1999 Gulf Stream seahawk 30fks isolator switch?

[Thorium]

Hello and thanks in advance to anyone who can help. I recently acquired a 1999 Gulf Stream seahawk 30fks fifth wheel. It needed *some* work. While ripping it down to the studs I replaced a ton of the electrical. Not knowing about isolator switched and the like, I wired some of the new lighting into the existing 110 system, but now those won’t work without an external power supply hooked in. Anyone know where (if) an isolator switch might be on this beast? If not, any suggestions on a new inverter I could install that would allow the 110 system to run off the battery? I have a large battery bank so I’m not worried about the power drain. I am going to be living part time in this so I need the 110 system to be able to pull from the battery at need (can’t run a generator all night!). Thanks for any help.

[Chuck v]

Not sure how an "isolation switch" is going to help -- what are you trying to isolate?


Most of the lighting in modern RVs is run on the house battery at 12 volts, so it is surprising that you changed anything over to 110 volt ac wiring and fixtures... Your best route is to restore the original lighting to 12 volts...but if you made all the hacks under the now replaced walls that may be difficult.


Running 110 volts from an inverter is quite inefficient for low wattage loads, as these inverter systems are sized for running near peak rating.


Chuck

[Thorium]

Looking around it seems some RV’s have a switch to isolate the battery from the 110 system or have that system pull from the battery. That’s what I’m wondering if this model has. I could rewire the original 12v for the lighting but that doesn’t solve the problem of not having use of the outlets when running off just the battery. I need the outlets to draw from the battery if needed, so rewiring would be pointless as I need to have the 110 be able draw from the battery if needed. I have 10kWh of storage so I’m not at all worried about the power drain.

I guess I’m just wondering how to get the 110 to draw from the battery. I am not going to pull my new wiring so any thoughts on how to make that happen would be helpful. I know it should be possible as the external power will charge the battery, so I just need to be pointed in the direction of how to make that happen.

[Chuck v]

Thorium,


I see now your confusion -- there is not an "isolator switch" to allow the 110 volt appliances/loads to operate directly from a battery...that function is provided by an INVERTER. Such an inverter uses sophisticated electronics to create a shaped waveform or even a 'true sine wave' output that is used instead of the generator or shore power. This process is less than 100% efficient (and so is the recharging of your batteries...) so the number of watt hours stored is not the number you will get from an inverter -- it will be less. The proper inverter system should have a transfer switch to automatically select between inverter output when available or the shore power (or generator) when it is not. It needs a large battery bank...my coach had 450 amp hours of 12 volts dedicated to just the inverter, separate from the other two banks for coach and chassis loads. That dedicated bank was comprised of four each 225 AH 6 volt deep cycle golf cart batteries.



Please describe what you have in your RV that you believe amounts to 10Kwh of storage. Batteries are rated in amp hours at a 20 hour discharge rate, so a 12 volt 10 Kw-hour bank would need to have a rating of about 833 AH or more. This is about 10 times the rating of a single normal 12 volt battery, but some of the better deep cycle RV batteries have about 100 AH ratings. Do you have eight or nine of these???


The attached diagram is for my large diesel pusher coach with three banks (one dedicated to the inverter...) so you can see what is involved:


Chuck

[Thorium]

I am familiar with how an inverter works, but thank you. I’m not super familiar with this RV yet so I was looking to make sure I needed to buy a new one, that it wasn’t hidden somewhere. I would take recommendations on good inverters that would perform the functions I need though! I am half way decent at electrical work I just…don’t like it.

As for the battery bank I have three 12v deep cycle 310ah batteries. They are expensive but I got them on a partial trade so it was actually a good deal.

[Chuck v]

Thorium,


OK, so you are using 8D size 12 volt batteries -- the big 190 lb ones ! Each of these is about the capacity of three normal RV deep cycle 12 volt batteries, so you do in fact have the equivalent of the 9 batteries I first asked about.


That gives a total of 570 lbs of batteries so I guess you have a good place to mount them and they just subtract a bit from your cargo weight to keep your rig within its load limits.


They do OK when charged/discharged in parallel if they are the same manufacture date and same brand and in the same condition. Charging them optimally would need about a 90 amp converter, so maybe your rig has more than the 60 amp unit most compact RVs have. Notice I said "converter" which is the appliance that makes 12 volts out of shore power and runs the lighting, furnace fan, etc and also keeps the house batteries up when at a developed campsite. All modern RVs have a converter, but many as you note do not have an INVERTER, particularly the 20 year old ones like yours.


To find an INVERTER if it is in your RV now, look for heavy gauge wires at your battery location that go to an electronics package -- these will be AT LEAST the thickness of car jumper cables since they need to carry large currents. How large? If you have an inverter of 2000 watt continuous 110 volt AC output (and presuming it is at least 85% efficient...) it will draw 196 amps continually from the battery bank at that output load. Even with your large battery stack, that amounts to a "5 hour" discharge rate...meaning it could provide this 2000 watts for only 5 hours before completely draining all charge from your batteries. Clearly you want to load an inverter with lower wattage loads and for sorter intervals -- this is why the RV air conditioners are not run on inverters.



The large inverter in my 43 foot long diesel pusher coach was set up to run the residential refrigerator (an intermittent load of a few hundred watts), the microwave (again a short duration use) and the TV. It did NOT run the washer/dryer, the air conditioners, the diesel engine block heater, etc for obvious reasons. It also had its own dedicated battery bank so it could not deplete the house battery bank or the engine starting battery bank.



If you find you do not presently have an INVERTER in your RV, there are many brands out there targeted at small vans through larger rigs. The solar industry has given rise to reasonably priced units. Some are inverters only -- others have battery chargers and management systems built in. Watch out for peak versus continuous ratings, as some inexpensive imported units are not meant to run a long duration without getting quite hot. The heat sink ribs on the cases of any inverter without its own cooling fan built in should be an indication that they need to have space around them and adequate air flow...


Good luck!


Chuck