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 > When on inverter am I using the batteries?

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valhalla360

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Posted: 02/07/18 02:30am Link  |  Quote  |  Print  |  Notify Moderator

msturtz wrote:


In 99% of the lower end motorhomes the inverters and most combined inverter converters have automatic transfer switches that will select external power when available. This is separate and distinct from the generator automatic transfer switch. In general there is an automatic transfer switch between shore power and the generator (some coach manufacturers bias the generator power when available) and then power is routed to the inverter incoming AC power supply inputs (not the DC side) if power is present on the incoming AC supply line for the inverter that closes an internal relay which turns off the inverter circuit and disconnects the inverter power circuits from the coach. This means the power provided to those outlets is provided by incoming shore power. There are a few variations that are very uncommon some especially older coaches had designated “inverter only” outlets that were only powered by the inverter. This method is very common in the towable market because they generally don’t have onboard generators. Another uncommon system is to have a phase locked paralleled inverter system. These combination inverter converters are generally referred to as “hybrid” inverter systems that will sync their line phase to the incoming AC if available. The inverter and associated EMS system manage the demand by load shedding. This means the inverter may come online and start powering certain circuits if the instant demand exceeds the available AC power supplied. For example, if a coach has 3 15K BTU AC units and the customer starts running the microwave the EMS system may direct the hybrid inverter to start powering the microwave by drawing power from the batteries at the same time it commands the battery charger (also called a converter) to stop charging. This is especially useful if the coach is plugged into a 15, 20, or 30 AMP shore power connection and 50 AMP split phase power is not available. These systems are generally only available on very high end coaches. It is also important to note that most inverters on most coaches provide square wave otherwise known as modified sine wave power not pure sinewave power. Many things do not work well with MSW power.


The problem is with your original comment, you made the assumption that is was a factory installed inverter/charger and had the transfer option.

His comment about plugging into the "inverter outlet" under the fridge initially supported the idea that it might be a stand alone unit.

For all we know, a prior owner installed a stand alone inverter (quite common), so it could easily have lead him to an incorrect assumption.

I was just clarifying for others who might take your blanket response to heart and have issues.


Tammy & Mike
Ford F250 V10
2008 Copper Canyon 5er
Catalac Catamaran 34'
Full Time spliting time between boat and 5er


dougrainer

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Posted: 02/07/18 05:39am Link  |  Quote  |  Print  |  Notify Moderator

What Mr Wizard states is TRUE. But not for the reason he stated. You ALWAYS disconnect Shore Power before starting the Genset AND turn off the Interior MAIN Breaker/s. You NEVER Transfer with a LOAD. This prevents arc'ing of the Transfer relay points, which causes wear and premature failure. Read posts from people that state they have multiple failures of Transfer boxes. Caused by transferring under load. You also Turne Loads OFF when turning the Genset OFF. Some Transfer boxes close a relay when connecting either Shore or Genset. Some, the Shore relay stays closed. Unless you know for sure which style you have always have NO LOAD when engaging various Power supplies. Doug

dougrainer

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Posted: 02/07/18 05:41am Link  |  Quote  |  Print  |  Notify Moderator

The 4th post on this thread stated the model Inverter/Charger. THAT should have stopped the rest of the Conversations. The OP's when plugged into Power will NOT draw Battery Power as it has pass thru relay. Doug

dougrainer

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Posted: 02/07/18 05:45am Link  |  Quote  |  Print  |  Notify Moderator

devildog1971 wrote:

If your inverter is off will your batteries still charge? I am new to the class A R V they are a lot different from the truck campers I have had until now. sorry to cut into the thread but maybe the op might need to know also.


You need to post the Brand and Model of Inverter and year/brand/model of RV. In simple terms, IF you have an Inverter/Charger, and you turn the Inverter OFF, only the Invert side is off, the charger remains ON. Since this is a motorhome forum, most motorhomes have an Inverter/Charger, not an Inverter ONLY. Doug

msturtz

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Posted: 02/07/18 10:49am Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

What Mr Wizard states is TRUE. But not for the reason he stated. You ALWAYS disconnect Shore Power before starting the Genset AND turn off the Interior MAIN Breaker/s. You NEVER Transfer with a LOAD. This prevents arc'ing of the Transfer relay points, which causes wear and premature failure. Read posts from people that state they have multiple failures of Transfer boxes. Caused by transferring under load. You also Turne Loads OFF when turning the Genset OFF. Some Transfer boxes close a relay when connecting either Shore or Genset. Some, the Shore relay stays closed. Unless you know for sure which style you have always have NO LOAD when engaging various Power supplies. Doug


I'm sorry to have to disagree with you. Proper transfer switches are designed to switch "under load". I have experience with RV type transfer switches but also automatic emergency generator systems. These systems routinely transfer "under load" by definition. The same is true for UPS systems which I have specified in my job. While it is true that the relays can wear out over time due to arcing that should be minimal as these devices are specifically designed to be operated in this manner. In fact, properly designed and implemented transfer switches should be completely transparent to any connected system i.e. the dropout should be less than a fraction of a phase cycle. The capacitors in most equipment should bridge that short of a mid cycle dropout. More advanced transfer equipment common in UPSes can actually use phase drift to wait until both sources are in phase prior to switching over. RV switch gear usually isn't that advanced unfortunately. Bottom line is with a properly wired and designed system (RVIA and NEC codes) in no case should anything bad happen if you have all three sources of power available at the same time. It CAN happen with a mis-wired coach or with defective equipment however the underlying problem MUST be corrected rather than masking it by turning off all sources of power prior to switching over. All this said if a person wants to cut all power and then start up the new source go ahead but it will only be a marginal at best savings on the transfer switch(s).


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wolfe10

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Posted: 02/07/18 11:28am Link  |  Quote  |  Print  |  Notify Moderator

msturtz wrote:

dougrainer wrote:

What Mr Wizard states is TRUE. But not for the reason he stated. You ALWAYS disconnect Shore Power before starting the Genset AND turn off the Interior MAIN Breaker/s. You NEVER Transfer with a LOAD. This prevents arc'ing of the Transfer relay points, which causes wear and premature failure. Read posts from people that state they have multiple failures of Transfer boxes. Caused by transferring under load. You also Turne Loads OFF when turning the Genset OFF. Some Transfer boxes close a relay when connecting either Shore or Genset. Some, the Shore relay stays closed. Unless you know for sure which style you have always have NO LOAD when engaging various Power supplies. Doug


I'm sorry to have to disagree with you. Proper transfer switches are designed to switch "under load". I have experience with RV type transfer switches but also automatic emergency generator systems. These systems routinely transfer "under load" by definition. The same is true for UPS systems which I have specified in my job. While it is true that the relays can wear out over time due to arcing that should be minimal as these devices are specifically designed to be operated in this manner. In fact, properly designed and implemented transfer switches should be completely transparent to any connected system i.e. the dropout should be less than a fraction of a phase cycle. The capacitors in most equipment should bridge that short of a mid cycle dropout. More advanced transfer equipment common in UPSes can actually use phase drift to wait until both sources are in phase prior to switching over. RV switch gear usually isn't that advanced unfortunately. Bottom line is with a properly wired and designed system (RVIA and NEC codes) in no case should anything bad happen if you have all three sources of power available at the same time. It CAN happen with a mis-wired coach or with defective equipment however the underlying problem MUST be corrected rather than masking it by turning off all sources of power prior to switching over. All this said if a person wants to cut all power and then start up the new source go ahead but it will only be a marginal at best savings on the transfer switch(s).


Here we are getting into "best practices" vs "what I got away with".

Both statements are correct. YOU have to decide which philosophy you want to follow.


Brett Wolfe
2003 Alpine 38'


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dougrainer

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Posted: 02/07/18 02:11pm Link  |  Quote  |  Print  |  Notify Moderator

Msturtz. You have "experience"? I have 38 years as an RV technician and still working. I guess I have experience also[emoticon] From just one of the various RV Transfer switch makers instructions. Doug

BEFORE TESTING:
Ensure air conditioning units and other high current users are switched off. It is
harmful for the transfer switch to switch over power sources while under load.
Shut down all power sources to the RV
Label power sources clearly that testing is in progress.
If accessible, remove the lid of the ATS to visually check function

msturtz

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Posted: 02/07/18 02:52pm Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

Msturtz. You have "experience"? I have 38 years as an RV technician and still working. I guess I have experience also[emoticon] From just one of the various RV Transfer switch makers instructions. Doug

BEFORE TESTING:
Ensure air conditioning units and other high current users are switched off. It is
harmful for the transfer switch to switch over power sources while under load.
Shut down all power sources to the RV
Label power sources clearly that testing is in progress.
If accessible, remove the lid of the ATS to visually check function


Are you saying that you have documentation from the ATS manufacturer(s) that state that all power must be removed when switching power sources? If so, I would absolutely love to see it. I have seen some crazy things in the RV world that would arguably not comply with NEC or any other rational code. That said I work for a heavy truck manufacturer in the Research department. I have specified, removed, & installed large UPS systems as well as I have installed standby generator system with 100 AMP split phase computer controlled transfer switch. I have also installed split phase 240 VAC EVSE equipment that similar to ATS equipment the transfer is ALWAYS done "under load". Your point about arcing across the contacts is possible especially with very old and slow switch gear but with modern switch gear the components should last the life of the coach. Having said all this it is usually a good idea to turn off large loads when switching especially when switching from shore to generator. The reason is many generators are under powered and will sag voltage and spike current when a sudden load is transferred over. It is better for the generator to have a smaller load transferred. In my coach the generator is biased by the switch gear so if the generator is on it is powering the coach. I also have an EMS system with a 2 minute delay timer. The net effect of this is the incoming power is delayed by two minutes before cutover. Also my coach as an AGS (Automatic Generator Start) system. By definition, I would not be able to run around switching off power before the system starts the generator. It happens automatically without any intervention from me. If it was damaging or unsafe to "hot switch" between inverter and generator power I'm quite sure that the coach manufacturer would not have installed such a system.

rgatijnet1

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Posted: 02/07/18 03:00pm Link  |  Quote  |  Print  |  Notify Moderator

When plugged in to shore power, on my coach, the 12 volt items are still connected to the batteries so any lights that I use, vent fans, etc. will still be drawing power from the batteries, even while I am plugged in to shore power. Naturally the inverter/charger will keep my batteries charged while plugged in.

wolfe10

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Posted: 02/07/18 03:00pm Link  |  Quote  |  Print  |  Notify Moderator

See my post above.

Can you switch under load, YES. Does it pit/burn the contacts, YES. Amount of damage depends on size of contacts, material they are made of and amount of current and(IMPORTANT)how frequently you do it.

There is always a point where the contacts are not yet in full physical contact, but the air gap has diminished to a point that electricity arcs across the gap.

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