Working on a project with a boat yard, they have pedestals as well as custom made charging stations. The voltage in the building is 208-3. The issue is that a lot of the appliances and loads in the boats require 240v. We will have panels that feed these pedestals and I was thinking about putting something before the panel to increase the voltage from 208>240. Not quite sure on the KVA yet. Wanted to get some opinions on whether I should increase the voltage before the panel (or) after on each circuit. Any opinions on this, and suggestions on what I should be using?
Marine Power 208>240
- Thread starter Npstewart
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
The key issues are geographic and aesthetic. Regarding geography, how long are the runs from the panels to the pedestals, and how do you get from the one to the other? I designed a marina that had long floating piers. I brought 480/3 to the head of the pier, and ran it to transformers and load centers along the pier. The conduits were run within the structure of the floating pier, and were therefore out of sight. Voltage drop considerations made it cost effective to use the higher voltage for the longer portions of the runs.
Regarding aesthetics, will the owner allow you to use transformers that would be visible to the users?
Regarding aesthetics, will the owner allow you to use transformers that would be visible to the users?
The runs from the electric room are going to be pretty close, I don't think voltage drop will be an issue but I will be checking that once I have all my loads figured.
This is marine power for boats, however the boats aren't near the water. This is more of a repair shop then anything.
We have custom made boxes with the required receptacles for most of the areas. So for instance, some of the charging boxes will have (1) 100A 240V receptacle, (1) 50A 240V & (1) 30A 120V and a few 20A GFI receptacles. So basically this is different then a pedestal in the sense that you cant just run a 240V circuit to power all the receptacles. Every receptacle in the box will need to have its own breaker (with exception to the 4 GFI receptacles.) With that being said, we were going to have a main panel which will feed 12 pole panels, and the 12 pole panel will feed the receptacles in the boxes ( a breaker for each receptacle).
Diagram below:
208Vpower--->240V xfrmr--->42P panel-->breaker--->12P panel---->charging box.
------
Additionally we will have standard marine pedestals which we can be fed from the 42P panel. I think it would be wise to loop feed the pedestals, so each pedestal feeds the next.
208Vpower-->240v xfrmr--->42P panel-->100A breaker--->pedestal-->pedestal
The loop fed ones will maintain the same wire size through out.
This is marine power for boats, however the boats aren't near the water. This is more of a repair shop then anything.
We have custom made boxes with the required receptacles for most of the areas. So for instance, some of the charging boxes will have (1) 100A 240V receptacle, (1) 50A 240V & (1) 30A 120V and a few 20A GFI receptacles. So basically this is different then a pedestal in the sense that you cant just run a 240V circuit to power all the receptacles. Every receptacle in the box will need to have its own breaker (with exception to the 4 GFI receptacles.) With that being said, we were going to have a main panel which will feed 12 pole panels, and the 12 pole panel will feed the receptacles in the boxes ( a breaker for each receptacle).
Diagram below:
208Vpower--->240V xfrmr--->42P panel-->breaker--->12P panel---->charging box.
------
Additionally we will have standard marine pedestals which we can be fed from the 42P panel. I think it would be wise to loop feed the pedestals, so each pedestal feeds the next.
208Vpower-->240v xfrmr--->42P panel-->100A breaker--->pedestal-->pedestal
The loop fed ones will maintain the same wire size through out.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
Do the custom boxes have a UL label?
Electric-Light
Senior Member
What exactly are they?
Many motors are rated 208/230 meaning that either voltage will work and resistive equipment will work fine on 208v, granted at 75% power. It's still 120v between phase to neutral, so if the controls are 120v, they work just fine.
I'm not sure how much portion of total load the pedestrals the boats represent and how they're wired, but in worst case, you will need three single phase 208v to 120/240 center tapped transformer. If they're spread out evenly across the phase, you can't just dump every load onto one phase.
I'm not sure about the legality of using an auto-transformer. While you can get 208v to 240v, it's more complicated when you have to make sure you have 120v between neutral and either hots and that neither hots are floating more than 120v with respect to ground.
Since the 208v service is phase-to-phase, you can't say do something like this:
L1/O1-----C----L2---O2
L=line
O=output line
If L to L is 208v, you will have 120v between L1/O1 to C, and C and O2, but the problem is that "C" won't be at the same potential as the service ground, so you can't just tie that to ground.
Leaving the 120-N-120 with the whole thing floating above ground is absolutely not permissible.
So, it looks like you're gonna have to sucker up for isolation transformer.
I'm not sure how much 120v you have, but do you suppose you can get the utility to convert to 240/120 Delta?
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