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Originally Posted by lolito_fr
Cathar, I have just been checking my calcs for the graphs in the nexxos thread. I have a problem regarding heat dumped into the loop by MCP650, which you give as 15w.
It seems this pump only draws 15-20w?
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What's the problem?
Typical real-world operating range is 250-500lph, or 17-18W as per Roscal's graph.
The pump transfers very close to 90% of its input power draw to the water as heat, and the other 10% exits via the plastic casing. 15W is a lower-end estimate for the heat dumped by the pump. In typical use it's more like 15-16W. I personally measured 16W with a Laing D4, and 15.5W with the MCP650, with a Cascade block in the loop as resistance.
If you're surprised at just what a large percentage of input power gets converted as heat, then don't be. Look at the pump's design. Metallic wetted body with eletromagnets attached to the metal that water flows over constantly. The electro-magnets produce most of the heat, and the water cools them almost directly. A small portion of the heat gets convected by air into the plastic pump body, as well as the small micro-controller generating some of its own heat - again - being dumped into the sealed plastic body - for which the heat can exit by the plastic housing, or through the wetted metallic end.