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Unread 12-11-2004, 01:44 AM   #188
Cathar
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Join Date: Sep 2002
Location: Melbourne, Australia
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A second DDC may well be a good idea, and given its characteristics it would generally be desirable to put them in parallel as you suggest. In-series would suit the incredibly high flow-resistance blocks (i.e. even the NexXxoS XP will only be borderling restrictive enough from a cursory examination of the curves to warrant an in-series setup).

In parallel at 12v, we are getting a curve that looks much like the MCP600 @ 13.8v, with heat dump being a little higher, but also slightly higher head. Haven't worked it out, but from a cursory glance it looks like using the MCP600@13.8v figures would be a very close estimate.

In parallel @ 13.2v, which is very easy to achieve even with a small DC-DC converter which can be bought for ~$30US or so, and the putting them in parallel looks something like the 2 x MCP600 @ 12v in series curve, but with more heat.

Generally speaking depending on how you set it up, you'll be hanging around the 21.0-21.3C mark sort of positioning in the above estimates.

I don't think it's wrong to covet 2 x DDC's, but like the scenario's describe, don't go expecting big gains. Don't let a few converters bother you. Generally better though to put some 3/8" ID (1/2" OD) tubing on the pump barbs, and then slip 1/2" ID tubing on top and clamp it on. Removes the need for flow restricting reducers and fairly handily converts the pump into 1/2" OD barbs. Only worry if there's enough room to do so. May not be possible with fat 3/4" OD tubing, but 5/8" OD tubing (7/16" ID) may work.

I had originally started this thread to figure out at what point pumps became "too big", but it sort of evolved into a quest for the best balanced single pump. I understand the enthusiast point of view of chasing even the last 0.5C, but I also want it in a single compact pump, and the DDC is not that, although if using 2 pumps it does come somewhat close-ish, at the extra hassle of routing and wyes as you say.
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