Draft of electric layout

[dwh]

So to revisit this, the running Watts of the Coleman Mach 8 13,500 are 1,599. So if I multiply by 5x it would seem I need an 8,000 Watt inverter. That does not seem right. When I look at the starting load on the Coleman Mach website they say to calculate 2.5x the running Wattage to start it. This would mean I need a 4,000 Watt inverter. Stills seems high though. Am I better off just connecting / running the AC to the Genset and Shore power only?

The compressor startup current draw (inrush current) depends on a few variables. Pressure in the freon lines (head pressure) and voltage drop being the main considerations.

But the inrush is momentary. Milliseconds.

So no, you don't need a 4kw inverter. You need an inverter with a rating like "2kw continuous, 4kw surge" (all generators and inverters have both continuous and surge ratings).

Also, there is a way to mitigate the inrush. A very common mod for RV a/c units is to add a "hard-start capacitor". There are kits you can buy, but you don't really need one:

http://www.modmyrv.com/2009/05/27/rv-air-conditioner-hard-start-capacitor

 

[mbsprinter144]

So the MS2812 has a peak wattage of 3,900 and the MS2000 has 3,300. Would either of these work for starting the AC unit? And if so, is the inverter now oversized for everything else I am using it for?

I am fine with running AC only off of shore and generator directly but would be nice to have the option of using it for short periods of time on battery power alone.

 

[dwh]

As to whether or not you'd be better off rigging the a/c shore/gen only...

That's up to you. Do you really want to buy a big enough inverter? Do you really need the feature that draws from the battery to supply loads too big for the gen?


Mostly though, how much battery will you have?

My 400ah (@12.8v) bank holds...

12.8v x 400ah = 5120 watt*hours

5120wh ÷ 1,600w = 3.2 hours

So three hours. And that's down to 100% drained. Half that if you followed the 50% rule.

If you had 400ah of battery, would it be worth it to build a battery/inverter system capable of running the a/c - but only for an hour and a half?

 

[mbsprinter144]

As to whether or not you'd be better off rigging the a/c shore/gen only...

That's up to you. Do you really want to buy a big enough inverter? Do you really need the feature that draws from the battery to supply loads too big for the gen?


Mostly though, how much battery will you have?

My 400ah (@12.8v) bank holds...

12.8v x 400ah = 5120 watt*hours

5120wh ÷ 1,600w = 3.2 hours

So three hours. And that's down to 100% drained. Half that if you followed the 50% rule.

If you had 400ah of battery, would it be worth it to build a battery/inverter system capable of running the a/c - but only for an hour and a half?

I would like to have 2 AGM batteries providing about 200 ah so it sounds like the thought of running the AC on that is not realistic at all. Wiring AC directly to shore / gen makes more sense. I think in that case I should plan on a roof fan as well as AC. Either a fantastic fan or a small round vanair for ventilation without AC.

 

[dwh]

I would always have a roof vent no matter what. If for no other reason than to extract condensation.

 

[mbsprinter144]

Do you think I need to add an AC to DC converter for using DC while on shore power? I suppose it is possible that the charger could keep up with the demand.

 

[dwh]

Do you think I need to add an AC to DC converter for using DC while on shore power? I suppose it is possible that the charger could keep up with the demand.

Yea, the charger should be enough. Say a 45a or 55a running from a Honda eu2000. Unlikely you'll draw more amps than that, except when running something like a microwave from a big inverter, but that's only for a few minute at a time.

 

[dwh]

A very common mod for RV a/c units is to add a "hard-start capacitor". There are kits you can buy, but you don't really need one:

http://www.modmyrv.com/2009/05/27/rv-air-conditioner-hard-start-capacitor

Whoops. What I meant to say is you don't need a kit because you can just buy a capacitor and DIY.

I did not mean you don't need a hard start cap - I think all RV a/c units should have one.

 

[DiploStrat]

There may be better products and better sources, but here is one: https://www.coastalclimatecontrol.c...asystart-364-compressor-soft-start,-115v.html

 

[DiploStrat]

Getting a Rush

The 5x rule is just that, a rule. As dwh pointed out it is a momentary surge and different inverters take it better or worse.

A Magnum Energy 2800w inverter will start a 6,000 BTU window air conditioner. The 2000w model will not. The surge rating on the inverter will give you a guess, but, in the end, you may be reduced to trial and error.

While the rule of thumb is that a generator can start an air conditioner without problems as the motor simply sags a bit, a quick search of various RV fora will show that this is not always the case.

Much as I love the concept of air conditioner without generator, part me is reaching the conclusion that the correct answer is one of two scenarios:

-- If you are near people - use shore power and be happy. You paid for it.

-- If you are away from people - use a small generator, perhaps with a large, twenty foot cord.

At the end of the day, energy is energy, the only question is where you are going to get it.

Here is a reasonable thread on this subject: http://www.classbforum.com/forums/f8/running-small-air-conditioner-on-an-inverter-2178.html

 

[mbsprinter144]

The 5x rule is just that, a rule. Ads dwh pointed out it is a momentary surge and different inverters take it better or worse.

A Magnum Energy 2800w inverter will start a 6,000 BTU window air conditioner. The 2000w model will not. The surge rating on the inverter will give you a guess, but, in the end, you may be reduced to trial and error.

While the rule of thumb is that a generator can start an air conditioner without problems as the motor simply sags a bit, a quick search of various RV fora will show that this is not always the case.

Much as I love the concept of air conditioner without generator, part me is reaching the conclusion that the correct answer is one of two scenarios:

-- If you are near people - use shore power and be happy. You paid for it.

-- If you are away from people - use a small generator, perhaps with a large, twenty foot cord.

At the end of the day, energy is energy, the only question is where you are going to get it.

Here is a reasonable thread on this subject: http://www.classbforum.com/forums/f8/running-small-air-conditioner-on-an-inverter-2178.html

I agree with this thinking. I think I am fine with not trying to run AC off of the battery bank.

 

[dwh]

Running a/c off batteries can be done. Just not for long.

To do it long enough to make it worthwhile only requires 3 things:

1. Way too much battery.
2. Way too much insulation.
3. The most efficient a/c unit possible.

Then to recharge it off solar only requires the addition of:

4. Way too much solar.


If I was building my own truck and it had say 20' x 7' of roof for solar then I'd certainly do it.

Otherwise...I'm an old electrician, I LIKE generators.

 

[mbsprinter144]

Latest Version

Latest version attached

 

[dwh]

The Magnum has a 30a transfer switch, so the Blue Sea selector switch is redundant unless you plan to exceed the 2000w the inverter can supply.

Is that LED light bar on the 12v fuse block for driving?

 

[mbsprinter144]

Yes - I planned to put LED driving light bar, rear led and side LED all on house 12V block. Would it make sense to wire at least the driving light bar to the sprinter 12v system for driving?

As far as extra transfer switch, I was thinking that I would use that to bypass the Magnum if I ever had an issue with it. By default it would be left on inverter source.