I have never had the pleasure of sizing a service for a marina until now, it is ridicules! The load calculations shown in article 555 when applied to my service would require a 1200A for the building and the docks. The load would never be anywhere close to the service. The marina would be in pennsylvania not florida or california where the boats are larger, and utalized year round. There are several other marinas in the area practically the size and they during peek times of the year operate at 100 to 200A. The code does not give any options for sizing a service for a marina, they either are built in florida or they are built in florida! Is there any way to size a service for a marina to the real anticipated load in-lieu of some way out there load that includes a small town?
Marinas
- Thread starter guesseral
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Marinas
Actually, I do not think the demand factors in 555.12 are out of line. If, for example, there are slots for 41 or more boats, you only have to provide power for half of them to be running at a time. Keep in mind that if you have both a 30 amp 125V plug and a 50 amp 125/250V plug for the same boat slip, you only have to count the load for the larger of the two (i.e., disregard the 30 amp).
Yes. Tell the owner not to put in room for as many boats!
Actually, I do not think the demand factors in 555.12 are out of line. If, for example, there are slots for 41 or more boats, you only have to provide power for half of them to be running at a time. Keep in mind that if you have both a 30 amp 125V plug and a 50 amp 125/250V plug for the same boat slip, you only have to count the load for the larger of the two (i.e., disregard the 30 amp).
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Marinas
I am referring to a single ?slip? (i.e., boat parking spot) that has two receptacles. The idea is that one type of boat might need the 30 amp receptacle, and a different type of boat would need the 50 amp receptacle. However, the code allows us to presume that no single boat would need to use both.
So if a single slip only has the 30 amp receptacle, then you count the load as 30 times 120 equals 3600 watts. If another slip has only the 50 amp receptacle, then you count the load as 50 times 240 equals 12,000 watts. If a single slip has both the 30 amp and the 50 amp, you only count the 12,000 watts. Finally, you add up all the loads, and apply the demand factor from Table 555.12.
I am referring to a single ?slip? (i.e., boat parking spot) that has two receptacles. The idea is that one type of boat might need the 30 amp receptacle, and a different type of boat would need the 50 amp receptacle. However, the code allows us to presume that no single boat would need to use both.
So if a single slip only has the 30 amp receptacle, then you count the load as 30 times 120 equals 3600 watts. If another slip has only the 50 amp receptacle, then you count the load as 50 times 240 equals 12,000 watts. If a single slip has both the 30 amp and the 50 amp, you only count the 12,000 watts. Finally, you add up all the loads, and apply the demand factor from Table 555.12.
stew
Senior Member
- Location
- federal way,washington
Re: Marinas
I have done several marina calcs recently and would be happy to assist you in this . How many slips do you have?
I have done several marina calcs recently and would be happy to assist you in this . How many slips do you have?
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Marinas
Not so fast, if you please. If these are 120 volt receptacles, and you serve them from a three-phase distribution, then that distribution is 120/208 volts, not 120/240. The calculation would go as follows:
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{Edited to correct a typographical error.}
[ December 01, 2004, 11:48 AM: Message edited by: charlie b ]
Not so fast, if you please. If these are 120 volt receptacles, and you serve them from a three-phase distribution, then that distribution is 120/208 volts, not 120/240. The calculation would go as follows:
</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">(30 amps times 120 volts times 240 slips) / (208 times sqrt(3)) = 2400 amps total. Apply the 30% demand factor of Table 555.12 and you get 720 amps.</font>
{Edited to correct a typographical error.}
[ December 01, 2004, 11:48 AM: Message edited by: charlie b ]
Re: Marinas
Just some food for thought
I recently investigated the breaker panels at my marina and found out that all of the 30amp twist locks are supplied by only a 15amp breaker (it is a club without individual metering per slip, so the thought is to limit use of power)
is it ok to under breaker a NEMA defined outlet?
and if so would this strategy allow for the calculations to be based on 15A/slip?
cheers
[ November 27, 2004, 12:54 AM: Message edited by: mikesorel ]
Just some food for thought
I recently investigated the breaker panels at my marina and found out that all of the 30amp twist locks are supplied by only a 15amp breaker (it is a club without individual metering per slip, so the thought is to limit use of power)
is it ok to under breaker a NEMA defined outlet?
and if so would this strategy allow for the calculations to be based on 15A/slip?
cheers
[ November 27, 2004, 12:54 AM: Message edited by: mikesorel ]
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Marinas
210.20(d) requires that the receptacle is not allowed to exceed the branch circuit rating found in table 210.21(B)(2) which would require a 15 amp receptacle on a 15 amp circuit.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Marinas
If the customer sees a receptacle that is marked as a 30 amp device, and if the customer plugs in a cord that is similarly marked as a 30 amp device, then the customer is going to try to use all 30 amps. If the breaker and branch circuit conductors are only good for 15 amps, you will have created a design that will frequently call upon its protective device to trip. A design should never do that. The design should only have the breaker trip when something fails, not when the customer is just trying to use the available load. That is the reason for the requirement that Wayne cited above. No, you don?t get to count them as 15 amp loads. Sorry.
If the customer sees a receptacle that is marked as a 30 amp device, and if the customer plugs in a cord that is similarly marked as a 30 amp device, then the customer is going to try to use all 30 amps. If the breaker and branch circuit conductors are only good for 15 amps, you will have created a design that will frequently call upon its protective device to trip. A design should never do that. The design should only have the breaker trip when something fails, not when the customer is just trying to use the available load. That is the reason for the requirement that Wayne cited above. No, you don?t get to count them as 15 amp loads. Sorry.
- Location
- Illinois
- Occupation
- retired electrician
Re: Marinas
Wayne,
I don't think that 210.21(B)(2) would apply as these are single receptactles. 210.21(B)(1) will permit a single 30 amp receptacle on a 15 amp branch circuit.
mikesorel
The statement to Wayne above is based on the rule in Chapter 2, the rules in Chapter 5 can modify the rules Chapters 1 through 4. 555.19(A)(3) requires that the branch circuit rating match the receptacle rating for shore power receptacles.
Don
Wayne,
I don't think that 210.21(B)(2) would apply as these are single receptactles. 210.21(B)(1) will permit a single 30 amp receptacle on a 15 amp branch circuit.
mikesorel
The statement to Wayne above is based on the rule in Chapter 2, the rules in Chapter 5 can modify the rules Chapters 1 through 4. 555.19(A)(3) requires that the branch circuit rating match the receptacle rating for shore power receptacles.
Don
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Marinas
Don I agree that 555.19(A)(3) should have been the correct article to apply to this question, but I don't think that we are allowed to use a single 30 amp receptacle on a 15 amp circuit or even a single 20 amp receptacle for that matter because 210.20(D) clearly requires that the outlet device is not allowed to exceed the branch circuit rating specified in 210.21 for outlet devices.
Which I should have used table 210.21(B)(3) which it says that the receptacle rating installed on a 15 amp circuit should be "not over 15 amps"
Which would be in line with the requirment of 210.23 "In no case shall the load exceed the branch-circuit ampere rating". which a 30 amp receptacle outlet on a 15 amp circuit would allow that to happen.
Don I agree that 555.19(A)(3) should have been the correct article to apply to this question, but I don't think that we are allowed to use a single 30 amp receptacle on a 15 amp circuit or even a single 20 amp receptacle for that matter because 210.20(D) clearly requires that the outlet device is not allowed to exceed the branch circuit rating specified in 210.21 for outlet devices.
Which I should have used table 210.21(B)(3) which it says that the receptacle rating installed on a 15 amp circuit should be "not over 15 amps"
Which would be in line with the requirment of 210.23 "In no case shall the load exceed the branch-circuit ampere rating". which a 30 amp receptacle outlet on a 15 amp circuit would allow that to happen.
- Location
- Illinois
- Occupation
- retired electrician
Re: Marinas
Wayne,
I don't agree. 210.20 is about the rating of the OCPD and not that of the outlet. 210.20(D) says that the rating of the outlet must conform with the rules in 210.21. 210.21(B)(1) permits the outlet device rating to exceed that of the branch circuit if the receptacle outlet is of the single type and if the branch circuit only serves that single receptacle outlet. The values in 210.21(B)(2), (B)(3), and Table 210.21(B)(2) only apply where there are two or more receptacle outlets served by the branch ciruit.
Don
Wayne,
I don't agree. 210.20 is about the rating of the OCPD and not that of the outlet. 210.20(D) says that the rating of the outlet must conform with the rules in 210.21. 210.21(B)(1) permits the outlet device rating to exceed that of the branch circuit if the receptacle outlet is of the single type and if the branch circuit only serves that single receptacle outlet. The values in 210.21(B)(2), (B)(3), and Table 210.21(B)(2) only apply where there are two or more receptacle outlets served by the branch ciruit.
Don
Re: Marinas
thank you to everyone weighing in so far
This marina was first constructed in 1927, so who know's when what was done.
This topic is quickly deserving it's own thread, but I would like to mention ranges are sometimes wired using a 14-50R which is a 50 amp receptacle on a 40 amp breaker. Perhaps this is a application of 210.21(B)(1)
thank you to everyone weighing in so far
This marina was first constructed in 1927, so who know's when what was done.
This topic is quickly deserving it's own thread, but I would like to mention ranges are sometimes wired using a 14-50R which is a 50 amp receptacle on a 40 amp breaker. Perhaps this is a application of 210.21(B)(1)
- Location
- Massachusetts
Re: Marinas
This came up before when a poster wanted to feed a 200 amp pin and sleeve receptacle with, if I remember 60 amps. They knew the load that was going to be used at this receptacle
No one could come up with a code violation in doing this with a single receptacle.
All that can be said is that it may be a poor design.
In the case of this Marina outlet I agree with Charlie B, it is a poor design to feed a 30 amp receptacle with a 15 amp overcurrent device. This will probably result in nuisance tripping.
I agree with Don, this is allowed.
This came up before when a poster wanted to feed a 200 amp pin and sleeve receptacle with, if I remember 60 amps. They knew the load that was going to be used at this receptacle
No one could come up with a code violation in doing this with a single receptacle.
All that can be said is that it may be a poor design.
In the case of this Marina outlet I agree with Charlie B, it is a poor design to feed a 30 amp receptacle with a 15 amp overcurrent device. This will probably result in nuisance tripping.
I was just as surprised when calculating the service size for an RV park
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