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Controlling hydro Air and Heat Strips

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Eire
Eire Member Posts: 8
in Thermostats and Controls
Hi
I’d appreciate some help with the following. I am replacing 3 existing Air Handlers and 3 external water to air coils
I also want to Install heat strips for emergency back up . The hot water is provided from an oil fired boiler with 3 independent zones with circulators. I have though about installing a heat pump . But that might complicate things too much. I’d like to use an ecobee type thermostat . My question is what the correct way to wire this type of set up and what over the counter products can I use do do so.
Thanks Brian

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  • HVACNUT
    HVACNUT Member Posts: 5,841
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    Before we get to "how", I'm interested in why. Unless the boiler or existing coils are grossly undersized, I can't see why you would want that setup.
    The only reason I can think of is you frequently run out of oil on a Friday and can't get a drop until Monday. But you're not Meatball so that can't be it.

    Are you looking to run the electric strips as a 2nd stage in conjunction with the hydro on a differential, or independent from the hydro (boiler circuit opens when the electric heat circuit closes?

    If your new air handlers comes with the electric strips, its basically a heat pump and you can wire the Ecobee and A/H's as such, according to the A/H wiring diagram.

    Using the "B" terminal or the prompt on the Ecobee will send 24v power in (in heat mode) back to the A/H.
    Instead of connecting to the O/B terminal on the A/H, use it to power a 24v coil isolation relay for the boiler. Connect TT from your boiler zone board to the N.O. contacts on the isolation relay.
    The electric heat will go from W1 on the Ecobee to W1/E in the A/H.
    If you want to run the electric independently from the boiler, configure the Ecobee for emergency heat, and connect to W2 in the A/H.

    That's the low volt side.
    On the line volt, what's energizing the blower motor on a (hydro) heat call? Aquastat, Ecobee, TDR?
  • Eire
    Eire Member Posts: 8
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    Hi HVACNUT

    Thanks for getting back to me. The reason for the heat strips is for future use as I will probably install a sizable solar array with net metering.
    To give you the full story we got a new house and it was sitting up for a while with no heat so the boiler coils and some plumbing didn’t do to well.
    The old system consisted of 2x2 ton and one 3 ton with carrier condensers and Lenox ai4 handlers all 3 systems had 15 x 24 x 3.5”coils mounted above the air handler below the plenum.

    I had a heat losss calculation carried and specd a boiler to suit the load. I have the boiler installed with 4 circulators 3 heating and one DHW.
    I was advised not to go with a hydronic type air handler so
    Just to get a Look, I purchased a water to air coil from BADGER same physical size as ones removed only difference it has 1” inlets. It does however requires minimum 1700 CFM so I’m not sure what 2 or 3 ton air handler that will give me that
    I also know that there are hot deck type coils that are custom to the actual air handler.

    I’m open to some advice as I haven’t yet purchased the air handlers or condensers / heat pumps. The duct work is exsisting and I’m not planning on changing that as the house is not that old and I assume it is sized correctly.

    The exsisting line sets R22 are I believe small 3/4 3/8. And I’m not sure what the joints are like So they probably need to be replaced.

    And then I am down to controls. I like the ecobee stats I have used them on a few occasions.
    I was looking into a taco or zone controller and taco hydro air fan controllers with pipe stats.
    And Ecobee thermostats.

    I really appreciate the help here I have no problem with plumbing and Electrical. Just not that versed on HVAC.
    Thanks
    Brian

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