These rigs are pretty efficient. We've spent many a week parked at a relative's house with a long extension cord to a 15 or 20 amp garage outlet. You just need to be careful what you turn on. A few lights and the fridge and maybe the TV, but no high-amp devices and make sure your HydroHot is on diesel only. We get away with using the microwave if I minimize lights and the TV is off, etc. But you can usually find estimates of each device's wattage and convert to amps by dividing by 110volts. Then you can know how many amps you run at any one moment, allowing that the fridge may cycle on and off, and don't allow the total to exceed the building outlet's circuit capacity (15 or 20 amps). You need to allow some room for voltage drop when using a long extension cord and/or one that's smaller than 12 guage. So if you have a long cord from a 20 amp garage outlet, I'd be careful loading it with more than 15-17 amps worth of devices.
As Bill mentioned he does, I try to remember - but often forget - to choose 15 amps on my Magnum remote panel over the entry door, so the inverter can help prevent the garage breaker from tripping if I overload things inadvertantly. The trick is to remember to reset it before plugging into the next RV park power post that's 30 or 50 amp. I've been at it long enough that both Lee and I are good about power management. A couple times hooked up a few days to an old 15 amp circuit and you learn the ropes, and how to keep an eye on the Aladdin's screen and electric leg numbers. Watch them change as you turn devices on and off, and you'll get the gist of it.
As Gerald explained, you have a Bidirectional Isolator Relay Delay (BIRD) system. It is a small black box probably like mine, found on the inside of the access door between your main battery switches. It controls the battery charging by way of the large solenoid also in that cabinet, dead center, called the Big Boy and which is the actual "isolator". When your house bank reaches about 13.3 volts it starts moving charge current from your inverter's charger over to the chassis bank. And it works both ways; when you are on the road and the alternator has bumped the chassis set to 13.3 volts, the BIRD closes the isolator then as well, and lets the house batteries share the alternator's production.
To echo others' warnings, if the coach is in storage make sure the HydroHot is protected with RV antifreeze - not doing diligence there can be a very expensive mistake.
Joel
