Installation of Power Inverter on a Egg Harbor 41SF

I decided to install a power inverter on my boat mainly to save generator-hours. When fishing for seven hours or cruising to the islands, I have to operate the 5.5 KW generator just to run the 275 watt refrigerator and perhaps 200 watts if ice maker. This is a large waste of diesel fuel along with generator hours (oil and filters), more heat in the engine room and the risks of generator failure while underway.

It is not easy task to select the correct size/type inverter that ensures the system (battery/inverter/load) will operate satisfactory.

The following questions need to be asked for a proper selection of an inverter:

1. SELECTION OF ELECTRICAL LOAD: You must decide which appliances will be running with the inverter. If your load includes AC motors, such as the refrigerator, freezer, ice maker, vacuum cleaner, or no motor loads, as in TV set’s, VCR’s. computer, fax, coffee maker, microwave, lamps, DC universal motors (drill, hair dryer, etc) or a combination of both types.
2. TOTAL WATTS: Add total nominal watts of select electrical load.
3. CHOOSE TYPE OF INVERTER: In the market today, there are mainly two types of power inverter operation, both with or without charger. Select the one more suitable for your type of load. APPROVED FOR MARINE USE.

• Modified sine wave (MSW). Recommended for loads that are not sensitive to the quality of signal, not AC motors. It has efficiency of 95%.
• True sine wave (TSW): Recommended for all types of loads, but mainly when there are A/C motors in operation. It has an efficiency of around 90%. It’s cost are considerably higher then the MSW type.

1. SELECTING INVERTER SIZE (Nominal Watts): For AC motor load, use four times the nominal watts. For example; The 250 watt refrigerator you would need a 1000 watt true sine wave inverter or 1500 watt modified sine wave (MSW requires more power due to harmonic distortion that affects starting torque on AC motors). Carefully review the efficiency curves and the temperature de-rating curve that is provided by the manufacture.

• EFFIENCY: This is the percent of AC power obtained from a DC source. This means that your 1500 watt unit at 90% effiency, rquires 1666 watts from a good 12 volt DC source (See effiency graph "A" further back)
• TEMPERATURE: Previous effiency is obtained at 30 degrees C or bellow. But is the ambient temperture rises to 50 degrees C, your unit looses 20%, so your 1500 watt inverter is only good for 1200 watts. (See temperature graph "b" further back in article)

1. BATTERY SIZE: You must decide which battery in your boat will run with your inverter. You will need to calculate your AMP-HOUR capacity of your battery for the laod selected. (See Battery Size "C" further back in article). Manufactures recommend Deep Cycle batteries for long run operation.
2. STANDBY IDLE CURRENT: It is important that your inverter saves battery draw when in low idle current, when at standby or on sleep mode operation. In the past the TSW inverter was thirsty in idle current (no load), compared with the MSW inverter. Today new TSW with sleep mode operation, draws only 1.5 watts DC.

• Electrical load selected = AC refrigerator and/or AC Ice Maker.
• Total Watts = 475 normal running operation
• Inverter type and size = TSW 1000 watts Prosine 1000 no charge and two GFCI receptacles. Approved for Marine Use
• Efficiency = 88.2% at 475 watts
• Ambient Temperature = Never higher than 30 degrees C (no loss of efficiency)
• Battery size = One 8D – 1300 Cranking amps 380 amp-hour reserve.
• Sleep mode = Yes

After this study and physically seeing many units shown at the Miami Boat Show, I purchased STAPOWER PORSINE 1000 without transfer switch. I prefer a TSW inverter, even it’s efficiency is only 88%. More information on Stat Power Inverters click here: http://www.aapspower.com/prosine1000.html

The unit is strong made with full protection and alarms for all type of DC and AC failures. A convenience digital display shows DC voltage, DC amps drawn for the battery, watts supplied by the inverter and ON/OFF switch, plus sleep mode operation. Thermal operated fan and two GFCI 15 amp receptacles. Approved Marine Use (See spec’s further back in article).

The inverter was installed under the galley hatch, vertically against the wood wall (see photo). This place is convient because takes no space and it is close to DC bars panel for the length of battery cables (less then 4 feet). Temperature in this area never should go about 35 degrees C.

REMOTE DISPLAY: This is an option. Standard display comes maounted in the unit. I installed the remote display with the ON/OFF switch in the galley at the top of the water level meter. (See photo).

BATTERY CABLE: #2 AWG, Red and black, 4 feet of ea. (see Photo)

FUSE: One 100 amp fuse to protect the battery from the inverter. I installed fuse inside electrical DC panel at engine room (see photo)

AC CABLES: 3 cables #12 AWG marine grade from the inverter to the electrical panel. Approx. 3 x 20 feet cable.

TRANSFER SWITCH: A two-way switch with 9 positions to connect phase-neutral-ground load from shore/gen or from inverter. Contact ratings 15 amps. I installed at electrical panel (see photo). A 120 VAC pilot light at the panel shows AC voltage OK at the transfer.

Note: You can buy the unit with the transfer relay incorporated, this makes installation less complicated, (no GFCI receptacles), but then you have to run cables from the electrical panel to the inverter and then back from the inverter to the electrical panel. It allows operating the inverter automatically, any time there is not AC power from shore or gen, even if you are not on the boat and the inverter is on.

AC CONNECTION ON ELECTRICAL PANEL: On the Egg Harbor electrical panel, all the AC loads are connected to a two electrical copper bars that operate either with SHORE or your GEN. The selected loads for the inverter have to be electrical isolated from this bar, otherwise the inverter will be connected to full bar AC load. This requires isolating the select load breakers from the copper bar, so they can be connected to the transfer switch. It is essential that transfer switch also isolates NEUTRAL and GROUD, otherwise the GFCI receptacle trips. I use on AC receptacle for refrigerator and icemaker, the other one is ready to use in case of emergency for lamps, drill or coffee maker, etc.

OPERATION EXPERIENCE: Under operation, the refrigerator takes 140 amps during starting for one second and 18 amps running. The ice maker takes 90 amps during starting for one second and 16 amps running. In normal operation both units draw 34 DC amps from the battery. While fishing or cruising with engines running, I operate both appliances without discharging the battery, since the engine alternator is rated to 50 amps. It is recommended that the select battery is in good condition. I placed a new 8D battery.

So far I am happy with the performance of the unit. No maintenance required only need to keep clean the air intake of thermal fan (once a year).