Converter or Inverter (they are different)

[wmtire]

One of the more often confused RV terminology things encountered is 'converter' and 'inverter'. Hopefully this thread will be able to simply explain what both are and their functions in a RV without getting too technical.

Most RV's will have two distinct electrical systems. One will be a 120 volt AC (Alternating Current) system like you are acquainted with using in a regular house. The other will be a 12 volt DC (Direct Current) system that you are familiar with in a vehicle with a battery. Your RV will have a combination of the two, with some things that only work off of 120 volt AC while other things that only work off of 12 volt DC.

1. When you are connected to some form of shore power (like at the campground power pedestal) or a generator that provides 120 volt AC, then you can use the items in your RV that work off of 120 volts AC. Usually this will be your air conditioner, microwave, television, water heater if equipped and utilizing an electric heating element, refrigerator if the type that can use 120 volt AC as an option or mode, and any of the 120 volt AC normal outlets in the RV that you would plug something into. When you are camping/boondocking without a form of shore power/generator, then you normally will not be able to use any of the aforementioned items/modes. 120 volt AC circuits in your RV will be protected by circuit breakers like in a house. (see pic below)

2. Now the 12 volt DC electrical system of your RV normally allows you to use your lights, furnace, thermostat, fans, water pump, radio, CO detector, slides if equipped, power jacks/stabilizers, brake breakaway switch, propane mode of a water heater, and propane mode of a refrigerator if equipped. This system will allow you to camp/boondock and use most of the necessity items in the RV except for those things listed in part 1. All you need is a charged battery (or batteries) to provide the 12 volt DC power. 12 volt DC circuits in your RV will be protected by fuses, like you see in a vehicle. (see pic below)



Next we will discuss what a converter does and it's function in your RV.

 

[wmtire]

CONVERTERS:

A converter takes 120 volt AC power and converts it to 12 volt DC power.

So why would you need such in your RV? If you recall from the previous post, we stated that you have certain items in your RV that only work on 12 volt DC (lights, pumps,fans, furnace, etc). When you use these items, then your battery (batteries) would provide the power for this. However after awhile, your battery would run down/deplete and you wouldn't be able to power these items any longer.

This is where the converter comes to the rescue. Your RV's converter will take 120 volt AC when you are plugged into shore power/generator... and convert it to 12 volt DC .....to power these 12 volt DC items instead of your battery. This converter keeps your battery from running down/depleting since the converter is now what is providing power to these items.....but only if you are connected to shore power/generator.

The converter also has one more very important function. It is also a battery recharger. Yes, when you are plugged into 120 volt AC, your converter will also recharge your 12 volt DC battery (ies).



Currently, the majority of RV's that have the 120 volt AC and 12 volt DC electrical systems will come equipped with a converter. That's converter with a "c".

Side Note: Since the converter takes 120 volt AC and converts it over to 12 volts DC, it is usually the only item in a RV that will have BOTH a circuit breaker for the 120 volt AC input to the converter.... and fuses for the 12 volt DC output from the converter.

One more point of confusion is converter amperage output, which will be measured in 12 volt DC. So say a converter is rated for 55 amps, this means it can output 55 amps in 12 volt DC to power items and/or recharge a battery. This is way different from how RV's are called 30 amp or 50 amp, which is measured in 120 volt AC. 30 amps AC would be over 330 amps DC.

Inverters explained in next post.

 

[wmtire]

INVERTERS:

An inverter takes 12 volt DC and changes it to 120 volt AC

Ok, now that we know just about ALL RV's will have a converter, let's discuss it's electrical opposite, which is an inverter.

An inverter allows you to power 120 volt AC items from your 12 volt DC battery (batteries). So why would you need an inverter?

Since an inverter takes 12 volt DC battery power and changes it over to 120 volt AC power, inverters used to be mostly only found on motorhomes which had a large bank of batteries to provide this power. You would use the inverter to power up items when camping/boondocking that needed 120 volt AC in order to use when you are not connected to shore power/generator. These items were mentioned in the first post.

As stated above, you usually only found inverters on motorhomes or RV's with an onboard generator, whereas the generator could be fired up to recharge the battery/batteries as they were depleted by the use of the inverter.

However, times are changing. Many RV's including travel trailers/5th wheels are now coming with a residential type refrigerator. This type of refrigerator ONLY works off of 120 volt AC. So if you want to boondock/camp without shore power and use this refrigerator, then you must have some form of a limited inverter (which will come factory installed on these type RV's).

Only some RV's will come equipped with an inverter. That's inverter with an 'i'.

Side note: There is a form of inverter/charger that you may see. It is a combination of an inverter, battery charger and transfer switch into one complete system. When AC power is available, the inverter/charger recharges the house batteries. It also allows any surplus AC power to pass through and power downstream AC loads, such as a television set or microwave oven. When AC power is disconnected, the unit inverts DC battery power into AC electricity.

 

[wmtire]

SOLAR:

We are going to briefly touch on solar power as it is also becoming more popular and many Forest River RV's are coming factory equipped with solar connections (aka zamp connections).

If your RV has solar panels or you install them after the fact, they are a different form of power but which takes solar power/sunlight and converts it to 12 volt DC.... and will recharge your batteries, and may also have some form of limited small inverter.

Here is a link to Forest River's brochure on zamp solar systems, which is a lot more detailed than we need to get into with this post:

http://www.forestriverinc.com/brochures/2014/2014zampsolarinfo.pdf

 

[wmtire]

I am adding this to remind our members that if they reverse their battery connections accidentally, they may also have to replace the reverse polarity fuses to the converter.

Have you possibly removed/replaced or connected/disconnected your battery cables. The reason for this is, if you possibly put the cables on backwards (even for a sec while the converter is powered)...then you will blow what is called the "reverse polarity" fuses that protect the converters circuitry. It's a good idea before removing any battery cables, to take a picture of their connections with your cellphone. This way you will have photos to make sure you reconnect them correctly, whether it be in a few minutes or a few months.

I would also suggest checking to make sure the converter is operating by either making sure it's circuit breaker is not tripped and/or the reverse polarity fuses (up to 3 total) are not blown. These reverse polarity fuses are there to protect the converters electronics should you connect a battery backwards, but we have also seen them blow when there is an inrush of current from the converter trying to recharge a depleted/bad/faulty battery sometimes. The converter is also a battery recharger when connected to shore power/generator.

If the 120 volt AC circuit breaker to converter has tripped... or the 12 volt DC fuses for the converter are blown, then the converter cannot recharge the battery. I would suggest checking both first to make sure. Once the battery runs down, then a depleted battery along with a non functioning converter, will not allow any 12 volt DC items in your RV to work even when connected to shore power/generator.

These fuses "can" be on the converter (if a deck mount type converter more common in 5th wheels) ... but many are also in the RV's distribution panel (see the two red 40 amp fuses below)..depending on make/model. See pics below for possible locations of the reverse polarity fuses.:

 

[wmtire]

Failed converter workaround

If you recall, in post # 2 above, it was explained that the converter will power the 12 volt DC items in the RV when connected to a form of 120 volt AC shore power/generator....as well as recharge the battery(s).

Sometimes the converter may fail. If this happens while you are camping, then the 12 volt DC items will simply get their power from the battery(s) in the RV...up to the point the battery(s) drain down from supplying this power...and since the non functioning converter is also the battery recharger, the battery(s) cannot be recharged. With a non functioning converter and drained battery(s), the 12 volt DC items explained in the first post above will cease working.

There is a workaround, so you do not have to cut your camping trip short. You can simply connect an automotive style battery charger (example below) to the battery(s), and charge the battery(s) this way.....so the 12 volt DC items can get power.

After connecting the recharger cables to the battery(s), just plug the battery charger into an outlet on your RV, or you can even use the 15/20 amp outlet on a campground pedestal if equipped.

This way you can finish your trip and then replace the converter at a later time. Everything will work.