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Thread: Sunheater S421 vs S425 Installation

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    Sunheater S421 vs S425 Installation

    I have two S421 kits that I installed last year but I don't know if I am getting the maximum heat transfer out of them. The S421 kit installation ( shows the panels are are connected in series on the feed side and capped on the opposite side. The S425 kit ( instasllation diagram shows a different configuration where as the panels are linked together on the far end then feed end. The S425 installation looks like it would absorb more heat as the water is forced through one panel at a time rather than the S421 installation that forces water through the same ends of all collectors. I checked the collector panel part numbers and to see if they are the same buy unfortunately the part number for S421 is not in the manual as is in S425. Can anyone confirm which installation would be better?

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    Mod Squad Bama Rambler's Avatar
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    Jun 2009
    SouthWest Alabama

    Re: Sunheater S421 vs S425 Installation

    They're just different designs. The 421's have a partition (blockage) molded into the feed end pipe to cause the water to flow up one half of the tubes and back down the other half. The 425's don't have this partition so the water flows the same direction in all the tubes. This is not the most efficient way to run the panels but it allows you to have a short piping run because the feed and return is on the same end of the panels. The most efficient way is to pipe all the panels in parallel but the 421 panels won't allow this unless you want to drill out the partition in the feed pipes which I bet will void your warranty.
    Dave J. TFP Moderator
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    Re: Sunheater S421 vs S425 Installation

    Thanks Bama. I wondered if it was two different designs.

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