Hard Start Capacitor for 5000btu AC - Fiberglass RV


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Old 05-21-2018, 07:50 PM   #1
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Hard Start Capacitor for 5000btu AC

So I'm thinking of modifying my 5000btu A.C. with a Dometic 3310727007 hard start KIT.

My thinking is that it would allow me to purchase a 1000w generator to run the A.C. or even start up the A.C. on battery and solar alone.

I haven't run the numbers on the A.C. as of yet so don't hammer me for posing the question.

Curious of your thoughts / experience.
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Old 05-21-2018, 08:00 PM   #2
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Do you know what the kit would bring the startup amps “down” to and how much your 5000 unit would pull once it’s running. Those would be critical to know befor more investment.
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Old 05-21-2018, 08:45 PM   #3
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It is an Arctic King 5000btu A.C. peak watts 527-590, running watts 446-485. 4 amps running.

Appears it would run on a 1000w generator. I wonder if it would start it.
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Old 05-21-2018, 08:53 PM   #4
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Quote:
Originally Posted by Markz View Post
So I'm thinking of modifying my 5000btu A.C. with a Dometic 3310727007 hard start KIT.

My thinking is that it would allow me to purchase a 1000w generator to run the A.C. or even start up the A.C. on battery and solar alone.

I haven't run the numbers on the A.C. as of yet so don't hammer me for posing the question.

Curious of your thoughts / experience.
I did not come up with this, so I don't know if it's accurate, but I think its close. It's also regarding a dometic 5000 btu AC unit.

"The AC uses about 560 watts. So 4.7 amps for 8 hours is 4560 watt hours.

But the inverter may be 90% efficient, so 5066 WH.

With deep-cycle batteries you want to discharge to about no less than 1/2 full, so double that to 10133 WH."

If these numbers are in the ballpark, you'd use close to 500 amp hours to run a 5K BTU AC unit for 8 hours. And remember, you don't want to drain your batteries below about 50% of their rated capacity. Better have alot of battery and solar capacity.

These type of scenarios have been discussed often, but personally I don't think it's practical to have a huge amount of solar and battery capacity just so you can run an AC unit.
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Old 05-21-2018, 09:05 PM   #5
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If it were me, and I thought I’d not want to ever try to run a bigger AC unit than the 5,000 unit, I’d look at buying a Honda 2000 unit which are competitively priced right now with the introduction of the new 2200s replacing them. That way you’d be sure you could start your unit on the generator without the cost of a starter kit. Plus it would run some other larger draw items you might want to use. Just a thought. I am an overkill kind of person so maybe that’s something too.
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Old 05-21-2018, 10:03 PM   #6
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I would do the same Dave. They can be had for $700-$800, run great, super quiet, and start a 5K btu AC without a hitch.
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Old 05-22-2018, 08:13 AM   #7
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I claim no expertise, but why would a 2000 W generator be required for a 500 W load? Especially as the capacitor is intended to provide the startup kick required.
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Old 05-22-2018, 08:55 AM   #8
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I claim no expertise, but why would a 2000 W generator be required for a 500 W load? Especially as the capacitor is intended to provide the startup kick required.
Certainly not "required", but as Dave points out, it gives you enough reserve power to run anything else. Charging would be better too. Just from an electronics standpoint, I'd much prefer an inverter generator as well. The power is cleaner.
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Old 05-22-2018, 09:04 AM   #9
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I claim no expertise, but why would a 2000 W generator be required for a 500 W load? Especially as the capacitor is intended to provide the startup kick required.
An electric motor, as in a AC compressor, has a starting load that is about three times the running load. So a 500 watt running load requires about 1500 watts to start. This starting load lasts for about 1/2 second or so.
A starting capacitor stores energy and can help with the initial starting load. Then it re-charges before the next start occurs.
A better solution is a Micro-Air EasyStart. It applies a current sufficient to start the motor slowly and spreads a lower starting current out over time. It matches the generator output to the load by monitoring the RPM of the motor and allowing it to take about twice as long to come up to speed, while keeping the load within the generator limits. It learns about the load and the generator during the first five starts to perfectly match the two. Instead of the motor starting abruptly in about 1/2 of a second, it starts smoothly in about a full second. This lowers the peak starting amps to about 1/2 of what they would normally be. So, a 500 watt running load can be started with about 750-1000 watts instead of about 1500 watts.
These numbers are general, but give you the idea. They apply to motor starting loads and not other loads, like a microwave or lights.
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Old 05-22-2018, 09:15 AM   #10
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Hardstart

I put a “micro air” set up in my Airstream ac unit, it allows my single 2000 watt Honda to run the Unit effortlessly
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Old 05-22-2018, 10:32 AM   #11
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Certainly not "required", but as Dave points out, it gives you enough reserve power to run anything else. Charging would be better too. Just from an electronics standpoint, I'd much prefer an inverter generator as well. The power is cleaner.
Thanks Robert,
We had capacitor start on a number of electrical devices in the municipal pools, park shops, irrigation systems with booster pumps. I always look for a solid solution that may be overkill but dependable and maintainable for the long “run”.
I don’t need a 27 hp engine to mow my lot but I like speed and power when I want it and my 27 Kaw does that for me. Blame my V-8 upbringing.
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Old 05-22-2018, 10:48 AM   #12
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I believe Raspy has it right on the initial load. On the other hand, the Honda 2000 is rated 2,000 watts peak load, but 1,600 watts continuous. Thus it matches pretty well with the peak demand of the AC unit. I'm not sure about the Honda, but many generators have reduced output at higher altitudes of 5,000 to 10,000 ft. So it is good to have some reserve power. The generator will probably run quieter if not running flat out.

I'm not here to argue whether your need for AC diminishes at higher altitudes. It does.
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Old 05-22-2018, 10:57 AM   #13
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A lithium battery bank could run the a/c with the right converter and they are lighter than traditional batteries, and don't have the 50% drain factor either, and I believe they charge quicker with less heat generation if I am not mistaken. The downside here is the price as lithiums of this size are about $3K each...
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Old 05-22-2018, 04:30 PM   #14
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I'm not sure about the Honda, but many generators have reduced output at higher altitudes of 5,000 to 10,000 ft. So it is good to have some reserve power. The generator will probably run quieter if not running flat out.
All naturally aspirated engines lose power as the altitude increases. The accepted amount is 3% per 1,000' elevation. So, at 3,300', the generator would be down on power by about 10%. That would reduce a 2,000 watt generator to about 1800 watts.
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