Only 90V AC Shore power

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If you boost the voltage before the existing isolation transformer (or on the dock) you can use what is called an "autotransformer".

An autotransformer does not give you isolation (which you have already and is a fraction of the weight of a conventional two-winding transformer. Autotransformers make sense when you are looking to change the voltage by only a few percent.

Here is a link to one: https://beaverelectrical.com/products/EER15KH8C

Agree. Looks like a nice unit. Darn shame that it would be needed. Personal preference would be to bypass isolation transformer or remove it first. Perhaps someone will start another thread to debate pros and cons of isolation transformers.
 
Agree. Looks like a nice unit. Darn shame that it would be needed. Personal preference would be to bypass isolation transformer or remove it first. Perhaps someone will start another thread to debate pros and cons of isolation transformers.

I like that auto transformer, too.

One key role of that isolation transformer is keeping swimmers, divers, and others in the water safe. This is true in salt water, but super true in freshwater.

The other key role of that isolation transformer is protecting the boat from stray current corrosion.

I would not remove the isolation transformer without also adding a galvanic isolator and boat-side ELCI.

I don't have an isolation transformer on my boat. But, I do have a galvanic isolator and an ELCI on each of the forward and stern shore power inlets.

A 1:1 isolation transformer is simple and the gold standard for the safety of the people and the vessel. If I had one, I would be very hesitant to take it out.

When I bought my boat, I had neither and there were delays getting an isolation transformer, so I put in the ELCI and galvanic isolator that were readily available. I won't say that I regret doing so -- but I do still wish I had an isolation transformer. One day I may put one in.
 
Ditto #20

Gary in post 20 and the reference to Red Pearls site is the key. I had the Blue Seas switch installed to give access to the 208 taps. $139 & $250 installation. We have hardly used it. MS 400 AC’s are rated 208/240 volts so are fine with 208. My AC circulating pump is 230 volts and will shut down (overheat?) around 200 volts. We can survive slower stove and toaster on 208 volt docks. I agree that 90 volts on outlets is surprisingly low if a digital voltmeter is saying so. My analogue panel meter is not accurate. This thread was thoroughly discussed years ago including references from an electrical engineer who designs Marina systems as to why 208 is widely used. STB ´s dockside boost transformer sounds good. Paul
 
Going back to the original post, there is one common "deception" that I have seen many of my friends make in troubleshooting low voltage on their boat. Very often they will go to the power pedestal with their voltmeter and measure the voltage and see a somewhat satisfactory voltage, then go to their boat and find low voltage, and then spend a great deal of time with many good and well meant suggestions, to no avail. What they don't realize and/or take into account is that when they measure the voltage right at the shore-power socket, they are doing so under a no load condition, but when they connect their boat up to it, there is almost always some load applied. If there was a dummy load applied at the shore-power outlet, they may very well find that the voltage was considerably less than the open circuit reading. The net result is that they spend a lot of time chasing an issue that really has more to do with the marina wiring than the boat, but does not show up when under no load.
 
what I do is test pedestal, plug in, unplug boat end and measure that with no load. It should be the same or else.

If the OP checked pedestal for say 110 and the end of cord unplugged and got 90v then either or both ends has got loose or corruded terminal wires. If ends are removable then it can be repaired. If sealed buy new cord or replacement ends
 
what I do is test pedestal, plug in, unplug boat end and measure that with no load. It should be the same or else.

If the OP checked pedestal for say 110 and the end of cord unplugged and got 90v then either or both ends has got loose or corruded terminal wires. If ends are removable then it can be repaired. If sealed buy new cord or replacement ends

You hit that nail on the head. I was just mentioning that in a DM to someone here who mentioned to me, "But the OP measured 208v at the pedestal".

That open load number accounts for neither the drop at the marine (due to the 1MOhm - 40MOhm impedence of the DVM) nor the drop from there to the boat or on the boat (due to being disconnected). I regularly find that it is significantly lower under load, even at the pedestal.

I recommend measuring it at the back of the shore power inlet or back of the main panel under load, being sure to have clean, unburned connections and a good cable. Or, if you are allowed in, within the shore power pedestal under load.
 
Issue drift as posts accumulate.

what I do is test pedestal, plug in, unplug boat end and measure that with no load. It should be the same or else.

If the OP checked pedestal for say 110 and the end of cord unplugged and got 90v then either or both ends has got loose or corroded terminal wires. If ends are removable then it can be repaired. If sealed buy new cord or replacement ends


I totally agree with this comment, however the original poster never stated such a condition as posed. His tests were done with an on-board load. In fact, with almost any connection at all,regardless of how resistively bad it was, it is nearly impossible to have this voltage drop in the cord alone with ONLY a digital voltmeter's input impedance drawing the current. Albeit any reasonable load on the cable would show a defective cable connection with the IR drop associated with a very few amps load, but the "I" drawn from just a multi-meter input impedance load would not drop any meaningful voltage even through a badly resistive connection in the cable fittings. Such a check would identify an actual open in the cord but would not detect a high resistance defect in the cord. However, this is all likely moot as in fact it seems that several posts back he determined his own issue.
 
Okay, this is what I would do.
Measure and the pedestal and the tail end of the shore power cable before it is hooked up to the boat. Measure the voltage at the boat breaker. Any loss, brighten all prong with your dermal tool, apply the proper grease to the prongs and reassemble.
IF you have a loss at the panel, get a marine electrican to chase a bad ground. (Between the onboard boat’s breaker and the panel??)
Of course, if you are reading 90 volts at the pedestal, it’s not your problem. Try another pedestal.

Never work on an energized system. It will hurt and maybe kill you.
The above is just my opinion, I am not a marine electrican or even regular electrican.
 
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You hit that nail on the head. I was just mentioning that in a DM to someone here who mentioned to me, "But the OP measured 208v at the pedestal".

That open load number accounts for neither the drop at the marine (due to the 1MOhm - 40MOhm impedence of the DVM) nor the drop from there to the boat or on the boat (due to being disconnected). I regularly find that it is significantly lower under load, even at the pedestal.

I recommend measuring it at the back of the shore power inlet or back of the main panel under load, being sure to have clean, unburned connections and a good cable. Or, if you are allowed in, within the shore power pedestal under load.

Agree there is voltage drop from pedestal under load. But consider the following:
1. Not the only boat at the marina or on the dock, so other boats already loading marina distribution system. So the 208 at the pedestal is a strong number.
2. Were talking 50 amp service, so shore power cord #6 awg. With full rated 50 amp load on a 50’ 50 amp #6 cord, voltage drop is less than 1% at 208v. (Check my math on boatwire.com voltage drop calculator). Shore power cord and pedestal connections assumed to be in good condition.
3. Voltage drop inside boat another discussion. Likely affected by corroded connections.
4. In summary, yes check voltage drop under load, but in this case, focus inside boat.
 
1. I don't think that #1 is always, or even overwhelmingly commonly, the case. It depends upon the marina and situation. No one is using the outlet on my pedestal that I use but me. The same is true of the breaker for that outlet and the wiring in that immediately serves it. Unless I load it, no one is.

Right now I'm pretty good. It is all pretty new and clean. But, before they replaced it? It was crispy wire from 1980s with brittle ends, the back of the socket was corroded and melting, and the breaker was corroded. There was a ton of loss there -- as the heat demonstrated -- but it would never have showed up testing unloaded. And it looked "okay" from the outside. Conditions at marinas vary.

As for the run from the marina distribution panel to my boat. It is probably 125ft. I dont know what the wire gauge is. That panel is outdoors, right near the saltwater, and not nearly airtight. I've seen inside. It is baked. Each breaker serves a few boats. Probably another boat on my breaker is pulling a load. But that isn't a guarantee. Some sailboats float off of solar and many boaters don't run AC when they aren't around. Very, very good chance of dock power float charging batteries nearby, but no guarantee.

Conditions in a newer marina are better. But, they are also more likely to have one boat per breaker in their panel, meaning that unless you are loading your run no one else is.

2) I'm not thinking so much about the cord as I am the connections. Here's an exercise for your. It is a game I like to play. Go to the marina on a beautiful hot summer Saturday when the docks are busy. As you wander down the dock chatting with neighbors, feel each cord right by the pedestal connection. How many are warm? How about darn right hot? Even on good looking cords? That's all loss before it gets to the boat not seen by testing at the pedestal. Many are quite the resistive heater.

Mine is spotlessly clean, relatively new, and in excellent condition. Same is true of the boat and pedestal end. I regularly run 25A on a 30A breaker. Yes. 83% load (Well, as.measured at the boat...) Real world. My connection at the pedestal side is always warm.

You'd be right if you'd suggest that that degraded marina wiring aint good. But, it is what it is. And, it's real. Salt air, humid climate, rain, salty water dripping divers plugging in, people who don't hose off cords after cruising. Time. Gravity, vibration, people tripping or moving cords. It all dirties, loosens, corrodes and otherwise degrade these connections.

Now, think about the other side of that cord. Where it goes into the boat. Want to play a game? Bet many are just as warm-to-hot. And that boat that has an extension with a connection mid-way? Guess what I think it might be?

This is all real-world loss before it gets into the boat, never mind to the main panel, never mind to the AC.

Conditions vary a lot. But, if there is a problem, something is wrong. Assumptions are bad. Testing is good.

I regularly find drop when testing under load. Maybe it shouldn't be. But, I often do.

A 230v namplated HVAC that complies with the NEMA (Not NMEA) 10% recommendation is supposed to run down to 207v (230v - 23v). And even then degraded performance is allowed.

If we are seeing 208v open at the pedestal, that may reasonably likely be 206v under load at the pedestal, and 204v after a 1v loss on the shore power cord and a 1v loss at the connections. By the time it gets to the AC it might be 202v in many real world boats. That's far from the appliances nameplatted 230v and well below the absolute minimum 207v required of a recommendation-compliant 230v AC unit.

All of these little losses add up.

Everyone likes to expect that the appliances will be tolerant of everything "at least 10%" they say. But they like to neglect the tolerances allowed for electrical distribution which allows a lot of loss, up to 11% and sometimes up to 13% by the time it gets to the appliance.

Running AC units nameplated for 230v electricity off of nominal 208v is only guaranteed to work under relatively ideal conditions and, in the real world, basic operation is often hit-or-miss and accelerating wear-and-tear may well be a consistent miss.

I can't emphasize enough that I don't think one should ever really expect AC units nameplated for 230v to run on nominal 208v in the real world (which can be within spec and well less than 208v). No one should complain to or about the marina when such appliances don't work. Well, says me, at the least.(Opinions seem to vary!).

Instead, I think one should be very pleased when such appliances happen to work under such circumstances, even if it seems to be somewhat often.

Step up transformers are the consistent fix here. And they consistently work. And they consistently work because they solve exactly this problem. By intention and design.

That's my thinking at the least. Obviously opinions vary!
 
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1. I don't think that #1 is always, or even overwhelmingly commonly, the case. It depends upon the marina and situation. No one is using the outlet on my pedestal that I use but me. The same is true of the breaker for that outlet and the wiring in that immediately serves it. Unless I load it, no one is.

Right now I'm pretty good. It is all pretty new and clean. But, before they replaced it? It was crispy wire from 1980s with brittle ends, the back of the socket was corroded and melting, and the breaker was corroded. There was a ton of loss there -- as the heat demonstrated -- but it would never have showed up testing unloaded. Conditions at marinas vary.

As for the run from the marina distribution panel to my boat. It is probably 125ft. I dont know what the wire gauge is. That panel is outdoors, right near the saltwater, and not nearly airtight. I've seen inside. It is baked. Each breaker serves a few boats. Probably another boat on my breaker is pulling a load. But that isn't a guarantee. Some sailboats float off of solar and many boaters don't run AC when they aren't around. Very, very good chance of dock power float charging batteries nearby, but no guarantee.

Conditions in a newer marina are better. But, they are also more likely to have one boat per breaker in their panel, meaning that unless you are loading your run no one else is.

2) I'm not thinking so much about the cord as I am the connections. Here's an exercise for your. It is a game I like to play. Go to the marina on a beautiful hot summer Saturday when the docks are busy. As you wander down the dock chatting with neighbors, feel each cord right by the pedestal connection. How many are warm? How about darn right hot? Even on good looking cords? That's all loss before it gets to the boat not seen by testing at the pedestal. Many are quite the resistive heater.

Mine is spotlessly clean, relatively new, and in excellent condition. Same is true of the boat and pedestal end. I regularly run 25A on a 30A breaker. Yes. 83% load. Real world. My connection at the pedestal side is always warm.

You'd be right if you'd suggest that that degraded marina wiring aint good. But, it is what it is. And, it's real. Salt air, humid climate, rain, salty water dripping divers plugging in, people who don't hose off cords after cruising. Time. Gravity, vibration, people tripping or moving cords. It all dirties, loosens, corrodes and otherwise degrade these connections.

Now, think about the other side of that cord. Where it goes into the boat. Want to play a game? Bet many are just as warm-to-hot. And that boat that has an extension with a connection mid-way? Guess what I think it might be?

This is all real-world loss before it gets into the boat, never mind to the main panel, never mind to the AC.

Conditions vary a lot. But, if there is a problem, something is wrong. Assumptions are bad. Testing is good.

I regularly find drop when testing underload. Maybe it shouldn't be. But, I often do.

A 230v namplated HVAC that complies with the NEMA (Not NMEA) 10% recommendation is supposed to run down to 207v (230v - 23v). And even then degraded performance is allowed.

If we are seeing 208v open at the pedestal, that may reasonably likely be 206v under load at the pedestal, and 204v after a 1v loss on the shore power cord and a 1v loss at the connections. By the time it gets to the AC it might be 202v in many real world boats. That's far from the appliances nameplatted 230v and well below the absolute minimum 207v required of a recommendation-compliant 230v AC unit.

All of these little losses add up.

Everyone likes to expect that the appliances will be tolerant of everything "at least 10%" they say. But they like to neglect the tolerances allowed for electrical distribution which allows a lot of loss, up to 11% and sometimes up to 13% by the time it gets to the appliance.

Running AC units nameplated for 230v electricity off of nominal 208v is only guaranteed to work under relatively ideal conditions and, in the real world, basic operation is often hit-or-miss and accelerating wear-and-tear may well be a consistent miss.

I can't emphasize enough that I don't think one should ever really expect AC units nameplated for 230v to run on nominal 208v in the real world (which can be within spec and well less than 208v). Instead, I think one should be very pleased when it happens, even if it seems to be somewhat often.

Step up transformers are the consistent fix here. And they consistently work. And they consistently work because they solve exactly this problem. By intention and design.

That's my thinking at the least. Obviously opinions vary!

The Marina pedestals are wired in parallel or daisy chained down the dock. So other boats at dock load the circuit even if not plugged into the same pedestal.

Yes a step up transformer is one solution. But why? Another piece of gear that you need to carry around. Hopefully most boats will leave the dock at some point. A number of posters on this thread have offered the solution of wiring out from the isolation transformer to a selector switch. Much better solution.
 
The Marina pedestals are wired in parallel or daisy chained down the dock. So other boats at dock load the circuit even if not plugged into the same pedestal.

That's only true with respect to the path from my boat to the breaker in the marina's panel serving my pedestal if all pedestals are served by exactly the same circuit breaker at the marina's distribution panel, which isn't true of any sizable marina.

My marina has more than 200 slips. They aren't all on the same breaker. :) Instead, groups of slips share a breaker at the distribution panel.

It's just like at home. Some outlets share a breaker, but not all outlets share the same breaker.

I agree that adjusting an isolation transformer to get a boost is a great option -- if one has an isolation transformer with the ability to be configured that way. It is close to free and flexible! There are a lot of boats wrestling with AC units that don't happen to be in that situation, though.
 
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That's only true if all pedestals are served by exactly the same circuit breaker at the marina's distribution panel, which isn't true of any sizable marina.

My marina has more than 200 slips. They aren't all on the same breaker. :)

Agree, not all 200 on same circuit. But on the other extreme, a single pedestal is not serviced by a dedicated marina distribution breaker. So there are a number of boats on the same dock on the same circuit. Can’t know, but suspect around eight boats, maybe more on a circuit (400 amp breaker, just as an example).
 
Agree, not all 200 on same circuit. But on the other extreme, a single pedestal is not serviced by a dedicated marina distribution breaker. So there are a number of boats on the same dock on the same circuit. Can’t know, but suspect around eight boats, maybe more on a circuit (400 amp breaker, just as an example).

Sure. Or the marina could be divided into several docks, each with 30 boats (15 each side), and have one panel for each dock, and one breaker for each boat or each pedestal. And, in any case, there is still the issue of that poor, but pesky pedestal.

I'd like to emphasize that, if we're trying to get an appliance nameplated for 230v to run on a nominal 208v, without adapting that voltage, we are already in super ticklish territory. Nearly all of the tolerance for reality was consumed at installation.
 
Sure. Or the marina could be divided into several docks, each with 30 boats (15 each side), and have one panel for each dock, and one breaker for each boat or each pedestal. And, in any case, there is still the issue of that poor, but pesky pedestal.

I'd like to emphasize that, if we're trying to get an appliance nameplated for 230v to run on a nominal 208v, without adapting that voltage, we are already in super ticklish territory. Nearly all of the tolerance for reality was consumed at installation.

As posted previously, haven’t seen that to be a problem on the FL central east coast marinas along the ICW. So do not agree a design or supply problem. But do agree, if marina distribution system degraded, or boat is degraded, then the margin is eroded.

Edit: Should also mention my marina on TN River is 208v with many large boats. Have heard no complaints. Have, however, heard a complaint the same as the original post about the isolation transformer yielding 104 on the 120v side. Which is what got me started on this post.
 
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Garmstro55: A wonderful solution!

It works for me but the credit goes to the owner of Red Pearl who created the write up. And, since I have the same boat as the OP I am pretty sure it will work for him too.
 

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