Which would produce more heat?

[evilkitty]

I have picked up the following boards

• EPS-15-12 (12v; 1.38A; 15W; ~50% Load)
• EPS-15-5 (5v; 3A; 15W; ~16% to ~33% Load)

I would expect the one running at a lower % would get less hot given they are both 15W, but only the 5v one has a heat sync
the 12v board has a STPS20S100CT with no heat sync and the 5v has a STPS30S45CT (assuming it starts with ST, there is a cap in the way) with a heat sync

If anyone is curious both boards have a mix of United Chemi-Con and Rubycon caps:

• KMG 33uf 400v cap X 1
• YXM cap 10uf 50 X 1
• ZLH 16v 1000uf X 2 (5v board only)
• KY 25v 1000uf X 2 (12v board only)

I am trying to deiced which board should get the more favorable position (top) for cooling, probably does not matter, but you know what lets over optimize cause we can

[sam_sam_sam]

Re: Which would produce more heat?

Do you like to live dangerously ( sad face ) but it looks neat and tidy just not enough space between them

( I am glad that you have asked the question about weather or not this would work))


if I were you I would put a little more space between those two boards or if you do not have the space then at least put a piece of plastic under the first board and on top of the stand-offs at a minimum

Now if you are talking cooling what ever board is at the bottom is going to suffer from HEAT -
(you are going to slowly cook those caps ) weather or not the IC chips has a heat sink or not

If it were me I would use some more stand-offs that are same long the length and take the half length out put it on top of the ones you already have it would be a lot better for both boards

I hope this helps

[budm]

Re: Which would produce more heat?

http://meanwellusa.com/productPdf.aspx?i=691#1
Where did you get the % load from?
+1 about the clearance.

[evilkitty]

Re: Which would produce more heat?

the load is the estimated load the unit will be under when in use, not asking them to run at 100% at all times
at the lowest point i have at least a mm of clarence between the boards, i could easily double this by trimming a few cap leads that could be a tad shorter

My original mounting plan just failed, over approximately 1 mm of clarence
plan B will not be as high limited and will work by the skin of its teeth, it will not be as hight limited as plan A, plan B2 involves titling the 400v cap to get a hair of wiggle room
plan C would eliminate stacking, but slotter my ventilation air flow
Plan B3 would require removing the 400V cap on the top board and extending the leads (still shorter then factory lead length) so i can re-mount it sideways to it will clear the fan

*the fan is set to turn on if the case temp reaches 7.5C above room temp and in plan B the bottom board will revive a large amount of the air flow

*Just trimmed the leads on the 470uf caps in case the below caps bulge, now i have at least 2mm clarence between the boards

[budm]

Re: Which would produce more heat?

But where did you see that load spec in the spec sheet? Or those are what your loads are going to be? I think I understand what you mean now.

[evilkitty]

Re: Which would produce more heat?

that is what the load is going to be well approximately

[Stefan Payne]

Re: Which would produce more heat?

I would expect the one running at a lower % would get less hot given they are both 15W, but only the 5v one has a heat sync

No, because the % load is irrelevant.
What is interesting is efficiency, heatsinking and air flow.

If something is loaded to 100% with 90% efficiency and dissipating 5W is the same as if it is loaded with 50% and 70% effiency and dissipating 5W...