Adding an Invertor

[Chalkie]

I will start with saying I am pretty much an idiot when it comes to electricity. My son, however, is a Journeyman Electrician, so I do have some expert help.

 

I have been considering adding an invertor somewhere in the trailer. When we are traveling from point A to point B we usually stop and have some lunch. I have to tell you, I am really tired of having a sandwich when that microwave could be making some soup or Chef Boyardee or something.

 

So where would the best place to hook in an invertor and have it be switchable (i.e., not on all the time) so as not to drain batteries?

 

If this query is not making sense then please call foul and tell me so. Thanks!

 

[RBH]

As close to the batteries as possible. As large a gauge of wire as the terminals will take. The higher end inverters have remote switches included or available as extra. You will probably need at least a 2000w to run a microwave. You could run romex to a dedicated outlet for the microwave but you'll get the most use if you install a sub box that carries a few circuits that you might want to use the inverter for. Your son will surely be able to help with the 120 side of things.

 

Rich

[Yarome]

It's certainly very doable. Rich gave good advice. To be of any help though we would need to know more about your current setup. Ie., battery size and type, battery location, size of microwave, distance from battery bank to power distribution panel, and/or distance from battery bank to microwave outlet, do you run a genset?, what type of camping do you generally do (cg's or dry)?, what type of converter are you using (stock/upgraded/stand alone charger)?

 

Nit picky stuff like that

[Chad Heiser]

There are several things to consider when deciding to add an inverter.

 

1. What all do you want to power with the inverter? Do you just want to power one or two items, or do you want to run a number of things?

 

2. What are your power needs? Do the things you want to power need clean pure sine wave power or can they run off of modified sine wave power?

 

3. What is your current battery bank capacity? A properly sized battery bank is needed to run an inverter effectively.

 

4. Do you have existing battery charging capabilities to replenish the power drawn by the inverter? This could be a genset or solar. This would also take into consideration your current converter/battery charger. Is it the standard "dumb" charger or does it have a "smart charge" capability?

 

5. Do you have battery monitoring capabilities above and beyond a standard voltage display?

 

There are other considerations, but these are the big ones.

 

In your post, you only talk about wanting to run the microwave for a couple of minutes when you stop while traveling. Is this the only thing you want to run off the inverter? Do you also maybe want to power a coffee pot or the television? Is your only consideration the convenience of cooking a quick meal while on the road? If this is the case, then adding a properly sized inverter and adding a couple of inverter specific plugs in key locations is relatively easy to do. This does require you to manually plug the couple of items you want to power with the inverter into those inverter specific plugs. Are your inverter wants/needs greater than just a couple of specific items needing power? If this is the case and you want to power several things (like the microwave, coffee pot, hair dryer, television/surround sound, etc - not necessarily all at the same time) while boondocking as well as cook a cup of soup in the microwave at a rest stop while on the road, then installing a properly sized inverter with a built in transfer switch that powers a small electrical sub panel with all of these circuits powered by the sub panel is the way to go. This type of set up is often referred to as a "whole house" set up. With this type of set up, you do not have to worry about moving plugs between outlets, you simply turn the inverter on and everything in the sub panel is powered just as if you are plugged into shore power.

 

As you specifically mentioned running a microwave, I would recommend a pure sine wave inverter. This type of inverter costs more initially, but supplies the same type of pure power that the local utility company supplies. It will not harm electronics or electric motors and is indecipherable from regular power. Modified sine waive inverters use squared power waves that mimic regular power, but are a little different. This kind of power can be hard on electronics and and other sensitive equipment.

 

You don't say in your original post what size or type of battery bank you currently have. Most RVer's with a moderate sized inverter (2000 watt or so) usually have a minimum of four 6 volt true deep cycle golf cart style batteries run in a series/parallel configuration to start with. You can get by with with a smaller battery bank for a small inverter used sparingly, but this is a good place to start.

 

I assume your coach currently has the OEM converter installed as your on board battery charger. If this converter has smart charge capabilities (or can be upgraded with a smart charge algorithm) and puts out decent amps, it may suffice as your sole battery charger in a moderate sized inverter set up powering a couple of outlets. If you want to go with a more involved whole house inverter set up that powers more items, then I would recommend buying a good inverter/charger that will replace your converter. Inverter/chargers will have high amp outputs to quickly recharge your battery bank using smart charger algorithms. This will reduce the amount of time you need to run a genset or plug in to shore power to recharge your battery bank. Also, if you do not have solar, this can be added down the road to help recharge batteries and further reduce or do away with the need to run gensets or plug in.

 

Finally, any inverter set up should have a proper battery monitor to allow you to know exactly what state your battery bank is in. You want to know what your current state of charge is, how many amp hours have been used, how many amp hours are still available to be used, etc. This can only come from a proper battery monitor like a stand alone Trimetric 2025 or an integrated Magnum BMK or something similar.

 

An inverter set up can be simple or complex or somewhere in between. It really comes down to what your needs are and how much money you want to spend. I have installed simple set ups that power a couple of plugs and complex whole house setups that power the entire RV. It all comes down to the needs of the user.

 

There are a lot of smart people on this forum that can give good advice so ask away. I know I and many others are happy to help.

[Chad Heiser]

I will start with saying I am pretty much an idiot when it comes to electricity. My son, however, is a Journeyman Electrician, so I do have some expert help.

 

I have been considering adding an invertor somewhere in the trailer. When we are traveling from point A to point B we usually stop and have some lunch. I have to tell you, I am really tired of having a sandwich when that microwave could be making some soup or Chef Boyardee or something.

 

So where would the best place to hook in an invertor and have it be switchable (i.e., not on all the time) so as not to drain batteries?

 

If this query is not making sense then please call foul and tell me so. Thanks!

 

To specifically address your questions in addition to my long post above:

 

1. The best place to locate an inverter is as close to the battery bank as possible. You want the DC cable run between the inverter and the battery bank to be short so there is little or no voltage drop. If your battery bank is a lead acid bank, then the inverter should not be in the same compartment as the battery bank due to the corrosive and explosive effects that the off gassing of a lead acid battery bank can have when combined with the electronics of an inverter.

2. Most decent inverters at least have an on off switch directly on the inverter so it is only drawing power from the battery bank when needed. Many inverters also have remote switches or displays with switches that will allow you to turn the inverter on and off as needed from inside the RV wherever you decide to mount the display/switch.

3. The AC output from the inverter can be run to pretty much anywhere in the coach that you can run wire for a plug. In the case of a whole house system, you only need to run an AC supply wire from the main power panel to the inverter and then an AC load wire from the inverter to the new sub panel. The circuits you want to power from the inverter will have to be moved from the main power panel to the sub panel. As long as the sub panel can be located close to the main panel, this is a relatively simply process.

[Bill B]

All good posts Chalkie. It really does get into the "it depends" realm.

I'll try something a little different.

Starting with you current configuration. 2008 Ford PSD SRW, 2013 Infinity 3640RL Fiver with Trail-Air pin box

There are going to be many assumptions here, that you'll need to clarify.

power panel in the basement - easy to get to the wiring
separate breaker in the panel for the microwave
Batteries - pair of 6 volt, 2-12's - your going to need more than 1 -12 volt
microwave size - standard RV?? 800 watt output with 1200 watt input??

How do you travel - campground to campground with a stop for lunch? - Wallydocking once in a while?

What are your expectations out of the system?

If your just looking to heat some soup, there is always the propane burner.

 

For your stated purpose, I would get a 1500 watt Pure Sine Wave (PSW for short), mount it as close to the batteries as I could, and run a piece of romex to a place by the electrical panel. I would pull the microwave feed out of the panel and replace it with a receptacle, put a cord cap on the line to the microwave and plug it into the power panel or inverter.

 

Getting fancier, there could be a remote for the inverter, small auto transfer in place of the cord, etc. If your son does the autotransfer, remind him that the ground and the neutral will have to switch. (all returns to the source of power)

 

12 volt power - a typical deep cycle battery holds / stores 100 amp hours of power. Usable power (without hurting the battery is about 50%). Quick, heavy loads (Inverter type loads) reduce that another 30%. So we end up with about 35 amp hours of "first use' power. (If we let the battery rest a bit between use, we get some of the 30% back).

 

So, we heat up the soup for 5 minutes. And we'll use the 1200 watt microwave input power from above. 1200 watt / 12 volt is 100 amps + 10% (The inverter doesn't do it for free) = 110 amps * 5 min (remember that the trailer micro is slower than the house one) / 60 min = 9 amp hours of our battery. Want a hot cup of instant coffee to go with that soup? Another 5 minutes, another 9 AH. Wife going to have a cup of tea? Another 5 min and 9 AH - and your single battery is getting into the loss of life range.

 

OK, lunch is done and we head on down the road for and hour. Hey, let's stop at the **** museum. Done with that? A cup of coffee / tea and on to the campground. That hour on the road may? have replaced 5 of the 27 amp hours you took out of the battery. It's a (electrical at 12 volts) stretch of mediocre wire from the front of the truck (alternator) to the trailer battery and back again (return path).

 

Not trying to discourage you, but trying to base some realistic expectations on the system. Just throwing an inverter in there requires a bit of planning thought.

[Chalkie]

Thanks for the above answers, especially to Chad Heiser and Bill B. (whose response came in just as I was posting) for the very detailed information.

 

I now appreciate that there is much more to this idea than I had initially imagined. While it would be far more money, I am almost thinking we might just want to invest in a genset. The trailer has a compartment for one and is all prewired for one. I think I can get my son over this weekend to closer study the possibilities.

[Bill B]

Hey Bud - Nothing wrong with a little EU2000i Honda. I have a 38' New Horizon, 800 amp hours of battery, 2500 watt inverter, 400 watt of solar and will still use the Honda. We have truck stopped, Wally Docked, and first thing in the morning, pop that puppy on, made coffee and breakfast (put some power back in the batteries from overnight), and on down the road. I bought that long ago (2 trailers) still use it a lot. Today, I would buy a Companion model (shows how long ago that I bought it, they didn't make that then). Have the son modify the trailer wiring for quick use,

 

I did mine so that I can use the generator under the fifth overhang (out of the rain). Open a compartment, take it out, 120 volt into the trailer, and things are powered. It cuts down even more on the noise, out of sight, out of the rain. Guessing 3 minutes from standing there to powered.

 

The FULL hookup is 125/250 volt 50 amp with several A/C's and the plug in in the middle road side.

[RickS]

Chalkie,

What is your budget for a project like this? We have travelled for many years and would not even consider not having an inverter. There are some great suggestions above. If, you are going the inverter route to power a microwave you might as well get the benefit of the expense and do a sub-panel and wire up most of the RV. You will find you will use it more than you think. We stop many night's while we're traveling at WM's and power on the satellite and entertainment center- microwave a bag of popcorn and just relax like we would if we were plugged into shore power. The battery bank we have is 690 a/h's and 705 watts of solar panels. We have a built in diesel 7500 watt genset that we use for AC if it is hot but like the quiet of the just using the inverter 98% of the time.

[Jack Mayer]

If you are going to get fancier than above, or want to expand out into solar, etc then you might find my website helpful. I cover most of the issues there. LINK

[Bill&Cindy]

I too am starting to think about an inverter and solar. I have seen a subpanel mentioned several times. When you install a subpanel and wire it to the inverter, does that mean the inverter runs those items 100% of the time or is there a switch that runs them only when not hooked to shore power

[Chalkie]

We have not really set a budget as this is still in the what-if phase.

 

Right now we have 2 12v Deep Cycle batteries wired in parallel. The batteries are in the front compartment with the hydraulic system. The breaker panel/converter/charger is located in a cabinet in the kitchen. The shore power plug is the rear of the trailer. As can be seen there is nothing close to each other, or precisely easy to get to. Since it is pre-wired for a genset there is a box in with the batteries that I "think" ties into everything as it is where the generator would hook up. I should be able to use that for a small portable generator although an Onan has a certain appeal too as it would allow us to turn on an a/c prior to arriving at a camping spot.

 

There is a company here in town that sells and installs Onans for far less than say Camping World. Think I will have to pay them a visit to see what I can learn.

[Chalkie]

If you are going to get fancier than above, or want to expand out into solar, etc then you might find my website helpful. I cover most of the issues there. LINK

 

Thanks for that link, Jack! Lots of info there to digest.

[Bill&Cindy]

I frequently go to Jack's site for info. It is one of the best I have found for those of us who are not electricity savvy.

[Yarome]

I too am starting to think about an inverter and solar. I have seen a subpanel mentioned several times. When you install a subpanel and wire it to the inverter, does that mean the inverter runs those items 100% of the time or is there a switch that runs them only when not hooked to shore power

 

Normally you would just pop a transfer switch in there so when you're on shore power.. everything is powered. On inverter.. only the items in the subpanel are powered.

[Bill&Cindy]

So you would run from the main panel to the transfer switch and then to the subpanel?

[Mark and Dale Bruss]

 

 

I too am starting to think about an inverter and solar. I have seen a subpanel mentioned several times. When you install a subpanel and wire it to the inverter, does that mean the inverter runs those items 100% of the time or is there a switch that runs them only when not hooked to shore power

Normally a good inverter/charger has a built-in transfer switch. So when shore power is available, the power flows through the inverter to the sub-panel. When the shore power is out, then the inverter powers the sub-paanel.

[Bill&Cindy]

I asked this question before and didn't get a clear answer. My trailer is prewired for a genset and has an inverter already wired. If I am careful about load management, can I wire the inverter to it? I realize I would need to turn off the converter & A/C and run the water heater and frig on propane

[Jack Mayer]

My trailer is prewired for a genset and has an inverter already wired.

I'm not sure I understand the question. If you already have an inverter why would you need another?

[Bill&Cindy]

My bad. I wouldn't if it was an inverter. What I meant to say was that I had a transfer switch in the prewire package. Can I wire the inverter to that transfer switch?

[Bill B]

Yes but --- big BUT, you will be in charge of things. YOU will be responsible to: turn off the 120 feed to the hot water, switch off the A/C's, turn off the converter, change the refrig to gas and any other 120 volt loads that are power hogs. OR, in the morning, wake to dead batteries.

 

It can be done, But not a thing that I would do.

 

It is a connection that is looking for bad things to happen.

[sushidog]

If going the generator route, just make sure your genset is big enough. The same goes for sizing an inverter. I have a small, Dometic 700w (output) microwave which the manual says draws 1,000 watts to run. I have a 1,200 watt/1,500 watt surge generator that won't run the microwave, yet it runs my 5,000 BTU AC just fine. The starting surge for the microwave is obviously more than 1,500 watts. An EU2000 Honda is a 1,600 watt generator with a 2,000 watt surge. It will probably run my little 700 watt Dometic microwave, but not a larger model.

 

Here's a good link that explains the surge that some electrical equipment takes to start: http://www.batteryspace.com/prod-specs/POWER_INVERTER.pdf

 

"If the microwave oven has peak surge which is 4 times the continuous wattage, the 1200 Watt continuous microwave ovens will have 4 x 1200 Watts = 4800 Watts peak surge. The recommended inverter to run 1200 Watt continuous and 4800 Watt peak surge microwave is 2500/5000 Watt inverter or larger."

 

They may be overstating their case a little, but their point is valid even if their numbers may error a little on the side of caution. Remember just because your car can do 120 MPH doesn't mean it's good for the engine to drive it at that speed all the time.

 

Chip

[wa_desert_rat]

I have one 1500-watt PSW inverter along with several smaller (under 200-watt) PSW inverters. The small ones are under $100 on Amazon and can be safely plugged into "most" cigarette lighter plugs (YMMV on this bit). I discovered that I can run my 24-inch LED HDTV set AND a Blu-Ray player easily on one of these small inverters (under 100 watts for both).

 

At some point I plan to install a larger load-sharing inverter and will take care of the additional wiring then. Until then I have no issues with using a appropriate extension cord from the 1500-watt inverter to do what needs to be done and the smaller devices otherwise.

 

WDR

[Bill B]

It was my understanding that Bill and Cindy wanted to put the inverter in place of the generator and feed the generator side of the transfer switch. Which would try to power up everything.