On Aug 17, 5:07 pm, Richard Kollmann
wrote:
Skip, I did estimate that the total load on your boats DC electrical
grid daily could exceed 200 amp-hrs. This estimate was based on you
removing the on board generator and providing AC power from an
inverter. The amp-hr estimate was based on experience with other boats
in the 46 foot range having similar energy consuming equipment, with
true refrigerator and separate freezer operated at low temperatures.
The boat was intended to be used for extended cruising in tropical
waters. In addition to refrigeration daily power consumption there is
typically an additional 50 amp-hours per day when at anchor. During
the concept design phase you should be able to project the size of the
DC power grid and size the alternator and sources of alternative
energy to replace daily the amp-hours used. It Sounds like you do have
an adequate power grid although I have no information on equipment
sizes.
If you have read the refrigeration study done by Cruising World some
20 years ago comparing manufactures equipment you will see my box Btu
heat loads are 50% higher than the others, that's because I use real
world conditions projecting daily product through put and tropical
conditions.
Here are the guidelines I use to project daily Btu and the amp-hours
needed for refrigeration on any sail boat:
1.All calculations are based on worst case tropical waters of 86
degrees and ambient air temperature of 90 degrees at midnight.
2. Refrigerator box insulated with 3 inches of moisture free
polyurethane and freezer to have at least four inches of polyurethane.
3. Each cu ft of refrigerator will require 600 Btu per day of heat
removal while each cu ft of freezer will require 1200 Btu removal per
day.
4. For each person above two onboard add an additional 1000 Btu
daily.
5. Refrigerator temperature maintained at 33 degrees bottom to 40
degrees at top, Freezer temperature 6 degrees bottom 22 degrees at
top.
For more detail on this see the slide show on my web site.
The amperage to remove this amount of heat will depend on type
refrigeration unit used and the efficiency of the refrigeration's
condensing unit.
Seawater temperature against the hull of a sailboat has a major affect
on cabin and refrigerated box temperature. I developed a correction
factor to my tropical daily power consumption. When the cruising area
water temperature is cooler than 86 degrees the daily amperage in my
estimate can be reduced 2% for each degree of cooler seawater.
Projected power consumption
I will list a chart of typical onboard electrical equipment you might
have on board so you can get an idea of what each piece draws, then by
adding the hours each item is used per day you can see how many amps
are needed daily to replace what is consumed.
First Skip's refrigeration. Six inches of polystyrene is equal to
four inches of polyurethane that OK.
Refrigerator 7 cu ft in tropical waters 4200 Btu per day, 3.5 cu ft
freezer 4200 Btu per day Total daily Btu heat removal required 8,400.
Estimated daily power consumed in tropics by Frigoboat Capri 50 with
SSC controller 120 to 140 amp hours depending on average speed of
compressor. Correction factor to refrigeration consumed in ocean off
New York where water is at least 15 degrees cooler today 84 to 98 amp-
hrs per day.
All other electrical equipment requiring current from DC power grid is
listed in watts per hour. Total all watts and divide by 12 to get DC
amps. AC 110 volt items to be operated by inverter increase by 10 % do
to inverter efficiency. The inverter manufacture may advertise 5% but
that is based on minimum current draw.
One Lap top computer 55 watts
Portable vacuum 506 watts
Coffee Maker 60 watts
Compact Microwave 935 watts
Anchor Light 12 watts
Steaming light 12 watts
Running lights 40 watts
Bilge Pump 50 watts
Fresh water pump 80 watts
Ham or SSB receive mode 30 watts Transmitting 300 watts
Weather Fax 30 Watts
Dept and speed log 12 watts
Radar 50 Watts
Windless 1000 watts
Spreader lights 90 watts
Auto pilot 50 watts
Florescent lights 10 watts
Cabin lights, radio, Water maker, or TV unknown watts
On Aug 17, 5:07 pm, Richard Kollmann
wrote:
Skip, I did estimate that the total load on your boats DC electrical
grid daily could exceed 200 amp-hrs. This estimate was based on you
removing the on board generator and providing AC power from an
inverter. The amp-hr estimate was based on experience with other boats
in the 46 foot range having similar energy consuming equipment, with
true refrigerator and separate freezer operated at low temperatures.
The boat was intended to be used for extended cruising in tropical
waters. In addition to refrigeration daily power consumption there is
typically an additional 50 amp-hours per day when at anchor. During
the concept design phase you should be able to project the size of the
DC power grid and size the alternator and sources of alternative
energy to replace daily the amp-hours used. It Sounds like you do have
an adequate power grid although I have no information on equipment
sizes.
If you have read the refrigeration study done by Cruising World some
20 years ago comparing manufactures equipment you will see my box Btu
heat loads are 50% higher than the others, that's because I use real
world conditions projecting daily product through put and tropical
conditions.
Here are the guidelines I use to project daily Btu and the amp-hours
needed for refrigeration on any sail boat:
1.All calculations are based on worst case tropical waters of 86
degrees and ambient air temperature of 90 degrees at midnight.
2. Refrigerator box insulated with 3 inches of moisture free
polyurethane and freezer to have at least four inches of polyurethane.
3. Each cu ft of refrigerator will require 600 Btu per day of heat
removal while each cu ft of freezer will require 1200 Btu removal per
day.
4. For each person above two onboard add an additional 1000 Btu
daily.
5. Refrigerator temperature maintained at 33 degrees bottom to 40
degrees at top, Freezer temperature 6 degrees bottom 22 degrees at
top.
For more detail on this see the slide show on my web site.
The amperage to remove this amount of heat will depend on type
refrigeration unit used and the efficiency of the refrigeration's
condensing unit.
Seawater temperature against the hull of a sailboat has a major affect
on cabin and refrigerated box temperature. I developed a correction
factor to my tropical daily power consumption. When the cruising area
water temperature is cooler than 86 degrees the daily amperage in my
estimate can be reduced 2% for each degree of cooler seawater.
Projected power consumption
I will list a chart of typical onboard electrical equipment you might
have on board so you can get an idea of what each piece draws, then by
adding the hours each item is used per day you can see how many amps
are needed daily to replace what is consumed.
First Skip's refrigeration. Six inches of polystyrene is equal to
four inches of polyurethane that OK.
Refrigerator 7 cu ft in tropical waters 4200 Btu per day, 3.5 cu ft
freezer 4200 Btu per day Total daily Btu heat removal required 8,400.
Estimated daily power consumed in tropics by Frigoboat Capri 50 with
SSC controller 120 to 140 amp hours depending on average speed of
compressor. Correction factor to refrigeration consumed in ocean off
New York where water is at least 15 degrees cooler today 84 to 98 amp-
hrs per day.
All other electrical equipment requiring current from DC power grid is
listed in watts per hour. Total all watts and divide by 12 to get DC
amps. AC 110 volt items to be operated by inverter increase by 10 % do
to inverter efficiency. The inverter manufacture may advertise 5% but
that is based on minimum current draw.
One Lap top computer 55 watts
Portable vacuum 506 watts
Coffee Maker 60 watts
Compact Microwave 935 watts
Anchor Light 12 watts
Steaming light 12 watts
Running lights 40 watts
Bilge Pump 50 watts
Fresh water pump 80 watts
Ham or SSB receive mode 30 watts Transmitting 300 watts
Weather Fax 30 Watts
Dept and speed log 12 watts
Radar 50 Watts
Windless 1000 watts
Spreader lights 90 watts
Auto pilot 50 watts
Florescent lights 10 watts
Cabin lights, radio, Water maker, or TV unknown watts
Hi, Richard, and thanks for the detail.
A couple of clarifications for calculation. I believe I may have
misspoken about the insulation. I used the extruded, very hard,
stuff, available in either pink or blue. Mine was pink. I think it
was polyurethane - in any case, it had an R value just slightly less
than that of polyisocyanurate, but not the water absorption problems.
Even so, I coated each piece with epoxy before assembly, and used
epoxy in the staggered joints (I used 2" and 4" pieces) as well, in
order to make the longest possible path for heat intrusion.
And, I see above one glaring difference - we never considered an AC
reefer system, nor air-cooled, nor waterpump-dependent as well. We
originally thought we'd wanted cold plates but decided against it for
the very accurate control an evaporator system could provide.
Our reefer and freezer are pretty uniform in temps due to the
circulating fans; the reefer we keep at 35, and the freezer at 8. The
fans are under .1A, and the LEDs which come on when the door is opened
are similar - about .07, actually.
All the heat extraction is done by the evaporator plate in the
freezer. I had to stuff the return in the spillover due to stuff
freezing in the reefer; it's extraordinarily efficient, and had I
known, I'd have used a much smaller fan for the spillover and a
correspondingly smaller return. As it is, the only air exchange is
through a very tightly stuffed t-shirt, the original design being the
same square inches of return as the fan, the fan being centered in the
wall (per engineering by SALT, the vendor, on my system specs), and
the return at the top, being an inch of depth in the entire width of
16.5". That tightly wedged cotton cloth seems to allow just air
enough exchange to make it stay cold, but not freeze, and reaches the
desired temp quickly despite the barrier, when new stuff is added.
My SSC usually runs at very low power, per the design (the computer
taking your resistors' trick to the ultimate, learning how long it
took to cool the last couple of times, and running at the lowest
possible speed), but for longer periods. Generally speaking, unless
I've put a half-gallon of warm water in to freeze (we then put regular
tank water in the frozen, making extremely cold water for the frig,
and the ice lasts for days that way), the freezer's right on target,
and even then it gets to temps very quickly, as I don't put the water
up against the probe, but instead against one of the sides of the
evaporator.
So, until I put up our energy audit, which will have all the details,
I'll just say that nearly every lamp aboard is either fluorescent or
LED, with most LED, and similar efforts in the other areas of power
consumption. I've also gone to the effort of isolating the various AC
devices, in order that none be on unless desired, or with ample input
of power (such as now, with the engine running and the batteries full,
or the batteries full and a piping wind outside), with each left
connected to power but with separate switching for convenience. So,
we anticipate (and so far are finding it so) that we'll have a pretty
reasonable power management scheme.
And, as you don't know, we have 370w of high-volt solar through an
MPPT controller, a KISS wind generator (running through a Xantrex C40,
with overload to a heat strip but a lamp to tell us so in order for us
to use the load more effectively, such as running stuff as above), and
for the times when it's a disaster outside, a Honda EU2000i to connect
to the shorepower which can then drive all the AC devices as well as
the 40A Xantrex TruCharge40 bought to replace the dead (well, presumed
dead - it didn't look healthy) NewMar 70A shorepower charger (and, of
course, the 94A alternator). Those are the only sources of power; we
hope to be in a marina as infrequently as possible, the last several
weeks being a horrible anomaly :{)) For example, we're currently
aside the free dock across from Atlantic Yacht in VA just under the
bridge. Free wifi, and our own power...
The one huge difference from your stuff, otherwise, is the monster
laptop that Steve at SeaTech sells to the unwitting buying his nav
package. That sucker draws 10 amps, and so I'm now in the process of
weighing tossing that and buying what I wanted to get in the first
place - a very energy efficient laptop. By contrast, Lydia's takes
3.5A. I dare say I could run my 2.9A 21" LCD (for movies) and a
desktop on less power...
Let me know if the above moderates your expectation on the reefer
load, and I'll come back in a week or so, once I've landed in NYC,
with my inventory and some RW experience under way. (We're headed for
Norfolk tomorrow, and as soon as we have the weather in hand and
satisfactory, we're out to sea until Sandy Hook.)
L8R
Skip
Morgan 461 #2
SV Flying Pig KI4MPC
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