Question to Electrician's - Why the 20 Amp AC Circuit Breakers

[kscherzi]

Looking at the AC electrical panel I noted that every circuit has a 20 amp circuit breaker - except main and air conditioner which are 30 amps. Two circuits are for outlets, and propane fridge. One is exclusively for the 700 watt microwave. Another is exclusive for the water heater. All interior romex is the yellow 12 gauge so is consistent with the rated circuit breakers. For comparison most circuits in my home use 15 amp circuit breakers.

To me this seems like overkill. Appliances plugged into an outlet are going to draw less than 15 amps, so if a short occurs hypothetically wouldn't a 15 amp breaker be safer? Why would a trailer have higher rated circuit breakers than a physical house? What's the advantage?

[uncle_bob]

Hi

The target max current for a circuit should be 80% of the breaker / wire rating. for a 20A breaker that would be 16A. For a 15A circuit, that would be 12A. Your microwave puts out > 700 or > 800W into the food. To do this it takes in more power than what gets into the food. If you check the nameplate the device likely is rated up around 1300 VA.

12A at 110V is 1200W. You may be lucky to get 110 at your local campsite. Writing the device with a 20A circuit does make sense.

Many modern kitchens are wired with 20A outlets. Often there are multiple breakers feeding various parts of the kitchen. There are a lot of kitchen appliances that are quite power hungry these days.

Bob

[Por Sonia]

Multiple outlets on each 20 Amp breaker?

[richard5933]

If a short occurs, both a 15-amp and a 20-amp breaker should trip instantly.

Using 20-amp breakers allow for the use of things like a space heater or any of a number of other appliances without problems. All outlets in a home kitchen are 20 amps, so I don't know how this is much different.

There are not that many outlets in a trailer and they have no idea where you will plug in different things. We use out toaster on the kitchen table, some will use it in the kitchen, etc.

[Bill M.]

Breakers are sized to protect the wiring. Not the appliances. I appreciate the 20 amps since we sometimes run electric heaters and a dehumidifier on the outlets.

[John Ware]

Houses around here are wired 20amps for outlets and 15amps for lights.

[10Smiles]

Originally Posted by Bill M.

Breakers are sized to protect the wiring. Not the appliances.

Exactly!

[kscherzi]

Thanks for all your thoughts. My house is older, built in the 1990's and all lights and outlets are 15 amp. Only the garage outlets are 20 amp. I guess that was/is normal electrical practice here.

Never had any problems, so just curious why something so much smaller (trailer) is wired heavier.

[ITSNO60]

Originally Posted by kscherzi

Thanks for all your thoughts. My house is older, built in the 1990's and all lights and outlets are 15 amp. Only the garage outlets are 20 amp. I guess that was/is normal electrical practice here.

Never had any problems, so just curious why something so much smaller (trailer) is wired heavier.

Your kitchen and dining room should be 20 amps, minimum of 2 circuits, your laundry should be 20 amps, if the dishwasher and disposal share the same circuit it will be 20 amps, if the original stove hood was a microwave hood it should be 20 amps, central vac should be 20 amps and depending on when in the 90's the house was built the bath receptacles should be 20 amps. The bath is the newest appearing in 1999, the kitchen/dining (small appliance) have been code since 1959 and the laundry since 1971. Garage 20 amp circuit is a very recent requirement but was sometimes put in voluntarily.
This is all NEC, in Canada some of this is done differently as they have their own code.

[DrivingDan]

There’s so few circuits in a trailer compared to a house that each circuit can be more loaded, is my guess. A modern kitchen typically has a handful of circuits so you can be doing multiple things.

We’re big electricity users and converted our house almost entirely to it (central heat is still gas due to heat pump expense). We love cooking with induction, it’s so much faster. So we’ll bring our professional portable induction along and do much of our cooking on it. No condensation from the propage, no gasses and a timer. We do a lot of pressure cooking.

Anyhow I’m planning on getting a second AC so we get the upgraded 50A system, I like having extra capacity.

[uncle_bob]

Originally Posted by DrivingDan

There’s so few circuits in a trailer compared to a house that each circuit can be more loaded, is my guess. A modern kitchen typically has a handful of circuits so you can be doing multiple things.

We’re big electricity users and converted our house almost entirely to it (central heat is still gas due to heat pump expense). We love cooking with induction, it’s so much faster. So we’ll bring our professional portable induction along and do much of our cooking on it. No condensation from the propage, no gasses and a timer. We do a lot of pressure cooking.

Anyhow I’m planning on getting a second AC so we get the upgraded 50A system, I like having extra capacity.

Hi

..... welcome to why 20A circuits ....

If you are doing all that on a 30A hookup, yikes. You very much need the 100A at 120V that the 50A plug will give you.

Bob

[DrivingDan]

Originally Posted by uncle_bob

If you are doing all that on a 30A hookup, yikes. You very much need the 100A at 120V that the 50A plug will give you.

Of course we’ll not be ‘doing all that’ at once as it depends on the situation, the exact hookup and climate. My wife asked about removing the propane but I’m keeping it as a backup. Anyhow we’ll also have a Silverado EV with 200kWh of available power (@ full charge), and it will have a 220/30A plug in the back too, not to mention a 7kW Honda whisper quiet generator if I can haul it (like I said I like electrons ).

Just thought of something, don’t know why my brain didn’t trigger on this before, but the shore power connection is 220V correct? Do they then simply pull 110 circuits off of either leg like is done in a house circuit? I wonder what the balancing is, ideally you generally want to pull from both legs somewhat equally. Checking your shore power connection is probably a good idea, sometimes shenanigans are done with such connections.

[ITSNO60]

Originally Posted by DrivingDan

Just thought of something, don’t know why my brain didn’t trigger on this before, but the shore power connection is 220V correct? Do they then simply pull 110 circuits off of either leg like is done in a house circuit? I wonder what the balancing is, ideally you generally want to pull from both legs somewhat equally. Checking your shore power connection is probably a good idea, sometimes shenanigans are done with such connections.

Yes it's a 240/120 hookup just like a modern electric range. It's wise to balance on the 2 legs with the 120 loads but can't always predict usage and loading up on one isn't going to hurt anything, worst that would happen is the main trips in the rare event you have loaded one leg to over 50 amps for any length of time. One AC unit on each leg would be best.

With load diversity you don't typically use as much as most people think, homes in the US with 200 amp services use on the average of 40 amps at a given time (from a study done several years ago, which may be higher now with EV's). In Mexico a 30 amp 240/120 service to a house is common and a 50 amp is normal for high end dwellings with air conditioning. The village we stay in has all 30 and 50 amp services, ours is a 50 with 3 mini splits, all electric house, never have a problem.

[DaveG]

Couple more thoughts maybe not directly part of the question but many may assume a 15 amp will trip before a 20 amp offering greater protection. Not necessarily so. The 20 could trip first. Like mentioned the breaker is sized to the wire. Also you can cook the wire without the breaker tripping. Best practice is to size the load to the circuit and follow the 80% rule.

[uncle_bob]

Originally Posted by DrivingDan

Of course we’ll not be ‘doing all that’ at once as it depends on the situation, the exact hookup and climate. My wife asked about removing the propane but I’m keeping it as a backup. Anyhow we’ll also have a Silverado EV with 200kWh of available power (@ full charge), and it will have a 220/30A plug in the back too, not to mention a 7kW Honda whisper quiet generator if I can haul it (like I said I like electrons ).

Just thought of something, don’t know why my brain didn’t trigger on this before, but the shore power connection is 220V correct? Do they then simply pull 110 circuits off of either leg like is done in a house circuit? I wonder what the balancing is, ideally you generally want to pull from both legs somewhat equally. Checking your shore power connection is probably a good idea, sometimes shenanigans are done with such connections.

Hi

The 50A pedestal should be freeding you 50A at 240V. A 30A hookup should be 30A at 120 V.

If you get out your multimeter, it's best to remember that "110V" hasn't been anything close to that for a very long time. You should see something in the 117 to 123V range. Despite that we *all* still call it 110 .

Why mention this? Well, if you just happen to pull over to a campsite that is running on a generator, somebody gets to set the voltage on that generator. If he happens to be a bit confused, then the generator is putting out 104 to 110 V as "110". When it dips to 104V, your EMS cuts out ..... I have empirical data on this .....

Bob

[LU86Guppy]

Looks like you got all the answers you needed. I stopped looking after the 3rd or 4th well worded one.
Professional licensed electrician since 1989.