208volt Problem at Marinas

[The Other Gary]

OK George.
If you use 50 amps of power at 230 volt there is 0 amps in the neutral because it is not used.
If you use 50 amps of power on EACH of the 120 volt legs there will still be 0 amps in the neutral because they cancel each other out.

 

[diver dave]

Not exactly right on the neutral. The breaker will not trip if both hot legs are at full capacity. Any 230 volt loads do not use the neutral wire at all and any 120 volt loads will only load the neutral with the difference between the two legs.
On a 50 amp circuit using 20 amps at 230 and you use 25 amps of power on the black leg at 120 volts and 30 amps of power on the red leg at 120 volt 25 of those amps are cancelled in the neutral and the neutral is only carrying 5 amps.

Gary; is this in response to my last post? lots of thought streams now, need a webinar!

* The neutral WILL trip below full line capacity if the two legs are in-phase. 30A L1 + 30A L2 = 60 Amps of neutral. This can easily be the result of a non-smart Y dock connector.

 

[The Other Gary]

Gary; is this in response to my last post? lots of thought streams now, need a webinar!

* The neutral WILL trip below full line capacity if the two legs are in-phase. 30A L1 + 30A L2 = 60 Amps of neutral. This can easily be the result of a non-smart Y dock connector.

True, in that set of circumstances it will trip. Hopefully most marinas have balanced out their services. I can see this happening if a vessel pulls into a slip and has to draw power from two different towers with a non smart 2 x 30 amp splitter. They would not have any 230 volt and if they were all 120 volt usage they could overload the neutral to 60 amps. Cobourg marina used to be like that until they installed their new visitor slips.

 

[Bob Cofer]

Fellas,
There is some confusion going on here.

1) Neutral wires are not over-current protected, they are routed through a current sensing CT which is connected to the GFCI trip unit on the breaker in a GFCI protected system. The GFCI is looking specifically for current potential between neutral and ground.

2) One neutral is shared between the phases on a two or three pole breaker.

3) Over-current on any one of the three phases will trip the breaker. In specific applications a significant imbalance will also cause the breaker to trip. This is not normally seen in this type of application.

4) There has been a recent change in the trip current limit in marina applications. It has been raised from 30 to 100 mA in an effort to decrease nuisance tripping.

5) ANSI C84.1 provides a standard for Utility Voltage Tolerance of -13% to +6%.

This equates to:

120v Low 104.4 - High 127.2
208v Low 181 - High 220.5
240v Low 208.9 - High 254.4

 

[diver dave]

Fellas,
There is some confusion going on here.

1) Neutral wires are not over-current protected, they are routed through a current sensing CT which is connected to the GFCI trip unit on the breaker in a GFCI protected system. The GFCI is looking specifically for current potential between neutral and ground.

Bob; The discussion was targeting the boat panel circuit breaker. For 240/120 service, that breaker has a pole for each phase and the neutral.

 

[Bob Cofer]

Got it. I was talking dock side.

 

[diver dave]

I just found this on the 208V supplied to induction motors:

240 vs. 208 volts – Do Motors Care? – Brithinee Electric

Some commercial customers have converted their building services from 240 volts 3-wire to 208Y/120 volts 4-wire. Seeing nameplates on equipment (especially HVAC) reading “208- 230” or “208/230” volts, they’ve assumed “no problem.” When motor failures then occurred, the complaint was “low voltage.” What’s the story?
First, motors are sold and warranted for voltages no lower than 10% under the value on the motor nameplate. This is a NEMA requirement. Standard motors are designed and nameplated “230” (or 230/460) volts. That means the minimum permissible terminal voltage (not back at the controller, or service entrance) is 90% of 230, or 207 volts. Second, an American National Standard (ANSI C84.1) prescribes the lowest allowable power system or supply voltage. For a “240” volt system, the service entrance voltage can be as low as 220; at motor terminals, the minimum is 212. Thus, the 207 volt motor minimum will always be met.
But suppose the same motor is connected to a “208 volt” system. The ANSI standard then allows minimum service entrance voltage of 191; 184 is permitted at the motor. Those values are well below the 207 volt level. That forces the motor current way up, so that the motor is likely to overheat, and is no longer warranted for normal performance or life expectancy. So what’s the meaning of equipment nameplates reading “208-230” or “208/230” volts? No such markings appear in any standard. All they mean, in commercial practice, is that the basic motor design (most often made for 230 volts) is satisfactory at a terminal voltage of 208 – no less. That’s not the same as saying “OK for use on a 208 volt system,” where supply voltage can dip well below what the motor will tolerate.
Because of the confusion this has caused over the years, NEMA motor standards are now being revised to make this distinction clearer. But the changes may not appear for some time. Meanwhile, remember this: The motor truly intended for use on any 208 volt system is one designed and nameplated for “200” volts — an existing NEMA standard motor nameplate voltage intended for this purpose.
Too low a voltage does more than raise motor current. It also sharply decreases accelerating torque. The motor may no longer be able to start its load.

 

[markpierce]

Gee, connecting to a 50-amp outlet using an adapter to make it 30 is easy, and if a 30-amp marina outlet the adapter isn't needed. Easy, peasy. Suppose boats with more demanding on-shore power needs have problems of their own making.

 

[caltexflanc]

Fellas,
There is some confusion going on here.

1) Neutral wires are not over-current protected, they are routed through a current sensing CT which is connected to the GFCI trip unit on the breaker in a GFCI protected system. The GFCI is looking specifically for current potential between neutral and ground.

2) One neutral is shared between the phases on a two or three pole breaker.

3) Over-current on any one of the three phases will trip the breaker. In specific applications a significant imbalance will also cause the breaker to trip. This is not normally seen in this type of application.

4) There has been a recent change in the trip current limit in marina applications. It has been raised from 30 to 100 mA in an effort to decrease nuisance tripping.

5) ANSI C84.1 provides a standard for Utility Voltage Tolerance of -13% to +6%.

This equates to:

120v Low 104.4 - High 127.2
208v Low 181 - High 220.5
240v Low 208.9 - High 254.4

Thank you Bob!

 

[caltexflanc]

Gee, connecting to a 50-amp outlet using an adapter to make it 30 is easy, and if a 30-amp marina outlet the adapter isn't needed. Easy, peasy. Suppose boats with more demanding on-shore power needs have problems of their own making.

And many comforts of their own making to go with it!

 

[sunchaser]

4) There has been a recent change in the trip current limit in marina applications. It has been raised from 30 to 100 mA in an effort to decrease nuisance tripping.

Is the increase to 100 ma a for sure or is it still in the discussion stage. The 30 ma limitation is nigh impossible for larger marinas. Even at 100 ma there will be some interesting times as boats scramble to clean up grounding systems.

The 3 ma trip out at the pedestal seems a US code issue, in BC the hydro guys just chuckle about it.

 

[Bob Cofer]

For sure in my part of the world.

 

[Seevee]

Question for you expert: When using the reverse Y to two 30 amp recepticals, how does on know if it's phased correctly?

 

[ranger58sb]

Question for you expert: When using the reverse Y to two 30 amp recepticals, how does on know if it's phased correctly?

Our Smart Y has a LED on it; if it lights, the two 30s are out of phase... and the boat gets power.

-Chris

 

[psneeld]

Question for you expert: When using the reverse Y to two 30 amp recepticals, how does on know if it's phased correctly?

If you are talking a 50A 125/240 shoreside and 2 30A on the boat, it isnt a smart y.

There are 2 hot lines in the 50A receptacle and each one feeds each of the 30 inlets on the boat. They should be out of phase, but it doesnt matter as I dont think I ever heard of a boat wired with 2 30A lines rigged for 240V inside in any way.

The adapter doesnt have exposed prongs once connected shoreside so that hazard doent exist.

 

[Seevee]

If you are talking a 50A 125/240 shoreside and 2 30A on the boat, it isnt a smart y.

There are 2 hot lines in the 50A receptacle and each one feeds each of the 30 inlets on the boat. They should be out of phase, but it doesnt matter as I dont think I ever heard of a boat wired with 2 30A lines rigged for 240V inside in any way.

The adapter doesnt have exposed prongs once connected shoreside so that hazard doent exist.

Psneeld,

No, just the opposite. 2 30 amp on shore, 50 amp on boat.

I did have a boat with the 2 30s on the boat, never had an issue.

 

[caltexflanc]

Our Smart Y has a LED on it; if it lights, the two 30s are out of phase... and the boat gets power.

-Chris

Yep.

 

[diver dave]

Question for you expert: When using the reverse Y to two 30 amp recepticals, how does on know if it's phased correctly?

It contains a relay that closes IF and only IF the 30A plug legs have 210V or higher across them. THat's my best guess, as Hubbel is very unlikely to release the schematic.

 

[O C Diver]

It contains a relay that closes IF and only IF the 30A plug legs have 210V or higher across them. THat's my best guess, as Hubbel is very unlikely to release the schematic.

Yes both Hubbell and Marinco do or did require 210V to energize both relays. With 208V only one side of the boat's 240V breaker panel receives power. Don't know if they have changed that now that 208V power is becoming more common on the docks. This has been a big problem on the docks where I summer. Every other slip has twin 30 amp receptacles and the smart Y adapters don't work on the 208V.

Ted

 

[caltexflanc]

I don't think it is so much a function of voltage, if at all, but that the phases are not 180 degrees, but 120.
After all there is 120 on each leg which is the first thing looked for. Perhaps one of the professionals can clarify that.

 

[diver dave]

I don't think it is so much a function of voltage, if at all, but that the phases are not 180 degrees, I think you should say Zero here but 120.
After all there is 120 on each leg which is the first thing looked for. that is not the rule of connection Perhaps one of the professionals can clarify that.

The rule that enables connection is that you must have "something over 200V between both HOT 120V legs". I don't believe that there is a vector voltmeter inside these boxes

Also, if I should hand you two wires, there is no way you could tell me if the wires are 180 deg out of phase or 120 degrees out of phase, since phase measurements are impossible with a 2 wire system. All you can tell me is that there is a sinusoid waveform on there with such and such an amplitude. On the other hand, if I hand you 3 wires out of one of these dock recepts, you can now develop the relationship, in time, between the 3 wires, and with that, tell me phasing info.

 

[Onward]

This string makes my eyes bleed. The poor guy is worried about bad power hookups between the north and Florida. I did have several "first class marinas" come up short with power substantially below 120 volts. I check first and if unhappy with power quality I advise the operator that I will be running a generator intermittently. They hang their head, but reluctantly agree. One villain was a "mega" marina in South Carolina.

 

[ranger58sb]

Yes both Hubbell and Marinco do or did require 210V to energize both relays. With 208V only one side of the boat's 240V breaker panel receives power. Don't know if they have changed that now that 208V power is becoming more common on the docks. This has been a big problem on the docks where I summer. Every other slip has twin 30 amp receptacles and the smart Y adapters don't work on the 208V.

Our Marinco Y says 208V (minimum) will energize the thing.

But most of the few times we've needed to use it, it just worked, so we haven't fooled around much with voltage measurements, so can't confirm.

OTOH, when we first bought this boat... our (then) marina's electrical system wouldn't work with the Smart Y. I believe it turned out all their twin 30A supplies on the same pedestals weren't different phases... so it probably wasn't a voltage issue, but rather a phase issue.

-Chris

 

[caltexflanc]

After all there is 120 on each leg which is the first thing looked for. that is not the rule of connection Perhaps one of the professionals can clarify that.
The rule that enables connection is that you must have "something over 200V between both HOT 120V legs". I don't believe that there is a vector voltmeter inside these bo

Thanks Dave, but: Well, is there a volt meter in there or what?

 

[diver dave]

Thanks Dave, but: Well, is there a volt meter in there or what?

If someone would send me their smart Y, I'd be happy to break it open and inspect it.

But, as a circuit designer, I can tell you that it is not difficult to turn on a relay at 200, something volts and not turn it on at 150 Volts. You don't have to actually measure the voltage with precision. Maybe that's the best way to leave it.

 

[FF]

The problem is most cruisers have one or two 120V circuits , and few (in USA) use 240 for anything.

So the question becomes how do you get two 120V circuits with a marina that has cheeped out on the wiring?

 

[MYTraveler]

The problem is most cruisers have one or two 120V circuits , and few (in USA) use 240 for anything.

So the question becomes how do you get two 120V circuits with a marina that has cheeped out on the wiring?

Is that the question? My marina is 208, and I get two 120v legs just fine. The problem I have is that I can't get 240, and although my ACs and clothes washer dryers, etc. "require" 240 volts (but run fine on 208), I do have one piece of equipment (high-capacity ice maker) that won't run on 208.

 

[tiltrider1]

The problem I have is that I can't get 240, and although my ACs and clothes washer dryers, etc. "require" 240 volts (but run fine on 208), I do have one piece of equipment (high-capacity ice maker) that won't run on 208.

The answer here is a step up transformer from 120v to 240v for only your ice maker.

My whole boat is 120v but I need 100a. The exception is my dryer. I have installed a step up transformer for the dryer. I have never had an issue with 208v marina’s, I am also able to function off of 50a 120v connectors if necessary.

 

[MYTraveler]

The answer here is a step up transformer from 120v to 240v for only your ice maker.

My whole boat is 120v but I need 100a. The exception is my dryer. I have installed a step up transformer for the dryer. I have never had an issue with 208v marina’s, I am also able to function off of 50a 120v connectors if necessary.

Based on input above (that stepping up 208 to 240 with a dock-mounted transformer would not drop my 120v), I have been considering, as you suggest, a step up transformer for the ice maker. But I was thinking of taking the 208 that feeds it now up to 240. Your thought, of stepping up 120 to 240 did not occur to me. Doing that creates a couple disadvantages: the wiring to the ice maker would have to be reworked, and with all the current coming from one leg, I risk overloading that leg, depending on the demand. So, is there an advantage to stepping up from 120, rather than from 208?

The other problem I have is that my genset producing 240, and most of the time that I am using the ice maker, I am powering it with the genset. So, I would need some fancy switching, and I would have to remember to flip the switches before I turn on the genset. But, frankly, my biggest problem is not knowing exactly which transformer to purchase. Any thoughts/suggestions as to any of the foregoing would be appreciated.

 

[diver dave]

My. What is wattage of icemaker? U need an auto-tap autotransformer. I’ll bet the other 240v motors would like the boost too. Shame the marina is so messed up.