Isoboost transformer: how useful?

Does anybody use one of these? They supposedly have all the benefits of an isolation transformer while boosting low shore power voltage from, say, being on the end of a long dock with a lot of other boats competing for power.

My questions: how often do cruisers in the real world see low voltage and how big a problem is it?

When we were in the United States we ran across low power at a number of marinas. Especially at the end slips reserved for visiting boats. It has been years so I don't remember the percentage. The Isoboost helped in those situations.

My reason for installing the unit was to use it as a means of converting European 220 voltage to North American 220 voltage. The European 50 hertz passes through however.

Probably would not have bought one without a specific marina problem in the United States if I hadn't planned on traveling outside of the North American electrical zone.

I had them on my Hatteras courtesy of the PO. They were a terrific thing to have while cruising the length of the east coast, western FL and adjacent waterways and islands. Lots of 208v docks out there, as well as the fact that we were often assigned , or chose, a spot at the very end of the dock. It was nice to never have to think about it. If you don't have a 240v system on board, they're not needed.

You can accomplish voltage boost with switched taps off isolation transformers, but have to remember to switch off the boost when departing; the next dock my have full power.

caltexflanc said:

You can accomplish voltage boost with switched taps off isolation transformers, but have to remember to switch off the boost when departing; the next dock my have full power.

Click to expand...

Thank you both. George, can you elaborate on this? Actually a switch or does it involve physically changing connections?

It is a nice EZ way to bring power to a Euro boat in the USA.

angus99 said:

Thank you both. George, can you elaborate on this? Actually a switch or does it involve physically changing connections?

Click to expand...

It normally involves a switch and a volt meter that reads incoming voltage so you can see whether you need to buck or boost.

Like this, only more vertical. Damn iPhone!

If you do a search through the Hatteras Owner's Forum there are several guys how have done a DIY version of what Bill pictured. The transformer has to be capable of being tapped.
There's no free lunch; whether auto or manual, the watts available stay about the same, so you have less amp capacity than if you were getting the right volts straight from the dock.

This is all really helpful. Even with Active Captain's Defender discount, a 50-amp, 12kVa Charles IsoBoost would dent the budget, given all the other stuff I'm doing.

I'm still unclear about what equipment is at risk from occasional low voltage other than perhaps A/C gear. Trying to think what other 110-V motors I have on board. Other than motors, what's going to suffer that I can't run from the inverter?

What appliances do you have?

caltexflanc said:

What appliances do you have?

Click to expand...

2 AC/DC fridges (which, you're right, include motors), electric stove/oven, microwave, TV and 3 A/C units No washer drier and no ice maker at the moment.

Well, I think it would be really nice to have one. My suggestion is that you go cruising for awhile and see what your real use for one might be. Do you have an isolation transformer now?

caltexflanc said:

Well, I think it would be really nice to have one. My suggestion is that you go cruising for awhile and see what your real use for one might be. Do you have an isolation transformer now?

Click to expand...

Excellent suggestion. Several decisions I made before really cruising would not be made again.

Bay Pelican said:

Excellent suggestion. Several decisions I made before really cruising would not be made again.

Click to expand...

I was lucky when I was an eager beaver newbie to big boat ownership. I was all filled with stuff that various internet experts and boaters I knew, and myself, for that matter, were must haves. The owner of the yard/marina I was at when, and after I bought the boat gave me that very sage advice for about half the things I had on my "List of Improvements". Of course, I was a customer for life from then on.

I also liked another thing he told me when I asked of the "do-ability" of one of my longer term customizations (what scheme it was I don't even remember today):

"George, yes, we can do all that and more. The only limitations are your imagination and your check book".

caltexflanc said:

Do you have an isolation transformer now?

Click to expand...

No, but I may have a deal on a nice one. My reason for starting this thread was to see if the considerably additional money it would take for an IsoBoost is worth it. The dock I'll be on this summer typically gets 208 volts and I'm told A/C use in the summer can run it lower. Trying to get a feel for how big a problem that would be and whether it would jeopardize appliances or equipment.

Bay Pelican said:

Excellent suggestion. Several decisions I made before really cruising would not be made again.

Click to expand...

Good advice from both of you. I'm actually deferring a lot of things and working on basics--new house and start banks, alternators, smart regulators, over current protection and wiring up to code. (My wife wants everything to work. ). For me, additional galvanic and stray current protection are also basic. From what I'm hearing, I'm leaning toward the plain isolation transformer for now.

angus99 said:

No, but I may have a deal on a nice one. My reason for starting this thread was to see if the considerably additional money it would take for an IsoBoost is worth it. The dock I'll be on this summer typically gets 208 volts and I'm told A/C use in the summer can run it lower. Trying to get a feel for how big a problem that would be and whether it would jeopardize appliances or equipment .

Click to expand...

If that is the case it could be a good investment.

Or you could but a boost transformer on the dock.

Capt.Bill11 said:

If that is the case it could be a good investment.

Or you could but a boost transformer on the dock.

Click to expand...

That's a thought; thanks, Capt. I can buy the isolation transformer that I know I want now and see if the need for a boost Xformer materializes. If my math is right, it will actually be cheaper to buy the units separately given the deal I'm looking at on the isolation unit.

I'm still not clear on what the risks are to motors or other AC gear if the voltage is too low. Do they simply shut down or does it damage them?

I have a Charles Iso-Boost and it has helped in at least two marinas in the Baltimore area where the voltage at the end of the t-head was down below what the 240 A/C units would tolerate. A sister boat to ours could not run their A/C units last summer and we could.

The newer Iso-Boost help with the newer shore power GFCI protection. I had to have a soft-start added to ours this winter to make it work.

If you are going to be spending a lot of time on a 208v dock with AC running, I'd advise doing something. Some sort of voltage booster will pay for itself over time in longer equipment life and usability of the boat. Find out if the isotransformer you getting a deal on can be tapped for switched boost. The manufacturer can tell you this and likely give instructions how. Or spring for the boost add on from Charles or Ward's (would be worth giving the latter a call and getting their advice).

caltexflanc said:

If you are going to be spending a lot of time on a 208v dock with AC running, I'd advise doing something. Some sort of voltage booster will pay for itself over time in longer equipment life and usability of the boat. Find out if the isotransformer you getting a deal on can be tapped for switched boost. The manufacturer can tell you this and likely give instructions how. Or spring for the boost add on from Charles or Ward's (would be worth giving the latter a call and getting their advice).

Click to expand...

Excellent. Much appreciated, George.

"I'm still not clear on what the risks are to motors or other AC gear if the voltage is too low. Do they simply shut down or does it damage them?"

Modern AC motors demand a certain number of watts to operate.

V x A = W

So a 120v motor requiring 1200w to operate will draw 10A from the source.

The same motor at 100V will tale 12A from the supply.

AS the voltage drops the amp draw goes UP , yet the wires that make up the motor do not get thicker to handle the higher amps..

After a low enough voltage ,, a better grade motor will pop an overheat sensor , or an internal circuit breaker ,

but the chance is the feared "white smoke" will come out , and the motor will need a rewind or replacement.

IF you can,, always purchase any AC motor "universal wound" meaning it will have brushes in a brush holder.

Will be marked AC/DC.

These are fantastic as feeding them low voltage does not increase the amp draw, it simply makes the motor less powerful.

These are a great yard sale find for power tools for on board work with a non sine wave inverter or small gen set with a low power factor.

Also nice at home where 250 ft of extension cord will still operate a chain saw , just a bit slower.

So here is my take...... A/C units.... even the most sophisticated newer models will accept voltages between 187 and 253 VAC for a 208-230 supply.
As mentioned earlier, when the voltage goes down, more current is drawn. When you are at the bottom of that range, a brownout/surge can have detrimental effects on not only HVAC/refrigeration equipment, but also any AC electronics.

One thing to take into consideration is how often you would be in this situation. Not all owners are subjected to a lot of different voltages, and in their case, I would not recommend the Iso-boost, unless they just wanted it to help with resale value later.
OTOH if they are coastal cruisers visiting many different marinas, I would recommend it.

There are ways to connect your isolation transformer to allow variable "taps". This is a more cost effective approach. That is if the isolation transformer has multiple taps for voltage adjustment. This setup would mean you would check the incoming voltage, set the tap to the proper incoming by a rotary switch prior to turning power on. IMHO this is as good an option as any.

Just my $.02

It is a shame that the isolation transformer folks do not add to their product line.

With little effort the unit could function as a great power supply.

Take DC from the alt , chop it up and reassemble as "house current" for any application'\

With a DC noisemaker the unit would work as well as the new Honda gas units ,
no fixed operating RPM, just enough to supply the load.

And of course they could operate as a boost inverter does , taking juice from the batts to help a rotten dock power source or a tiny noisemaker get that 2nd or 3rd air cond started.

caltexflanc said:

If you are going to be spending a lot of time on a 208v dock with AC running, I'd advise doing something. Some sort of voltage booster will pay for itself over time in longer equipment life and usability of the boat. Find out if the isotransformer you getting a deal on can be tapped for switched boost. The manufacturer can tell you this and likely give instructions how. Or spring for the boost add on from Charles or Ward's (would be worth giving the latter a call and getting their advice).

Click to expand...

I believe Charles sells a 50 amp Isoboost isolation transformer.

Bay Pelican said:

I believe Charles sells a 50 amp Isoboost isolation transformer.

Click to expand...

Yes, I had two of them on my Hatteras. They also sell boost-only for those who already have an isolation transformer and can't, or don't want to, hassle with tapping and switching. Wards makes one too and sells all.

seadogmike said:

So here is my take...... A/C units.... even the most sophisticated newer models will accept voltages between 187 and 253 VAC for a 208-230 supply.
As mentioned earlier, when the voltage goes down, more current is drawn. When you are at the bottom of that range, a brownout/surge can have detrimental effects on not only HVAC/refrigeration equipment, but also any AC electronics.

There are ways to connect your isolation transformer to allow variable "taps". This is a more cost effective approach. That is if the isolation transformer has multiple taps for voltage adjustment. This setup would mean you would check the incoming voltage, set the tap to the proper incoming by a rotary switch prior to turning power on. IMHO this is as good an option as any.

Just my $.02

Click to expand...

Thanks, Michael. Sounds like it's rolling the dice to assume shore power will be adequate and not damage equipment unless I have a boosting transformer.

Unfortunately, the unit that sounded like such a good deal doesn't allow variable taps. So I'm thinking I'll bide my time and ponder this some more.

I have also seen ACME buck and boost transformers advertised as "marine" units that are priced appealingly, but they don't mention ABYC compliance.