Hi friends, Does anyone know of any demand factors that can be applied to the service calculations for a commercial laundromat? The projected load calls for 51) 3ph washers, 20-80 lb capacity and 30) 1ph gas dryers. I haven't found anything yet but hope someone here has had some experience on this one. Thanks in advance. JDB
Laundromat service calc's
- Thread starter jbrown
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ryan_618
Senior Member
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- Salt Lake City, Utah
Re: Laundromat service calc's
The only thing relevant that I can find is 220.3(B)(1), which tells you that your out of luck
Sorry.
The only thing relevant that I can find is 220.3(B)(1), which tells you that your out of luck
Sorry.
Re: Laundromat service calc's
Thanks for the response Ryan. I kind of figured there wasn't a good chance but the word in the wind here is that the local inspector can determine/change the demand factors. I just wanted to find some reference that I couldn't find in the book. The follow up question is what are the chances that any percentage of this load could be considered continuous?
Thanks for the response Ryan. I kind of figured there wasn't a good chance but the word in the wind here is that the local inspector can determine/change the demand factors. I just wanted to find some reference that I couldn't find in the book. The follow up question is what are the chances that any percentage of this load could be considered continuous?
Re: Laundromat service calc's
mr. brown noticed in one of my course books ive been studying.. it states the nec does not permit a demand factor for commercial dryers therefore the dryer demand load must be calculated at 100%. futher states table 220.18 does not apply to commercial dryers . if the dryers are on continuosly the conductor and protection device must be sized at125% of the load. ? what is the service demand load for ten 7kw dryers located in a laundry room? ans.70kw hope this helps j.....keith
mr. brown noticed in one of my course books ive been studying.. it states the nec does not permit a demand factor for commercial dryers therefore the dryer demand load must be calculated at 100%. futher states table 220.18 does not apply to commercial dryers . if the dryers are on continuosly the conductor and protection device must be sized at125% of the load. ? what is the service demand load for ten 7kw dryers located in a laundry room? ans.70kw hope this helps j.....keith
- Location
- Massachusetts
Re: Laundromat service calc's
Demand factors are used when it can safely be assumed all the loads will not run at the same time.
This is a a safe bet in a apartment building that each unit has a dryer, very little chance all tenants will do their drying at the same time.
A commercial laundry is a different situation all together, it is highly likely, almost a certainty that all the dryers will sometimes be running at the same time.
You can not apply a demand factor to this occupancy, if you did the service would be undersized and would trip out when all the dryers where running.
Demand factors are used when it can safely be assumed all the loads will not run at the same time.
This is a a safe bet in a apartment building that each unit has a dryer, very little chance all tenants will do their drying at the same time.
A commercial laundry is a different situation all together, it is highly likely, almost a certainty that all the dryers will sometimes be running at the same time.
You can not apply a demand factor to this occupancy, if you did the service would be undersized and would trip out when all the dryers where running.
pierre
Senior Member
- Location
- Westchester County, New York
Re: Laundromat service calc's
Sizing for continuous loads is 3 or more hours of use - what washer or dryer is in use for 3 hours continuous?
Pierre
Sizing for continuous loads is 3 or more hours of use - what washer or dryer is in use for 3 hours continuous?
Pierre
- Location
- Massachusetts
Re: Laundromat service calc's
With my two young girls my dryer seems to run all day. :roll:
Just kidding around, I agree with Pierre even commercial dryers will shut down every 30 to 90 minutes.
That would make it a non-continuous load.
Pierre With three girls of your own you should not have to ask that.
With my two young girls my dryer seems to run all day. :roll:
Just kidding around, I agree with Pierre even commercial dryers will shut down every 30 to 90 minutes.
That would make it a non-continuous load.
pierre
Senior Member
- Location
- Westchester County, New York
Re: Laundromat service calc's
Bob
You are right about my three girls, but it is not the clothes dryer - it is the blow dryers and straighting irons
Pierre
Bob
You are right about my three girls, but it is not the clothes dryer - it is the blow dryers and straighting irons
Pierre
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Laundromat service calc's
The NEC defines a ?Continuous Load? as ?A load where the maximum current is expected to continue for 3 hours or more.? I don?t believe that that definition could be used to force a commercial laundry to apply the 125% factor to the dryer load. Nevertheless, as a design engineer, I would apply the 125% factor. I am certain that I could convince the owner that the benefits would outweigh the slight additional cost. I have two reasons; both are related to design considerations, not to code issues.
First, this is a kind business that cannot afford interruptions in service. If a circuit breaker trips, whatever the cause, you will have unhappy customers. Not only will there be a delay, while the breaker is located and reset, but the customers will also have to put in more coins, since a loss of power could cause the timers to reset. This will cost the owner money, and its not worth the risk.
Secondly, whatever physics might be involved in the 125% factor, I believe that the short periods that a dryer is not running (e.g., until another coin is inserted or while the dryer is unloaded then reloaded) will not allow the electrical components (i.e., breakers, wires , and terminations) enough time to cool off. Over a full 8 ? 12 hour day, I believe that they will behave the same way they would behave if they were never turned off during the whole day.
Here again, code does not require using the 125% factor, but I would use it anyway.
The NEC defines a ?Continuous Load? as ?A load where the maximum current is expected to continue for 3 hours or more.? I don?t believe that that definition could be used to force a commercial laundry to apply the 125% factor to the dryer load. Nevertheless, as a design engineer, I would apply the 125% factor. I am certain that I could convince the owner that the benefits would outweigh the slight additional cost. I have two reasons; both are related to design considerations, not to code issues.
First, this is a kind business that cannot afford interruptions in service. If a circuit breaker trips, whatever the cause, you will have unhappy customers. Not only will there be a delay, while the breaker is located and reset, but the customers will also have to put in more coins, since a loss of power could cause the timers to reset. This will cost the owner money, and its not worth the risk.
Secondly, whatever physics might be involved in the 125% factor, I believe that the short periods that a dryer is not running (e.g., until another coin is inserted or while the dryer is unloaded then reloaded) will not allow the electrical components (i.e., breakers, wires , and terminations) enough time to cool off. Over a full 8 ? 12 hour day, I believe that they will behave the same way they would behave if they were never turned off during the whole day.
Here again, code does not require using the 125% factor, but I would use it anyway.
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