Sun Tanning Salon Diversity Factor 2

[GodNMe]

I am performing a load study to hopefully recommend reducing the size of the main circuit breaker of several future tanning salons that will be similiar in size to existing ones. The salons have different numbers of beds of different kva ratings. The NEC does not address tanning salons. How can I determine the diversity factor for the tanning beds in the salons?

 

[dpc]

Load measurement over a period of time. Then you can calculate the diversity yourself.

The companies that manufacturer the tanning beds may have some data - I'd check with them.

Also, there may be a trade association (Skin Cancer R Us?) that might have some ideas.

You could also review the electric company bills for the existing sites to determine at least an average kW, after factoring in working hours, etc.

 

[davidbeach]

Everything dpc says is true, but the inspector is under no obligation to accept any of it.

 

[7anoter4]

Usually a tanning bed requires 100-200 w and it is connected through a flexible cord to the receptacle.
According to NEC art 220-13 Receptacle Loads-Nondwelling Units and Table 220-13 for first 10 KVA Demand Factor will be 100% and for remainder over 10 Kva 50%.
The lighting [ 2-3 VA per sqr.ft] load may be added, but Air Conditioning load [3-4 VA per sqr.ft] has to be separated 100%.

 

[GodNMe]

Thank you dpc and davidbeach. I've been going round and round without any new ideas. I'll do some more research for a trade association. Be Blessed!

 

[GodNMe]

7anoter4,

I'll re-visit that article. Thank you and be blessed!

 

[dpc]

Everything dpc says is true, but the inspector is under no obligation to accept any of it.

That pretty much sums up my dealings with inspectors over the years.

 

[burnt2x]

According to NEC art 220-13 Receptacle Loads-Nondwelling Units and Table 220-13 for first 10 KVA Demand Factor will be 100% and for remainder over 10 Kva 50%.

I tried but can't find it at 2008NEC. I found it at 220.44 instead.

 

[stevenal]

NEC is only a starting point. Do these things cycle when in use? If not, I would plan on 100%. If the salon installs X beds, that means that at some point they expect to fill all X.

 

[7anoter4]

It seems to me that a salon tanning bed may be provided with 30-60 lamps[each one of 100-200 w].So the required load peak may be 10 KW or 12 KVA .NEC [art 220 ] refers only to devices connected to receptacles by means of a flexible cord [with an average load of 180 VA!].It is not correct then to use the demand factor as per NEC art 220.I have to apologize!
But I think is exaggerated to use 100% installed power. Usually the demand factor is formed from Kload*Kdiv
If the bed will work only 10 minutes with 10 minutes pause then Kload=0.5.If 15 beds from 30 are working together in the same time then Kdiv=0.5.So the demand factor may be 0.5*0.5=0.25.Lighting and HVAC -calculated per sqr.ft -may be taken as 100%.

 

[stevenal]

"If the bed will work only 10 minutes with 10 minutes pause then Kload=0.5"

During the on period, the circuit breaker doesn't know about the approaching off period.

"If 15 beds from 30 are working together in the same time then Kdiv=0.5"

When the economy improves, I'm sure the salon owner is hoping the noon time rush will fill all 30 when they will all switch on within minutes of each other.

Salon will be losing customers and revenue if the main breaker starts tripping.

 

[7anoter4]

You are right, stevenal, using demand factor it is not any guarantee for non-tempestuous tripping. For a Power Station, of sure, I don't propose this. The demand factor is a statistical way to take into consideration a minimum breaker number of trips and so to reduce the expenses of entire installation. Utility never use 100% installed power in order to calculate a rated power of a step-down transformer or an overhead line and the demand factor may decrease up to 25-30%.
In 1981, Nickel & Braunstein from Arkansas Power and Light, introduced the coincident factor and I think the demand factor is always based on this: Fco=1/2*(1+5/(2*n+3)) where n is the number of receivers [lighting lamps ,motor and so on]. One may see that for 1 receiver Fco= 1 and for 100 is 0.51.

 

[stevenal]

Sure, big difference on the utility side. Utilities generally protect for faults, not overload. If you're not occasionally overloading the service transformer, you are paying too much for the losses. The OP deals with the main breakers, customer side. Seems like it would take a lot of salons to pay for the study.

dpc has the right idea, install a recorder at one of the existing salons. The serving utility should be able to do this.

 

[7anoter4]

I agree with you it could improve the demand factor [nevertheless NEC states to do it in the actual installation- that means after all the equipment is in operation].But still is a demand factor and none could say if no trip ever will occur.

 

[waross]

In Canada, an initial installation must be in compliance with the CEC (Canadian Electrical Code).
If new loads are to be added to an existing installation recording meters may be used to demonstrate to the UHJ that the actual demand factor is lower than the demand factor stated in the CEC. If there is no demand factor given in the CEC for a planned installation, a factor of 100% must be used.
I suspect that the demand factor for tanning beds wil be close to 100%.
I suspect that the NEC is similar.

Bill
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"Why not the best?"
Jimmy Carter