Inverter questions

[RickNC]

Onan Emerald 4000 Generator quit a few days ago. After testing and partial disassembly I found a short in the stator. Instead of replacing $1000 stator on a 23 year old generator (and at DW's insistence) I'm going to put in a new Onan 2800. Why a 2800? it is the only size currently made that fits into that space (26lx16w x 14H). That is enough power to run the a/c(at start-up) and 12v converter but nothing else.

To make up the lost 1200 watts (4000-2800) I am thinking of installing an inverter to run the microwave(1000 watts),refrigerator (200 watts) and a hot water heater element (700 watts). I intend to use a transfer switch to isolate the inverter from the generator and shore power. Most importantly it will allow me to run the refrigerator on the inverter while underway.
What I cannot figure out so far is will I need to up the alternator capacity from it's current 105 amp output to charge a single 120 ah deep cycle g31 battery and run a 2000 watt inverter while the engine is running. Any advise?

[okcnewbie]

Do you have a residential fridge? Is you water heater electric only?

I would think the fridge could run off the current alternator ( about 15 amps draw ). You wouldn't have to run the AC and the microwave at the same time. The water heater heats pretty quickly and could be heated before use.

With just one battery you would really only installing the inverter for while on the road. This seems like overkill unless you plan to install solar later. Unless you run new circuits I'm not sure your transfer switch alone will allow what you're after.

Even if you don't install solar I would consider installing a battery meter like the trimetric 2030.


I believe the onan emeralds were highly sought after. You might want to check over at smokstak.com and see if someone has a stator if you're able to do the work.

[RickNC]

Originally Posted by okcnewbie

Do you have a residential fridge? Is you water heater electric only?

I would think the fridge could run off the current alternator ( about 15 amps draw ). You wouldn't have to run the AC and the microwave at the same time. The water heater heats pretty quickly and could be heated before use.

With just one battery you would really only installing the inverter for while on the road. This seems like overkill unless you plan to install solar later. Unless you run new circuits I'm not sure your transfer switch alone will allow what you're after.

Even if you don't install solar I would consider installing a battery meter like the trimetric 2030.


I believe the onan emeralds were highly sought after. You might want to check over at smokstak.com and see if someone has a stator if you're able to do the work.

The fridge is a Dometic 2551 gas/elec (4 years old). I was looking at current draw for the electric operation and was surprised to discover it is only 175 watts and that is to run the little heating element for the gas absorption unit. I emailed Dometic support and confirmed with them. They said they are unaware of any issues using a inverter of the proper size but strongly recommended I use a pure sine wave converter.

The way I want to set this up is to install the inverter and the battery in the right rear storage compartment. The single 12/2 110v wiring that supplies the fridge, water heater and microwave passes through there and I can easily put in a junction box. The transfer switch is actually going to be a simple on/off/on 30amp Leviton 1287 wall switch to toggle between Shore/Generator power and inverter power. I would run a 8g wire from the engine battery/alternator post back to the inverter's battery. I'm going to use a solenoid wired to the ignition to disconnect the inverter battery from the engine battery when the engine is off. Sound reasonable so far?
BTW no plans for solar

[RickNC]

Originally Posted by okcnewbie

.......... I believe the onan emeralds were highly sought after. You might want to check over at smokstak.com and see if someone has a stator if you're able to do the work.

The genny has 1800 hours on it, It is also a PITA to service. Just to change oil and filter I have to drop the genny from under the floor. New ones are far easier to service through the access door.

[JollyCamper]

I have looked at doing something similar on my old rig. Is the battery you are using for your inverter the same as the battery already in your rig? The problem you will have is getting your batteries to charge and discharge equally with a single alternator. A more plausible plan would be to add a second battery, and make sure the batteries are the same. Let the inverter pull from both batteries, and they should charge and discharge somewhat equally, and have a well operating system. You are not looking at a huge power usage, or even a constant power usage. Are you wanting something to use while driving, or something to use when dry camping? That will make a difference. Do you have the option for propane use on the water heater? And also on the fridge?
I have looked at the option of installing a second alternator, and having a completely separate charging/battery/inverter system isolated from the chassis system. But I have that as an easy option because my rig runs a small block chevy, and no a/c for the cab, so there is plenty of room, and it is plenty easy to install a second alternator. What powertrain are you running? You may be able to work something out to add a second alternator and do the same thing. Also, if you do some creating wiring, you have a redundant starting/charging system for the chassis...also, second thought...does your rig have a house battery? I talked at length with the guys at a local battery shop about my ideas, and they estimated if I had a 100 amp alternator, group 31 battery I should be able to use that to properly power a 2000/4000 inverter, and even have enough reserve in the battery for engine off run time. Your plan is completely plausible...with the correct battery, charging set up and inverter, you could just replace the generator with the inverter system.

Hope that I didn't overload you with ideas/information.

[okcnewbie]

Originally Posted by JollyCamper

. Your plan is completely plausible...with the correct battery, charging set up and inverter, you could just replace the generator with the inverter system......

I agreed with you up to this. He wants to be able to use the rooftop AC. That's not going to be done without a generator.

[JollyCamper]

I did mis-type...I guess what I meant there is if he can isolate the needed circuits it could take up the loss of current he would experience going to a smaller generator.

But...
With enough battery you could run a 3k inverter and possibly completely replace the generator. Beauty of an inverter is a 3k inverter has a 6k surge rating.

[RickNC]

Thanks for the input. I installed the converter two days ago and based on the best advice I could find here is what I did;

I mounted the inverter inside a cabinet with a 12ft run of #1 battery cable between the inverter and the Alternator/Engine Battery terminal. I isolated the inverter from the engine's battery with a solenoid switched by the ignition. I protected the cable run with a 100 amp fuse.
3' past the converter I mounted a NPP gel 150 amp deep cycle battery. The appliance circuit is switched between inverter and generator/shore power with a leviton 1286 double-pole/double-throw wall switch. The double pole switch is also intended to switch the inverter itself on and off, but I am waiting to add that function until I have had more time to thoroughly test.

Checking charging voltage at alternator/battery terminal I read 14.3 volts, at the inverter battery I read 14.0 so a voltage loss of 2% for a 15' run of #1 cable.

Since the primary function of the inverter is to run the refrigerator (200 watts) My first test was the battery only run time using two 100 watt light bulbs to emulate the refrigerator's consumption and a electric timer. The inverter shutdown voltage is spec'ed at 10.5 volts dc. The two bulbs and clock ran for 3 hours and 4 minutes before the inverter shut down. The battery voltage read 10.75 volts

Testing the 1000 watt microwave on battery I ran the microwave 15 minutes Battery voltage dropped to 11.25 volts.

I did not test the hot water heater draw on battery since we won't be using it without the engine running or on generator/shore power/propane. Since the heating element is spec'ed at 400 watts and it usually takes about an hour to heat 6 gallons of water. I would assume based on the refrigerator's power consumption of 200 watts and 3 hour run time, that a tank of water could be heated while on a 150 amp battery.

Costs; New 2.8K watt generator $2447 ( with $25 coupon)
2K BCI Inverter $190
150 amp battery $275
Switch $22
Solenoid $32
16' # 1 battery cable $39
Terminals and Misc ~$20
Amazon Card 5% discount ($30)
Total $3005

New 4.0K watt generator $2991 to replace orginal 4K wouldn't fit ,so for a $14 up charge I made up for lost capacity and added functionality

Leaving next week for a 4 day trip and will see how everything performs in actual use.

[okcnewbie]

Good for you. I hope everything works as you planned.

The only thing I would add is that I probably wouldn't let my loaded batteries get below 11.5VDC or so. (depends on the load)
I would think that if you let the batteries get below 12VDC unloaded and at rest you will shorten the life.

[Slackmason]

Hey Rick, sorry to jack your thread, but, I just had a problem with my Onan emerald. I broke the adjustable main jet! Saw here that you just swapped yours out, I'm wondering if you have it laying around still and would be willing to send me the jet from the bowl of the carburetor!?

[SurfsideGolfer]

You need to figure your wattage requirements, and adjust number of batteries too. Running on an inverter will work fine, as long as your batteries are sufficient for the load and time required.

Originally Posted by RickNC

Onan Emerald 4000 Generator quit a few days ago. After testing and partial disassembly I found a short in the stator. Instead of replacing $1000 stator on a 23 year old generator (and at DW's insistence) I'm going to put in a new Onan 2800. Why a 2800? it is the only size currently made that fits into that space (26lx16w x 14H). That is enough power to run the a/c(at start-up) and 12v converter but nothing else.

To make up the lost 1200 watts (4000-2800) I am thinking of installing an inverter to run the microwave(1000 watts),refrigerator (200 watts) and a hot water heater element (700 watts). I intend to use a transfer switch to isolate the inverter from the generator and shore power. Most importantly it will allow me to run the refrigerator on the inverter while underway.
What I cannot figure out so far is will I need to up the alternator capacity from it's current 105 amp output to charge a single 120 ah deep cycle g31 battery and run a 2000 watt inverter while the engine is running. Any advise?

[RickNC]

Originally Posted by Slackmason

Hey Rick, sorry to jack your thread, but, I just had a problem with my Onan emerald. I broke the adjustable main jet! Saw here that you just swapped yours out, I'm wondering if you have it laying around still and would be willing to send me the jet from the bowl of the carburetor!?

Sorry, I didn't see your message earlier. I sold it to a guy that needs the rotor and control parts, I have his email and will check with him to see if he will let go the main jet or carb assembly.

[Slackmason]

Thanks, that would be a huge help for me!

[Slackmason]

Hey, just curious if you've heard back from the guy.
Still trying to get this carb fixed in my generator, it's been a nightmare. If you could, I'll pm you my contact info to forward to him. Thank you amigo!