Power consumption question

GlockG20 · 03-09-2016, 11:00 AM

My family and I are currently living in our Jayco trailer while building our home. For the time being we are at a friends and using their shore power so power consumption is moot. BUT as the we are finishing the driveway (right now getting a trailer down there is a bad idea, even with a 1 ton truck), we plan to move the trailer onto our property.

There is no PG&E and most likely won't be as we intend to remain off-grid. The question I have pertain to how much each component consumes over a 24hr period so I can size the batteries and inverter correctly. I already have a 2.5kW @ 24VDC solar array with an MPPT charge controller to recharge batteries and a stand-by generator (we are using it to power tools on the job site) in the event solar isn't enough during the rains.

The power converter is one component that according to my manual consumes 8A of power when on shore. That seems a bit much and over a 24hr period would mean I am burning 192AH / 23kWh just for that component alone... doesn't sound right. Now maybe I have it incorrect and it's 8A @ 12VDC then that is a more reasonable number to work with...

Next while on shore the fridge will according to the manual consume 6A which over a 24hr period would mean I am burning 144AH / 17.3kWh. This sounds a bit high too.

All the other components I have accurate power figures from and have them accurately accounted for.

So can someone please tell me the following:
The 8A draw for the power converter, is that based on DC or AC voltage?
And is the 8A a continuous draw or peak, and if it's peak what would continuous draw be?
What is the accurate AH draw @ 120VAC for the Norcold 6CuFt fridge, I can't find the answer in the manual provided.

Currently I am under the impression I will need at least a 740AH array @ 12VDC (4 L16E batteries) with a 4,000W 12VDC inverter. How far off am I?

Additional information:
We don't use the microwave.
As it is still winter and a bit chilly (warm compared to other places) we are using the heater when home. It's off at night when we are sleeping.
The big uses are the fridge and converter, the TV's each consume about 70W of power (32" LED TV's with built in DVD).
All lights are LED
AC will only get used during daylight and for short periods of time during the summer, solar is more than adequate to carry the load and charge batteries.
The home will be set up with a 48VDC array sometime next year, I am actually considering 24VDC battery array for the trailer with a step down for 12VDC components.

**norty1** · 03-09-2016, 11:44 AM

If you locate the make and capacity of your converter you can get the load info online. I have looked at mine on the Surge Protector when nothing else was on in the rig and it was drawing about 9 amps. Mine is a 90 amp Progressive Dynamics converter.

Your calculations may be correct. Another option would be to measure it.

hoppers4 · 03-09-2016, 12:59 PM

The converter is used to keep the house batteries charged so should not be activated when you're using your house batteries. The current rating would be for 115VAC when charging the batteries.

My 10 CF Norcold absorption fridge draws 2.6A @ 115VAC (300W) when on shore power. When using propane it draws .5A @ 12VDC (6W).

Subaru297 · 03-09-2016, 01:07 PM

Quote:

Originally Posted by hoppers4

The converter is used to keep the house batteries charged so should not be activated when you're using your house batteries. The current rating would be for 115VAC when charging the batteries.

My 10 CF Norcold absorption fridge draws 2.6A @ 115VAC (300W) when on shore power. When using propane it draws .5A @ 12VDC (6W).

+1

This is essentially what I was going to say as well. Is the solar controller is maintaining your batteries I would just disable the converter all together. You should have a breaker that can turn it off.

4000 Watt inverter sounds a bit large as well for a trailer. What do you have that needs that sort of power? Just the AC?

If you absolutely need the 4000W inverter for something I would recommend getting a small inverter for general use and only turn on the 4000W one when needed. It will have a large idle current as well.

Cheers

Jagiven · 03-09-2016, 02:48 PM

I do not know your answers, but if you truly are going to be off the grid, a good multimeter and amp meter will be your best friend. I would buy one, also buy the outlet adaptor for the amp meter. This will allow you to be able to check and test each device.

I also have a Kil-O-Watt meter. You plug into the wall, plug your device into it. You can read instant power usage and long term.

**Mustang65** · 03-09-2016, 02:58 PM

Quote:

Originally Posted by Jagiven

I also have a Kil-O-Watt meter. You plug into the wall, plug your device into it. You can read instant power usage and long term.

x1

The meter is good up to 15 amps.

I would be more concerned about the 4000 watt inverter. I do not think you will be using that much power, but if you were, there could be issues. 4000 watts @ 12Volts equates to 333 amps. You will need some big time battery cables for that. If you feel you will need 4000 watts, buy a 24 volt inverter, @ 4000 watts that is a more manageable 165 amps, still a load.

Don

GlockG20 · 03-09-2016, 10:26 PM

So essentially I flip the breaker off for the converter when on batteries which will actually be running an inverter to power the AC side of things.

With the breaker off for the converter it will still allow the AC side to function as well as DC but it will not attempt to charge the batteries.

I am going to rephrase my question to make sure I am understanding correctly:

That asked/stated, since solar will be charging and maintaining the battery state I don't need the converter to be powered on. But it will still continue to function as a breaker / fuse panel allowing everything to work. Is this correct?

I am still learning about trailers and how the power is set up and distributed. I am more of a mechanic than an electrician. Although I do understand the basics well enough to not let the smoke out.

So if I don't need to run the converter then that load can be removed from my power calculations... that's a game changer there. Also with the NorCold numbers provided by hoppers4 that brings the power consumption down to a more realistic range.

As for the inverter size, yes it would be used to run the AC during peak summer when it's hotter than hades, otherwise I already have a 200W inverter that runs my TV off batteries when we lose shore power (where I live... that happens quite a bit during the winter.). It also runs my satellite internet modem and to ensure smooth transfer I run through a UPS to prevent sag/swell surges when shifting power.

I just read that my heater runs off the 12VDC side of the house (makes sense if you are independent of 115VAC electricity). So by the time we move to our property the cold weather will be pretty much a moot point.

Well that's it for now... I am sure I will be back with another question sometime in the future.

hoppers4 · 03-10-2016, 08:49 AM

Quote:

Originally Posted by GlockG20

So essentially I flip the breaker off for the converter when on batteries which will actually be running an inverter to power the AC side of things.

With the breaker off for the converter it will still allow the AC side to function as well as DC but it will not attempt to charge the batteries.

I just read that my heater runs off the 12VDC side of the house.

The question about turning the converter off and still retaining AC power distribution is something I don't know. I would hope that the breaker just turns off the battery charger portion of the converter but I don't know for sure. Somebody else is going to have to answer that one.

Yes, your propane furnace is powered by 12VDC. My furnace draws 7.0A but that's not continuous since the furnace cycles. Most of that 7.0A is fan. Some other numbers of interest are the water heater (.7A @12VDC propane, 11A @ 115VAC shore power), water pump ~4A @ 12VDC, propane/CO detector 1.3A @ 12VDC, antenna booster .1A @ 12VDC, my TV+inverter+booster uses 3.2A @ 12VDC but yours will be different dependent on your TV. LED light use between .2A and 1.2A depending on the number of lights in each area.

As far as how much solar you need, there's other folks on this forum that know a lot about solar so I'll leave that to them. One of those good sources would Mustang65 who chimed in above. I see that he included a link to his solar project and I'm betting that would be a big help.

Subaru297 · 03-10-2016, 09:27 AM

Yes your DC side and AC side of things will operate properly with your converter turned off. The converters job is to charge your battery and supply 12v DC power to your trailer when you are not plugged in. If you disable this your battery will supply 12v power to everything that needs it and your solar system will be charging your batteries.

I turned off my converter at the breaker shortly after installing solar and have never needed to turn it back on.

And for completeness the converter is only a small part of the load center or power distribution center that includes the converter, breakers, fuses, wiring, AC and DC side of things.

Someone please correct me if I'm wrong.

Can your battery bank handle the draw from the AC unit? If this is the biggest draw you will experience and we assume it draws 1500 watts then that is around 125 amps.

With 740Ah capacity and 370Ah available (50%) you could theoretically get around 3 hours of AC running without any other loads or power draws or efficiency losses. I would say around 2 hours to be safe.

Your 2500W panel array should produce around 100amps. So theoretically you will only be running AC when it is hot and sunny so you may only be pulling 25Ah out of your batteries and 100Ah directly from your panels.

150Ah for the fridge
250Ah for 2 hours of AC (4 hours with 50% duty cycle???)
100Ah for other miscellaneous stuff (guessing)

500Ah total. I think this is a pretty heavy estimate but if it is close to correct then you would need 5 hours of good sunlight everyday to break even.

I think the math works out in your favor!

Cheers

Subaru297 · 03-10-2016, 09:30 AM

What is the actual amps your panels can produce?

And are these mounted on the house you are building?

GlockG20 · 03-12-2016, 12:57 PM

No, ground mounted. The MPPT charge controller actually increases efficiency of the panels and takes the voltage and converts it for me. I have the panels wired for max voltage in 3 panels in series per string. This will allow the panels to still produce sufficient power even on cloudy days to keep batteries at least on some charge.

Excluding the AC and heater my total estimated load is approximately 127AH/24Hr. I found Trojan has 420AH 6VDC deep cycle L16's. Two of those my load would be about 30% of capacity. Which is right where you want to be.

jayco1485 · 03-14-2016, 06:29 AM

1.
The Xantrex site has good FAQs, App Notes, and Load Worksheets to help size systems,,,, and their inverter manuals answer a lot of questions.

2.
Clamp-on ammeters can measure instantaneous AC current and the Kill-A -Watt - as already suggested - can measure usage over time.
Portable generators and inverters produce "modified sine wave" power - so the accuracy of the Kill-A-Watt device may be affected by this but it will be a good approximation.

3.
If the new home will be "off-grid", I strongly recommend the following:
- install two inverters so you can have 120/240 volt power. This will give you the option of running 240 volt well pumps, etc, and a crude back-up solution if one inverter fails.
- size the system well above what your calculations indicate your needs will be. Many installers quote bare minimum systems to get the business. It's much easier to add capacity now than to retro-fit later. A friend of mine has two 3600 watt Xantrex inverters.
- wire in the connection (permanent or twist-lock + cable ) for a back-up generator so that it will be ready when needed.

jayco1485 · 03-14-2016, 08:42 AM

1.
The Xantrex site has good FAQs, App Notes, and Load Worksheets to help size systems,,,, and their inverter manuals answer a lot of questions.

2.
Clamp-on ammeters can measure instantaneous AC current and the Kill-A -Watt - as already suggested - can measure usage over time.
Portable generators and inverters produce "modified sine wave" power - so the accuracy of the Kill-A-Watt device may be affected by this but it will be a good approximation.

3.
If the new home will be "off-grid", I strongly recommend the following:
- install two inverters so you can have 120/240 volt power. This will give you the option of running 240 volt devices like well pumps, etc, and a crude back-up solution if one inverter fails.
- size the system well above what your calculations indicate your needs will be. Many installers quote bare minimum systems to get the business. It's much easier to add capacity now than to retro-fit later. A friend of mine has two 3600 watt Xantrex inverters. The house is quite small.
- wire in the connection (permanent or twist-lock + cable ) for a back-up generator so that it will be ready when needed.

GlockG20 · 10-13-2017, 06:40 AM

Quote:

Originally Posted by Subaru297

What is the actual amps your panels can produce?

And are these mounted on the house you are building?

On a normal summer day, 40-50A, on a cold day... 55-65A. Three monocrystaline 260W panels wired in series through an Outback MPPT charge controller. Right now with smoke from the fires I am producing about 3.8kWh/day otherwise I produce between 4.5-5kWh/day.

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