T&T: Buck/boost transformers
Milt Baker
From time to time I take my Nordhavn 47 to docks were the power starts from a nominal 208-volt connection for my 50-amp service and goes steadily downhill. By the time it reaches the boat, especially when the weather is hot and there's lots of demand for air conditioning on the piers, voltage coming onto the boat is often down to 200 volts, sometimes less. Knowing this is playing havoc with some of my onboard systems such as air conditioning compressors, I'm seeking a way to boost the voltage by about 10% so a nominal 208 volts would be boosted to (208 + 20.8) about 229 volts and even a puny 199 volts would be boosted to (199 + 19.9) about 218.9 volts.
One suggestion has been to install a Charles SmartBoost 12kVa (50 amp) universal AC voltage booster designed to increase incoming AC shore power voltage. When dockside power drops below 210 VAC, SmartBoost provides a 15% AC voltage boost to any existing 50 AMP straight transformer. However, this unit is big (close to 13 x 13 x 9 inches), heavy (50 lbs) and expensive ($5,637 list). Charles also offers a Universal AC Voltage Booster which, according to the company website, could be used with my existing isolation transformer and "provides a 13% AC voltage boost to any existing 50 Amp straight transformer when dockside power drops below 208 VAC." It's equally big and heavy though a bit less pricey: 13 x 13 x 9 in., 50 lbs., $2,444 list.
I'm thinking there's likely a better choice, preferably something smaller, lighter and less expensive. Since my main AC power consumers are my air conditioning compressors and I almost never need more than about 30 amps at 240VAC, why not use a run-of-the-mill buck/boost transformer such as a Federal Pacific FT2007? This transformer is just 6.5 x 5.25 x 11.25 in., 28 lbs., would be satisfactory for a draw up to 41.67 amps at 208 VAC, and is available from TEMCO for $196. See http://temcoindustrialpower.com/products/Transformers/FT2007.html
Frankly, this seems too good to be true. By going with a transformer like the FT2007, I'm wondering what what I'd be giving up, other than automatic switching which I don't really need? (If I see the incoming voltage is low, flipping a switch to go into boost mode is well within my capabilities.) Said another way, why are people paying more than 10 times the money to buy the Charles products above when it appears something far simpler will more than do the job?
For the record a buck/boost transformer is definitely something I'd have professionally installed. I know my limitations!
Many thanks for any ideas and insights,
--Milt Baker, Nordhavn 47 Bluewater
A 12 kVA isolation transformer is provided for the SHIPS SERVICE connections that transfers the 240 VAC input forward and boosts the 120 VAC input to 240VAC when connected to the 120 VAC connections. The 240VAC AIR CON connections at each location is a dedicated power supply to the 240 VAC 50/60Hz AIR CONDITIONING SERVICE panel. The shore power circuit breakers, rated for 60 amps (240 VAC) and 30 amps (120 VAC) are located inside enclosures in the guest cabin overhead (FORWARD connections) and in the lazarette starboard side (AFT connections).
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Adam Block
SmartBoost 50A for much cheaper. Here it is for $1,400:
http://www.marinedeal.com/product_p/93-smtbst50-a.htm
Also, Mark Knoll has one of these installed on N47 Sandstone and I think he
has had good results. He installed it under the port side drawer at the
front of the pilothouse settee (the one where the manuals go). He had the
bottom of the drawer raised by a cabinet maker so the drawer slides over the
SmartBoost.
It's worth noting that you'd need two transformers, one for your regular
shore power and one for the A/C service connection, if you wanted to
normalize voltages on both inlets.
/afb
On Tue, Oct 19, 2010 at 12:40 PM, Milt Baker <milt...@mindspring.com>wrote:
>
> One suggestion has been to install a Charles SmartBoost 12kVa (50 amp)
> universal AC voltage booster designed to increase incoming AC shore power
> voltage. When dockside power drops below 210 VAC, SmartBoost provides a 15%
> AC voltage boost to any existing 50 AMP straight transformer. However, this
> unit is big (close to 13 x 13 x 9 inches), heavy (50 lbs) and expensive
> ($5,637 list). Charles also offers a Universal AC Voltage Booster which,
> according to the company website, could be used with my existing isolation
> transformer and "provides a 13% AC voltage boost to any existing 50 Amp
> straight transformer when dockside power drops below 208 VAC." It's equally
> big and heavy though a bit less pricey: 13 x 13 x 9 in., 50 lbs., $2,444
> list.
Marc Slemko
a combination isolation transformer and automatic boosting transformer. It
weighs a whole lot more than 50 pounds (200 maybe?) and is very $$$. Their
SmartBoost Universal A/C Voltage Booster is presumably just a buck boost
transformer with some automatic switching, and is a lot cheaper but still
expensive compared to a normal transformer, especially since it doesn't need
the specific safety features that a marine rated isolation transformer needs
so there is less reason to have such a markup.
A buck boost transformer is a great solution, assuming you either don't want
an isolation transformer (eg. are happy with a galvanic isolator) or already
have one and you are functional enough to properly turn it on or off.
I would strongly recommend you pick one which is rated appropriately for 50
amps of input, there is no reason to skimp. I don't think 1 KVA quite cuts
it. I used an Acme T-1-11684, which is rated for 1.5 KVA which translates
into around 15KVA of boosted power aka around 62 amps. You should be able
to pick on ebay or at a surplus store for around $150. Federal Pacific may
have a 1.5 KVA option too, look around to see what the best deal you can get
is, they aren't complicated or rare things.
Acme has some good documentation about buck boost transformers in their
catalog:
http://acmepowerdist.com/pdf/acme_fullcat.pdf
...starting on page 104, including a section on how they work and are rated,
and a selection guide for sizing.
The wiring can be slightly annoying and you have to make sure to get all the
details right and think about just how you are going to switch it in and out
of the circuit, but the concept is fairly straightforward.
On Tue, Oct 19, 2010 at 12:40 PM, Milt Baker <milt...@mindspring.com>wrote:
Al Thomason
purchase a local Boost transformer and have it wired into a box that you can
set on the dock. Just put on the 50A connectors on each end. This would
provide a solution to the '3-phase 208V issue' without carving up your boat.
If however you travel to a lot to many docks, then perhaps one of the auto
selecting solutions would be a good investment. . . .
-al-
Jim Healy
This problem is caused by the electrical distribution system installed at the
marina. Instead of a 240VAC single phase, center tapped service, which gives
the North American standard voltages of 240VAC and 120VAC, the marina is wired
with three phase wye-connected service, which gives 208VAC and 120VAC. This
is common in light commercial buildings, townhouses/condos, etc., but in that
case, the household appliances are made for 208VAC services. You will
encounter both types of services if you cruise, so it's really a problem you
have to own.
The buck/boost transformers are an elegant solution for the problem.
Piggy-backable inverters can also be used if the battery bank can handle the
loads. Both solutions are bulky and expensive. If you know that you never
draw more than 30 amps on the 240VAC side, what you propose seems fine to me.
***Check that the Fed Pac transformer has an isolated ground shield. If it
does not, it does not meet ABYC standards.*** Reference the 2009 E-11
Standard for an explanation of that requirement.
If this is your 'home marina' where you stay for long periods of time, you
might want to take it up with the marina manager, because all 240VAC motors
(compressors, pumps, blowers, etc) are compromised, and unless you can monitor
incoming shore power, there's no way for you to know what you have. Prolonged
operation in this state will overheat the motors and shorten their service
life, especially if there are brownouts that reduce the nominal 208VAC even
further. I would think marinas would get into law suits over this stuff.
Jim
Peg and Jim Healy aboard Sanctuary
Currently at Rock Creek, Pasadena, MD
Monk 36 Hull #132
MMSI #367042570
AGLCA #3767
MTOA #3436
Joseph Pica
Instead of a 240VAC single phase, center tapped service, which gives
the North American standard voltages of 240VAC and 120VAC, the marina is
wired
with three phase wye-connected service, which gives 208VAC and 120VAC. This
is common in light commercial buildings, townhouses/condos, etc., but in
that
case, the household appliances are made for 208VAC services. You will
encounter both types of services if you cruise, so it's really a problem you
The upstream city marina(managed by Marina Max) on the Tennessee River in
Chattanooga was wired that way. Several boats could not get power passed
thru by the invertors or recognized by smart "Y"s. As I have dual invertors
(expensive as pointed out by Jim) with a power assist function I was able to
get power once I set them to recognize the three phase 120 degree sine wave.
So far, I have encountered that only at one other marina in Canada,
(Pentanguishine). I think the problem is not that wide spread based on our
experiences. But you may be stuck if you only have one available marina.
Good luck.
Joe
Carolyn Ann
GH N-37
A H FOSTER
To: Trawlers and Trawlering List
<trawlers-an...@lists.samurai.com>
Subject: T&T: Buck/boost transformers
OK, guys, this one is above my paygrade, and I'm looking for advice and
counsel. Help me out of my ignorance!
>snip<
Frankly, this seems too good to be true. By going with a transformer like the
FT2007, I'm wondering what what I'd be giving up, other than automatic
switching which I don't really need? (If I see the incoming voltage is low,
flipping a switch to go into boost mode is well within my capabilities.) Said
another way, why are people paying more than 10 times the money to buy the
Charles products above when it appears something far simpler will more than do
the job?
For the record a buck/boost transformer is definitely something I'd have
professionally installed. I know my limitations!
Many thanks for any ideas and insights,
--Milt Baker, Nordhavn 47 Bluewater
I can see no reason it wouldn't work. On the boat I run we have 2 buck/boost
transformers. One for each incoming 100a line. One boosts automatically and one
I have to push the boost button when needed.
Capt. Bill
Currently in Shelter Bay Marina Panama
R C Smith Jr
wrote:
> why not use a run-of-the-mill buck/boost transformer
Milt, the Hatteras 58 Long Range Cruiser had two buck-boost transformers as
standard equipment. While one transformer was replaced by a prior owner, the
second, which I believe was original, died recently after 33 yrs of service.
It is an Acme product:
http://www.acmepowerdist.com/products.asp?PAGE=prod_landing.html
Other than to say (1) the boosting transformer worked well in practice
boosting 208 to 240v and (2) the Hatteras electric panel has a manual switch
to engage the boost, I am, as usual, blissfully ignorant of such highfalutin
electrical doohickeys.
Bob
________________
Robert Calhoun Smith Jr in DC
M/V MARY KATHRYN
Hatteras 58 LRC
Lying South River
Annapolis, MD
Marc Slemko
***Check that the Fed Pac transformer has an isolated ground shield. If it
> does not, it does not meet ABYC standards.*** Reference the 2009 E-11
> Standard for an explanation of that requirement.
>
>
I don't believe that using a buck boost transformer is covered specifically
by E-11. The only requirement I recall for an insulated shield (that can
carry a full fault current) is when using a transformer as an isolation
transformer that isolates the (green) grounding conductor. The shield is
not required for a polarization transformer, which is wired similarly to an
isolation transformer but only isolates the current carrying conductors and
not the grounding conductor.
The isolation transformer can protect against galvanic currents, reverse
polarity and neutral drop out on a 240V setup, while the polarization
transformer only protects against reverse polarity and neutral drop out but
not galvanic currents.
A buck boost transformer is neither of these and protects against none of
these conditions as it does not carry the full load, hence why it is be
smaller and rated for a lower capacity. The grounding connector absolutely
needs remain connected in this case.
The requirement for the insulated shield on an isolation transformer is what
makes it so expensive to buy an isolation transformer since it isn't a
feature commonly found on industrial transformers so you are limited to a
couple of expensive options.
I forgot to mention in my previous note that 10% is an "ok" boost but the
15% that the Charles provides is better matched to this situation. I
decided it wasn't worth the extra cost to me as my home marina has a 208V
setup with very little voltage drop even under peak load.
Milt Baker
I'd like to single out David Sidbury, owner of the Northavn 68 Grace of Tides, who (offline) gave me book-chapter-verse and parts list for constructing a portable boost transformer apparatus that will plug in between the shorepower cord and the yacht's 50 amp inlet and provide boosts of 24 volts, more than sufficient for my needs. Wards Marine Electric sells one for $1700 that's a lot like what David described; it looks like the parts to build a comparable one can be had for a little over 1/3 of that.
Again, my thanks to everyone who contributed to increasing my knowledge on buck/boost transformers!
--Milt Baker, Nordhavn 47 Bluewater, Fort Lauderdale
Milt Baker
A friend was shopping Fort Lauderdale's inimitable used marine gear emporium, Sailorman, yesterday morning and came across a used Wards Marine Electric portable booster transformer. The asking price was $1200, but with a little four-way negotiation (Sailorman-owner-friend-myself) the seller came down to $500 and I bought it, tested it on the pier, and pronounced it perfect for my needs. It goes between the shorepower outlet on the pier and inlet on my boat, handles 50 amps at 190 to 240 volts, and boosts the voltage 10%, meaning I can boost 200 amps to 220 and 208 to about 229--no manual override so voltage is boosted 10% regardless of input voltage. The sucker is heavy (I estimate 30-35 lbs.) but I think it's perfect for my needs. And at $500 it came in at close to the same price as the parts for building a new one.
The good news is that there was another identical used one offered by the same seller at Sailorman. If you're interested, call 'em at 954-522-6716 and tell them you want the one just like item number C6588-1 I bought yesterday. It's my guess the seller will let it go at the same price but YMMV. Shipping will be expensive because of the weight and I cannot say whether Sailorman will ship so that's definitely something to ask about.
Again, thanks to everyone for all the help.
Milt Baker
For the record, this transformer has no selector switch of any kind. As I said in my post, no manual override so voltage is boosted 10% regardless of input voltage. In other words, one uses a device like this at one's own risk and pays attention to the input voltage before hooking up. I like to carefully monitor input voltage for the first 24 hours I'm plugged in to a new shorepower situation and after that I relax a little.
As my good friend Scott Flanders often says in his great Voyage of Egret blog, you get the picture. My apologies if I misled anyone.
--Milt
Dennis wrote:
I think Milt Baker needs to brush up on his electrical knowledge, you cannot
boost 50 amps up to 200 plus with that transformer,also, the transformer should
have a
selector switch to select the voltage of the shore power you are connected to,
if you want to have 240 V when connected to 208 shore, then the switch will be
set
to 208 and then it will boost to 240. if connected to 240, set the sw. to 240
and no boost will take place, if the transformer will automatically boost any
input voltage by a set % then you are at risk of overboosting 240 input.