Generator load question

[4Gcampers]

Hello, we have a new Sunseeker coming and I have a question about the 4kw Onan that it comes with. The whole purpose of upgrading to a motorhome was to be able to use some medical equipment while traveling down the road. We upgraded to the 15k btu a/c since we live in FL, not thinking of higher loads on the gen. Additionally our medical equipment requires about 500 watts, (not sure about peak or constant) Anyone have any advice or experience using the 15k AC unit plus about 500 watts? Thanks!

[dalford]

I went to the dometic site and it is recommended to have a minimum 3.5W genet for one 15K btu a/c. The unit is protected by a 20 amp breaker (2.4KW) but the unit draws about 15 amps (1.8KW). I assume there is a surge current but that is momentary.

https://www.dometic.com/01face5d-12b...3ce3bca2.fodoc

I don't know what your shore power is (30 amp or 50 amp) but each of those is 3.6KW and 6KW respectfully.

I would assume when traveling down the road you can use the dash air and not the cabin air thus no problem. It is only when you don't have access to shore power that you have an issue. You have to remember you will also be drawing power for other things. You can keep ref rig and hot water on gas.

If it is not too late you might want to get the next larger genet.

I don't know what medical equipment you are using but let me just say this about genets and this is my experience from MH's and boating. They can be really unreliable. Of all the problems I have had on my boats, the gensets take the cake. So, what I am saying if your medical equipment is critical keep your genset maintained and even then you can't always depend on it. I have become a pretty good genset mechanic over the years.

[dalford]

4G, I forgot to mention you may want to look into an inverter for your medical device especially for back up if it is a critical device. Inverters are pretty inexpensive for 700-1000 watts. Just check it out...

[RamblerGuy]

We also have a Sunseeker with an Onan 4KW generator and the 15,000 BTU A/C - heat pump option. The generator will handle the A/C - heat pump and other loads but does not have as much surge capacity as your shore line can provide. One time our generator stalled and shut off while running the water heater, heat pump and other normal loads, including the convertor working to charge the coach batteries, which were low. I suspect that what happened is that the starting load for the heat pump was too much with the water heater and other loads already on the generator. I just switched the water heater off, restarted the generator, and had no more problems.

I suggest that to be sure you have the 500 watts for your medical devices when you need to run the A/C or heat pump that you switch the water heater off. Don't add more loads such as an electric space heater.

Also, I don't think you can get a larger generator on a Sunseeker. You could check with your dealer or call Forest River customer service. Ask for April Conner.

[4Gcampers]

Thanks folks dalford and rambler guy! We used to have a TT with a 15btu AC, but never had a generator. We always camped with shore power. I had no idea 30a shore power only provided 3600 watts. We never tripped any breakers before. Yes, D, one of our medical machines is over 20k dollars, so we have to protect it! Rambler, it's good to hear you haven't had any issues. I rarely see us using the heat pump, just Ice cold air! We could work around leaving the water heater off during treatments. What do most class c owners do traveling down the road, use the cab AC or the dometic? My kids will be sitting on the couch and dinette behind us. We may not even need the 15k unit running.

[4Gcampers]

One more thing, there was no option I could see to upsize the genset on the Sunseeker beyond 4kw.

[bclemens]

No option for larger Gen. The 15k does draw more than the 13, but I'm not sure if going back to the 13.5k is enough of a difference to make everything OK for the medical equipment. As others have said, run the dash air when in transit and the medical stuff will be fine.

Is it too late to switch back to the 13.5K?

[4Gcampers]

Bclemens,

I think our unit comes off the line at the end of Feb. I'm apprehensive to make any more changes at this point since we already some changes to the original order like interior decor and side view cameras. If I try to change one more thing we get a big surprise during delivery! Our local FR rep, Chris was nice enough to see that we got the cabinet installed over the door to hold all the extra meds we have to carry too. We have a 30" model and with all the florida camping we do I really think the 15K unit will better meet our demands on shore power. Do most people just rely on cab air to keep the coach cool when traveling?

[kenandterry]

4G......

Just a thought for cooling off while travelling down the road........

If the situation allows.......meaning no one in the rig other than two people riding up front in the cab.....and cooling from the dash air vents is not enough......you can do as some people do (Class A, B, and C motorhomes) where you can install some form of drapery or curtains behind the front seats to make the cabin area smaller.

Sometimes the dash air can't handle cooling off the entire rig, but can handle the smaller cockpit area. (this same condition applies to heating capacities for some rigs) If hanging a fabric behind the driver's seat blocks some of your visibility rearward, then try using a clear plastic shower curtain to allow some light or visibility as needed.

[dalford]

Originally Posted by 4Gcampers

Thanks folks dalford and rambler guy! We used to have a TT with a 15btu AC, but never had a generator. We always camped with shore power. I had no idea 30a shore power only provided 3600 watts. We never tripped any breakers before. Yes, D, one of our medical machines is over 20k dollars, so we have to protect it! Rambler, it's good to hear you haven't had any issues. I rarely see us using the heat pump, just Ice cold air! We could work around leaving the water heater off during treatments. What do most class c owners do traveling down the road, use the cab AC or the dometic? My kids will be sitting on the couch and dinette behind us. We may not even need the 15k unit running.

4G... Power(watts) = volts X current, for your future reference. I also mentioned an inverter but be real careful here. Your medical equipment is very expensive and the 120 volts ac provided by some or most converters is, let me say, not a clean sine wave. If you should want to go that route just make sure the unit generates a good output waveform

Also, if you don't already have one you need to get a good surge protector for your shore power when at a RV site. RV parks can have issues with their power and you certainly don't want a transient damaging your medical equipment or any other electronic equipment on board.

Search - surge guard - Camping World

[4Gcampers]

Thanks or the numbers Dalford. I did check with the mfg. of the medical equipment and they advised against use with an inverter, but no issues with proper generator use. We'll have to work around the loads and see how it is going down the road. We could use the AC to cool for awhile, them shut it down for an hour during treatments. Plug in a small fan, etc. Ironic you mentioned the surge protector. We just bought a nice unit from progressive technologies at the Tampa fl. RV super show. It seems to handle any power problems you can come across.

[RamblerGuy]

This is a little long, but with your situation and being new to the motorhome, these thoughts may be useful.

The two of us had no problem staying cool in west Texas driving all day in 104 degrees with only the cab air conditioning. The relative humidity was 4% and there was a 20 mph wind. It was probably in the high 80's in the coach when we stopped for the night so I set up a fan to blow air on us while the A/C cooled the coach. It took several hours for the A/C to cool it down to the low 70's. If you are in 100 degree Florida humidity the coach A/C won't cool as well as it did for us in dry Texas because some of the A/C output is being used to remove humidity. You may need to run the generator and coach A/C because when you stop for the day it would take a longer for the coach to cool down. The generator uses between 0.5 and 0.7 gallons per hour of gasoline when it is running loaded.

To cool the coach down faster, you can open the downblast vent on the A/C unit, close the ceiling vents in the rear of the coach including the bathroom, and close the door to the rear. This puts more air into the living room area so it will cool faster. Just open up the rear area after the front has cooled off.

Would you be in difficulties if you had no shore power and the generator failed or didn’t start? You may still want to consider an good inverter so you can run your equipment off the coach batteries in case the generator fails. (You’ll have to get someone else to tell you what inverter to get so it doesn’t harm your equipment.) I believe the Onan is quite reliable, but things happen. The coach’s automatic transfer switch could fail. You could get some bad gasoline, etc., or the gasoline could go bad during storage. Small engines don’t tolerate bad gas as well as automotive engines. If the coach batteries are low you can run the chassis engine for 12 volt power. The coach’s battery control center will connect the chassis 12-volt system to the coach’s 12-volt system so the chassis’s alternator will provide 12 volts to the inverter. (On the other hand, if you are in a campground I have no doubt that you could get someone else with a generator to supply power to you.)

Here’s another tip about the generator. The generator is normally started by the coach batteries. If the coach batteries are too low, you can’t start the generator with them, but if you start the chassis engine, the battery control center will connect the 12 volt systems and the generator can be started. You can stop the chassis engine as soon as the generator is running.

Also, be sure the dealer gives you a thorough check-out on the coach’s electrical systems. You need to know where the coach’s 120 volt circuit breakers are, which receptacles are on which breakers, and especially where to find and reset the generator’s built-in circuit breaker. You may trip a breaker if you are running your equipment and another heavy load like a space heater is on the same circuit. There is a GFI receptacle in the bathroom that feeds other receptacles. If the GFI is tripped there will be no power at those other receptacles. The GFI can be tripped by accidentally pushing the test button and you will have no power even though the breaker in the coach’s panel is still on.

If you have a problem during a trip and have a laptop or smart phone, you can post a message to this forum. If you title the message with something like “Help – on the Road” you may get a reply pretty quickly.

[4Gcampers]

Wow Ramblerguy, thanks for the wealth of information you provided. Lots of things to consider and yes, I will have to pay close attention during my PDI so I learn all the electrical systems on the coach. Much more elaborate than my one 12v battery on my Travel trailer. To answer your question, we only really camp in parks with hookups, so generator usage will be used mainly on the road, or out on day trips. If we ever had an issue with the coach genset and we were away from shore power we would have to look or a hotel. I also have a 30a rv outlet at my house, so we'll keep the batteries charged good. I'm crossing my fingers that during most of our road trips the van AC would cool enough, unless it was just extremely hot. Again, thanks for all the good points you brought up, I will certainly look into them and if I'm ever stranded, this is where I'll look for help!

[RamblerGuy]

Glad to be of help.