Cockpit Fridge: Adding Inverter

Liberty44140

Looking for thoughts on how to add an inverter for my cockpit fridge.

A few years ago I added a Dometic CD 20 drawer fridge in my cockpit. It is AC only, I ran an outlet to a cabinet for it. Smaller drawer fridge, can hold a case of beer and thats about it (and that was the plan!). I'd like to add an inverter so that we can do some more overnights on the hook and not have to transfer its contents to a cooler. Admiral would also like to run the genny less when we anchor out for the day.

Currently it is on an AC breaker that supplies power to this drawer fridge, A Uline Ice maker, and a cockpit outlet. I am open to the inverter powering the entire breaker if possible.

Right now I am thinking I just run cables from my house bank (two group 31's) to the cabinet that holds the drawer fridge, and install a 500w inverter in that cabinet. I have easy access to the back of the fridge without pulling the fridge out. When I am on the hook, just unplug AC and plug in to inverter.

I am open to adding a 3rd 31 to the bank. charger is a 50a. The galley fridge is a fridge/freezer unit which is ac/dc so the bank would need to run the cockpit and galley fridges for 8 hours.

Thoughts on a better way?

Here is the thread from when I installed it for pics:

https://rinkerboats.vanillacommunities.com/discussion/12272/thoughts-on-dc-cockpit-fridge/p2 

LaRea

It would be nice to run the icemaker on an inverter, so your ice doesn't melt.  It would chew up batteries in a hurry, but you'd have the option to turn it off when you need to extend battery life.  

If you have room for a third Group 31, do it!  

The easy way would be to add the third battery in parallel with the house bank, so it just increases the capacity of the house bank.  It would run 50% longer -- but also take 50% longer to charge.

Here's another way that would be harder and more expensive, but maybe better.  Instead of an inverter, install a separate charger-inverter with its own AC power supply.  Your original house bank would stay unchanged.  The new battery would form a stand-alone AC/DC system powering the drawer fridge (and ice maker if you want).  

That would reduce the charging time because you'd run both chargers at once.  It would also prevent the ice maker from draining your main house battery.  

YYZRC

I have a Victron 12/3000 charger inverter setup with a Victron lithium battery and highly recommend it. You can set it up so that as soon as you come off shore power it kicks on and provides AC power. 

I only use the generator for air conditioning now. I think I maybe put 5 hours on the Kohler this season. 

PickleRick

The po of my boat ran a second battery house bank for their trips to the Catalina Islands (didn't seem amused when I asked if it was a ducking Catalina wine mixer). 

They ran the AC inverter power line to the breaker panel so all AC circuits could be run off of the secondary house batteries by flipping the AC selector switch.  


Adding a 3rd dedicated charger would not be difficult .  The bayliner has only one house battery so they took a cheaper route and put in a heavy duty manual isolator switch and heavy gauge wiring to connect the spare bank to the main house battery.  After the charger read full on the main battery they would flip to charge up the inverter bank.  Not the route I would have taken,  an automatic isolator or extra charger wouldn't cost much but I guess they only used it when they were on vacation. 

Liberty44140

Thanks gang, definitely got the ideas flowing.

I love the idea of the inverter/charger, but for just a small fridge, maybe the ice maker.... I think I can achieve the goal for a fraction of the cost of one of those. I'll probably go a lower cost route since this is more of a nice to have than a need (and yes, boats have needs!  )

Ok so it sounds like adding a 3rd 31 in parallel is needed, that is easy. The two I have are in parallel so this would be another in line.

From there I am wondering if I should add a 1000w inverter at my panel. On the DC side of my panel there is a "cockpit fridge" switch that is not in use since I didnt have one from the factory. If I could rig this so that the DC "cockpit fridge" switch sends the inverter's power to the AC circuit that feeds the ice maker & drawer fridge, that would be ideal. Indeed if I found the ice maker was too big of a drain I can always turn it off.

1 - Does this sound doable to use that extra DC switch to send DC power to the inverter to then feed an AC circuit?

2 - What would happen if I accidentally had both the AC and DC/Inverter switches on for this line? Would one blow? Is there a way to fail safe that?

3 - What is the best way to have the AC power from the inverter take over the AC line already feeding the ice maker and drawer fridge from the shore power/genny. Can I just tie them together or do I need a switchover due to the concern in question 2?

Thanks!

PickleRick

The easiest way to prevent letting the smoke out of something.   You could mount one by your fridge to switch between power sources for said fridge. This one is just an example.    Rated for way more amps than your fridge since it's designed for your breaker panel so it might be over kill.  Search 120v marine transfer switch.  They make them with 2 throws, 3 throws, etc.  You'd probably only want shore and inverter. 

If you hit that fridge with power from genny/shore power and inverter all at once something is going to have a bad day.  

Feed ac from inverter to your wanted bank of the switch and the shore power to the other bank.   Power out from switch goes to outlet of fridge.   

I don't know jack about proper sized wiring for the amps your fridge draws. 

This just makes it impossible to melt anything so long as it's hooked up properly (by rinker standards this means something the coasties wouldn't balk at or an insurance adjuster) 


This is of course if the fridge is all you intend on powering but could be added to the breaker panel if you wanted all things to run off the inverter, should you choose.   


I still have the inverter out of the bayliner as I'll never use it.  Will be glad to send you info/sizing and if you want it just let me know what you think its worth to you and it's all yours.   

PickleRick

I do have the red protector for the positive cable as well as the remote on/off switch that I would have to remove from the boat.  I have never tired to use it biur would gladly take it to the shop and attach it to a test battery to very it runs a drill press and bench grinder 

YYZRC

You can get those switches for $20ish, just search rotary selector switch on Amazon. Or you could get fancy and install an automatic transfer switch so when the shore power is disconnected, the ATS kicks over to the inverter. 

PickleRick

YYZRC said:

You can get those switches for $20ish, just search rotary selector switch on Amazon. Or you could get fancy and install an automatic transfer switch so when the shore power is disconnected, the ATS kicks over to the inverter. 

12.99!   The little box even looks water proof 

Liberty44140

Thanks gang!
Rick - Appreciate it. I'll let you know on the inverter. I am trying to nail down the exact startup and running watts on the fridge and ice maker to be sure I get one big enough, but not too big as the space where this will go is not very big. 
YYRC - Great call on the switch. I wasnt loving $250 for a switch but yea $10 - $20 is glorious and this would be mounted in the cabin so easy, dry and extra safe. Would stink to ruin an $800 fridge or $2000 ice maker to save on the switch!

So will it be ok for a dedicated switch on the DC panel to power the inverter? No need to run it direct to the battery?

MH342

Liberty … for some extra bucks you can also get inverters that can automatically switch between AC and DC. Here’s a promariner example but they come in other capacities … https://a.co/d/4qkALRO

Usually Inverters are only a 5-10% penalty meaning that a 1000W AC load will draw 1100W of DC. Divide watts by 12 and you get the DC amps. My guess is that using the original circuit is fine since they sized it for the draw of a fridge anyway. Adding another load to the inverter could be an issue.  If you can find the wire gauge on your cables, there are tables online that will tell you the max amps for the gauge and length of run.  The only issue is that a smaller wire can still be safe, but have too much voltage drop. 

https://www.westmarine.com/west-advisor/Marine-Wire-Size-And-Ampacity.html

A word of warning, the compressors can pull a lot of startup current, so you’re better off upsizing the inverter.  For example, I was really surprised that my Honda 2000 generator couldn’t start my ice maker in Eco mode (worked if it turned it off). So that is pulling probably close to 2k watts on startup.  A larger inverter won’t pull more current, it will just have more top end available. 

Liberty44140

MH342, thank you. I looked at the pro mariner just due to the good brand but didn’t think much of it. Now seeing the ac pass through option is awesome. Eliminates the need for a switch! Very cool and auto. I’ll likely go with this.

Question: friend of mine who is also looking in to adding an inverter to his 41 SR told me that the inverter must be wired direct to battery, and ideally is within 3 ft of the battery bank, could go to 6 with very heavy wires. Can anyone help me here? I wanted to put this much further away from the battery bank and not in the engine room. Thanks!

YYZRC

My 3000w charger/inverter called for 1/0 gauge wire. What is your amperage? I imagine 10 max. 

Liberty44140

Agree not more than 10, realistically 5 as the ice maker draws 2.5 so the drawer fridge has to be less.

that pro mariner inverters installation instructions say no more than 5 ft cables and 1awg cable for the 1500 watt, 2awg for the 1200 watt. The 1500 and 1200 are the same price on Amazon so I’d go with the 1500 watt and 1awg cable.

Liberty44140

While I loved the idea of the auto switch in the pro mariner, it is a "modified wave" inverter which is not good for refrigeration with the compressor spikes. I need a "pure sine wave" inverter which is MUCH more $$$ from Pro Mariner and Vitron. Will probably go with an off brand pure sine wave inverter, and a separate manual or automatic switch.

Currently trying to understand restrictions for placing the inverter. Looks like regardless of the brand, it must be within 5 ft of the battery bank which is ok but changes my plan quite a bit. 

LaRea

I think the 5-foot limit is based on hard-wiring direct to the battery.  If that's true, then a longer cable should be okay with a terminal fuse block at the battery.  This is what I used for the stereo circuit on the 370, and it's rated for up to 300 amps.



https://www.amazon.com/Blue-Sea-Systems-5191-Terminal/dp/B0019ZBTV4

GMSLITHO

Why don't you just buy a 12 volt fridge 

Liberty44140

LR - thanks. I know I'll need a some kind of fuse at the battery, that looks perfect and easy. Yea from what I read an inverter that is over 500w or so really should be attached direct to the house bank with 0/1 or 0/2 cabling due to heat and voltage loss. Of course looking for any feedback there. 

GMSLITHO - To move to a 12v fridge I'd have to run 12v wiring from the panel to the drawer fridge which is a pretty long and complicated run. No existing DC there. If I am going to sign up for that much work, I might as well install the inverter which is the same amount of work, less money, and will make my fridge, ice maker, and cockpit TV all work on 12v. Way bigger bank for the buck both labor and money wise. 

Liberty44140

Ok, I've attempted to draw this out. I am not the electrician or schematic drawer that some of you are so bear with me. But very open to feedback on things that wont work, or opportunities to streamline and eliminate steps.

Primary concerns right now are still properly attaching the inverter to the battery bank, and grounding the inverter. I am also concerned that there is no fuse or breaker between the inverter and the AC appliances/outlet. The inverter is self protecting but I am surprised that nothing I am seeing online says to fuse it. There is a lot about a fuse and switch between the battery and inverter, but nothing after the inverter:

LaRea

Be sure to follow the conventions for wire colors.  The AC wiring should all be black/white/green triplex boat wire, not red/black.  And of course the rotary switch must be designed for 120VAC, not a regular battery switch.  

FYI.  In some marinas, my boat will trip the shore power unless I turn off the inverter.  Inverters can be finicky with newer shore power pedestals that have modern safety features.  

Liberty44140

Thanks LR, great info as always. I adjusted the drawing for the triplex. That is absolutely what I would use. When I ran the cockpit outlets years ago for the TV and fridge I used 12g marine triplex and will order the same for this project.

Rotary is indeed 120v, it actually says rated for up to 440v. Link below. My drawing shows green going through the switch but I still need to confirm ground (3 wires) can run through it. May need to attach 3 greens all together separately in the switch's box?

Upon further research it looks as if I  need a 20A breaker after the inverter but before the switch. Again open to feedback on all of this. 




https://www.amazon.com/APIELE-Warranty-Changeover-Terminals-Universal/dp/B07ZV8DSHR/ref=pd_ci_mcx_mh_mcx_views_1?pd_rd_w=jaR6w&content-id=amzn1.sym.225b4624-972d-4629-9040-f1bf9923dd95:amzn1.symc.40e6a10e-cbc4-4fa5-81e3-4435ff64d03b&pf_rd_p=225b4624-972d-4629-9040-f1bf9923dd95&pf_rd_r=W6HXZN8SV4R74FDH2YDR&pd_rd_wg=Byl79&pd_rd_r=e7ffc8b9-05bd-47ef-a994-1f3c2ce89cab&pd_rd_i=B07ZV8DSHR&th=1 

LaRea

LaRea said:

... This is what I used for the stereo circuit on the 370, and it's rated for up to 300 amps.



https://www.amazon.com/Blue-Sea-Systems-5191-Terminal/dp/B0019ZBTV4

@Liberty44140 - if you need one of these, PM your address and I'll send you one.

Liberty44140

Sent! Many thanks!