Load Calculations

Status
Not open for further replies.
F

FrancisDoody

Senior Member
Location
Durham, CT
A customer wants to add a 50 amp hot tub to thier existing service. Would the Hot Tub be considered an appliance and recieve the typical 25% demand factor reduction given to appliances fastened in place.
 
F

FrancisDoody

Senior Member
Location
Durham, CT
Fastened in place

Fastened in place

I think that "fastened in place" applies only to 120v appliances. May be wrong but that would require the hot tub to be calculated as a miscellaneous 240 volt load. 128 amps to 158 amps
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
FrancisDoody said:
A customer wants to add a 50 amp hot tub to thier existing service. Would the Hot Tub be considered an appliance and recieve the typical 25% demand factor reduction given to appliances fastened in place.
Click to expand...

I totally don't understand any consideration for any deduction of 25%(as the OP stated it). I do understand the statement of accounting for circuits of 220.83(A)! :)
 
kwired

kwired

Electron manager
Location
NE Nebraska
220.14(A) says it is calculated on the amperage of the appliance or load.

Only demand factor that may apply is in 220.53, which is 75% of 4 or more appliances fastened in place but does not include ranges, dryers, space heating or air conditioning.

If you don't have 3 other qualifying appliances you must use 100% of rating.

50 amps may be breaker size but actual load is likey less. Probably has 5-6kW heater plus pump.
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
A hot tub is an appliance? I gotta that a far stretch of reasoning, but maybe. I dunno.

Appliance. Utilization equipment, generally other than industrial,
that is normally built in standardized sizes or types
and is installed or connected as a unit to perform one or
more functions such as clothes washing, air conditioning,
food mixing, deep frying, and so forth.
 
V

Volta

Senior Member
Location
Columbus, Ohio
I can go with a hot tub as an appliance.

Normally built as a standardized type, performs a function.

But it seems that the list of appliances not allowed for the deduction are all likely to be large loads. Obviously applying a demand factor to such a large load can leave a feeder too small, especially when the other three or more items are comparatively small loads and/or durations.

Maybe the section would be better written if it didn't allow the demand factor reduction for the largest load in the group.
 
kwired

kwired

Electron manager
Location
NE Nebraska
jumper said:
A hot tub is an appliance? I gotta that a far stretch of reasoning, but maybe. I dunno.

Appliance. Utilization equipment, generally other than industrial,
that is normally built in standardized sizes or types
and is installed or connected as a unit to perform one or
more functions such as clothes washing, air conditioning,
food mixing, deep frying, and so forth.
Click to expand...

What art. outside of 680 applies?

Remember Ch 1-4 typically applies to everything with special conditions being addressed in Ch 5-7

Of all the Ch 4 articles, appliances is only one that I see that applies.


680 only adds special conditions to what you alread have to comply with in Ch 1-4. Articles like 210, 215, 220, 240, 250, 300, 310, are more common to have something specifically addressed in 680.
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
Read "here" and learn, I did: I've never used 220.53.

I can't see it as an appliance load because said article is under III. Feeder and Service Load Calculations.

It's a motor in a hot tub, 680 tells one what to do.
 
V

Volta

Senior Member
Location
Columbus, Ohio
cadpoint said:
Read "here" and learn, I did: I've never used 220.53.

I can't see it as an appliance load because said article is under III. Feeder and Service Load Calculations.

It's a motor in a hot tub, 680 tells one what to do.
Click to expand...

The motor is only a minor fraction of any hot tub load, the majority goes to heating the water.

What section of the NEC do you guys feel overrides 220.53? Or do you feel that the tub doesn't fit the definition of 'appliance'?
 
kwired

kwired

Electron manager
Location
NE Nebraska
Volta said:
The motor is only a minor fraction of any hot tub load, the majority goes to heating the water.

What section of the NEC do you guys feel overrides 220.53? Or do you feel that the tub doesn't fit the definition of 'appliance'?
Click to expand...

680 has nothing when it comes to branch circuit and feeder calculations. CH 1-4 apply.

A hot tub has a motor, heating elements, and possibly other accessories. It also has a namplate with supply circuit information. The supply current rating is the rating that should be used for feeder or branch circuit calculations.

Look at section titles in Ch 4, I see no other section that applies except for appliances. Parts of 430 that do apply,do so because 422 sends you there
 
G

gndrod

Senior Member
Location
Ca and Wa
Appliance

Appliance

FrancisDoody said:
A customer wants to add a 50 amp hot tub to thier existing service. Would the Hot Tub be considered an appliance and recieve the typical 25% demand factor reduction given to appliances fastened in place.
Click to expand...

Hi Francis,

I believe the fastened-in-place hot tub rated 50A appliance can be addressed under [220.14(A)]"Specific Appliances" for a calculated rating to apply to [220.53] standard demand factoring. The hot tub unit NPR is used in this case to be added to loads other than electric ranges, clothes dryers, space heating equipment, or air conditioners that are served by the same feeder or service. So if there are 3 other additional appliances, the 75% DF is applied.

If [220.82] or [220.83] optional methods are used then the hot tub is applied in the F-I-P 100% NPR total calculation.
 
Last edited:
cadpoint

cadpoint

Senior Member
Location
Durham, NC
FrancisDoody said:
Read "here" and learn, I did: I've never used 220.53.
I believe that
Click to expand...

I've been blessed with doing new construction on large jobs(period)! It's work that mostly doesn't involve any requirement to question anything; mostly the drawings are engineered correctly to not require this. It’s not that sometimes things don’t get questioned or that situations don't present themselves.

Volta said:
The motor is only a minor fraction of any hot tub load, the majority goes to heating the water.

What section of the NEC do you guys feel overrides 220.53? Or do you feel that the tub doesn't fit the definition of 'appliance'?
Click to expand...
Depends on whether they use * Residential Standard or Optional Calculation.

Ok, it's an appliance, its equipment with either a name plate that includes all or some of Article 430.7 (A) & (D). It’s funny that both
Tables 240.3, 430.5; don’t have anything listing of Article 680. My thinking is right along what was stated by kwired, and now gndrod.

This has been tumbling around in my head for days.

If one reads both items appliance and equipment in the Index, they both contain each other words in the definition, I’ll surrender that it’s an appliance.

My underlying thought has been, is that one is trying to use a two circuit appliance circuit as a cure.
OK, tell me what one has used please.

Mike Holt on the Home Page has Free Stuff, in there is a * Residential Calculator.
Please download to follow along at your 10-20!

Well go figure this out! Using the First Box one can change from Residential Standard to Optional, please note that the articles change per the desired selection. :)

Please also read all the authors’ notes way below the input areas!
 
Last edited:
Status
Not open for further replies.
Top