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Xantrex: GT 3.3 Inverter Operating Temperature
http://solar-guppy.com/forum/viewtopic.php?f=19&t=663		 Page 1 of 2
Author:  Marshall [ Thu Jul 31, 2008 3:14 am GMT EstGMT ]
Post subject:  Xantrex: GT 3.3 Inverter Operating Temperature
Greetings,

Just wondering what temperature range I should be seeing on my GT 3.3 inverter heat sinks? The 2 inverters are installed in my garage. The highest temps I am seeing are around 132 degrees. Should I install a thermo switch with cooling fans or is a temperature of 132 degrees in the acceptable range for the inverter heat sinks?

Thanks

Marshall
Author:  mike90045 [ Thu Jul 31, 2008 9:47 am GMT EstGMT ]
Post subject:  Re: GT 3.3 Inverter Operating Temperature
I used a small fan, on a timer, to cover the hot part/high production portion of the day. Others have used fans for their indoor installations too. Apparently, intended install was outdoors, where there would be some air movement. Just a little air movement cools them down, a small fan is fine
Author:  Solar Guppy [ Thu Jul 31, 2008 10:44 am GMT EstGMT ]
Post subject: 
The GT's were designed for outdoor mounting, indoors, its like being in an oven as the air is heated by the inverters and garages can be exceptionally hot as the tend to get heating via IR and just store the heat with no ventilation

In this case something as simple as a desk fan on a timer ( 20 bucks ) can add years of life to the inverters running cooler
Author:  Marshall [ Fri Aug 01, 2008 12:12 am GMT EstGMT ]
Post subject: 
Solar Guppy and Mike,

So what is a good number to shoot for as far as the daily high heat sink reading on the inverters? I personally do not think 130 degrees is that high, but maybe it is for these inverters. Are you guys saying that with my heat sinks getting up to 132 degrees every day for a few hours that this will or might shorten the life of my invertes? I do realize that electronic components do not like heat. And I am not trying to question your knowledge, just trying to understand what my target heat sink temperature should be and get a real number as a guide line.

Thanks

Marshall
Author:  mike90045 [ Fri Aug 01, 2008 9:26 am GMT EstGMT ]
Post subject:  Re: GT 3.3 Inverter Operating Temperature
The inverters have (now) a 10 year warranty. I'd expect them to last 10 years at any temp below their rated point [?}. Running a small fan to keep them cooler, I'd expect 10+ years. In spacecraft, we consider every 10F reduction in temp, to roughly double the life, but that's starting at 190F. With heatsink at 140F, I don't know what the internal thermal gradient is, how hot the innards of the power FETs are.
Author:  Marshall [ Fri Aug 01, 2008 1:03 pm GMT EstGMT ]
Post subject: 
Well my two GT 3.3 inverters were just replaced last week. The orginal inverters were a little over two years old. Installed in March of 2006. They worked great for 2 years then the first inverter would not come online. The company that installed my system came out and replace the inverter, then a week later the 2nd inverter would not come online. The solar install company came out and replaced both my inverters with new ones. I am impressed that Xantrex stood by there product and took care of me. I did notice that these new inverters run much cooler than the old ones. The old 3.3's would run at 146 degrees mid day. These new 3.3's run at 132 degrees mid day. The installer says that these are the newest version of the 3.3's something about them being UL 5's.
Author:  Solar Guppy [ Fri Aug 01, 2008 2:43 pm GMT EstGMT ]
Post subject: 
146F would start derating the output, it must be pretty warm in your garage, running day after day at derating is not the best means for long life

The new units are more efficient and will help in putting less heat into the heatsink. Personally, I would have a small clip on desk fan on a timer to blow so air on the heat sinks maybe 3 hours a day. Cost penny for the electric and should give you mosre year for your inverters
Author:  Marshall [ Fri Aug 01, 2008 3:37 pm GMT EstGMT ]
Post subject: 
Solar Guppy,

I am a little surprised at your suggestion regarding using a timer to activate a fan to cool the heat sinks on the inverters. I thought that you liked to conserve power as much as possible. How about cloudy days when the inverters do not get up to higher temperatures that need cooling?? I have not actually looked at inverter temperatures on cloudy days, so it may be moot point. I would think that running a fan on a timer would be wasting power if it was a cloudy or really hazy day. How about using a thermal switch? I have some thermal switches already and would not have to go out and buy one. Again, I am a newbie when it comes to this solar stuff, that's why I am asking all the questions.

Note: I did turn on a fan around mid day to see what it would do to the heat sink temperatures on the GT 3.3's. Before I turned the fan on, inverter #1 heat sink was runnung at 136 degrees, inverter #2 heat sink was running at 132 degrees.

With the fan on, inverter #1 heat sink is running now at 106 degrees, and inverter #2 heat sink is running at 99 degrees. WOW!!!!!! Major differnce! :shock:

My next decision will be how to implement activation of the cooling fans.
I am leaning towards a thermal switch to conserve power rather than a timer. What do you think?
Author:  mike90045 [ Fri Aug 01, 2008 4:05 pm GMT EstGMT ]
Post subject: 
I hadn't found a source for a simple thermostat. I wanted to use a clothespin to clip it to the heatsink, nothing that would mar it, or cause a warranty problem. (You GLUED a thermostat to the heat sink ! No wonder it died, sorry no coverage.)

I'd thought of a mineral oil cooling loop to a small radiator, and using paper clamps (binder clamps) to clip tubing to a couple of fins. Too much tubing involved, a timer and a fan were the things I used.
Author:  Solar Guppy [ Fri Aug 01, 2008 5:22 pm GMT EstGMT ]
Post subject: 
It's about solving the problem, solutions have some costs

You installed 6 kW of solar inveters in a hot box with no ventilation, the simple solution is a cheap maybe 10 watt fan that runs midday and keep things cool

Lets say it takes 100 watt/hr a day for a pair of fans a a cheap timer,

Cost, lets say 15 cents kWh ... so we have 365 days @ 100 wHr day = 36.5 kWr / year @ 15 cents kWh = $5.40

So , what would some fangled thermsat save? at most $5.40 if it never turns on

Run the fan, make your inverters live an extra 8 years for 5 bucks a year, figure a timer and fans might be 30 bucks initial outlay

Oh, the inverters are more efficient the cooler the heatsink is ( the FET's have lower losses ) so in reality, the fans probably net energy, not use it, but I thought a little math would drive the point home
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