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  1. #1
    Join Date
    Oct 2009
    new jersey
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    Pnumatics piping question

    Hello. I see in a hydronic unit ventilator the branch air comes in and goes to the low limit. Then to the ep relay. Outlet of relay to heat valve and damper actuator. Why didn't the branch air control the heat valve before the ep. Now heat valve is always open unless the fan switch is on. When it is not supper cold the fan is off.

  2. #2
    Join Date
    May 2014
    Bay Area California
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    Maybe to keep the coil hot so it never freezes (?)

    I've got this one building that has ten perimeter fan coil boxes. No actuator valves anywhere. Fan comes on when there is a call for heating. Doesn't seem the most efficient way to me, but it looks like that's how it was installed. No chance of these coils freezing; just an odd design.

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