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Old 11-06-2011, 08:36 AM   #1
flight-guardian
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Join Date: Sep 2011
Location: SoCal
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1500w Inverter Install

I have tweenage kids therefore I am a big believer in inverters to run the TV, charge computers and cell phones, and power other misc electrical equipment. I had a very basic 800w Harbor Freight inverter installed in my last TH but the install left a lot to be desired...remote switching wasnt there, it was far from the batteries so it was not efficient, it only powered 2 receptacles in the very back of the TH. So here is how I fixed all those issue with my new TH. Hopefully this write up will help to demystify some things and help some with designing their system.

Where to put it...inverters should be as close to the power supply batteries as possible. DC voltage drops as it travels away from the source so the further away the inverter is from the batteries the lower the its input voltage will be due to line loss. For the Samlex Modified Sine Wave 1500continuous/3000 momentary watt inverter the manufacturer recommended no more than 5 feet of #4AWG cable for the supply. I got it to 6 feet so pretty close.


The batteries being mounted on the hitch frame just in front of this photo. The cables go up into the very front wall and come out into the pass through space. I mounted the inverter to the ceiling of the pass through space to keep it from getting bashed up by equipment. The positive cable has a 200ADC fuse in line to protect the system.

My TH can have 2 power sources plugged in at the same time...shore power can be plugged in without unplugging the generator supply. If the generator is started the control system sees the gen power and chooses it as priority over shore power. As you can see I have the shore power cable plugged directly into the inverter powering every circuit in the coach. I wanted this because I wanted to have access to every AC outlet on inverter power. It does however cause some problems. (explained later)

This is the space in the coach where all the wiring comes together. It is pretty much in the middle and directly above the refer.


I added a very simple voltage meter next to the battery disconnect. Wired it into the fused side of the radio power supply.

You should also notice the unlabeled toggle switch on the lower left of the photo. This switch toggles off/on 3 things - the AC, microwave, and charger converter. Very important to turn these items off when the inverter is powering the coach as the inverter is not near big enough to run the AC, the inverter is modified sine wave so can't run the microwave, and the inverter would be horribly inefficient if it were trying to charge the batteries while its using battery power to do so. The switch will eventually be labled something like this: "ON - Home or Site With External AC" and "OFF - Dry Camping With Inverter ON".

The problem with using a manual toggle switch to turn certain things off is you have to remember to turn the switch back on when you start the gen, most importantly the charger converter. We do mostly dry camping and it is imperative that every time the gen is started the batts are getting a little charge. So I installed a 3 pole contactor to handle this job.


This is a 3 pole Normally Open Contactor with a 120VAC activation coil. It is rated at 25Amps AC per circuit. The 3 switched items are wired into and out of the contactor. The activation coil is wired to the generator supply cable. When the generator starts to produce AC power the coil senses the power, closes the contacts, and power heads toward the 3 pieces of equipment bypassing the ON/OFF switch. When the gen is de-powered the contactor opens and the power supply to the 3 items once again defers to the ON/OFF switch.

So when we head to the dez we throw the ON/OFF toggle switch into the off position and that is where it stays until we get home. Everything else is automated...except the turning on and off of the inverter. I can't tell you what a pita it always was for me to go out into the 35 degree windy cold a$$ night to turn the thing off (or unplug it) after watching a movie before bed. Most of the time I chose to stay warm and let it run needlessly all night long.

So here is the very simple little remote on/off control and monitor panel for the inverter. And it's mounted right next to my bed. Ahhhh life is good.


So, I am not an electrician or electrical engineer. I have tested the system and it seems to work as I have designed it. No smoke from anything. No fuses/breakers blowing. I hope it stays that way.

Comments? Suggestions? Let me know.

-Eric
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Old 11-06-2011, 11:31 AM   #2
Johnnyfry
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Inverter

Nice looking set up. You covered all the right bases.

John
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Old 11-06-2011, 02:18 PM   #3
flybouy
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That is a very dangerous set up. The contactor needs to be in a NEMA enclosure (metal box) with the proper strain reliefs on the cables. The contacts will arch creating a spark every time they are engaged or disengaged and can cause a fire or explosion. The coil can also burn up and catch on fire as they often do with a little bit of moisture and vibration.
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Old 11-06-2011, 03:50 PM   #4
flight-guardian
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Quote:
Originally Posted by flybouy View Post
That is a very dangerous set up. The contactor needs to be in a NEMA enclosure (metal box) with the proper strain reliefs on the cables. The contacts will arch creating a spark every time they are engaged or disengaged and can cause a fire or explosion. The coil can also burn up and catch on fire as they often do with a little bit of moisture and vibration.
there are strain reliefs not in the picture.

the nema metal box is on my todo list. I didn't realize it was that important. that being said I know tons of guys with contactors and double pull relays that aren't in boxes. the contactor is a closed version so no sparking will escape. and there is little amperage on the lines when the contactor activates...only the clock on the micro and the start-up power on the converter which is pretty low.

but I take it under advisement and appreciate your input. it will be easier in a box as well. the mounting to the ceiling of the converter compartment was a royal pita.

-E
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Old 11-09-2011, 04:57 PM   #5
flybouy
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Wink

Quote:
Originally Posted by flight-guardian View Post
there are strain reliefs not in the picture.

the nema metal box is on my todo list. I didn't realize it was that important. that being said I know tons of guys with contactors and double pull relays that aren't in boxes. the contactor is a closed version so no sparking will escape. and there is little amperage on the lines when the contactor activates...only the clock on the micro and the start-up power on the converter which is pretty low.

but I take it under advisement and appreciate your input. it will be easier in a box as well. the mounting to the ceiling of the converter compartment was a royal pita.

-E
Don't want to be an alarmist it's just my nature to be cautious (I instructed 2 electrical courses as adjuct faculty for an HVAC program at a community college for several years ) and I have been in the construction/facilities managment buisness for many years. With that being said,I have seen many of these arch with a little bit of moisture to the enclosue which is by code grounded, leaving telltale black streaks and pitting.
The strain relifs would hold the wires and prevent them from pulling loose and touching. If the live feed wire suppling voltage pulled loose and touched the ground it would ruin your trip.
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Old 11-10-2011, 11:14 PM   #6
flight-guardian
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Once again I take it under advisement.

There are lots of things going on here that may or may not be to code...as generally understood code goes. Floating neutrals instead of bonded neutrals...etc. The system seems to be designed to work with many variables and issues that may otherwise be considered safety concerns. No enclosures anywhere on my coach are grounded metal enclosures. They are flame resistant (not flame proof) plastic or wood by design.

I have posted this setup, with the admonishment that I will be getting a fire box for the relay, on a couple other websites for advice...and this is the only negative response I have gotten.

Thanks,

-E
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Old 11-11-2011, 08:23 AM   #7
flybouy
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Great set up, just be safe
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