MEP-803A for 5 ton AC with soft start?

Jeff d

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I've been looking at buying an MEP-803A to use as a standby generator at my house in southern Louisiana. I already have a proper 50 amp inlet and breaker interlock that I use with a cheap 5,500/8,250 watt Briggs and Stratton generator. This works fine but is loud and obviously I can't run the 5 ton AC on that so I haven't ever tried. Gasoline supply was an issue after Ida but pretty much any gas station that had power to pump had diesel with no line. We have natural gas so the AC is the only major load. I'd manually manage any other high draw electrical appliance (oven, clothes dryer, etc) with the AC.

Anyway, running amperage on the 5 ton unit is 28.9, which is fine, but the LRA on the unit is 169 amps, which is too much. I'd rather not have to step up to a larger generator that will then mostly run with a small percentage load on it and then have to deal with relatively high fuel consumption and increased likelyhood of wet stacking. So, I'm wondering if an electronic soft start controller would do the trick. They (the various manufacturers of the soft start controllers) claim a 70% reduction in LRA on single phase units. That would put me at about 51 amps before it settles to 29 amps when up and running. Is this cutting it too close? Do I either need to get something 15kw or just give up on the idea of running the 5 ton unit?
 
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Coug

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You definitely need the soft start kit for that, but it should work no problem.

So for comparison (not a direct comparison I know), I have a 3 ton ECU (aircon/heater) that's surplus military. The aircon starts and operates fine with my MEP-802A, and only draws about 60% load. Startup surge is very short, and the generator is easily able to get past it.
There is a guy on the youtoob that has run 4 of this aircon unit in cooling mode from a single MEP-803A.

There is even a chance it can do it without the soft start kit, but the kit will definitely make it nicer for everything else plugged into the generator.
 

Elijah95

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Soft start should be fine. The lock rotor amp rating is generally so fast without a high end meter you won’t even catch it on the display as it’s <1 second in duration.

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Jeepadict

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Soft Start units are highly popular in the RV world and make a drastic difference on the load shock to any generator. I put one on my trailer when I added my tiny gennie and it made everything work flawlessly.

The MEP units have much more of an operating envelope than their specs lend credit to. I've meter verified my 802 only reads 75 PRC at rated load (which makes sense as that's where the green tick is on the meter), and I live at almost 7000 ft! There's some fairly awesome overload protection built into these units, see attached pic for the spec from a guy much smarter than I.

I'd wager the 803 could easily broach the 13-14KW threshold without difficulty. I've had my 802 at 95% PRC with an estimated 6900W...and the overload protection doesn't begin until 110% and above.

If it was me in your described scenario, I'd totally rock the 803 and send it! If you worry about wetstacking, buy an old electric range off Craigslist to use as a load bank...easily stores out of the way under a tarp and is plenty power hungry to keep you running clean.


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Jeff d

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It seems strange that soft start controllers aren’t more commonly installed along with most standby generator installs. Seems like a $280 no brainer vs. going bigger on the generator.
 

Russ Knight

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I have a 3 ton heat pump with a 4 ton air handler at home and when it's running my MEP803A is at about 25% load. When my electric water heater kicks on it goes up to around 50%. I have two 5 ton heat pumps and a mini split at my business and the generator will run one of the units, the mini split and lighting (all LED), but if the second 5 ton comes on, the generator will disconnect from the load.
 

Light in the Dark

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Soft Start units are highly popular in the RV world and make a drastic difference on the load shock to any generator. I put one on my trailer when I added my tiny gennie and it made everything work flawlessly.

The MEP units have much more of an operating envelope than their specs lend credit to. I've meter verified my 802 only reads 75 PRC at rated load (which makes sense as that's where the green tick is on the meter), and I live at almost 7000 ft! There's some fairly awesome overload protection built into these units, see attached pic for the spec from a guy much smarter than I.

I'd wager the 803 could easily broach the 13-14KW threshold without difficulty. I've had my 802 at 95% PRC with an estimated 6900W...and the overload protection doesn't begin until 110% and above.

If it was me in your described scenario, I'd totally rock the 803 and send it! If you worry about wetstacking, buy an old electric range off Craigslist to use as a load bank...easily stores out of the way under a tarp and is plenty power hungry to keep you running clean.


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All 803s I test at 13.5KW. If they won't hold that with ease, they arent ready for sale. The engine is specified from the manufacturer as good for like 18KW, its limited by electronic controls in these units.
 

impi

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Loxahatchee, FL
My 803a runs a 5 ton and a 2 ton unit without problem with sequential start up. The 5 ton is equipped with an Easy Start, the 2 ton is not. I recently replaced the AC units and moved the Easy Start over to the new Carrier unit which has a dual speed compressor - all still functions as it should. 803 will trip if you try to start a 5 ton with it without an easy start - the initial amp load on startup pushes it over the edge - at least it did on a single speed compressor. Did not try to start the new dual speed unit up before moving the Easy Start over. It's well worth the investment in the unit.
 
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