Nominal ratings of inverters and overheating near limit

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Nominal ratings of inverters and overheating near limit

Postby Ozziozzi » Sun Feb 23, 2020 11:17 am

I have a system of 6.5kW panels and Sungrow 5kW grid connected inverter that regularly shows 5010 W Pac on its built in display. What are the tolerances of inverter outputs, +/_ 10% maybe. The maximum P out was set by the installer and Limited (probablyj by the wholesaler or retailer. Does anyone know what these upper limits are in terms of inveter safe operation/lifespan and allowed by retailers wholesalers?

I am also concerned that my Sungrow nominal 5kW inveter regularly reads 5010-5015 W for Pac output. It also runs very hot on these days. Is this something to be concerned about?

My other question is whether the nominal 5kW is the NET amount allowed to be EXPORTED to the grid before limiting occurs or the maximum GROSS power produced for use within the property by the inverter.
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Re: Nominal ratings of inverters and overheating near limit

Postby jules » Mon Feb 24, 2020 2:36 pm

For components like diodes, triodes and capacitors, lifespan is very closely related to operating temperature, so that operating at high temps will inevitably shorten their working life. In your situation it might mean that you get 10 years rather than 15 out of your inverter. Maybe I should express that as 2/3 of possible expected lifespan as I don't know how long a Sungrow would normally last.

As far as tolerances go, 10 to 15W above 5,000W should be ok but again, operating temp. is important. In winter with an ambient temp. of 15C the inverter should operate very comfortably. If your inverter is installed in a place where the temp. can go above 40C in Summer that's very different. Even if it's operating within its nominal power output limits, high temp. operation does take a toll on lifespan.

It could be worth installing a cooling fan or considering other ways to improve airflow.

I can't comment on anything grid related unfortunately :)
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter. Off grid for 30 years.

Spares; 5 x 12V, 1,000 Ah batteries plus a couple of regulators
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Re: Nominal ratings of inverters and overheating near limit

Postby australsolarier » Wed Feb 26, 2020 6:31 am

yes, a cooling fan is a good idea to prolong inverter life. and if the sun gets to it build a roof over it.
and if the inverter is made in china half the rated output is more like the real thing.
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Re: Nominal ratings of inverters and overheating near limit

Postby Ozziozzi » Wed Feb 26, 2020 1:26 pm

I have sent a couple of PMs after a searchof the forum for fan cooling of inverters, But not received a reply yet. Can anyone give mefurther info or point me to a site? I thought of a Couple of excomputer fans driven by a small solar panel attached to a little verandah over the inverter. Fans Placed below inverter close to brick wall as heatsink of inverter is on back with airspace to wall. I suspect ANY assistance with airflow would be better than just convection cooling and that there is no such thing as too much cooling. Any comments?
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Re: Nominal ratings of inverters and overheating near limit

Postby jules » Wed Feb 26, 2020 2:36 pm

Inside or outside [as in exposed to the weather]?
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter. Off grid for 30 years.

Spares; 5 x 12V, 1,000 Ah batteries plus a couple of regulators
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Re: Nominal ratings of inverters and overheating near limit

Postby jules » Wed Feb 26, 2020 3:01 pm

RS has a wide variety of fans like ...

https://au.rs-online.com/web/p/axial-fans/7604769/

I've used these to assist a fridge in the past. I think you'd need a bit more oomph than a computer fan would deliver.

Is 240V an option? Might be easier in some ways.
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter. Off grid for 30 years.

Spares; 5 x 12V, 1,000 Ah batteries plus a couple of regulators
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Re: Nominal ratings of inverters and overheating near limit

Postby Ozziozzi » Wed Feb 26, 2020 3:13 pm

Inverter is on brick wall outside under fairly wide eaves so protected from rain and sun until about 1pm. Exposed to sun 1-6pm facing NW. About 3cm air space between inverter heat sink and brick wall.Actually, fans are from a laboratory fumehood so rated for continuous use and Much more powerful than computer case Fans. I Have 100 mm and 150 mm sizes. Just said computer fans as they look exactly like that, but with aluminium cast frame and fan blades.
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Re: Nominal ratings of inverters and overheating near limit

Postby jules » Wed Feb 26, 2020 4:41 pm

Lab fume-hood fans sound very impressive as long as they aren't 1 HP or something massive like that :D . Could you arrange some shade as well? Direct sunlight is serious heat.
Primary system: .8KW Trina panels; Plasmatronics PL40; 1,000Ah VRLA 12X2V battery bank; 1.7KW Selectronic inverter. Off grid for 30 years.

Spares; 5 x 12V, 1,000 Ah batteries plus a couple of regulators
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Re: Nominal ratings of inverters and overheating near limit

Postby Ozziozzi » Sun Mar 01, 2020 7:04 pm

My fans look very similar to the RS ones mentioned earlier, but 12v models drawing about 120 mA. Even running at 6v they put out quite a breeze. At present I am thinking a piece of galvanised sheet metal as a small verandah over them and maybe 4 fans below inverter to assist with convection cooling. Whatever I use should be easily removed for when the "solar police" :o come around. I don't think they approve of jerry-built constructions near grid-connected equipment. Perhaps I will stick with plastic for construction and insulation. :shock:
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