hardwire 1000 Watt Inverter

[pixurit]

I have a true sine 1000 watt inverter that I'd like to hardwire into my breaker panel.  Had it mounted under the dash with an extension cord coiled in the driver's footwell.  Extension cord is awkward and the inverter's cooling fans are too noisy.  I'm going to change the location to a basement storage compartment closest to the house batteries and then run the 120V outlet power to my breaker panel.  Operating temps of the inverter are -20 to +40 Celsius (-4 to +104 Fahrenheit) so locating it in a dry but unheated storage compartment should be fine.  I'll be sure to use wiring and parts suitable to handle the full 30A that my motorhome is designed for, to allow for future upgrades.

Automatic transfer switches are too expensive here in Canada so I'll build my own using 120V relays.  Don't need a time delay as the stock transfer switch already handles the switchover from shore power to genny.

I'm trying to figure how many relays I'll need. The only wiring diagram I can find for a commercial auto transfer switch (suitable for use with an inverter) does not switch the ground wire, only the hot and common.  Is this standard/OK?

Thanks for your help.

 

[Great Horned Owl]

When you set it up, make sure that the inverter does not supply power to your converter. Otherwise, the converter will be charging the batteries with power that comes from the batteries. The heat losses involved will run down the batteries rather quickly.

Joel

 

[John From Detroit]

You don't even need to go with relays, First relays that heavy can be pricy but they make 30 amp manual transfer switches, 50-100 bucks US, that's how I'd do it.

 

[Alfa38User]

I'll be sure to use wiring and parts suitable to handle the full 30A that my motorhome is designed for

Your 1000 watt inverter will be capable of putting out only about 8 amps of power at 120V, so I wondered about your statement quoted above. You should only be wiring it to certain dedicated outlets at this time to avoid the potential problem of having it accidentally connected to your 120V system at the same time as either the generators' output or external power.

By all means, make provisions to add the inverter to the main panel but don't do it until you need to and then do it by integrating it in such a way as to REPLACE or lock out the other sources of 120V power when in use.

You will need a BIG battery bank and charging facilities to use a potentially larger capacity inverter. 30 amps = 5500 watts @120V but would require 300 amps at 12V without taking into consideration the inefficiencies of the inverter. It is not likely you would ever want to do that so dedicated outlets is likely the best way to go.

 

[Just Lou]

I have a true sine 1000 watt inverter that I'd like to hardwire into my breaker panel.

Your inverter is not designed to be integrated into your house wiring.  It is intended to power portable plug-in appliances directly from the provided outlets.  I would recommend using an inverter designed for this application

I'll be sure to use wiring and parts suitable to handle the full 30A that my motorhome is designed for, to allow for future upgrades.

You will, in fact, need to ensure 30amp capability of all wiring and components that support the pass through of shore and generator power.  It has nothing to do with "future upgrades".

I'm trying to figure how many relays I'll need. The only wiring diagram I can find for a commercial auto transfer switch (suitable for use with an inverter) does not switch the ground wire, only the hot and common.  Is this standard/OK?

Yes it is...

Bottom Line....  Having to remember to prevent all usage of air conditioners, the converter and any other appliance requiring more than the small 1000 watt inverter can handle, would outweigh the convenience of the installation as planned.  JMHO

 

[pixurit]

Thanks for all the replies.  You've helped to clarify my thoughts greatly.

Good point Joel.  I had considered that I couldn't have the inverter supplying power to the converter/charger and thus back to the batteries and the inverter, creating a loop.  I also don't want the inverter supplying power to the AC units, or the fridge (which runs fine on 12V).  I was thinking of interrupting these circuits with more relays.

I had considered a manual transfer switch, John from Detroit.  The issues with this start with my desire for convenience, I'd like to just push the button on my inverter's remote "on" switch, and have it work as I designed.  Another issue is that I want to power a couple of individual circuits (just outlets for now).  I'd need individual manual transfer switches for each circuit I wanted to power from the inverter.  The last issue I considered was location.  I really don't have a convenient place to mount manual transfer switches that would have the access needed to operate them.

You've nailed my thought process Alfa38User.  To provide the full 30A @ 120V I would need a 3600 Watt inverter.  Unfortunately I haven't been able to find one (true or modified sine) that has an operating temperature range that will allow it to work in an unheated space during a cold boondocking trip.  Besides, like you say, 3600 Watts from a 12V battery bank will draw 300 Amps.  My (2) 232 Amp 6V batteries would drain to 50% in less than 30 minutes.  Powering just a couple of individual circuits from the inverter, with appropriate automatic switching is my goal.  I'd like the convenience of being able to power my alarm clock and TV in the back bedroom, and the TV up front, without running extension cords the length of the motorhome.  The statement you question simply means that I will use 30A relays and 10AWG Romex to carry the 120V, just in case I decide to upgrade the inverter in the future.  Overkill for the 8 Amps my current inverter will provide, but it won't hurt.

Just Lou -

I realise that my inverter was not designed for this application.  However, it is providing 1000W on one 120V circuit so doesn't require any internal modifications to do what I want.  Do you forsee any issues specific to this type of inverter?  I'll just run Nomex with a grounded plug on the inverter end from the inverter to the breaker panel.  Like I mentioned, I haven't been able to find a more suitable inverter with the operating temperature range that I desire.

The inverter has no pass through or built in transfer switch capability.  I do realise that anything I use to switch/interupt the existing 120V wiring must have the capacity to carry the load.  Sorry for any confusion.

Thanks for answering my main question about switching the ground.  I didn't think it was necessary, but read another post here that mentioned switching all three 120V wires.


In conclusion ... After considering all replies I'm now planning on powering just a couple of individual circuits (outlets only) with the inverter.  I'll wire my home-made automatic transfer switch(es) into the circuits after the stock breakers and rely on the inverter's overload protection to protect the circuits.  That is how it was designed to operate after all.  I'd rather have the added safety of using the existing breakers in the inverter power circuit but that doesn't seem possible without adding a sub-panel, which I don't have room for.  The only option that allows use of the existing breakers is wiring the inverter power into the main feed to the breaker panel and then manually switching breakers off (too much chance of forgetting), or installing an auto transfer switch on each circuit I wish to disable when on inverter (very costly).

 

[Gary RV_Wizard]

A double pole, double throw switch will do the job of a transfer switch. They can be hard to find, though, because they don't have much use in residential wiring. Two common  single pole, double throw, switches, ganged together, will substitute nicely to switch hot & neutral feeds to the load center. Drill a hole through the switch handles and put a piece of stiff wire through to gang them up. An SPDT switch is often called a three-way switch (even though it is really only two way) and is quite common.

If you want to switch individual circuits (recommended), then just switch the individual hot wires with a SPDT switch for each one.

 

[Gary RV_Wizard]

Besides, like you say, 3600 Watts from a 12V battery bank will draw 300 Amps.  My (2) 232 Amp 6V batteries would drain to 50% in less than 30 minutes.

Just for the record, your two 6v batteries would last no more than a few moments at 3600 watts (a 300 Amp load @ 12v). You have only 232 amps available because they are wired in series to get 12v. And the voltage in those batteries would drop below the inverter's input power threshold (about 10.5v) within a very few seconds.

 

[pixurit]

Thanks Gary.  The 3-way switch (SPDT) idea would be an inexpensive manual switching option indeed.  Unfortunately my experience with trying to teach wife and kids how to operate such innovative systems has taught me to keep everything as simple as possible.  It has to be auto transfer switching for me.  I actually have some relays kicking around that I had used to power more Christmas lights from a musical controller than it was designed to allow (using the controller's output as a relay trigger voltage).  I believe they are DPDT but will have to check.  Maybe I can recycle them in this project.

Yeah, I kinda figured that my batteries couldn't supply 300 Amps for any length of time.  Even though the capacity should be mathematically capable of providing the 300 Amps for 40 minutes +, the voltage drop would kick out the inverter very quickly.

Thanks for your input.

 

[Just Lou]

[quote author=Gary RV Roamer]
If you want to switch individual circuits (recommended), then just switch the individual hot wires with a SPDT switch for each one.
[/quote]

Since you're feeding these circuits from an output receptacle on the inverter, I assume you mean both hot and return wires.

 

[Bob Buchanan]

It has to be auto transfer switching for me.

We all have different needs, plus having family involved in usage is certainly a consideration. I'm a solo RVer, so was only concerned about my own needs - and finances, when I installed an inverter.

Mine is a 1500W Statpower (the vendor at the time). I bought it in '95 and have moved it 4 times to each RV since to it's current location in my Class A MH. The location has always been as close to my battery bank as possible - currently about 2 feet. AC output goes to my converter/charger passing though a DPDT 30A switch. This is hardwired into the inverter vs. using the plugs on the inverter. On my last rig (a Class C), I did the manual switch that Gary mentioned here - in that I bought 2 switches, placed them side by side w/one upside down. Then passed a metal dowel through both switches. And if I could press a magic button, I would have it in my current rig vs. the auto switch I had installed instead.

The good news about the manual switch, and cooresponding bad news about the auto switch is the auto switch delay. If, e.g., my shore/genset power is entering the switch - and I am currently on inverter power, the switch will not throw. It is first come first serve. If I then shut down the inverter, it takes 20 seconds for the switch to happen. So in the meantime, the TV and every other AC appliance shuts down. The 20 second delay always happens, even when initially hooking to power. With the manual switch, I just throw the dowel switch and have power moved to the other source immediately - either way I was moving the power between sources. So if on shore power and switching to inverter I would turn on the inverter and through the switch with no lost of power. I used it this way for 4 years or so of fairly heavy usage w/no problems.

My rigs have always been newer than '95 and younger than '99 - so the converter/charger boxes have always housed a separate charger. On some rigs it was on a separate breaker, another plugged into a 110 outlet under my bed, and the '94 Winnie I just cut the wire within to the charger unit. Point being I never again wanted to use the chargers that came with my rig. To match the Statpower Inverter I purchased a 40a statpower 3-stage charger. It has always been mounted on a bulkhead beside my inverter and close to the battery bank. It is then plugged into the closest 110 wall outlet for power. Actually, it is plugged into a power strip with anything else in that location that I want OFF when on inverter power.

So that is what I can do that I can see would cause you problems. I have a series of power strips throughout my rig - and a list of which ones are on and which ones off when under inverter or shore/genset power. And to complicate things, if I am boondocking and do not need A/C, I use a 2000 Honda genset vs. the built in 5000 Onan built into my rig - which creates a differnet set of ON/OFF rules.  ???

However, I "did" want to mention my manual DPDT switch and it's ease of use, and effective use vs an auto switch, FWIW. 

 

[Just Lou]

Bob, the condition you describe in the third paragraph of your post indicates that the auto switch is installed with the wrong priority selected on input power.  You could/should swap the inputs to make the presence of shore/gen power cause the switch (the default, on loss of power would then auto switch the inverter into service).  When external power is restored (gen or shore) the auto switch from inverter to pass through of the restored power would occur.

If the 20 second (approx) delay on initial power up is a problem, it can easily be crippled by an existing dip switch located within the auto transfer switch.  You wouldn't want to cripple the delay on the switch providing generator power, because it is needed to allow the gen to completely come up to speed and voltage.  That delay is not needed in switching from shore power to inverter power.

 

[Bob Buchanan]

Bob, the condition you describe in the third paragraph of your post indicates that the auto switch is installed with the wrong priority selected on input power.  You could/should swap the inputs to make the presence of shore/gen power cause the switch (the default, on loss of power would then auto switch the inverter into service).  When external power is restored (gen or shore) the auto switch from inverter to pass through of the restored power would occur.

If the 20 second (approx) delay on initial power up is a problem, it can easily be crippled by an existing dip switch located within the auto transfer switch.  You wouldn't want to cripple the delay on the switch providing generator power, because it is needed to allow the gen to completely come up to speed and voltage.  That delay is not needed in switching from shore power to inverter power.

Thanks, Lou. I hate it when I am boondocking, watching a good flick or whatever -- and I run into genset shutdown time by the park or campground. I then turn on the inverter and shutdown all the "not needed when on inverter stuff" -- then shut down the genset. And then have to turn the TV and DVR back on. Or, have to reboot a computer system or peripheral. A UPS is nice, but takes more power while boondocking. Sometimes I might be in the middle of doing remote with a client or whatever. Are you writing that the delay is always only one way?

I plan to take your post to Quartzsite in January and ask for guidance from those that know a lot more about this than I do to help check out your suggestions. I didn't install the switch - but rather had it installed by Holly Generators in Sacramento. They are the premiere genset folk in NCal. My new hips prohibit crawling around attempting stuff on the back side of my converter. That area on my rig is a zoo to begin with. The water heater is just under the fridge and behind the converter. However, it appeared like a box with wire holes but I didn't see any dip switches. Not to say they are not there tho.

I prefer not having the delay either way. I used the manual switch for over 4 years without a problem. When I shut down the genset at night and go to Inverter, or e.g., during the day if I see my battery voltage getting low and go back to genset. I do let the genset warm a bit before switching. So if possible to dip switch the delay off either way, that is what I most likely will do. So thank you again . . .

 

[pixurit]

Lou, that's what I thought at first but after puzzling out Bob's "first come first serve" comment and the other described switch operations I've come to suspect that he has some kind of latching relay with a 20 second delay before switching.  I've never heard of this in an RV Automatic Transfer Switch (ATS), but it may be possible with a custom relay setup.  If Bob's relay is a standard RV ATS then I agree, it sounds like the inputs are reversed and the dip switch is set for a delay which is not needed in his circumstance.  The 30A DPDT relay I checked on today responds in milliseconds and does not latch ($50 CDN available locally).

Bob, I don't understand why you have the inverter's output wired to your converter/charger, even if the charge side is disabled.  Also, how are you powering some outlets and not others?

I'm still working on my design.  Today I corrected the labeling on the breakers in my panel (4 out of 8 mislabeled + 1 not labeled at all).  I found that my front overhead console and the back bedroom are on the same circuit.  I'd hoped that they were on separate circuits so I could switch them separately and avoid parasitic loads when not in use.  The overhead console contains the surround sound processor, DVD recorder, TV, etc., things not at all necessary when powering my alarm clock at night.  If I don't find a junction box in this circuit (with wires running forward and back) when I pull out the breaker panel I guess I'll have to unplug items to avoid the parasitic loads.

I've reconsidered the manual switching option, using (2) "3-way" switches for each circuit, because of the parasitic loads.  With this design I could switch individual circuits on and off as needed.  I have 3 circuits I'd like to power from the inverter so I'd need 6 switches (8 if I can divide the front console/back bedroom circuit). .... No, that's too much.  I think it'll be much simpler to power the whole breaker panel through a 30A DPDT relay and then use the breakers to switch off any parasitic loads.  I know that circuit breakers are not meant to be used as switches but this will be occasional use, not used for many on-off cycles every day.  I did find that I already have (4) 25A DPST (normally open) relays that I can use to disable the circuits that I definitely don't want powered by the inverter (A/C units, fridge, microwave, converter/charger).

The plan is progressing, thanks for all comments.

 

[Bob Buchanan]

Bob, I don't understand why you have the inverter's output wired to your converter/charger, even if the charge side is disabled.  Also, how are you powering some outlets and not others?

Am I using wrong terminology - should I be writing breaker panel? One side of the switch is from my 30Amp shore/genset cord and the other side is from the inverter. So yes, either way, all outlets in the rig have power. When I unhook from a park power post, I plug my 30amp power cord into the genset.

All of my rig 110 outlets are now concentrated between two breakers. Generally, I have the front of my rig (TV, DVR, AC lamp, 30A charger - and/or a laptop) from one breaker and my office (1 or 2 desktops, printer, AC lamp, modem and such under the other. On another breaker I have my microwave and hot water probe through a switch with red light when ON. If on Inverter I turn off that breaker. If I use the microwave while under inverter, I can switch off the hot water heater. And the A/C on another breaker. If on inverter power, I turn off the Office breaker and use my laptop up front, or watch TV, or whatever.

Within that area via power strips, I can, e.g., turn off the charger when on inverter - and the DVR and TV if working on the laptop, and so forth. Sometimes late at night while boondocking and not sleepy I will turn off "everything" in the rig (including the DVR) except my 32" HDTV and my smartphone charger (from the inverter) and connect the smartphone to the TV via HDMI cable. That allows me to watch HD movies, youtube, surf the net or whatever all night if I want using hardly any battery power. Can do the same thing from my 19" HDTV in the bedroom. Or, can turn on my DC electric heating pad. I have installed two 12V connections there for the heating pad, to keep my phone charged, or whatever. They are wired directly to the batteries (w/in line fuse and through the shunt and Trace Meter).

If I need to use my main development desktop while on inverter power, I will have the office breaker on vs. the front breaker, but via power strips turn off the printer, scanner, modem, and everything else in the office.

I have two 3x5 cards - one labled Inverter Power, the other labled Shore/Genset. Each has list of what to turn on and/or off accordingly. Takes less than a minute. If I miss something going to inverter, it will scream at me and shut down. Actually, I have another scenario if boondocking using my Honda i2000EU genset or if in need of A/C, my built in Onan 5000. If the Onan, I might as well turn on everything because am using about the same amount of gas either way. So I try to avoid that.

I find myself in parks at times that charge extra for park metered power - such as on a monthly stay. When that is the case, I continue to use only the necessary power by only allowing power to what I am using at the time. So my setup is not just for boondocking. It is amazing how much more power we use when on shore power and just leaving everything ON. In AZ and CA I find parks charging as much as $.21/kWh. Parks around the country using my SW I see the lowest at $.06 and at all amounts in between. My reservation software batch computes monthly metered customer bills - so I see these wide swings in bills with the same KWh totals.

Have also found myself in places that are charging me electric based on how much their bill goes up while I am there. Yikes!! That is why under another topic I am putting together a KWh meter to use. If I am conserving I want to pay for only what I use vs. an estimate.

Wally installed a Trace meter (in my rig and Jim Johnson's) that I use to monitor everything in or out of my batteries. That's how I know exactly what my electric bed pad heater uses or an individual light. And how I have run down every phantom load in my RV. He also installed two 80W solar panels that are wired through the meter as well. Am looking to add another larger panel this fall if I can find the right price.

 

[pixurit]

Ahhhh ... now I understand.  Sounds like a good system.  Your cards allow you to avoid the parasitic loads that I am now trying to minimize.  I too use power bars but the one for my front entertainment system is behind all of the components and the one for my desktop computer, printer, etc. is behind the sub woofer on the floor under the dinette.  Both are very awkward to get at.  I can probably improve on these setups.

Your use of the breakers to switch off unneeded circuits is what I am planning to do as well.  Good to know that someone else is doing this without problems.

I agree that we use much more power when connected to shore power than when boondocking.  Right now I have 2 lights on, twice as many as I'd use if boondocking.  Electricity is $0.09446/KWh where I am now (on private property).  I am plugged into a 15A circuit so I can use a cheap ($25) digital usage meter that I picked up from a local home improvement store.  This meter simply plugs into a 15A outlet and has an outlet on it's front to pass the power through.  I enter the electricity cost into the meter and it tells me KWh used and total cost (it stores the price, I don't have to enter it every time).  It also tells me voltage at the outlet, amps drawing in real time, and lots of other info that I never use.  The only RV parks I've stayed at that charge extra for power have had a meter on the power pole at each site.  In your circumstance I can see the need for the 30A meter.  I saw your post but didn't follow the link(s).

If you're happy with your trace meter can you please supply a link so I can check it out.  I'd definitely be interested in installing one in my rig.  Right now I have (1) 130W solar panel but am considering adding another (my controller can handle it).  The price keeps dropping on solar panels, about 40% in the last 2 years, I'm just waiting for the right deal.  If I could figure out an appropriate mounting system I'd also add 2 more batteries, to double my power storage capacity.  I'm staying here in the Okanagan Valley for the winter.  We get fairly mild winter temps (for Canadian winters), but very little sunshine.  Not great for solar.  I'll be moving to an RV park soon but would like to try your ideas for power conservation when connected to shore power.  Last winter my power averaged about $100/month on top of the $180/month for propane.  It was a mild winter.  My summer power consumption is less than $20/month with propane about the same from May to October.

Thanks for sharing your experiences and ideas.

 

[Bob Buchanan]

If you're happy with your trace meter can you please supply a link so I can check it out.  I'd definitely be interested in installing one in my rig.

THIS Trace site details how the meter works, how it is programmed, and what it displays. I see them advertised anywhere from $295 to $380. A bit pricey, but I can't imagine boondocking without it.

Initially after installation I program in the AH total from my batteries. In my case that is 345 - so I went conservative and programmed 320. When I arrive at a location and intend to dry camp, I set the AH in/out of the batteries to 0.00 on the Trace display. Assuming the batteries are now full after driving X miles. As AH's then go out, that display will display that total. Not what I have left. If I have used 10 AH, that display show 10. So if using my inverter, the number display will begin to rise. If I turn on my charger or or solar, the display number will fall back towards zero - or a full battery again.

I can then toggle the display to show % of charge, amps going in/out, or volts. I watch the Volts closely and try not to get below 12.1 or 12.2.

 

[PJ Stough]

Not to be too picky Bob, but when you assume that your batteries are fully charged after driving x miles may not be accurate unless your alternator is programmed to charge your batteries in accordance with the battery manufacturer's specs, but if you are keeping an eye on your batteries voltage you will, no doubt, be ok.

Just my thoughts,
Paul

 

[Bob Buchanan]

Not to be too picky Bob, but when you assume that your batteries are fully charged after driving x miles may not be accurate unless your alternator is programmed to charge your batteries in accordance with the battery manufacturer's specs, but if you are keeping an eye on your batteries voltage you will, no doubt, be OK.

Just my thoughts,
Paul

Thanks, Paul . . .

Fortunately I can see the display while driving - and will see around 13.1 or so Volts. My alternator and batteries have never met, so was not even aware that there was such a setting between my alternator and  house battery bank. I "do" look at the voltage and % of charge each time I park for boondocking. If the charge level is not 100%, I don't reset the Ah dial to zero. When full, it shows the text, FULL, vs. 100%.

 

[Just Lou]

Bob, I have the Trimetric 2025RV, and though I don't do a lot of extended boondocking, I do use it to keep an eye on my battery performance and condition.  It satisfies my need for tech toys and provides a useful function in the process.  I found that after the novelty wore off, the meters biggest contribution is spotting anomalies and trends.