Power flow chart

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Power flow chart

Postby m.glisson003 » Thu May 04, 2017 6:00 pm

Pretty soon I will start the process of converting a 8.5x20 cargo trailer to a toy hauler. I've determined which amenities I would like to have and evaluated my electrical needs. I'm trying to get my head wrapped around how the power will flow with all of the electrical components.

Does this make sense and seem right to you?

Am I missing something important?

Thanks for your input.
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Re: Power flow chart

Postby H.A. » Thu May 04, 2017 8:57 pm

Looks ok excepting the inverter output should connect to the transfer.(Btw, transfer relay is sort of pointless unless using a built in generator.) Simple & foolproof method is dont use a transfer & plugging the inlet to the generator, inverter or mainspower as desired.
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Re: Power flow chart

Postby m.glisson003 » Thu May 04, 2017 10:03 pm

H.A. wrote:Looks ok excepting the inverter output should connect to the transfer.(Btw, transfer relay is sort of pointless unless using a built in generator.) Simple & foolproof method is dont use a transfer & plugging the inlet to the generator, inverter or mainspower as desired.


Could you explain that last part. I didn't really follow that.

This part "plugging the inlet to the generator, inverter or mainspower as desired
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Re: Power flow chart

Postby troubleScottie » Fri May 05, 2017 2:51 am

It probably is not a good idea to connect the invert to the distribution panel. Most likely it will not have sufficient power or sufficient quality or will be very limited by your batteries to powering only a small subset of AC items and only for short periods. You might be better off just plugging items into the inverter as needed.

Then there is the odd circuit, the battery is powering the inverter which is powering the distribution panel that is powering the charger that is charging the battery. Most likely you are not looking to do this. You would have to disconnect the charger when using the inverter.

In addition, the inverter consumers power when just connected. You want to disconnect it whenever it is not in use.
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Re: Power flow chart

Postby H.A. » Fri May 05, 2017 4:32 am

[qung.
Last edited by H.A. on Thu Jul 06, 2017 4:13 am, edited 1 time in total.
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Re: Power flow chart

Postby m.glisson003 » Fri May 05, 2017 2:03 pm

troubleScottie wrote:It probably is not a good idea to connect the invert to the distribution panel. Most likely it will not have sufficient power or sufficient quality or will be very limited by your batteries to powering only a small subset of AC items and only for short periods. You might be better off just plugging items into the inverter as needed.

Then there is the odd circuit, the battery is powering the inverter which is powering the distribution panel that is powering the charger that is charging the battery. Most likely you are not looking to do this. You would have to disconnect the charger when using the inverter.

In addition, the inverter consumers power when just connected. You want to disconnect it whenever it is not in use.


Thanks for the advice! That makes sense. I will tweak my chart and repost.
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Re: Power flow chart

Postby m.glisson003 » Fri May 05, 2017 6:44 pm

Thanks everyone for the advice. It definitely helped me get a better understanding of how things work together. I've re-worked my chart to reflect the suggestions made. I've removed the transfer relay and changed the inverter routing. I plan on using the fridge and microwave (not very often) when only on battery bank power so I put those coming off of the inverter.

Here is my next question...If I was to be plugged into shore power or have the generator running would it make sense to use the microwave and fridge off of the inverter and battery bank power and let the shore power charge the battery bank? Because it seems to me like that's what will happen here. Or would it make more sense to have the microwave and fridge run off of the shore power when available? In that case I would have to pull the plug and move to an outlet that's receiving shore power. Is there an easier way to set this up so that fridge and microwave can run off of inverter and battery bank when shore power isn't available and run directly off of shore power when available? I feel like that would make sense as it would put less use on the battery bank and inverter.

Also, does everything in the chart here seem to make sense now?
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Re: Power flow chart

Postby troubleScottie » Fri May 05, 2017 11:02 pm

It is unlikely you can run the microwave off the inverter. Someone else can step in but I think this will burn through your battery. You are better off waiting for a shore power source eg shore power or the generator is on. You might be surprised on the amount of power needed. A 1500W generator supports only 1 hairdryer. Typical microwaves are in this same power range.

Although there are frigs/freezers that run on DC or AC, again I am not sure if (1) the inverter has the correct wave output for a frig as motors like pure sine wave output (if a compressor a big motor??) or (2) enough power to run a household frig, even a small one. The inverter is inefficient, so you will use even more power. Good ones are 90%, average ones only 80%. There are others with more complete analysis.

The DC frigs use a different, lower power mechanism to cool. Thus can run on a battery without draining it immediately. If you are getting a DC/AC frig, you want to wire to both DC for when you are on battery and for AC when on shore power. Obviously switches to select source.

BTW, you left out the towing vehicle. You may need/want to run wires like you are putting a big audio amplifier in the trunk of a car. Great source while traveling for charging the battery or running your frig. Most of the other appliances are off while traveling.
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Re: Power flow chart

Postby GuitarPhotog » Sat May 06, 2017 12:39 pm

Scottie is correct. The starting current of many compressor refrigerators is much too high for an inverter. Search here for examples and the math, but as I recall a compressor motor often draws 3X it's rated power at startup. When that happens, the inverter will "bottom out" and the motor will stall and burn up. Usually destroying the inverter.
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Re: Power flow chart

Postby m.glisson003 » Sat May 06, 2017 6:30 pm

A couple of things I forgot to mention that might be helpful for situational awareness

1. I plan on having four 6V golf cart battieries for a total of around 460AH of 12V power.
2. I plan on having 200-400W of Solar on the roof.
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Re: Power flow chart

Postby m.glisson003 » Sat May 06, 2017 6:50 pm

troubleScottie wrote:It is unlikely you can run the microwave off the inverter. Someone else can step in but I think this will burn through your battery. You are better off waiting for a shore power source eg shore power or the generator is on. You might be surprised on the amount of power needed. A 1500W generator supports only 1 hairdryer. Typical microwaves are in this same power range.

Although there are frigs/freezers that run on DC or AC, again I am not sure if (1) the inverter has the correct wave output for a frig as motors like pure sine wave output (if a compressor a big motor??) or (2) enough power to run a household frig, even a small one. The inverter is inefficient, so you will use even more power. Good ones are 90%, average ones only 80%. There are others with more complete analysis.

The DC frigs use a different, lower power mechanism to cool. Thus can run on a battery without draining it immediately. If you are getting a DC/AC frig, you want to wire to both DC for when you are on battery and for AC when on shore power. Obviously switches to select source.

BTW, you left out the towing vehicle. You may need/want to run wires like you are putting a big audio amplifier in the trunk of a car. Great source while traveling for charging the battery or running your frig. Most of the other appliances are off while traveling.


Based on some math I found http://www.livesmallridefree.com/blog/residential-fridges-in-boondocking-rvs at this awesome write up the fridge I am looking to use (3.2 Cu ft) should use around 30AH of battery power per day. I have read in other places and in that article that household appliances like fridges may require a Pure Sine wave inverters. So I know I must get a pure sine inverter. Now I just need to figure out the minimum size inverter I need to get based on running the fridge the entire time and other needs.

After reading your comments and doing some further research on how much juice microwaves eat up I have decided its probably best to only use it on shore/generator power or get a MASSIVE inverter. So I will do that.

I think while traveling I should be fine with the amount of solar and size of battery bank I plan on having. Since like you mentioned I would only plan on running the fridge while traveling. Having my truck charge it is a good idea though. I will consider that for sure. It will be a good feeling to know I am 100% topped off when I get to my destination.
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Re: Power flow chart

Postby H.A. » Sat May 06, 2017 7:22 pm

Fwiw,
As far as refrigerators. Had you considered a AC-DC 'fridge such as ARB or Norcold ?
Quite thrifty on power consumption, albeit fairly expensive buying...

Microwave ovens, Years ago, There were 12 & 24 DC volt "travel" models, But stupidly expensive.
Now days they use an inverter with the microwave separate appliance.
The Microwave is pretty much like any other, But modified for travel such as its glass turntable has cleats what hold it from bouncing off.
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Re: Power flow chart

Postby bdosborn » Sun May 07, 2017 12:28 pm

m.glisson003 wrote: Based on some math I found http://www.livesmallridefree.com/blog/residential-fridges-in-boondocking-rvs at this awesome write up the fridge I am looking to use (3.2 Cu ft) should use around 30AH of battery power per day. I have read in other places and in that article that household appliances like fridges may require a Pure Sine wave inverters. So I know I must get a pure sine inverter. Now I just need to figure out the minimum size inverter I need to get based on running the fridge the entire time and other needs.


30AH a day will take a fair amount of PV to keep up with. Have you looked at how a big a PV panel it would require? Without doing any math I'd guess at least 200 watts for a flat panel and that's only for the fridge, not any other loads. Doing an energy evaluation is the first step to sizing your system; how much power do you need and how much energy will you use in a day? Also, your diagram shows the fridge running off the inverter all the time, which is hard on your battery. You should consider a manual transfer switch so you can run it straight off shore power when available.

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Re: Power flow chart

Postby m.glisson003 » Mon May 08, 2017 6:15 pm

H.A. wrote:Fwiw,
As far as refrigerators. Had you considered a AC-DC 'fridge such as ARB or Norcold ?
Quite thrifty on power consumption, albeit fairly expensive buying...

Microwave ovens, Years ago, There were 12 & 24 DC volt "travel" models, But stupidly expensive.
Now days they use an inverter with the microwave separate appliance.
The Microwave is pretty much like any other, But modified for travel such as its glass turntable has cleats what hold it from bouncing off.


I did look into the ARB model. I like that you can use it as a cooler and take it with you. And I was pretty impressed with the construction. Just very expensive...
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Re: Power flow chart

Postby m.glisson003 » Mon May 08, 2017 7:18 pm

bdosborn wrote:
m.glisson003 wrote: Based on some math I found http://www.livesmallridefree.com/blog/residential-fridges-in-boondocking-rvs at this awesome write up the fridge I am looking to use (3.2 Cu ft) should use around 30AH of battery power per day. I have read in other places and in that article that household appliances like fridges may require a Pure Sine wave inverters. So I know I must get a pure sine inverter. Now I just need to figure out the minimum size inverter I need to get based on running the fridge the entire time and other needs.


30AH a day will take a fair amount of PV to keep up with. Have you looked at how a big a PV panel it would require? Without doing any math I'd guess at least 200 watts for a flat panel and that's only for the fridge, not any other loads. Doing an energy evaluation is the first step to sizing your system; how much power do you need and how much energy will you use in a day? Also, your diagram shows the fridge running off the inverter all the time, which is hard on your battery. You should consider a manual transfer switch so you can run it straight off shore power when available.

Bruce


Based on my energy evaluation I figure I will use around 60-80 amps per day. I believe with 400 watts of solar on a good sunny day I can generate somewhere around 150-200 amps of solar depending on amount of sun we have that day. So I think I should be fine.

I'm interested in learning more about the transfer switches. Is there a benefit from using a manual transfer switch over an automatic transfer switch? How would that work with the fridge situation? So I have the fridge plugged into the inverter. I get to the campsite and hook up shore power and then turn inverter off. Do I then have to pull the power cord from the inverter and then move it to an outlet receiving shore power? There has to be an easier way
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