Foretravel Owners' Forum

I have a 2001 Foretravel u320 stock inverter. My question, when I am using my inverter to power the motorhome from the house batteries, my voltage doesn't show in the pro-sine display, but when plugged into shore power or running from the generator it will show voltage. I can run my A/C units on shore/generator power, but when I try to run one zone A/C unit by inverter power it will not start. My inverter is powering up the microwave and 110 outlets but will not even try to start A/C. Can anyone run their A/C units from inverter power on the stock system in their u320? When inverting, does the voltage show on pro-sine display? I won't be running my A/C unit on house batteries but seems it should still work since I have soft start capacitors installed.

Front of bed has two breaker panels.  Both work on shore/gen.  Only one works on inverter.  Roof air's are not powered from the inverter breaker panel.

A general rule when inverter is active is all devices will run down battery.  When battery is reduced it wears battery a little and the generator is needed to replenish the battery.  In many cases like with big current draws like microwave, it may be much better to start generator before using microwave, so you don't have to start generator later just to replace current used by running microwave.  No free lunch. . .

from the factory the inverter feeds a panel that supplies power to some limited, dedicated loads. Initially inverters were supplied to operate TV sand later maybe a microwave and a few other appliances. To run an AC off the inverter would require a larger inverter, typically 3000 watts and a battery supply to support it. hen to run an AC off the inverter being powered from the alternator would also require a much larger or multiple alternators. Since the overall design is to use the generator when campground power is not available, it is just an extension to use the generator to run the AC's while driving when needed. To put things in perspective running an AC would require at least a 150-amp alternator each. Many early coaches do not have much more than that to begin with.  Yes some Prevost's and other coaches have true over the road air or enough engine alternator capacity to do more. There are now even 24- and 48-volt systems to make that happen. But those even back then were coaches that cost 3X what a Foretravel costs.

PTF  As Barry said, to run your roof air while on the road you would have to transfer the ac output over to the inverter panel (#9 breaker on our coach).  This lets the front air con run on inverter.  Your ProSine 2500 should allow ou to run the air but you probably need a SoftStart on the unit to get by the startup surge.  Next issue is your house batteries.  For any reasonable use you will need at least 1000 amp hours of battery capacity.  This really means going to lithium.  Although the 2500 is a good inv/charger it is really dated.  If you really want to go this route you will need a new Inv/charger at 3000 watts and lithiums.  A fair amount of coach bucks to solve a problem that is easily handled by your Genny over the road.  If you are into upgrades, it is very doable.  We did the switch with a Victron Multiplus, 1600 AH of lithiums and can get 7 hours of run time from the front A/C to discharge to 50%.

As mentioned above, I suggest you simply use your generator to power air conditioner(s) when running down the road.  If you tend to normally "camp" in locations with full hookups, you probably don't use your generator much, if at all.  Generators like to get some vigorous exercise now and then - keeps their innards freed up and happy.  As they say "Use it or lose it".  8)

Thank you to all with the technical information, this is so helpful. Just one last Question? When inverting the power doesn't show in the pro-sine display I take this as normal operation?  It does show when plugged into shore power or using generator. 

I believe the line voltage displays are fed from two breakers that are in the main electric panel, not the inverter panel.  Therefore they will not show inverter power.

Are you referring to the powerline monitor?  FT Power Monitor (https://www.foreforums.com/index.php?topic=23208.0)

It's not part of the Prosine, it's a separate device that has 2 plugs on the back, each of which plugs into a different AC power leg.  They are connected to the main breaker circuits, not the sub-panel fed by the inverter.  See breakers/circuits labeled "Power Watch" in the schematics:


So no, it won't show AC voltage levels when running on inverter power.