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EG4 flexboss21 & gridboss with 2 Powerpro wall mount batteries to start a 5 ton A/C unit

louis25th

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Dec 13, 2024
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Washington State
Hi all,

I see on the EG4 website saying that a FlexBoss21 "Starts a 5-ton AC unit easily". However I couldn't find any details about this claim in the spec sheet. I don't know under what setup is this claim supposed to be true. I assume it is without grid or generator input, but is it with or without PV? There is no LRA number mentioned in the spec sheet either. The peak power on battery only is 18kw for 1s, but it doesn't seem to be enough to meet the need. 5 ton AC compressors don't have same LRA, but it's usually around 150A at 240V (so 36kw?).

My prospective setup is a FlexBoss21, a GridBoss with 2 Powerpro wall mount batteries. And I want to know whether they can start my 5 ton A/C unit without grid or solar power (battery only). The claim on their website is so vague it is not helpful. Anyone here have a first hand experience? Or maybe @EG4TechSolutionsTeam could help giving more details about it?
 
Hi all,

I see on the EG4 website saying that a FlexBoss21 "Starts a 5-ton AC unit easily". However I couldn't find any details about this claim in the spec sheet. I don't know under what setup is this claim supposed to be true.
24kW for 0.5 seconds, 18kW for 1 second. Eg4 believes that is enough to start a 5 ton ac.
 
I would assume this is with soft start on the compressor. Without soft start, the initial current surge is huge.

Mike C.
 
I wouldn't put any A/C on any inverter without a softstart unless it didn't overload. Not a good idea to overload any inverter at any time.
 
Hi all,

I see on the EG4 website saying that a FlexBoss21 "Starts a 5-ton AC unit easily". However I couldn't find any details about this claim in the spec sheet. I don't know under what setup is this claim supposed to be true. I assume it is without grid or generator input, but is it with or without PV? There is no LRA number mentioned in the spec sheet either. The peak power on battery only is 18kw for 1s, but it doesn't seem to be enough to meet the need. 5 ton AC compressors don't have same LRA, but it's usually around 150A at 240V (so 36kw?).

My prospective setup is a FlexBoss21, a GridBoss with 2 Powerpro wall mount batteries. And I want to know whether they can start my 5 ton A/C unit without grid or solar power (battery only). The claim on their website is so vague it is not helpful. Anyone here have a first hand experience? Or maybe @EG4TechSolutionsTeam could help giving more details about it?
It's not on any specs sheet I could find but here's what James eg4/sig solar owner said on flexboss 21 vs 18kpv:

"- Motor surge was increased 50% to 190RLA for 5 ton ACs"

Post in thread 'EG4 new products at RE+' https://diysolarforum.com/threads/eg4-new-products-at-re.90618/post-1222946
 
Oh, that's very interesting finding! Could the "RLA" be a typo of "LRA"? Still it's unclear whether it's with battery only or with PV as well though.
I'm certain he meant LRA. Unsure on if it needs PV I'm guessing it can do that with just the 12kW from the battery.
 
I have tested my single flexboss with starting a 5 ton HVAC in heat pump mode. It works, but I can tell the voltage drops some. I plan to try to catch it on a scope, but I have other things to fix first. Here is the nameplate from my system:

1736695684143.png
 
153 amps locked rotor, wow.

Seems like a soft starter might be a good idea if you try to start with other loads going at the same time.

Just because it can doesn't mean it is a good idea.

To be clear, this was with grid down? If grid up, that's no test.

Mike C.
 
153 amps locked rotor, wow.

Seems like a soft starter might be a good idea if you try to start with other loads going at the same time.

Just because it can doesn't mean it is a good idea.

To be clear, this was with grid down? If grid up, that's no test.

Mike C.
Grid down. (off at my disconnect)
 
Grid down. (off at my disconnect)
I'm impressed.

Still think soft start is a good idea, but nice to know you would then have margin.

Also, compressor start might vary with conditions, harder when colder outside, for example.

Mike C.
 
I'm impressed.

Still think soft start is a good idea, but nice to know you would then have margin.

Also, compressor start might vary with conditions, harder when colder outside, for example.

Mike C.
Not trying to be snarky, just adding a little more info.... This test was performed while the temperature was in the low 20's. Fahrenheit. With a water heater running. EV charger was not on.
I think the EG4 spec for the Flexboss is 190 LRA. I was skeptical too.
This testing was done while working another issue. If you want to see that thread, it's here.
 
My 18Kpv pair will start my 4T Goodman without a soft start but it dims the lights. That's when it's 115F outside, and extremely hot. I put the micro air on it. Sometimes it still bothers the cheapo LED's in the middle of the summer. I think it's just a really good idea to put the thing on there. Oddly, my heat pump just cut on while I was typing this, I only heard the noise, no blinky it's a package unit on the roof above my office. Some of the early firmware struggled a bit on the inverter, they got it fixed.

After using the soft start for a time, if I didn't have an inverter compressor, I'd put one in no matter what, even if I didn't have a solar inverter. A couple hundred bucks is nothing, and it can't be a bad thing to control inrush to any equipment. I'm a fan, not a shill.
 
Not trying to be snarky, just adding a little more info.... This test was performed while the temperature was in the low 20's. Fahrenheit. With a water heater running. EV charger was not on.
I think the EG4 spec for the Flexboss is 190 LRA. I was skeptical too.
This testing was done while working another issue. If you want to see that thread, it's here.
50% more LRA than the 18kpv per eg4 James.
 
Not trying to be snarky, just adding a little more info.... This test was performed while the temperature was in the low 20's. Fahrenheit. With a water heater running. EV charger was not on.
I think the EG4 spec for the Flexboss is 190 LRA. I was skeptical too.
This testing was done while working another issue. If you want to see that thread, it's here.
This is impressive. Especially if your water heater draws ~5kw when on like mine does.

For reference my 18k can easily start a 4 ton AC without a soft start when there are NO other loads. When I had 4.5kw of loads running and that same 4 ton AC w/o soft start kicked on the inverter blew up. Soft starts are on now and make a huge difference. Here's the thread of my inverter blowing up for reference: https://diysolarforum.com/threads/18kpv-blew-up-and-breakers-never-tripped.93192/
 

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