Engineering Opinions Wanted

Blackcherry04 · February 2013

If you were designing a Inverter and you had a choice when mounting the Ventilation Fan for the direction of air flow, would you design it where it pulled air over the transformer and then exited or where it blew over the transformer and heated the other components prior exiting ??

To me, I'd want to pull in ambient air and then locate the fan and exit as close to the largest heat source ( Transformer ) as I could.

Thoughts ??

The reason I am asking Is I have a OutBack VFX apart on my bench, it has a 5" vent fan that takes air in and blows it across the transformer on to the FET board and then exits. To me, I should turn the fan around for maximum cooling.
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BB. · February 2013

Re: Engineering Opinions Wanted

Electronics tend to be more temperature sensitive--so I would send the cool air there first.

Also, I would suggest a good/large filter-fan-inverter type setup... Dirt/dust/bugs is a real issue when moving air through electronics. Pressurizing the case keeps dust from leaking in through corners of the case (positive pressure inside inverter).

You can argue that the fan motor is generating heat and bringing it into the inverter--But I would not worry about it. The turbulent air flow from the fan will help "scrub" the heat from the hot components better than laminar air flow. Holes/Bars/Screens right near fan blades can cause noise (siren effect--don't ask how I know

... It was stupid).

-Bill

NorthGuy · February 2013

Re: Engineering Opinions Wanted

In all the devices that I've seen, the cooling fan pulls the air out of the device. I think that is because if you blow the air in, you can create a turbulence which will return the heated air back to the components that you want to cool.

If I had other components that are likely to overheat, such as FETs or diodes, I wouldn't let the air from over transformer to go over them. I would probably build a deflector or used a separate fan for these components.

I would test different configuration to see how I get a better cooling.

I'm not an electrical engineer and I do not design inverters. This is just my opinion.

Blackcherry04 · February 2013

Re: Engineering Opinions Wanted

BB. wrote: »

The turbulent air flow from the fan will help "scrub" the heat from the hot components better than laminar air flow.

-Bill

I picked this inverter ( OutBack vfx ) down at the Inverter Service Center free, It came out of a tour bus. it was covered with road crud dust and the FET board is out and who knows what else, all I wanted was the case. Anyway I was looking at the cooling scheme and it seemed backwards to my thinking. I might do some testing, where I am going to install the Inverter I am putting the case on will have a fairly high ambient temperature at times of the year.

BB. · February 2013

Re: Engineering Opinions Wanted

I have designed/manufactured good sized systems that have done both... And in the same system (push and pull) passed Bellcore/Telcorida (telephone company qualification tests) just fine.

In terms of dust control (I had less of a problem because large computer systems are installed in a conditioned/locked down space), pressurizing is easier to keep the dust out. And, I believe, keeping the dust out of the electronics helps with a long life (if you have humidity issues, doubly so).

Any power system that needs directed air flow because of high power density/waste heat--Better have redundant fans/fault detection/shutdown circuitry. Fans are the weak point of any system. Fans have a limited mechanical life unless you spend big bucks on high end fans.

-Bill

ggunn · February 2013

Re: Engineering Opinions Wanted

Blackcherry04 wrote: »

I picked this inverter ( OutBack vfx ) down at the Inverter Service Center free, It came out of a tour bus. it was covered with road crud dust and the FET board is out and who knows what else, all I wanted was the case. Anyway I was looking at the cooling scheme and it seemed backwards to my thinking. I might do some testing, where I am going to install the Inverter I am putting the case on will have a fairly high ambient temperature at times of the year.

In the first place, you are unlikely to come up with an idea for cooling that the engineers for the inverter company did not consider, especially if it's just turning a fan around. In the second place it makes less of a difference if the fan is blowing or sucking than the direction of air flow. The air movement from natural convection is going to be from bottom to top and you want the fan to work in cooperation with it, not in opposition to it.

Blackcherry04 · February 2013

Re: Engineering Opinions Wanted

I am not going to criticize OutBack , They are obviously been successful with the cooling scheme they have, but it's weird the way they have the cooling set up. On the Sealed Unit ( GTFX ) it has the same 5 " fan the vented model has. all it does is beat the air around in the case and uses the Case as a big heat sink and heating everything inside. The Vented case is the same case with venting holes cut in it and a opening for the fan. The FET board has a bunch of clamp-on heat sinks on it. Just seems weird.

mike95490 · February 2013

Re: Engineering Opinions Wanted

I like a filtered, thermostatic controlled, intake fan at the bottom, that pressurizes the case, with adequate exit vents near top. Also, locating expensive hot parts near the top. I've seen too many fans cooked to death sucking hot air past themselves.

Blackcherry04 · February 2013

Re: Engineering Opinions Wanted

ggunn wrote: »

The air movement from natural convection is going to be from bottom to top and you want the fan to work in cooperation with it, not in opposition to it.

Yep, you could be right with this. If the fan was in a constant on mode, then it might be best to have cool air coming in at the bottom and hot going out the top with the fan blowing OUT. With the fan having a thermostat demand, to get passive convection cooling it may be more efficient to let fan run in the opposite direction and let the heat out the bottom when the fan is on.

Blackcherry04 · February 2013

Re: Engineering Opinions Wanted

I want to thank Everyone who posted. In the end I put it back together the way OutBack designed it ( fan blowing into the case ). I left a way to insert a probe and I'll test the temperatures when charging and Inverting, I can always change it. I am trying to see if I can reclaim the 600-800 watts that OutBack de-rates their sealed outdoor units to. I bought a new GFX 1312 and mated it to a FX vented top. I am guessing it will be fine as the Inverter already had a 30 Minute 1800 watt rating. Time will tell. Being cheap, I am trying to take a $900 Inverter and turn it into a $1,700 for free, of course nothing in life is free.......lol I am truly more interested to the charger output being at the max.

BB. · February 2013

Re: Engineering Opinions Wanted

You might run into some hard coded firmware limits for the sealed unit (if different firmware or factory configuration programming)...

-Bill

Blackcherry04 · February 2013

Re: Engineering Opinions Wanted

BB. wrote: »

You might run into some hard coded firmware limits for the sealed unit (if different firmware or factory configuration programming)...

-Bill

Thats true Bill, I'll be watching for the Limits if I see them. All I'd like see is if their published outputs will work without the disclaimers * " Depending on the Ambient Temperature " thats code for the 70 amp charger will only put out 30 amps most of the time.

Engineering Opinions Wanted

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