Series VS Parallel
Author: JFettig
The articles shows you the difference between Series and parallel. It will help you decide on what configuration will be best for you.
Which is better? Thatís a good question many people have been asking lately, both in radiator and waterblock arrangements. Unfortunately, there is no correct answer. Why? Well it all depends on your waterblocks and the rest of you system.

When it comes to radiators, you always want to run them in parallel. Why? Well, the longer that the water stays in the radiator the more time it has to cool. If it rushes through multiple radiators itís only going to cool so much. What's more, radiators in series will be more restrictive to the water flow.

If youíre running dual processors, or multiple blocks, you can figure out weather or not to run in series or parallel by flow testing. For example, running dual Gemini Spiral blocks would be quite restrictive. Suppose the pump you are using is an Eheim 1250, which will put out upwards of 200-300gph of unrestricted flow, and each block can only handle around an estimated 60-80gph. When these blocks are run in series, flow is cut down even more. To get maximum flow you would want to run them in parallel. This would also reduce extra head loss, causing extra heat from the pump.

Simple flow testing can help you determine wether your system will benefit from series or parallel waterblocks. Take your pump and attach a few feet of hose. Get a one-gallon jug (milk carton), or five-gallon pail (spackle bucket), and time how long it takes to fill it up. Donít bother finding the GPH, only be concerned with the time it takes to fill up the container. Next, hook up a waterblock and time how long it takes to fill up the container with just the one waterblock attached. If it takes 2x or more time to fill up the container, then you should run in parallel. If it takes less than 2x the time to fill the container, then you should test both blocks together. If this test returns results equal to half or less than the initial flow, then you still should run in parallel, if its more than half of the flow then you can run in series.

When running two or more waterblocks, you may want to run a series-parallel configuration, for an example, if you have high flow CPU waterblock and two other low flow waterblocks (Ex. GPU and Chipset), you may want to go from source, to CPU, to a Y, have it split off and send some to the GPU and some to the chipset, then come back together in another Y, then into the radiator, and finally back to the source.

If you are running two non-restrictive blocks in parallel, you will most likely loose a lot of performance. This is caused by lower water velocity (the speed at which the water travels through the blocks) through the blocks. Typically, the higher the water velocity is, the better the blocks will perform. When blocks are run in parallel, half of the water goes two one block, half goes to the other, decreasing the water velocity, yet reducing the restriction added to the system. If the blocks are non-restrictive in the first place, then running them in series will allow you to achieve a higher water velocity.

With a little bit of testing, you should be able to determine the best configuration for your cooling components. The differences between series and parallel could be minimal, yet at the same time they could be drastic.

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