Promising initial Off-grid AC test

[gkb2016]

For the first time today, I ran my AC unit off battery only for an extended period of 3 hours, where compressor ran 100% of time (no cycling) and from battery only (disconnected solar input).

Ran air conditioner with doors open so it had no chance to cycle off, and wattage varied between 390 and 430 according to KillaWatt meter. dunno why the variation, but after first hour it stayed pegged closer to 430 Watts.

I am curious, if the unit is only drawing 390-430 watts... If you shut the doors to keep the cool air in (especially if you're van is insulated), what percentage of the time is the AC actually cycled on? Seems if it's running anywhere less than 75% of the time, that amounts to a pretty large difference in actual energy usage. Could make AC a much more viable option for many.

 

[Canine]

Good show,Brad.Have you totaled up the cost for your system?I have an 8000 btu unit but don't know how many amps it draws.I may check around for some prices on new Energy Star models.

 

[SternWake]

Not being familiar with AC, what is the start up surge on these window shakers? Like minimum size inverter required......

When they cycle on and off, does it use another ~100 watts that first minute after cycling on?

I am not considering it for my rig, I do not have the need, roof space or desire, just curious.

 

[BradKW]

I am curious, if the unit is only drawing 390-430 watts... If you shut the doors to keep the cool air in (especially if you're van is insulated), what percentage of the time is the AC actually cycled on? Seems if it's running anywhere less than 75% of the time, that amounts to a pretty large difference in actual energy usage. Could make AC a much more viable option for many.

That is certainly part of the reason I am putting a lot of effort into insulating, especially the floor as well. I would be pleased with a 75% run time, but actual numbers will have to wait a bit until I'm further along.

I also have it designed so that I can use a thermal curtain of some sort to section off the AC and sleeping area, reducing the sq/ft of cooling by 50% if I find it necessary...

 

[BradKW]

Not being familiar with AC, what is the start up surge on these window shakers?  Like minimum size inverter required......

When they cycle on and off, does it use another ~100 watts that first minute after cycling on?

I am not considering it for my rig, I do not have the need, roof space or desire, just curious.

On this particular unit, start up surge is basically negligible...powering on puts it at 115 watts for 3-4 min before compressor cycles on, at which point there is no surge I can identify. 

I know people with larger units that say they have a surge that has developed over time that can trip up their generator, and have installed a "soft start" thing inside the AC unit. I forget what exactly it's called, but I have one in pile of parts that I was given...not looking like I'll be putting the effort into installing it though.

 

[amwbox]

Again...this sounds like a pretty special AC unit if you're starting a compressor without a surge...

 

[jimindenver]

Brad

If this is the same unit I use it does have a surge. It is so quick and quiet that I have to check the killawatt to make sure it is running, You don't notice with a good bank and the solar running but a small bank or generator will show it. It happens so quick normally that my killawatt and clamp on barely show a jump before dropping again. A weak bank however delays the start up and the meters have a chance to show it and they can really climb fast. My little 800/1000 watt inverter generator will not start it either. The A/C attempts it, the lights all blink and it goes back to fan only for another 3 minutes before trying again. This happens so quickly that the generator doesn't even stall from the overload. The overload light comes on but the A/C gives up so fast that it doesn't stall. I have to run the converter on the generator and the A/C on the inverter to be able to have the bank absorb the surge and then the generator runs it.

The only compressors that I know do not have that kind of surge is the swing compressors in Engel fridges.

 

[SternWake]

I saw on Amazon yesterday, a Kill a watt competitor which records compressor start up surges:


https://www.amazon.com/Ensupra-Elec...F8&qid=1489692370&sr=8-5&keywords=power+meter

Scroll down to video review.

I wonder what the start up surge is on a Danfoss.  I notice mine sounds a bit different on start up when battery is low at 12.2v, vs being held at 14.7v.

My DC clampmeter does not record  start up surges, and my DC wattmeters say they do record  Peak watts peak amps, but if they do the danfoss surge is not much more than the running wattage, or happens faster than they record pretty much negating any extra hardship on the battery supplying the surge.

 

[jimindenver]

The lower the voltage the higher the amps. It was too much for my old 8-D starting battery unless the 750w solar system was running. Then it was fast and quiet.

 

[BradKW]

I saw on Amazon yesterday, a Kill a watt competitor which records compressor start up surges:


https://www.amazon.com/Ensupra-Elec...F8&qid=1489692370&sr=8-5&keywords=power+meter

Scroll down to video review.

I wonder what the start up surge is on a Danfoss.  I notice mine sounds a bit different on start up when battery is low at 12.2v, vs being held at 14.7v.

Just for the heck of it I ordered one...will check out the surges on AC and danfoss when it gets delivered.

Definitely can't see it on the KilloWatt though, as I've sat staring at it a few times waiting for the compressor to kick in...

 

[SternWake]

The data you collect could be invalueable.

Should be also interesting to compare Kill a watt with Ensupra Meter.

I'm lacking on AC meters.

Gonna hook my wattmeter back upto my fridge. Will report its Peak watts/amps

 

[SternWake]

My danfoss bd35f runs at slowest possible compressor rpm, 2000. It does not vary rpm as some danfoss powered chest style models do

My GTpower wattmeter is registering a 55.4 watt Peak load on startup at 12.6v. 70 f ambient 32.5f interior

Its wattage thereafter tapers from 40 watts to 32 in the next 15 seconds Tapers to 27.5 watts before end of compressor cycle ~4.5 minutes later

 

[SternWake]

Ok 74 hours later, my wattmeter is registering peak watts of 56.5.

It is registering as having consumed 43.43AH, and I will add 3AH, one for each day, to this for the small unregistered load of interior 40MM 0.03a fan and parasitic load (0.02a) as controller waits for signal from thermostat to turn on.

So, 0.63 AH consumed each hour on average. This is with overnight lows around 60 and max daytime highs of about 75f and the fridge as I normally use it with likely about 15 to 20 door openings a day and maintaining low 30f inside. Right now coldest spot on floor registering 27.5f, warmest spot 34.5f.

I bet I could knock off 20% with better door sealing/insulation.