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  1. #1
    Join Date
    Feb 2001
    Posts
    445
    I'm in discussions with a manufacturer of energy recovery ventilators. They recommend that their ERVs be served by a dedicated circuit. When I ask why, they say, "In order to protect ourselves and our customers we recommend a dedicated circuit," but they refuse to elaborate on why or how a dedicated circuit protects them or their customers. They say it's a "legal" issue. These units are so energy-efficient (as low as 34 watts) that I can't believe they are concerned about overloading a shared circuit. Does anyone know of other reasons why a dedicated circuit would be advisable?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,750
    Just a guess.

    If the unit is hard piped, what if lightning strikes, and blows out a recepticle near some one.

    If its a dedicated circuit, the strike would have to go to the panel box first, and the earth ground would carry alot of the current oout of the house.

    Just a guess.
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  3. #3
    Join Date
    Mar 2005
    Posts
    17

    Circuitry?

    My guess is that they require a dedicated circuit for their ERV/HRV so as to remove any chance of electrical interference from another device on the same circuit. Fluorescent light ballasts are notorious for fouling the power on a given circuit (anyone ever have to install a capacitor/noise filter on the inlet power to a furnace that didn't have a dedicated circuit because of signal interference?) Perhaps there are delicate or sensitive circuits in your particular erv that the manufacturer thinks might be susceptable to interference from the other devices on that circuit.
    Just a thought,
    Jim

  4. #4
    Join Date
    Apr 2003
    Location
    Eugene, Oregon
    Posts
    1,209
    These are not electronic marvels that a twinge of a spike is going to fry something. Recommendations are one thing, code will dictate what you really "must" do.
    Proud supporter of Springfield Millers and Oregon Ducks.

  5. #5
    Join Date
    Jul 2004
    Location
    Kent, WA
    Posts
    129
    None of your circuits are really isolated, as they all come together at the main panelboard. A short dedicated circuit with a noisy fluorescent light next to a short dedicated circuit for a piece of sensitive equipment is not a whole lot different than one longer circuit with both items on the same one. Wire length is about your only filter unless you install an actual filter device, and wire length can be had on either a shared or separate circuit.

    I can see no reason why they say what they say. Hopefully, the instructions "recommend" rather than "require" a dedicated circuit. I see many things in manufacturers instructions that seem pointless or even dangerous. But the electrical code says you have to follow their instructions.

    Personally, I'd find some other circuit with fans on it (kitchen, bathroom, attic) and extend it to the ERV. Perhaps the airhandler circuit would be the best choice if there is one, its a 15A or 20A circuit, and the furnace has some connection to the running of the ERV.

  6. #6
    Join Date
    Mar 2005
    Posts
    17

    Urban Legend?

    I learn SO much here, I really do.....I had been told repeatedly over the years that this "dedicated circuit" thing was critical to stop any possible interference from another device on the same circuit. I'd been told this so often, by so many people, that I never questioned it. Indeed, there is nothing in a panel that isolates one circuit from another within a house. Thank you for not laughing me out of this forum.
    Humbly,
    Jim

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,750
    Some times a dedicated circuit, is confused with a dedicated ground circuit.
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  8. #8
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    dedicated grounding circuits are HAZARDOUS!

    and, IMHO, dumb!

    any troubles associated with grounding, are probably poor design, installation, etc.

    at ICP there were two sheet metal brakes (benders) with digital back gauge readouts. One probably worked 5% of the time, despite change out of the main panel twice, boards many times, etc = PIA over 10yr. When we moved the department, I found a grounding rod beside the problem unit, with a wire connected to the electronics panel = dedicated grounding.

  9. #9
    Join Date
    Apr 2004
    Posts
    7,680
    I think they are merely protecting themselves as they should. Leaving it open to OK a shared circuit opens the door to pandora's box. If the other loads on the same circuit were to cause a voltage drop the end result could very well be a burnt up motor on the ERV. They cannot possibly fathom the combinations in the field if the green light is given. Thats why they tell you to use a dedicated circuit. A furnace on the otherhand definately has to be dedicated.

    I suspect a little common sense goes a long way but there are plenty out there who simply do not have any like the label on the unit that shows the fingers being cut off by the fan, Duh... but you know its because someone did it.

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