110 vs 220 power question

[savarese1]

We have a 1972 53 my. Our shore power has the option of 1 50 amp 220 volt power cord or 2 110 30 amp cords. My question. Is there any advantage to utilizing the 2 110 cords, since I am assuming this generates a total of 60 amps versus a single 50 amp. Also will the 2, 110 cords complete the circuit and give me 220 volt allowing me to utilize the stove and oven? Thanks for your help!

 

[Boatsb]

First remember that an amp is based on voltage.

A watt is a watt.


50 amps 240 volt is equivalent to 2 50 amp 120 volt cords. That means the total power of your 240v cord is 50 x 220 or about 12kw.

30 amps 120 volt is 3.6k w x 2 is 7.4kw.

There is more powe available on the 50 amp cord.

 

[SKYCHENEY]

And no, you can't use 240v loads on the two 120v inlets.

 

[SEVEN]

Well described.

 

[davidwigler]

And no, you can't use 240v loads on the two 120v inlets.

I'm not sure about that. The isolation transformers may covert to 240 volts. My 50 amp 120 does.

 

[madhatter1]

And no, you can't use 240v loads on the two 120v inlets.

Well you can if the 2 30 amp circuits at a post are on separate phases. That is where the 208, 220 , or 240 is derived from. Boatsb is correct in that the 50 amp @240 amp cord and breaker will deliver more than 2 30A 120V lines. Assuming the load is balances between phases the double pole breaker with the lower gauge conductors (thicker wire) will do a better job.

But a much bigger variable is what is the condition of the pedestal receptacles, conductors, and (here is the biggie) condition of terminations from receptacle to utility. Any can of these result in resistance and voltage loss which drives the amps up (based on load) and then the breaker will trip even if in theory the boat should not be drawing too much.

Way to much to think about when you just wanna plug in, be cooled off, and grill/chill/drink.

 

[saltshaker]

You should get 220v from the 110 service via the transformers. That's what I do when I'm on the hard. I have a cord with a standard Edison plug and a 50/125 female for the boat. Only way to run the battery charger.

 

[Pascal]

The early 53s don't have transformers

Using the 30 amp is really a last resort if you re in crappy slip without 220/50.

You can run 240v stuff if you connect using a smart y which will make sure the hots are on opposing phases

 

[SKYCHENEY]

I'm not sure about that. The isolation transformers may covert to 240 volts. My 50 amp 120 does.

No iso trans on a 1972

 

[SKYCHENEY]

Well you can if the 2 30 amp circuits at a post are on separate phases. That is where the 208, 220 , or 240 is derived from. Boatsb is correct in that the 50 amp @240 amp cord and breaker will deliver more than 2 30A 120V lines. Assuming the load is balances between phases the double pole breaker with the lower gauge conductors (thicker wire) will do a better job.

But a much bigger variable is what is the condition of the pedestal receptacles, conductors, and (here is the biggie) condition of terminations from receptacle to utility. Any can of these result in resistance and voltage loss which drives the amps up (based on load) and then the breaker will trip even if in theory the boat should not be drawing too much.

Way to much to think about when you just wanna plug in, be cooled off, and grill/chill/drink.

Yes, with a smart Y. However, the OP was asking about using the 2 OEM 30amp inlets on a 1972 53MY.

 

[MikeP]

Yep - about 6 years ago we moved from a slip with 240/50A to a new slip which had two 30A 120's. It was a total PITA because we had to constantly be aware of what we had running to avoid tripping the shore breaker. When we got the 240/50A installed at the new slip, that problem went away.

The interesting part is that when I was talking about the problem to some marina-mates, the majority had the view that there was something wrong with our boat's internal system because they believed that the two 120/30A circuits could provide more power than the one 240/50, figuring the same thing - that two 30's make 60...which, in this case, it does not. One of the people who claimed that was allegedly an electrician...scary stuff..

 

[Boatsb]

Yep - about 6 years ago we moved from a slip with 240/50A to a new slip which had two 30A 120's. It was a total PITA because we had to constantly be aware of what we had running to avoid tripping the shore breaker. When we got the 240/50A installed at the new slip, that problem went away.

The interesting part is that when I was talking about the problem to some marina-mates, the majority had the view that there was something wrong with our boat's internal system because they believed that the two 120/30A circuits could provide more power than the one 240/50, figuring the same thing - that two 30's make 60...which, in this case, it does not. One of the people who claimed that was allegedly an electrician...scary stuff..

2 x 30 is 60.

2 120 volt 30 amp circuits are a total of 60 amps @ 120 volts.

1 single 50 amp 240 is 50 amps @ 240 volts

more amps does not mean more power. Look at my first post if thats not clear.

 

[Pascal]

Two 120-30 connections will feed two 30 amps 120v sub panels for a total of 60 amps

One 120/240-50 connection will feed two 50 amps 120v sub panels

How is this not "more power"?

 

[Boatsb]

Two 120-30 connections will feed two 30 amps 120v sub panels for a total of 60 amps

One 120/240-50 connection will feed two 50 amps 120v sub panels

How is this not "more power"?

1 x 50 amps 240 volts is 50 amps.
2 x 30 amps 120 volts is 60 amps.

a single 50 amp 120/240 is considered 50 amps. it is not 100 amps.

Back to basics. Its not amps its watts.

 

[MikeP]

2 x 30 is 60.

2 120 volt 30 amp circuits are a total of 60 amps @ 120 volts.

1 single 50 amp 240 is 50 amps @ 240 volts

more amps does not mean more power. Look at my first post if thats not clear.

Perfectly clear to me - but obviously isn't to some people, apparently including some electricians! I had to argue with folks at the marina re the problem at the new slip. Their elec guy said that twin 120/30 produced more available power than the 240/50. As you pointed out, Watts are what matters. Heck, I learned that as a 7 year old with electric trains...transformers with higher wattage ratings could run more trains!

(still have all my Lionel stuff including the honking ZW transformer!)

 

[Walter P]

Several years ago at our club, I moved my 1982 48 MY to a new slip that only had 2 30 amp outlets. I
used a Hubbel smart adapter (which I guess is not too smart) and plugged into the 50a, 240 inlet. The
current was substandard so much that it was a chore to boil a pot of water or even charge an 18 V Lithium
battery. We had the club electrician bring in new service (50 A, 240 V) and it helped a lot, but still no joy.
I bought a voltage booster transformer (very expensive) and the problem was solved. Our club has 208V
service coming in from the electric company and I guess with all the conversions etc., it got a little crazy.
I am aware that our isolation transformers on Hatteras boats can be altered by adding a selector switch
so that we can select the correct setting for the voltage available at the dock. I am not aware of how to
do it and even if I could, electricity scares the hell out of me. (I have a built in heart device) I wish I could
have an electrician who knows how to do the job perform the work for me. I guess with electricity I'm
like the kid whose mother yells at him...."Get away from that wheelbarrow, you don't know nothing
about machinery"

Walt

 

[yvella]

How is best method to find decent marine electrician for older Hatts. Seems everytime in my area i mention 1973 Hatt MY they almost run away. Off subject but any thoughts.

 

[MikeP]

Sorry I can't help with finding someone but any "marine electrician" should be able to work on a Hatt. The OEM wiring is generally very well done. Maybe the techs you have encountered are concerned about the 32V systems but there is no difference in DC electricity/operation whether its 12, 24, 32, 36, 48, whatever.

It would be interesting to hear the "electricians'" specific issues that would make them run away... If they really are concerned about 32V...they shouldn't be "marine electricians"

 

[Pascal]

Call it what you want ... With a 120/240-50 I can run the whole boat... With two 120-30 I can't...

Been there done that. When connecting a boat with twin 120/240-50 no problem, everything works
Connect the same boat in a crappy slip with just two pairs of 120-30 and I can't run the whole thing...

 

[saltshaker]

You're both saying the same thing but misreading each other's post. In summary 2 30/125 provide 60A 120V and a single 50/250 can provide 100A 120V or 50A 240V.