Iso boost question

[Dive Girl]

Hi all!

We are in the process of purchasing a new to us 460 Sundancer. It has an Iso Boost. It's a 50amp boat, but some marinas here only offer 30amp power. Can we use 30amp shore power with this Iso Boost, or are we 50amp only?
Thanks!!

 

[hughespat57]

An Iso boost is a 208 or 240 input, it can output both 240 and 120.
But the input is not 120 volt.

A 50A shore connector is based on 208/240 volt four wire, which is two hot and neutral and ground.
Without the transformer, many boats use this as two 120 volt inputs Hot1/Neutral and Hot2/Neutral

there is no simple way to use 30A 120v with a 240v based system.

 

[Jaybeaux]

We just purchased a 48 which is 50 Amp 240 Volt boat....up from a 420 which was twin 30 Amp / 125 Volt boat. I'm sure what @hughespat57 said is absolutely correct, but from a non-electrical guy, what I had to do yesterday when moving the boat into a new slip was to borrow what I called "a combiner". It was two 30 Amp plugs going into the pedestal at 125 volts each. There is a box in this "combiner" where I believe the magic happens. Think of it like the circuit in your house for your electric dryer, which is commonly 240 volts. The take two legs of the 120 and combine them to give you the 240 volts. The only trick is to make sure that they are out of phase (I think that's the way sparkies say it) but that is usually taken care of at the pedestal wiring. Anyway, this is what "I think" I need for traveling when I get put on a slip with only twin 30 Amp recepticals....

https://www.westmarine.com/buy/mari...-to-50a-125-250v-female--10072957?recordNum=5

I'm sure someone much smarter than me will correct me if I'm wrong, but for now, this is what I think I need.

Jaybeaux

 

[ttmott]

We just purchased a 48 which is 50 Amp 240 Volt boat....up from a 420 which was twin 30 Amp / 125 Volt boat. I'm sure what @hughespat57 said is absolutely correct, but from a non-electrical guy, what I had to do yesterday when moving the boat into a new slip was to borrow what I called "a combiner". It was two 30 Amp plugs going into the pedestal at 125 volts each. There is a box in this "combiner" where I believe the magic happens. Think of it like the circuit in your house for your electric dryer, which is commonly 240 volts. The take two legs of the 120 and combine them to give you the 240 volts. The only trick is to make sure that they are out of phase (I think that's the way sparkies say it) but that is usually taken care of at the pedestal wiring. Anyway, this is what "I think" I need for traveling when I get put on a slip with only twin 30 Amp recepticals....

https://www.westmarine.com/buy/mari...-to-50a-125-250v-female--10072957?recordNum=5

I'm sure someone much smarter than me will correct me if I'm wrong, but for now, this is what I think I need.

Jaybeaux

You are right @Jaybeaux
If his boat has an isolation transformer then it will only interface and operate with the primary voltage which for most of our boats is 240 volts (two 120 hot legs out of phase); there is no split 120-neutral-120; that simple. The secondary on the transformer however does split to 120-neutral-120 so both the 240 and 120 devices on the boat operate.
Now, if the marina has dual 120V 30 amp receptacles for your slip (read that for a single slip) then the two 120 hot legs are probably out of phase and will properly operate the iso-boost transformer with the appropriate 'Y' adapter.
I see this occasionally on my boat that has a rather large isolation transformer in small marinas and that is why I carry that adapter.

 

[Jaybeaux]

So @ttmott , to be clear.... the link I posted is the correct adapter that I need when faced with dual 30 Amp pedestal?

 

[ttmott]

So @ttmott , to be clear.... the link I posted is the correct adapter that I need when faced with dual 30 Amp pedestal?

I believe so; you need to verify the 125/250 volt end compatibility with your shorepower cord - two male 30 amp 125 volt to a single 50 amp 125/250 V female. Man that thing is expensive!
It is important that the two 125 volt male plugs are mated with circuits that are out of phase on the dock. Otherwise the transformer will not operate at all. You must be able to measure 240 volts across the two hot legs of the two 30 amp supply at the dock.
I have been to marinas that have multiple 30 amp receptacles at a power pedestal and found out they were all fed from the same phase so that needed 240 volt differential isn't available. There is nothing a boat that has an isolation transformer can do - dead in the water as they say....

 

[The Bill Collector]

I believe so; you need to verify the 125/250 volt end compatibility with your shorepower cord - two male 30 amp 125 volt to a single 50 amp 125/250 V female. Man that thing is expensive!
It is important that the two 125 volt male plugs are mated with circuits that are out of phase on the dock. Otherwise the transformer will not operate at all. You must be able to measure 240 volts across the two hot legs of the two 30 amp supply at the dock.
I have been to marinas that have multiple 30 amp receptacles at a power pedestal and found out they were all fed from the same phase so that needed 240 volt differential isn't available. There is nothing a boat that has an isolation transformer can do - dead in the water as they say....

And that is why I carry over a hundred feet of 30amp cord to feed my 240v addiction in some marinas >> looking for that outlet on a different phase.

 

[The Bill Collector]

$236.99 nevermind they want $200 for shipping

https://www.cvjayaabadi.com/boat-pa...ale-to-2-30a-male-reverse-y-cable-ry504-2-30/

 

[The Bill Collector]

$307.99 + $11.99 shipping

https://www.anchorexpress.com/Marinco-RY504-2-30-50A-Female-to-2-30A-Male-Reverse-Y-Cable-RY504-2-30

 

[ttmott]

An Iso boost is a 208 or 240 input, it can output both 240 and 120.
But the input is not 120 volt.

A 50A shore connector is based on 208/240 volt four wire, which is two hot and neutral and ground.
Without the transformer, many boats use this as two 120 volt inputs Hot1/Neutral and Hot2/Neutral

there is no simple way to use 30A 120v with a 240v based system.

If your boat has an isolation transformer the shorepower neutral isn't used and the ground is only bonded to the transformer's iron core. The shorepower neutral and ground is not and should not be any part of the boat's circuitry. The whole idea of the isolation transformer is to eliminate the instability and spikes that shorepower can transmit as well (and most importantly) eliminate the galvanic electrical connectivity. The below sketch is actually how they are wired (pay no attention to the other wiring; that is my inverter configuration).

 

[hughespat57]

We just purchased a 48 which is 50 Amp 240 Volt boat....up from a 420 which was twin 30 Amp / 125 Volt boat. I'm sure what @hughespat57 said is absolutely correct, but from a non-electrical guy, what I had to do yesterday when moving the boat into a new slip was to borrow what I called "a combiner". It was two 30 Amp plugs going into the pedestal at 125 volts each. There is a box in this "combiner" where I believe the magic happens. Think of it like the circuit in your house for your electric dryer, which is commonly 240 volts. The take two legs of the 120 and combine them to give you the 240 volts. The only trick is to make sure that they are out of phase (I think that's the way sparkies say it) but that is usually taken care of at the pedestal wiring. Anyway, this is what "I think" I need for traveling when I get put on a slip with only twin 30 Amp recepticals....

https://www.westmarine.com/buy/mari...-to-50a-125-250v-female--10072957?recordNum=5

I'm sure someone much smarter than me will correct me if I'm wrong, but for now, this is what I think I need.

Jaybeaux

Your experience explains both things I said.
You had a boat with dual 30A 120v shore power inlets. This is one way as boats got bigger to add more capacity.

The next evolution was to take the same boat, use a 50A 240/120 shore connection as I described where each hot leg is used at 125v with the same split AC panels. The boat would have no real 240v appliances they would all be 120v.

Now more common is 50A 240V with some true 240V appliances for HVAC, stoves, clothes dryers.
This is why the Iso Boost; Commercial power is usually 3 phase 208 Delta, 240V appliances will work but not as well and often with difficulty. So this is an Isolation transformer AND auto-transformer in one. The auto function boosts the 208V up to a full 240V to prevent appliance problems.

Grounding is a whole nother topic.

The adapter for two 30A Female from one 50A Male is half the price because again as I described that ability is alreay there.

The two Male 30A to one 50A Female adapter is inherently dangerous. You have two ends with exposed terminals.
If it was simply a wired Y, and you plugged in the boat or transformer first, then one of the 30A, the other 30A male would have a pin that is live 120V to ground or neutral which is the other two pins.

The special box in the middle is a solid state contactor that disables the cable unless it see 208v or higher from both male 30A.

 

[importmonkey]

A little overlap from another thread...sorry.

Timely thread, as I just learned the marina we are getting into has 208 3 phase at the pedestals. The 560DB has a 240V 50A and a 120V 50A. Pedestals are 208V (3 phase) 50A and a 110V 30A.

How/Where do you mount the booster?

 

[Jaybeaux]

So in our old slip, where the 420 was, we had twin 30 amp service from the pedestal. When we moved the new 48 into the same slip, we "borrowed" an adapter from the marina for a day or two. I noticed during that time, that the Iso-Boost would show that it was boosting the voltage from time to time. This morning, we moved to a slip that has a 50 Amp 240 Volt pedestal and I have not seen the Iso-Boost indicate boosting. I chalked it up to dock demand and connection issues, FWIW.

Jaybeaux

 

[importmonkey]

So in our old slip, where the 420 was, we had twin 30 amp service from the pedestal. When we moved the new 48 into the same slip, we "borrowed" an adapter from the marina for a day or two. I noticed during that time, that the Iso-Boost would show that it was boosting the voltage from time to time. This morning, we moved to a slip that has a 50 Amp 240 Volt pedestal and I have not seen the Iso-Boost indicate boosting. I chalked it up to dock demand and connection issues, FWIW.

Jaybeaux

Do you have any pictures of the booster setup?

P.S. Well done on the 48, btw!

 

[Shaps]

So @ttmott , to be clear.... the link I posted is the correct adapter that I need when faced with dual 30 Amp pedestal?

@Jaybeaux
That is the adapter I use and take with me when I travel.
The "Reverse Y"
and as others have said, each 30 amp leg needs to be in a different phase.

 

[Dive Girl]

Wow! Thank you so much!! You are all wonderful!
We are moving the boat to a new "slip boathouse. It has 2 30amp female outputs on the wall wired to a circuit breaker box. We think they are on separate phases. We have the adapter that Jaybeaux linked to. I guess we should verify if the 30 amps are really on separate phases. Thoughts?

 

[Shaps]

@Dive Girl
if you plug that adapter into the 2 30 amp outlets and the red light on the box is illuminated, you should be good to go.
Definitely think worth knowing BEFORE you put your boat in the slip.

 

[Dive Girl]

@Dive Girl
if you plug that adapter into the 2 30 amp outlets and the red light on the box is illuminated, you should be good to go.
Definitely think worth knowing BEFORE you put your boat in the slip.

Yes, we are hoping we don't have to re-wire the house to add the 50amp!!