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brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548

Posted: 06:09am 28 Sep 2019

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I've got a 60 amp/48 volt solar regulator -brand new ,that I may use on my new installed 2.5 Kw stand alone panels.

It's a CM 60 48 no other name on it , but I think it cost about $100 today -one of those Chinese black finned type ,no fan .

(I have been using on a smaller system a similar model ,but 30 amp. It has been going years ,no problem.

Anyhow, I'm a bit worried about the "no-fan" bit , thinking ,maybe, I should install a fan behind it to suck some air through the finned back section ??

I'm feeding it with 2.5 Kw of panels, through about 12 mtrs of 10mm square cable All the panels ,14 , are fed to a disconnect junction box up near the panels with 6mm solar cable.

Any thoughts

Bruce

Bushboy

Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 1578

Posted: 08:44am 28 Sep 2019

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Short answer: Having a fan on it sure as heck won't hurt even if it doesen't Help. :0)

Ranting thoughts:

I have a couple of GTI inverters with no fans as seems to be the fashion these days.
The things get uncomfortably hot for my Liking. knowing electronics and particularly capacitors which these things are filled with, don't like heat, I like to reduce the internal oven like atmosphere as much as possible.

I have a large tube fan on one blowing down and the amount of heat that comes out of this 5Kw unit completely defies the supposed efficiency Multiplied by the power handling. The hot air coming out of it is easily greater than what comes out of a 2 Kw fan heater.

I have a temp sensor coupled to a relay stuck on the side of the GTI so it turns on automatically.

If one looks at how these GTI's ( don't know about DC units but I imagine they would be the same) reduce output when they get hot and the temp curve/ reduction, does not take much to see on a day where it is already 30-35o let alone beyond, the power draw a fan is going to make which is very small, is made up for many times over by the losses that would be incurred if the inverter/ controller was throttling to reduce it's own temp. Once they go into self Limiting, the output falls of REAL fast.

Many of these products are made to function on the thin edge even if they will achieve full rated power at all. They want to reduce not only manufacturing costs by reducing the amount of metal and components, but also the shipping cost in weight and Size. It's easy for me to assume they will do whatever they can at the expense of longevity to save in these areas.

I did some tests with an old Fridge years ago. It was pretty much built in to the kitchen cabinets but there was no vent behind the cupboards above. I put a wattmeter / logger on the thing and ran a 80 MM computer fan above the fridge sealed to the top of the fridge and the wall behind. I didn't bother with the sides as the thing was a tight fit anyway. Didn't surprise me that running the fan 24/7 resulted in a lower power consumption for the fridge than not having the fan. Had I set the fan ( which was 6W? from memory) on a relay so it only came on when the fridge compressor activated, I could have got a better result still, insignifican't in reality of over all home power use as it may have been. Probably use more power boiling the kettle once than what the fan used in a couple of days.

I believe my New Fridge which has a smooth tin back and an inlet at the bottom is probably fan forced air over the covered coils.

Forced air cooling is magnitudes more effective in thermal dissipation than convection alone. You don't have to blow a Cyclone across these heat sinks but merely moving the air more rapidly than thermosyphoning as it were, will make the device run MUCH cooler and I believe greatly extend the units life.

I am about to move my fan cooled inverter to a sheltered spot outside where it will get afternoon sun. I'm going to put a couple of brackets on the wall either side and put maybe some fabric or foam in front of the thing wight a good air gap to keep the direct sun off it and I will put 3-4 Large computer fans across the top as well. I believe going against the natural convection with forced air is also more effective as well as being easier from a mounting POV.

Even if the fans don't do anything, which I highly doubt, they give me peace of Mind and comfort that I am improving the life of the unit and giving it an easier time and increasing it's efficiency by doing all I can to keep it from de-rating itself.
Thinking of all those components baking away at the over 60O the unit gets to otherwise going by my known threshold of what I can touch/Hold, as against sitting closer to 40O with the fan is enough convincing for me this is worthwhile. If it's 60 on the outside, not hard for me to imagine it's 80oC+ inside the unit as not everything is heat sunk anyway.

Again, even if fans do nothing, they sure aren't going to be a detriment and the small cost and potential gains are well worth the minimal effort to me. :0)

brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548

Posted: 11:12pm 28 Sep 2019

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Thanks Dave,

I have a couple of small (50mm) fans from pc's that would appear to be suitable.

Plus ,years ago ,I purchased a temp sensor ,which I never used. So ,maybe now is a good time to attach it to the controller side/top.?.

thanks for your story.

Bruce

Bushboy

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