Looking for some insights on Class C Motorhome with 30 Amp and LP Generator

[DebedLep]

Looking at purchasing a class C 25' motorhome.  There is 30 amp service with LP Generator, solar and batteries.
Refridgerator is a compressor.  SITUATION: I am plugged to shorepower, my refridg - hot water heater - AC, TV and booster are all running...

1. Do I have to manually turn on generator before I use Microwave or coffee maker?  ---- some sales people say yes, some sales people say no, most say "you SHOULDN'T have to".  RV manufacturer not getting back to me.

2. Want to be able to park RV in lot with Generator running with AC on for dog while we grocery shop, visit Casino watch Hockey game .... how long till LP runs out since the permanent LP tank is only 12.2 gallons?  Heard range of 18 to 22 hours - accurate??
Thank you for any insights and information shared.  Don't want to buy something we will regret immediately.

 

[HappyWanderer]

Anyone who answers Question #1 with a yes is obviously clueless. You can use shore power OR the generator, but not both at the same time. There is either an automatic transfer switch, or you need to plug the power cord into the generator.

You can use up to 30 amps, however you choose to. If you exceed 30 amps, the main breaker will trip.

As to how long the propane will last, I?ll leave that to others.

 

[Larry N.]

2. Want to be able to park RV in lot with Generator running with AC on for dog while we grocery shop, visit Casino watch Hockey game .... how long till LP runs out since the permanent LP tank is only 12.2 gallons?  Heard range of 18 to 22 hours - accurate??

You're saying that the generator runs off of LP rather than the same fuel as your road engine. If so, run time will be fairly short, compared with those run from the same fuel tank as the road engine. If you don't yet have the unit, I'd suggest looking for one that doesn't use LP. Although if you're looking a one with a Mercedes Sprinter chassis, then a diesel generator still isn't going to have a lot of run time compared to rigs with larger fuel tanks. Most gasoline class Cs have larger fuel tanks.

I'm surprised the fridge is a compressor type -- I didn't know that any class C rigs had a residential (compressor) type fridge. Usually they have the absorption type (typical RV fridge) which can run from either AC electric or LP.

 

[Isaac-1]

Depending on the model of the generator and how much of a load it is under you are looking at will consume about 1/3 -1/2 gallon of propane per hour while running the air conditioner.  As to the propane tank size, check to see if that is actual tank size or the amount of propane it will fill, by law propane tanks are only filled to 80% capacity, so a 12 gallon tank would only hold around 10 gallons of propane. 

 

[Molaker]

You don't say which model generator you have, but your description of your RV sounds like it might be on a Mercedes Sprinter chassis. Typically, those use an Onan 2500 KW which have a 20 amp circuit breaker built in. Meaning, you can't use "up to 30 amps" while on generator power. Only up to 20 amps. Otherwise, you'll find yourself crawing underneath to reset the breaker.

 

[Gary RV_Wizard]

You can use a maximum of 30 amps (3600 watts) at one time, regardless of whether the source is shore power or generator. Circuit breakers will trip if exceed the 30A combined limit.

The a/c plus the water heater will come very close to the 30A limit but only when the heater is actually heating water. It has a thermostat. so the heat switches on & off as needed.  You can shift the water heater to using propane instead of electric to eliminate that uncertainty. The fridge doesn't use a large amount of power, so not usually a problem. A coffee maker, though, is an electric heater and it too use a substantial number of amps - typically around 8 amps when brewing and 3-4 amps when warming.

The 3600 watt Onan LP generator uses about 0.7 gallons/hour at 50% load (1800 watts). 1800 watts will run the a/c and a few smaller items.  If you have a full 12 gallon LP tank, it would last about 17 hours at 50% load.  Longer if less load, shorter if greater.
This article may be of help:  https://www.lichtsinn.com/blog/should-i-get-diesel-or-propane-lp-generator/

 

[Isaac-1]

Note the dependency above partly depends on if the model you are considering comes equipped with the Onan QG2500 propane generator or the QG3600, the larger generator will consume slightly more fuel when running the same size load, in this case the air conditioner.