Standard Calculations- dryer 220.54

[chris68]

I have enrolled in a code review class. We were given the following question:

"Using the conventional calculation, determine the minimum size service conductors on a 240v, single family residence with the following load. 4000 square feet, a 12kw range 120/240v, disposer 6 amp 120v, dishwasher 9 amps 120v, trash compactor 10 amp 120v, hot water storage tank 4.5kw 240v. Note: include the required small appliance and laundry loads in your general lighting calculations."

I am the only one in class that added 5000va for a dryer...even though it's not specified in the question. Logic being, "no nameplate was given. 5000va is larger than zero va per 220.54.

Arguements have been provided as follows:

1. yeah, how about 220.82 (I ruled invalid because it's part of the optional feeder calculation)

2. How about something from 210.52F (I chose to ignore...seemed like it listed the required branch circuits, not the feeder calculations).

As far as I can tell, when you size a service for a single family dwelling...even if you aren't given any information about a dryer you should include at least 5000va in the standard feeder calcs.

I welcome your comments, I'm hoping to print this discussion and take it back to class with me on Thursday oct 5

 

[LarryFine]

I agree with you. Laundry circuits are required, so their projected loads must be.

 

[iwire]

Laundry circuits are required, so their projected loads must be.

Only one 20 amp 120 volt laundry circuit is required.

There is no requirement to provide a 30 amp 240 volt laundry circuit.

The home in the example may be getting a gas dryer.

 

[bphgravity]

As Bob suggests, many homes have gas appliances and would not require a demand on the service or feeders for those appliances. Water heaters, heating equipment, dryers, and sometimes cooking equipment will be supplied be by gas.

In the event all appliances are indicated on the submitted plans to be electric and no dryer is indicated, it will be noted in the plan review for field verification by the inspectors. If a dryer circuit is installed, the 5kW demand will have to be added to the service. In most if not all cases, the service is well oversized and the 5k load has no bearing on the installation.

When it comes to exams or practice materials, unless the questions specifies the appliance or circuit, I would not add the demand as it is not a required load.

{Moderator's note: I edited out an unintended and unfortunate typo. The letter "s" does not appear twice in the word "add."}

 

[chris68]

This is not in reference to the 20a 1500va laundry branch circuit. I am not asking if the dryer circuit is mandatory. This specifically refers to standard feeder calculations, should you include a 5000va minimum whether or not a dryer is mentioned?

 

[cpal]

This is not in reference to the 20a 1500va laundry branch circuit. I am not asking if the dryer circuit is mandatory. This specifically refers to standard feeder calculations, should you include a 5000va minimum whether or not a dryer is mentioned?

I think Bob has the better answer

If a dryer is not indicated the calculation need not be made.
Most Code tests are generally looking for an answerthat provised a "minimum" capacity. This is a key that is mentioned in many formal test taking texts. From a practical point wither to include the allowance for a dryer or to excllude the allowance is a business choice. at 5kW another 30 A may have a profound impact on the size of a service.

I believe the the test was written to include the 12kW range to possibly distract you towards adding the dryer circuit (although not mandatory in the NEC (IWIRE)), I will guess that the a,b,c,d, distractors provided a answer that agrees with a calculation that included the dryer load and one that agrees with the omission of the dryer load.

The class room is a great place to straighten out the hooks.

 

[chris68]

Odd as it sounds, with a gas dryer as part of your reply. 220.54 still mandates 5000va because a gsa dryer would still use less than 5000va...right? (5000va or nameplate whichever is larger).

Perhaps this section should include a specific exemption if you have a gas line piped to the laundry area? If anyone knows of such an article please cite it.

Thanks again,
Chris

 

[cpal]

Odd as it sounds, with a gas dryer as part of your reply. 220.54 still mandates 5000va because a gsa dryer would still use less than 5000va...right? (5000va or nameplate whichever is larger).

.

Thanks again,
Chris

I do not agree!

 

[bphgravity]

Why would anyone want to add 5kW to an already very conservative calculation when the load is not present?

 

[charlie b]

220.54 says to include 5000 VA (or the nameplate rating, whichever is higher) for each dryer served. I infer that if no dryer is served, then you can omit the 5000 VA. However, it is a poorly worded test question that does not make clear the issue of whether or not an electric dryer is to be included. My approach would be to include the 5000 VA, unless the question specifically tells me not to.

In this case, the question is specific and clear that it is looking for the minimum. Here, I infer that the author of the question does not want you to include the 5000 VA. If that is the way in which the author is conveying the intent of the question, then I call that person a poor writer.

So what do you do with such test questions? If your instructor is present during the test, then ask the question. In any event, it would be worth the effort to ask the instructor to state the ?default? conditions of his or her test questions. Examples: (1) If the question does not tell you which method (standard or optional) to use, then you should use whichever method gives the lower answer. (2) If the question does not tell you whether or not a dwelling unit will be permitted to have laundry facilities, then you should assume that laundry will be permitted.

 

[chris68]

Only one 20 amp 120 volt laundry circuit is required.

There is no requirement to provide a 30 amp 240 volt laundry circuit.

The home in the example may be getting a gas dryer.

Charlie...how do you interpret 220.54?

Bryan, thanks. I'll agree that the house in the example will be adequately served in either instance.
What do you think of the response, "The builder most likely intended for this dwelling to have a gas dryer."? Maybe that's a seperate question, when told to use the standard feeder calculation, should a gas dryer recieve 5000va?

 

[iwire]

Chris I need to look at my books but I am starting to think you may be correct even though I do not believe the intent is require 5000VA for a gas dryer.

I serve a gas dryer with a circuit.

This stinks I was on the same side with two Charlie's and now I think I have to change my mind.

 

[iwire]

Chris I went to my truck and got my 2005.

The first thing I notice is 210.54 applies only to electric dryers.

Gas dryers even though suppled by an electric circuit are not commonly called 'electric'

Beyond that I see what Charlie B pointed it out.

210.54 applies only to each dryer served.

Zero electric dryers means no electric dryers are served so you do not have to provide 5000VA (or more).

One electric dryer and you must include 5000VA (or more).

Two electric dryers and you must include 10,000VA (or more).

So that said I am not changing my mind and stay with the two Charlies.

 

[chris68]

Bob and Charlie, thanks a ton. "Served," that one little word destroys my whole method of thinking...wow, thanks again.

I will accept an "Electric Dryer" refers to the heating element being an electrical one...not a gas one.

Chris

 

[George Stolz]

I do not believe the dryer should be included unless specifically mentioned. As mentioned, it could be a gas dryer.

In addition, if the test writer did not think to mention it, chances are fairly decent that the writer also did not put a dryer into the calculation.

 

[tallgirl]

I vote "trick question".

There are no gas appliances in the description, so why would someone assume there is a gas dryer, except if they forgot about 210.54?

 

[George Stolz]

There are no electric dryers mentioned in the description, so why would one assume there is one at all?