Loading a 20 amp circuit breaker

[eeee]

Re: Loading a 20 amp circuit breaker

French Electrician. The receptacles for the bathroom are on the same circuit as the wash room and living room are for one of the sides of the two rooms (which share a bathroom). We are combining the two rooms in to one.

Other Previous Responder: Not everything will be on at the same time. It is realistic to think that there is a 30% probability that 80% of the items are on at the same time. I would think that 30% is high enough of a probability, so I have my two 20 amp breaker limits exceeded already with 80%.

I will be adding another circuit and 120Y/208YVolt panelboard once I figure out the AIC figure I should expect as related to the expense factor in buying a new panelboard and breakers for it. The issues of GFCI only applies in the wash room and bathroom since water is there.

 

[charlie b]

Re: Loading a 20 amp circuit breaker

Originally posted by eeee: It is realistic to think that there is a 30% probability that 80% of the items are on at the same time. I would think that 30% is high enough of a probability, so I have my two 20 amp breaker limits exceeded already with 80%.

We are not granted the privilege of making our own estimates of probability. The NEC gives us demand factors for some situations. Those demand factors are based in part on the probability of having many things on at the same time. If you find a demand factor that applies to a given situation, then you can use it. But if the NEC does not give a demand factor, then you have to take all loads into account as though all would be on at the same time.

Originally posted by eeee:The receptacles for the bathroom are on the same circuit as the wash room . . . .

What is the difference between these two rooms? Just curious.

 

[eeee]

Re: Loading a 20 amp circuit breaker

The rooms are identical to each other and share a bathroom. Each room has a bedroom and a washroom. Each bedroom has 6 outlets. Each washroom has two outlets of which a minifridge uses one of them and a microwave uses the other.

These rooms will be combined in to one suite where one of the bedrooms will be converted in to a TV viewing room most likely like you would see in a sute at a hotel.

All outlets are duplex.

The only two 20 amp breakers I am concerned with are the recptacle breakers (for the outlets), since these are the breakers where I am loading up appliances.

All lights, fans, heaters, etc. are on other breakers.

My panelboard is full.

 

[frenchelectrican]

Re: Loading a 20 amp circuit breaker

The rooms are identical to each other and share a bathroom. Each room has a bedroom and a washroom. Each bedroom has 6 outlets. Each washroom has two outlets of which a minifridge uses one of them and a microwave uses the other.

I hope you know what you are doing with this design here and washroom do have a sink there ?? if so then you have to understand you need a GFCI repectaile and running wire in bedroom and bathroom in same circuits iam not too keen with this you may have to check with the AJH for this details.

Merci , Marc

 

[jimwalker]

Re: Loading a 20 amp circuit breaker

Bottom line is you better be ready for everything to be on at same time and perhaps a few extras if this is a long stay type room.If breakers start tripping it will be you they call.I would be very clear on what your installing and any limitations that may happen.One never can predict how many may be in them rooms or what they might be running.From what you mentioned i would go with no less than 3 circuits and maybe even 4

 

[George Stolz]

Re: Loading a 20 amp circuit breaker

Originally posted by charlie b:

Originally posted by georgestolz:
If that is the case, then he can load his circuit such that if all his listed loads are on, he's at 100% of the branch circuit rating.

Which of these "listed loads" (i.e., loads from his list) are you omitting, when you say they add up to 100% of a 20 amp circuit?

 

[George Stolz]

Re: Loading a 20 amp circuit breaker

As I start, bear in mind I am looking at the 2002 NEC, and some things have changed. 2005's in the truck.

Originally posted by jbwhite:
1. If we know the rating of the equipment to be connected, why dont we have to size the circuit based on the nameplate rating?

220.17 allows us to apply a demand factor of 75% to four or more appliances on a feeder or service in a dwelling unit. The idea is, chances improve that not all appliances will be on at the same time. This doesn't apply to branch circuits. The reason I say this is because 220.17 is contained in Part II of this article, and is named "Feeders & Services."

This section doesn't apply to the original question, as a hotel room isn't a dwelling unit. eeee has no demand factors to use in this application, so the full nameplate rating must be considered.

2. Is it ok to size these loads at 100 percent.

210.23 states that in no case shall the load exceed the branch circuit rating, which is the rating of the OCPD (overcurrent protective device) that supplies the circuit.

The subsections of 210.23 place more restrictions on circumstances, but the general rule is that you can load a twenty amp circuit to twenty amps. More accurately, see 210.20(A). I don't believe any of these loads are continuous, but that is in the eye of the beholder. On the safe side, the engineer should consider the television, the lamps, and the coffee maker continuous, IMO.

3. From an engineering standpoint, (and a business standpoint), why would you want to put so much equipment on a circuit as to almost guarntee nusance tripping?

The more circuits that can be trimmed from an installation (safely) in the design process, the less equipment to buy.

I work in houses, so I tend to think small. Imagine a 500 room hotel with 2 extra circuits a room. That's a heap of extra breakers!

 

[apauling]

Re: Loading a 20 amp circuit breaker

and how is a motel not a dwelling unit?

 

[George Stolz]

Re: Loading a 20 amp circuit breaker

It's open for debate, but I would argue that a microwave doesn't constitute "permanent provisions for cooking." I just looked up the definition of cooking and seized the first one I could find: "the act of preparing something (as food) by the application of heat."

Bombarding an item with microwave transmissions is not the same as applying heat.

[ December 01, 2005, 09:31 PM: Message edited by: georgestolz ]

 

[charlie b]

Re: Loading a 20 amp circuit breaker

Originally posted by apauling: and how is a motel not a dwelling unit?

Originally posted by georgestolz: It's open for debate, but I would argue that a microwave doesn't constitute "permanent provisions for cooking."

I agree with those who take this side of the debate. But then, I live in a state that takes the other side. Anything related to food preparation is going to get the room called a "kitchen" in Washington.

 

[charlie b]

Re: Loading a 20 amp circuit breaker

Originally posted by georgestolz: Bombarding an item with microwave transmissions is not the same as applying heat.

I have a dictionary that lists, among others, the following definition of "heat":

Added or external energy that causes a rise in temperature.

So, George, would that alter your view of a calling a motel a "dwelling unit"?

 

[George Stolz]

Re: Loading a 20 amp circuit breaker

Charlie, I thought I already had?

But sure, if the powers that be decided that a microwave was a permanent provision for cooking, then I would not have much to support an argument to the contrary.