Inverter Install Question

[GonzoF1]

Hello again everyone!

Ok, so... After my full DC system upgrade (and y'all were a huge help... thanks), we have taken the boat out to anchor a few times and realized we could probably use a small inverter to power a couple of fans in the bedroom while we sleep and the TV/Roku. Maybe give us a few other conveniences too like coffee in the morning. Nothing major like a microwave though. For that, we will fire up the genny.

I am thinking of getting a Victron Phoenix 800-1000 watts and even that might be a little larger than I need. My panel has two breakers that I assume are 20A that power all the 120V outlets throughout the boat (there are 10 outlets total). My question is: How do I energize just those two breakers with an inverter-only unit? Will there need to be a sub panel of some kind with wires to the current breakers? Or this less appealing way... Do I need to energize the entire 120V side of the bar and turn off the breakers/systems I don't want?

Below is a picture of my panel for no particular reason. The outlet breakers are at the top of the far left column.

Thanks y'all!

 

[Stu Jackson]

Gonzo, there are many different ways to do what you propose.

Essentially, your choices are two:

1. Wire everything to the AC side of the inverter - this requires you to MANAGE the use to keep demand within the size of the inverter

2. Wire only selected outlets - this minimizes management chores, but requires additional wiring and/or a subpanel

Almost all inverter manuals show myriad methods of wiring. I know my 1998 Heart Freedom 15 manual certainly did.

You also have to (i.e., MUST) know if the inverter you get has an ATS. If not, you'll need a manual one to absolutely make sure shorepower and inverter are never on at the same time.

Good luck, be careful. If you don't know 120V AC find someone reliable who does.

 

[Benny17441]

There is a couple of things to bear in mind, an inverter is most efficient when the size of the load is matched to the output of the inverter. I would look at the items or combination of that I would most frequently like to run and would consider to size the inverter a tad above that (the efficiency gains are just a few percentage points but if the inverter will be used frequently then the Ah usage will add up). I would also weigh my interest in perhaps running a large item like a microwave against sacrificing some efficiency(once again this would depend on how frequent are you going to use the inverter). Also when considering the items you want to operate, you want to consider their task and running time. A microwave oven when ran for 20 seconds to heat something will use significantly less battery power than an electric coffee maker which will draw power for minutes. The battery/inverter system will run a TV and a Roku adapter real good but might have a problem running household fans. The electric motor driven fans consume a large amount of power and may require up the 3-5 times their rated power just to start and they are usually ran for hours. LED bulbs are good but heaters are any other resistance appliance are not. I would suggest to perhaps do a little homework about sizing the inverter before committing to one.

 

[Stu Jackson]

Benny just gave me a thought.

Turning the generator on to rn the microwave seems a tad wasteful to me. Why? 'Cuz I put in an inverter, way back in 1998!!!, to deliberately run my microwave, and it works for anything smaller. I run it when underway, sometimes to reheat coffee, sometimes for a quick microwave snack or lunch. Even at anchor. I don't have a generator.

As Benny said, you have to do the sizing and USE homework before you buy. Remember the ATS, it's important, especially if you wire the entire AC side of the boat, regardless of use.

 

[JK_Boston_Catalina310]

Just to add to your decision process, almost everything you want to do can be accomplished in 12 volts more efficiently. Fans, TV, possibly Roku (I don't have one so this is a guess). As far as making coffee, that takes a lot more power than you think. My 2,000 watt inverter trips when I try to use our electric tea kettle to boil water but I can use my heat gun to shrink wrap wires.

By the way, we use a French press and hand grinder to make coffee. Just need to boil water on the propane stove.

 

[Benny17441]

I was playing around one day and decided to see if I could run a 5,000 BTU A/C unit from a 1000 watt inverter and a single DC Group 27 battery. I was impressed that it started and ran flawlessly for around 6-8 minutes before the low voltage alarm went off and the inverter cut out. This just helps illustrate the point of the relationship between the sizes of loads, inverters and battery banks. The thing is that running an A/C unit for 6-8 minutes serves no practical purpose. The inverter has to be sized adequately to provide the amount of power required to operate the devise for the length of time it is needed to perform a useful function. You can find small microwave ovens that draw 600-750 watts and can be used to heat a cup of water or a dinner by only consuming 1- 2 Ah. A coffee maker heating element uses 6-9 Ah just in the time it takes to brew the coffee and not considering running the warming plate. That is around 15% of the useful capacity of a 100Ah battery. You can add to the mix of variables your next opportunity to recharge batteries and there is a whole new ball game, it could mean you are welcome to run that coffee maker after heating up breakfast in the microwave. PS Some coffee makers draw 1,200 watts and would require a larger inverter and consume more power. Fans with induction motors are other power hogs as we would want to run them for hours.

 

[Stu Jackson]

http://www.westmarine.com/WestAdvisor/DIY-Selecting-an-Inverter-or-Inverter-Charger

and the rest of the WM Advisors on Electrical Systems, if you're not aware of them yet.

 

[scottdube]

I have both a genset and inverter. I had a xantrex 3000W modified sine wave inverter for many years. I recently replaced with a Magnum 2000W pure sine wave. More expensive but Sooooo much better. It uses less energy in standby and the appliances like the pure sine wave much better. I use a mini kuerig coffee maker with it no problem. It does as pointed out earlier use at lease as much energy as my microwave. My advice is not cheap out on the inverter, especially if you plan to use it for longer periods of time like powering small devices like roku and tv's. Why not 12 volt fans?

 

[Terry Cox]

If all you want is to power a few small appliances that you reference (small fan, TV, etc.), consider a small car inverter that works quite well. Walmart carries them for under $30. http://hunter.sailboatowners.com/mods.php?task=article&mid=45&aid=100063&mn=42

On the other hand, if you want to run a microwave, hot plate, etc. then you will need something far more robust. Of course that something more robust will need a battery bank with enough power to drive it. The unit that we have on our boat for those larger more robust requirements is: http://www.ebay.com/itm/Xantrex-Fre...arger-2500W-/271820847472?hash=item3f49c8f970

Our battery bank consists of two ADM 8Ds that delivers almost 500 amps, or 250 amps of useable power. About the only time I use the inverter function on the Freedom is for the entertainment system and/or coffee grinder. However, the Walmart model should handle a coffee grinder.

 

[GonzoF1]

Thanks for the input everyone! Y'all have made some good points.

Let me add a few more things as talking points. I have a fairly decent size bank of 6V GC batteries. Eight total with 450 usuable amp hours. I HAVE thought about using 12V fans, but honestly, it is almost easier to wire an inverter to the outlets rather than install all new wiring to the stateroom for 12V. That said, the fans are just those cheap Honeywell fans from Target and draw only .3 Amps when on high. The coffee maker, however, draws 850W and I may opt to still fire up the generator for the initial brewing and let the inverter just keep it warm for a few mins. Anyway, I don't want to dwell on the coffee maker to make the case for an inverter or its size. There is more than one way to make coffee on a boat One final point on this topic is that the TV and the Roku are capable of 12V use. I bought them specifically for that, but like the above fan issue, it is almost easier to use an inverter rather than rig an all new 12V circuit just for this.

So regarding my original question, it seems to me that it is better, easier, and cheaper to just wire the whole 120V buss to an inverter, no matter the size, and just manage the load via the breaker panel. Seems like a tad more work, but is offset by a much easier installation. Am I right?

 

[Ch0pp3r]

An inverter is inefficient as has been noted... Here is what I did instead of buying a $500 marine TV.

I went to Best Buy and inspected all of their 24 inch flat screen TV's looking for a model that the 120VAC power supply brick converted to 12VDC. I found it in the Insignia 24 inch LED TV. Cut the brick off and wire the pigtail that goes to the TV to your 12V source on your boat. Make sure it goes to a correctly sized breaker or is properly fused. The Roku plugs into a HDMI port and is USB powered and the TV has a USB port. They now make the same model TV with Roku built in I believe.

I have used this setup for the last year and it works great. The TV was around $110.

Chuck

 

[Brad Hoff]

Like Chuck, I went to Fry's and looked behind the TV's and found one that had the 12v external power supply. Only had to match the plug from the power supply 12v side to wire in. I use the Xantrex Prowatt SW 1500 watt pure sine unit. These go for about $300 (got it on sale for $200) which just about the lowest price for a pure sine inverter. Instead of wiring into the 120v side, I mounted several extension cords run to six plug style surge outlets. I know it is not the best setup but it as worked for me for years. Didn't need 120v power more than about 12' from the inverter. As for coffee, the little Italian Bialetti units are excellent. I have two, one that is two cup and one four. There are whole coffee snob forms on these makers as they have been around for about 100 years. The inverter runs my grinder!

 

[GonzoF1]

You guys seemed to have missed the part where I said I already have a TV/Roku capable of 12V. ;-)

 

[Ch0pp3r]

we could probably use a small inverter to power a couple of fans in the bedroom while we sleep and the TV/Roku.

You don't need an inverter to power a 12V TV. Your problem is solved...

Chuck

 

[DaveJ]

TV/Roku?
You could always just watch Netflix and chill.....
Only some will get that, my 28 year old explained it to me......

Cheers

 

[JK_Boston_Catalina310]

You guys seemed to have missed the part where I said I already have a TV/Roku capable of 12V. ;-)

So what do you want the inverter to run?

 

[Bill Roosa]

To only drive the outlets you want you need a source selector switch that supports that AND an AC power buss that has two separate buses. Basicly you need a three way source selector switch. These are rather expensive BTW. The selector switch turns on both buses while on shore power and only the "inverter bus" when on sea power. So water heater, Air Conditioner, .... on the shore power buss and the outlets on the sea power buss.
You are going to find that your coffee pot will kill you battery bank in very short order while the microwave will not.

 

[GonzoF1]

To only drive the outlets you want you need a source selector switch that supports that AND an AC power buss that has two separate buses. Basicly you need a three way source selector switch. These are rather expensive BTW. The selector switch turns on both buses while on shore power and only the "inverter bus" when on sea power. So water heater, Air Conditioner, .... on the shore power buss and the outlets on the sea power buss.
You are going to find that your coffee pot will kill you battery bank in very short order while the microwave will not.

Sounds like a complex install. A complete reinvention and re-engineering of the breaker panel just to power a few outlets for fans? There has to be a better way than this. But regarding the coffee maker... I think you're right. Maybe I'll stick to a few .3A fans.

 

[JK_Boston_Catalina310]

Sounds like a complex install. A complete reinvention and re-engineering of the breaker panel just to power a few outlets for fans? There has to be a better way than this. But regarding the coffee maker... I think you're right. Maybe I'll stick to a few .3A fans.

Another option is to just install one or two new outlets wired directly to the inverter. Those can never be powered by shore power so you don't need the complicated switching mechanisms.

But if the purpose is to power fans, why not just add 12 volt fans. We have 6 of them on our 31 foot boat living in the Caribbean. They run almost nonstop. Far more efficient than running them through an inverter.

 

[Ch0pp3r]

Also of note... We use a coffee press onboard our boat. Hot-up some water on the stove and the press makes great coffee. Works well at sea even in big swells. Use a teapot for it's no spill safety. Due to an inverters gross inefficiency we chose not to install one. Every system is 12V except the Air Conditioning when we are at the dock.