mike93lx
ALLIANCE MEMBER
Just considering this compressor plus the air handler, how much generator would you say I need? Would I need a soft start?
Generator size needed to start my 2.5 ton a/c
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HamAndEggs
Well-known member
I would get a soft start for sure, not only does it make it easier on the generator but it extends the life of the compressor too
I would go for a minimum of a 6000w generator there with a soft start just to give some room for other appliances and the inrush of the AC
I have a 4 ton unit with a Hyper Engineering soft start and a Champion 8750w (Model 100520) and it runs it with ease, including a bunch of other stuff in the house
I would go for a minimum of a 6000w generator there with a soft start just to give some room for other appliances and the inrush of the AC
I have a 4 ton unit with a Hyper Engineering soft start and a Champion 8750w (Model 100520) and it runs it with ease, including a bunch of other stuff in the house
HamAndEggs
Well-known member
With a soft start I bet your 5500w unit will work. Does it have a 240v output? Is it an inverter unit?
Yes on both. 240v inverter. But it only has 1kw of surge capacity
I also have two fridges, a freezer, and a septic pump that I would need to run.
This generator did the fridges, freezer, a well pump and all the lighting I wanted at my last place, but I never ran an a/c on it.
Now in VA, the interior temp rises very quickly when the power is out, but thankfully that is rare.
I have two of those units (1st and 2nd floor). I wouldn't need to run both, but it would be nice to have one
HamAndEggs
Well-known member
As long as your wattages work out under the 5500, I would just make sure to turn the AC on first, then once its running do the rest
Walkers
Well-known member
You have a minimum amps of 19.3 and a maximum breaker of 25, so 5757 Watts. I would consider a 6kw generator marginal at best. Personally, I would look at my electric bill for my highest KW peak and consider that the generator size I would need. YMMV
HamAndEggs
Well-known member
Its worth noting my 8750 starting watt generator is just 7000w running. Runs my 4 ton AC/Air handler, 10a (120v) of computer's, lights, fridge etc with no problem
Dagny
Well-known member
R22 air conditioners are very close to one HP per ton. I would ask the people who made it what is the largest motor it will start.
theoldwizard1
Well-known member
Everyone needs to be aware that there is more than one kind of "soft starter" !
The inexpensive one are basically another big capacitor and do NOT do the best job at limiting "in rush" current. The better one actually limit the amount of current that can be drawn during startup. Yes, this means that it might take a fraction of a second longer to start, but the current is controlled.
SweetD
Well-known member
May consider having a window unit or two in storage and just run those via genny during the power outage?
510ebl
Well-known member
This is what I do, using the same Champion inverter generator as HamAndEggs has. Mainly because the 5ton AC is nearly 30 years old and I don’t want to put it under undue stress trying to kick over on generator power (regardless of generator size).
We keep one in a bedroom window and one in a living room window all summer. Both face the woods, so we don’t care how it looks from the outside. Sheer curtains hide them from the inside. We might lose power once or twice a year.
To stay on topic, a soft start will certainly help your situation. Is your generator 5500 surge, or 5500 running watts? That is, is it 5500/6500 or is it 4500/5500?
510ebl
Well-known member
Ah, I missed that yours is 2.5ton. I’d invest in a soft start and take it for a spin! What does the septic pump draw? 120 or 240? Can it and the fridges be shut off while the air is running?
HamAndEggs
Well-known member
Does your current generator have the functionality to be run with a parallel kit? Then you could just get a second one day and have double the power
510ebl
Well-known member
I am on board with that! Now you get to weigh the balance between generator size, convenience, and fuel consumption.
Unfortunately, no. That would be my first move if it was possible.
Seems like something that should be able to be rigged up
That said, if it could run one on the units, I'd have no problem switching them both to a separate transfer switch and running it to a second generator, with my primary running the rest of the house on my interlock. At that point, I might even be able to get away with a smaller 120v inverter as I don't have any other critical 240v loads.
HamAndEggs
Well-known member
Personally I would just buy a larger single unit. Down here in Texas at least, generator fetch a premium since stock is so low everywhere, and you could get close to retail for it
HamAndEggs
Well-known member
Nothing to say a larger unit can't be inverter
theoldwizard1
Well-known member
Best solution, especially if you don't want to invest in a whole house solution.
AP514
Well-known member
Here is a thread on my Softstarts for my 2.5 ton AC
www.garagejournal.com
I got 2 these off EBAY been working good but only tested them...I have not run my Generator for long peiods off them yet.
That being said they are running every day off the local powergrid..at least from the day I installed them.
HYPER SURESTART - Soft Start
Well, I just Purchased a HYPER SureStart to try to get my 2.5ton AC unit to start using my 7000/12000watt Generator. I figured I would show the Kit and what it looks like. I will show the hook-up and running and let everyone know the results. I am hopeing for a 40% decrease in Power...
www.garagejournal.com
I got 2 these off EBAY been working good but only tested them...I have not run my Generator for long peiods off them yet.
That being said they are running every day off the local powergrid..at least from the day I installed them.
ThanksHere is a thread on my Softstarts for my 2.5 ton AC
HYPER SURESTART - Soft Start
Well, I just Purchased a HYPER SureStart to try to get my 2.5ton AC unit to start using my 7000/12000watt Generator. I figured I would show the Kit and what it looks like. I will show the hook-up and running and let everyone know the results. I am hopeing for a 40% decrease in Power...
I got 2 these off EBAY been working good but only tested them...I have not run my Generator for long peiods off them yet.
That being said they are running every day off the local powergrid..at least from the day I installed them.
Before you do anything or make any changes, you need to find out what amps your big appliances are using. Not estimating, but taking actual readings using your choice of ammeter. I did this with my home and was surprised with how much my refer and freezer(20 yrs old) were using. Also, my ac/furnace motor used over 11a just pushing cold ac air.
My gen produces 50a of 120v. I can run my 5ton ac with soft start and furnace motor using 44a, but not much else.
However, I can run my refer and freezer along with all my 120v lights, ceiling fans, tv and a big 240v window ac using less than 30a. My old Honda at 6000w can run 30a easily with plenty to spare.
My gen produces 50a of 120v. I can run my 5ton ac with soft start and furnace motor using 44a, but not much else.
However, I can run my refer and freezer along with all my 120v lights, ceiling fans, tv and a big 240v window ac using less than 30a. My old Honda at 6000w can run 30a easily with plenty to spare.
I agree.
What happens if all your appliances are trying to run at the same time? Personally, I believe you need 8,000 watts, but add a freezer and a fridge and it may need larger. People forget all the other stuff they might be running. Also the blower in the furnace or air handler is going to take 5-10 more amps.
I used to sell and service Generac generators. I had someone call with a complaint on a generator they they bought elsewhere. They were looking for an "second opinion". I went over and it turned out they had a 4 ton heat pump and a 10K generator and the generator would not start the heat pump. Right off I told the homeowner they needed at least a 14K but we got talking about other loads. I also spent some time on the phone with Generac and they also said the 10K was too small, and a 14K was the minimum they would recommend. After a long conversation with the homeowner about other loads in the home we sold him a 20K, (which was a bit large, we were at a 16K but that was the minimum with other loads), and he was happy. he was able to get the first company to take back the generator. Some mention of an attorney and they became agreeable!
What happens if all your appliances are trying to run at the same time? Personally, I believe you need 8,000 watts, but add a freezer and a fridge and it may need larger. People forget all the other stuff they might be running. Also the blower in the furnace or air handler is going to take 5-10 more amps.
I used to sell and service Generac generators. I had someone call with a complaint on a generator they they bought elsewhere. They were looking for an "second opinion". I went over and it turned out they had a 4 ton heat pump and a 10K generator and the generator would not start the heat pump. Right off I told the homeowner they needed at least a 14K but we got talking about other loads. I also spent some time on the phone with Generac and they also said the 10K was too small, and a 14K was the minimum they would recommend. After a long conversation with the homeowner about other loads in the home we sold him a 20K, (which was a bit large, we were at a 16K but that was the minimum with other loads), and he was happy. he was able to get the first company to take back the generator. Some mention of an attorney and they became agreeable!
4 ton single stage, or a 4 ton inverter air conditioner. Big difference between the two on starting load.
I am amazed an 8K will start 4 ton.
HamAndEggs
Well-known member
4 Ton single stage, 14 SEER
theoldwizard1
Well-known member
Many of the cheaper "soft starters" are just large capacitors and THAT IS THE PROBLEM PORTABLE GENERATORS HAVE !
A discharged capacitor "looks like" a short circuit. Or if you like the water analogy, and empty bucket that demands to be filled as fast as possible. The only way to do this is with a bigger bucket !
In the world of electricity, you limit current flow by inserting a resistor in series with the load, but only temporarily, until the start capacitor ("bucket") fills up, probably less than 2 seconds/
A discharged capacitor "looks like" a short circuit. Or if you like the water analogy, and empty bucket that demands to be filled as fast as possible. The only way to do this is with a bigger bucket !
In the world of electricity, you limit current flow by inserting a resistor in series with the load, but only temporarily, until the start capacitor ("bucket") fills up, probably less than 2 seconds/
In a related question what’s is this box ?
3
Have seen the SOFTSTART RV used on 13.5k to 15k RV AC units that will start and run on quality 2000 watt inverter generator. Vs the dozens of hard start CAPS that look similar to this for a faction of the price:
3Have seen the SOFTSTART RV used on 13.5k to 15k RV AC units that will start and run on quality 2000 watt inverter generator. Vs the dozens of hard start CAPS that look similar to this for a faction of the price:
dcg9381
Well-known member
Are clamp on amp meters sensitive / reactive enough to actually get a good reading on in-rush current? If so, I think that'd take out a lot of guess work.
I'm shocked at how little power our house pulls 2 AC (2 ton, 3 ton) and it's not a small house. I installed a 20KW generator and I've only seen the house draw 10KW once. But then again, I have no idea what the demands are for inrush current.
I'm shocked at how little power our house pulls 2 AC (2 ton, 3 ton) and it's not a small house. I installed a 20KW generator and I've only seen the house draw 10KW once. But then again, I have no idea what the demands are for inrush current.
wyliesdiesels
Well-known member
Its a little more complicated than that. You need a clamp meter that has circuitry for reading in-rush current. Not all clamp meters have this. Fluke has several models that do. Theres an in-rush current button on them
You've got a nominal value of 11.8 + 0.9 Amps, and let's say 220 V that comes out of the generator.
A motor is somewhere around 80% efficiency, so 13 x 220 / 0.8 = 3750 W.
Without a soft start, I'd say you'll need around double of that to be comfortable.
With a good soft start, this drops to 20 - 25% additional.
Don't forget that "crude" gen sets can mess up a lot of the electronics in household devices. Those will probably be fine for that A/C. You can throw almost anything at electric motors.
An invertor would be ideal to feed any "smart" devices (that need a stabilized sinusoidal volt/current power supply like hifi, most electronics, ...).
A motor is somewhere around 80% efficiency, so 13 x 220 / 0.8 = 3750 W.
Without a soft start, I'd say you'll need around double of that to be comfortable.
With a good soft start, this drops to 20 - 25% additional.
Don't forget that "crude" gen sets can mess up a lot of the electronics in household devices. Those will probably be fine for that A/C. You can throw almost anything at electric motors.
An invertor would be ideal to feed any "smart" devices (that need a stabilized sinusoidal volt/current power supply like hifi, most electronics, ...).
A Klein CL390 will read max amps for your startup just fine. Less than $100.
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dcg9381
Well-known member
Is there a general "rule of thumb" for inrush scaled to size of the AC or indicated amp draw on the plaque?
wyliesdiesels
Well-known member
HamAndEggs
Well-known member
I have (had..) that Klien meter, it did not read inrush well at all. I got a Fluke 374 to replace it
theoldwizard1
Well-known member
Concur ! Very difficult to measure ACCURATELY !
The best is a shunt and digital recording oscilloscope.
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