Upgrade from two 30 amp to one 50 amp

[Helmsman]

My understanding is that isolation transformers are preferred over galvanic isolators. That aside, how is going from 60 amp available power to 50 amp, an upgrade? He wants to go from (2) 30 amp to (1) 50 amp.

See post 30 above. The 50 amp is a 120/240, which is what you would find on most boats using a 50 amp feed. The 50 amp 120 volt can be found on older boats, but Very few, if any, newer boats.

 

[backinblue]

Several questions regarding why I would consider moving from 30 amps to 50 amps. To understand why it would be an advantage requires a little math.

A 30 amp feed supplies 30 amps x 120volts equaling 3,600 watts. Since the boat has two 30 amp feeds, that equates to 7,200 watts of available power. A single 50 amp 120/240 volt feed has two load lines. So, the math there is 2 x 50 amps x 120 volts or 12,000 watts.

Therefore the change would be entirely motivated by getting more power on the boat from the available shore power. That would provide the ability to run more high amperage equipment at the same time. With the equipment I have spec’ed for the boat, I am at close to the upper end of the power capacity for two 30 amp feeds. It is entirely and completely a convenience thing.

The discussion has zero to do with with what type of connection is available at a particular dock. I have a 50 amp pedestal at my home dock. While there are some docks out there which have limited electricity available, there are very few out there that don’t have the industry standard 50 amp or 30 amp available. These can be used with either service (for the most part) on the boat, by using adaptors for either. With two 30 amp connectors on a pedestal, there will be the wattage constraint illuminated above in terms of how much amperage is available. Not a big deal, as many 50 amp boats deal with that as they travel. So, availability of one or the other is a moot point, for me, at least.

I hope that helps.

Thanks for the education. I never had 50 amp boats, so I assumed it was just single phase 120V 50 amp. It all makes sense now.

 

[Helmsman]

Thanks for the education. I never had 50 amp boats, so I assumed it was just single phase 120V 50 amp. It all makes sense now.

I should have been clearer in my first couple of posts. By not doing so, I created unnecessary confusion.

 

[backinblue]

No worries. I should add that my boat has (2) 30 amp plugs. I don't know if it's common, but it allows my to combine them at the electrical panel such that 1 power cord can power everything al long as I don't overload it. That is how I usually manage my power and have never needed to bother with the second cord. I've never come close to 30 Amp total draw, I think I would really have to try, so it's never even really a consideration.

 

[Helmsman]

I have been following the discussion and wondering why is the suggestion to switch the panel and everything over to 50 amp. I currently have two 30 amp cords which each feed half of my panel. We usually have a pigtail which connects the two 30 amp cords to the pedestal. Couldn’t we just convert to having a single 50 amp cord from the boat to the dock and then have something that effectively splits the power inside the boat to two 30amp feeds which feed the existing panel just like the pigtail did?

There really isn’t an advantage to doing that inside the boat. You would still end up with two 30 amp feeds totaling 7,200 watts. The reason you have 30 amp breakers on the boat within 10 feet of the boat outlets is to protect the wires to the panel by limiting it to 30 amps. So, unless you switched completely over to 50 amp 120/240v you would just be moving a connection from externally on the SP cable to inside the boat.

 

[psneeld]

No worries. I should add that my boat has (2) 30 amp plugs. I don't know if it's common, but it allows my to combine them at the electrical panel such that 1 power cord can power everything al long as I don't overload it. That is how I usually manage my power and have never needed to bother with the second cord. I've never come close to 30 Amp total draw, I think I would really have to try, so it's never even really a consideration.

Ever liveaboard with 2 or more people?

If not or the people aboard are minimalists, then I can understand not wanting a 50A 125/250V supply. A 50A 125V (only) is only half the power and even less than a good 2x30A setup and maybe good enough for weekending, using marina facilities or again....being minimalists.

Either hot or cold requiring 2 ACs or space heaters on high plus a water heater will trip a 30A circuit.

I upgraded my boat to 50A 125/250V and had the panels set up to use even just a single 30A if need be and the inverter powered all outlets onboard for convenience.

 

[Helmsman]

I'd think it'd be cost effective to replace the two 30A isolation transformers with a single 50A isolation transformer.

Assuming afterwards sell-off of the 30s.

-Chris

Chris’s comment creates a question for me. It appears that Charles is out of the marine business. I don’t think Victron makes a 50 amp isolation transformer. Does anyone know which 50 amp isolation transformers are the highest quality?

 

[backinblue]

Ever liveaboard with 2 or more people?

If not or the people aboard are minimalists, then I can understand not wanting a 50A 125/250V supply. A 50A 125V (only) is only half the power and even less than a good 2x30A setup and maybe good enough for weekending, using marina facilities or again....being minimalists.

Either hot or cold requiring 2 ACs or space heaters on high plus a water heater will trip a 30A circuit.

I upgraded my boat to 50A 125/250V and had the panels set up to use even just a single 30A if need be and the inverter powered all outlets onboard for convenience.

But my boat is much smaller than yours. Only 1 AC/heat unit, 2 burner electric stove, hot water heater, microwave, battery charger, fridge, ice maker, TV. I'm sure I would exceed 30 Amps if I ran everything at the same time and maybe a hair dryer plugged in. But my point is, 2 of us on board at a marina don't normally come close to that, so it's easier to just use 1 power cord and combine the 2 circuits at the power panel. I'm glad I have 2 outlets if needed, just never have in the few years I've owned the boat. More often than not, we are away from the dock at anchor and on generator if A/C power is needed anyway.

 

[psneeld]

Chris’s comment creates a question for me. It appears that Charles is out of the marine business. I don’t think Victron makes a 50 amp isolation transformer. Does anyone know which 50 amp isolation transformers are the highest quality?

Not sure about a marine version...but an RV version may be suitable and adaptable.

It may need specific investigation for adaptability.

 

[Bmarler]

Chris’s comment creates a question for me. It appears that Charles is out of the marine business. I don’t think Victron makes a 50 amp isolation transformer. Does anyone know which 50 amp isolation transformers are the highest quality?

Try hubbell. They have 25 kva marine units in boosted and non boosted forms.

 

[ranger58sb]

Chris’s comment creates a question for me. It appears that Charles is out of the marine business. I don’t think Victron makes a 50 amp isolation transformer. Does anyone know which 50 amp isolation transformers are the highest quality?

If it helps, ours is a Charles "12 KVH" unit per our boat build sheet. Probably should be KVA?

I dunno about "boost" from ours; that'd be one of the docs that I haven't gone scrounging for softcopy yet...

Anyway, I see this, from quick on-line search:
https://www.aquamaremarine.com/us/product/marine-iso-boost-transformer-50a-12-kva/

A few other names I didn't recognize came up, too...

-Chris

 

[psneeld]

But my boat is much smaller than yours. Only 1 AC/heat unit, 2 burner electric stove, hot water heater, microwave, battery charger, fridge, ice maker, TV. I'm sure I would exceed 30 Amps if I ran everything at the same time and maybe a hair dryer plugged in. But my point is, 2 of us on board at a marina don't normally come close to that, so it's easier to just use 1 power cord and combine the 2 circuits at the power panel. I'm glad I have 2 outlets if needed, just never have in the few years I've owned the boat. More often than not, we are away from the dock at anchor and on generator if A/C power is needed anyway.

Some day you may see the need.

 

[tiltrider1]

Industry standard for marine pedestals is 1 30a 125v and 1 50a 125/250v socket. That said be aware that 50a 125v is still out there.

30a 125v is a 3 wire system
50a 125v is a 3 wire system
50a 125v/250v is a 4 wire system

50a 125v/250v is 100 amps of power at 125v or 50 amps of power at 240v.

Transformers are magical things that can turn 125v into 250v but a transformer is not necessarily an isolation transformer so don’t confuse the two.

Isolation transformer is a big subject that really hinges on what the end user’s goal is. The answers is almost always yes but!

 

[Helmsman]

Try hubbell. They have 25 kva marine units in boosted and non boosted forms.

I looked at theirs after starting this discussion. Roughly $7500 and couldn’t find a vendor with them in stock. That is with boost which I guess I wouldn’t need. Looks like about $2,500 for the non boost 50 amp one.

 

[tiltrider1]

I have been considering this system. Low weight and very versatile.

https://www.bridgeportmagnetics.com/wp-content/uploads/2020/12/Marine-Puck-Sales-sheet.pdf

 

[backinblue]

Some day you may see the need.

I think you misunderstand me. I have nothing against lots of available power and not rallying against it. I was just trying to make a point, that for my situation and my boat, one 30 amp cord suffices, even though I can connect 2. If I can avoid the space and weight of carrying an extra cord that I don't really need, I'm all for that. Also, some transient marinas will charge per hookup, so 1 is cheaper than 2. Didn't mean to disparage anyone who can or wants more.

 

[boating rich]

Thanks guys for this discussion. I too didn’t know the differences, but I do know.

 

[backinblue]

That's the beauty of TF!

 

[Helmsman]

I have been considering this system. Low weight and very versatile.

https://www.bridgeportmagnetics.com/wp-content/uploads/2020/12/Marine-Puck-Sales-sheet.pdf

Interesting. I didn’t see anything on the cost. The grounds don’t terminate at the transformer. I suppose that would work, just not the way I usually think of the wiring on one.

A mention of cost for the 30 amp version here:

https://www.baylinerownersclub.org/...gc15/499442-marine-puck-isolation-transformer

 

[Helmsman]

This forum post is informative. Evidently, the schematic is incorrect. Therefore the polarity light was coming on. Also a story of good customer service.

The TugNuts • View topic - Isolation Transformer Question

 

[tiltrider1]

Interesting. I didn’t see anything on the cost. The grounds don’t terminate at the transformer. I suppose that would work, just not the way I usually think of the wiring on one.

A mention of cost for the 30 amp version here:

https://www.baylinerownersclub.org/...gc15/499442-marine-puck-isolation-transformer

I do not remember what the price was for two of the larger units but it was less than I expected based on what I was seeing for a 50a 125v/250v unit. Its a bit of an odd set up. The unit is 25a in each direction. It requires 2 units to get 50a but then you have two lines of 50a so it works. Then there is the issue of two 125v lines vs one 250v. This will confuse most so be careful. 220 appliances use two hots and no neutrals. Boats with two 125 lines still need a neutral if they plan to run off of just a 30a occasionally. The Bridgeport can be wired to be a two 125v line set up. I then take one of the lines and run it through a transformer jumping it up to 250v. This means I can stay at a 208v dock and still get either 125v or 250v with out using a boost transformer. I can also run off of 30a but I won't be able to run Heat/AC or the dryer.

 

[mdstrum]

We went from 2 30amp 120 to 1 50amp 240....that splits inside the boat to 2 120 banks (50 amp each) that we balance the loads on best we could. We have 3rd bank that is for our inverter as a side note.

We love that we did this. we do carry a few adapters on board to work with various marina's and can run the boat with only 30amps or two 30 amps to the 50, and we 50/120 to 50/240 adapter as well. Basically one cord, lots of options.