would definitely be instructive to know what you call this type of wire.

Thanks again!

Edit: what Demac Said regarding extension cord.

SJTW is stranded (not solid) Junior (up to 300v) thermoplastic insulation approved for outdoor use (the W).

I think that cord is extension cord, a.k.a. 'flexible cord', in which case you really don't want to use it in the bus. Specifically, running it through holes behind walls. It's a no-no per National Electric Code.

This stuff appears to be used where devices that are otherwise permanently connected may need to be removed/unplugged for maintenance or repair.

Probably NOT the wire you want to have in your bus from a 'definitely safe' point of view.

How much of this do you have and can you use it elsewhere?

[HamSkoolie]

Considering the minimal number of circuits to run and the short distances to run them when building a bus it looks like THHN is indeed the best bet for the OP.
With the on hand wire being the wrong stuff, purchasing new wire presents the issue of cost versus quality. With the small amount needed, quality isn't all that more expensive unless one wanted to go for the armored cable option (I wouldn't because it's just a pain).

[Jolly Roger bus 223]

ok i caint lie.
in my big bus i had loads of extension cords laying around because they couldnt go back on base until they were fixed by a qualified electrician just to replace the ends on them type mess.
i used extension cords for all of that wiring but it was all 12v wiring and i ran 10 guage extension cord and anywhere that was a rub point got a piece of garden hose or tubing zip tied or taped and everything was secured in place.
my 120 volt is 2 8 guage extension cords at 100' long coiled up and hanging under the bus and run through a sleeve into the bus to serve only a battery charger maintainer to feed the 12v fuse box and because my multi strip kept tripping trying to run an electric heater i added the second at the campground for it.
luckily we were only 10-min. from the house and i had more.
the reason for 90 plus feet under the bus hanging was so i could move my loud ass generator as far away as possible if i had to use it.
my wifes second bus is going to be completely different and correct as far as electrical
all 12v is in wire loom with a spare for each circuit all 120v loads are on the same side as the service entrance in pvc conduit or liquid tite.
30 amp plug with 6-guage stranded to breaker box and as of now the three things on the breaker or could be is only 3' max away if you actually measure wire length the longest one will be the minisplit at 10' and am debating using the SO/SWO/SJ?
i have to pull it out and look at it? or just run another conduit and stranded wire
my thing is in my work i have always heard and been told that you cant run control wires (low voltage) and voltage wires in the same conduit because they will cause interference with the whatever?
so i would like to caution running 120v with 12v wiring without the 120 being in a conduit.
and to be honest i am kind of on the fence for that because all of my equipment at work.
mitsubishi/ trane, carrier/daikin LG(LAG? opinion?) almost all has the high voltage terminal connections and low voltage connections not covered and within a 1/2" of each other with no problems. except the 460 volt systems but the line voltage passes close enough and in front of the low voltage terminal screws that you have to play the game with high voltage on sometimes just to get the multi meter probes on the terminals.
ok sorry rant over i have been shocked enough to have caution.
and i dont like playing the 460-480 game but you cant check low voltage if the high voltage powered units control board isnt sending the control voltage out because it is powered down.

[Rucker]

If there are rules for 12v skoolie wiring, rule #1 should be make sure each conductor is sized according to length and load and fused according to wire.

Doing this helps ensure if anything fails, it won't immediately fail, and should fail safely.

[DeMac]

The thin walls & ceilings we build are the exact reason to use Metal Clad or Conduit.

The following refers to non-metallic sheathed cable:

NEC 300.4 Protection Against Physical Damage

(d)....cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 1-1/4 in. (31.8 mm) from the nearest edge of the framing member where nails or screws are likely to penetrate.





Tougher for a novice to know how to apply the many additional safety requirements added to non-mc cable.

Read NEC 300-4 for more about 'not less than 1-1/4" ':