Vacuum Air Tube (VAT) motor demand factor

[jcarter052496]

I'm working on a Credit Union with (6) VAT drive-up units. Each blower motor needs 9A @ 120V. The commercial drive-up has (2) motors, so there are (7) motors total.

I've guessed that only (2) of the motors will be on simultaneously for my load calc. In other words, I put (5) of the motors under non-coincidental or non-peak loads.

Is there anything in the NEC that covers this?
Similar to Table 220.54 for clothes dryers.

The reason is that it's a renovation job. The main 400A panel (A) has a 100A breaker feeding a 200A panel (B) that in-turn feeds (2) more panels (C&D). If I leave ALL the blowers at 100% demand, panel B calculates at 115A which is too much for the 100A feed.

I could reconfigure the one-line and feed panel C or D from panel A, instead of B, but why spend the money since the blowers are not likely simultaneous.

 

[Cold Fusion]

.... In other words, I put (5) of the motors under non-coincidental or non-peak loads.

...why spend the money since the blowers are not likely simultaneous.

Hummm .... Somehow, "not likely" is not the same as "non-coincidental". My question would be, "Are the motors interlocked?"

 

[jcarter052496]

Not interlocked, independent with valves to direct air toward customer or toward teller.

Of course the commercial one is interlocked, so I can confidently throw out (1) of the (7).

Unlikely & non-coincidental: I just reread NEC 220.60. It's difficult to interpret, but it seems to say if they probably won't be on at the same time, you can throw some out.

 

[petersonra]

Not interlocked, independent with valves to direct air toward customer or toward teller.

Of course the commercial one is interlocked, so I can confidently throw out (1) of the (7).

Unlikely & non-coincidental: I just reread NEC 220.60. It's difficult to interpret, but it seems to say if they probably won't be on at the same time, you can throw some out.

220.60 Noncoincident Loads. Where it is unlikely that
two or more noncoincident loads will be in use simultaneously,
it shall be permissible to use only the largest
load(s) that will be used at one time for calculating the total
load of a feeder or service.

It sure does seem unlikely that all of them would be on simultaneously, especially considering the duty cycle of these things is probably no more than 2% while the bank is open, and when the bank is open it is rare that all the lanes are in use.

 

[jcarter052496]

Thanks Bob. I'm okay if (2) are simultaneous. The bottleneck is at the 100A feed, so (3) blowers would have to be simultaneous while ALL of the loads on (3) panels are full, so I think I'm good.

The code would be better written without "noncoincident" in it because by definition, noncoincident will NEVER be in use simultaneously:
Where it is unlikely that two or more noncoincident loads will be in use simultaneously, it shall be permissible to use only the largest load(s) that will be used at one time for calculating the total load of a feeder or service.

 

[Cold Fusion]

Not interlocked, independent with valves to direct air toward customer or toward teller.

Of course the commercial one is interlocked, so I can confidently throw out (1) of the (7).

Unlikely & non-coincidental: I just reread NEC 220.60. It's difficult to interpret, but it seems to say if they probably won't be on at the same time, you can throw some out.

I went back and re-read 220.60. Even checked back to 1999 code (220.21). It all reads the same. There is no NEC definition of "non-coincident" or "unlikely", and since you are the engineer of record, you get to choose what they mean.

I've always picked 'non-coincident" to mean "interlocked". And I defined "interlocked" to be either hard-wired or programmed (as in PLC), but not administrative or independent controls. But I also work exclusively heavy industry - one fubared 1hp motor can bring the whole process down. Makes my orientation toward really high reliability.

As pererson said:

It sure does seem unlikely that all of them would be on simultaneously, especially considering the duty cycle of these things is probably no more than 2% while the bank is open, and when the bank is open it is rare that all the lanes are in use.

For your case, if the universe lined up to cause a yearly cb trip, likely no one would notice.

I think you are good to go.

cf

 

[jcarter052496]

Thanks for the help guys. I feel much more confident now.

My comment about "by definition" was coincidental = simultaneous, so the sentence doesn't make sense.

"Where it is unlikely that two or more noncoincident loads will be in use simultaneously." My point is noncoincident loads will NEVER be simultaneous, so the NEC should take out the word "noncoincidental".

"Where it is unlikely that two or more loads will be in use simultaneously", Ahhh, now this makes sense.

Thanks again,

Joe

 

[Cold Fusion]

...My comment about "by definition" was coincidental = simultaneous, so the sentence doesn't make sense.

...My point is noncoincident loads will NEVER be simultaneous, so the NEC should take out the word "noncoincidental".

"Where it is unlikely that two or more loads will be in use simultaneously", Ahhh, now this makes sense.

Joe -
I'm okay with 220.60 exactly the way it reads. I believe I understand clearly what that section is for. It is a design issue and I really don't need or want a code to try and tell me how to deal with specific design issues.

For example:
Air Conditioners and heat are non-coincident loads. If they have one thermostat that does not allow the heat to be set above the A/C they they are "likely non-coincident". If there are two independent thermostats, then the loads are not "likely non-coincident". I think I can figure out how to handle the two cases.

AHJs and code are the enforcement agency and spec to limit lowballers from building below a minimum. I'm all for leaving them right there.

cf

 

[petersonra]

For your case, if the universe lined up to cause a yearly cb trip, likely no one would notice.

The chances of the Cb tripping even if all the loads were on at the same time is remote. They only run a few seconds at a time and the thermal delay on the main breaker probably won't allow it to trip.