Maryland Auxiliary heat for recovery

Discussion in 'General Discussions' started by cfergu22, Jan 8, 2020.

  1. cfergu22

    cfergu22 New Member

    I'm new to Geo, we have been using it for around 6 months. I have a question about the best practices of using a programmable thermostat. But here are the specs of the house so you'll have enough background information to answer the question.

    I have a 3100 sq foot 2 story house that was finished in July 2019. It's insulated fairly well, above builder grade spec, but not spray foamed. We have a lot of windows, something like 30, but they are new, decent quality windows. We have a 2 zone geothermal HVAC system. Upstairs we have a 2 ton Water furnace 5 series unit, and downstairs we have a 3 ton Water furnace 5 series unit (the footprint of our first floor is larger than the 2nd floor, the 1st floor unit also heats and cools the unfinished basement). Both units have a 95% efficient propane backup. We have a horizontal ground loop with 6 total lines that loop something like 400 feet, about 6-8 feet beneath the ground.

    Up until last week, we have been maintaining constant temperatures on both floors because we've had guests staying with us on the 1st floor and someone was home all day. The propane heat never gets used running the system this way.

    Now we are back to our normal routine with my wife and I both working all day so no one is home from 8-5. Also, no one is sleeping on the first floor. So I've programmed the 1st floor thermostat down to 66 at night, and 66 during the day when we're gone. It just rises to 70 degrees for wake up time and evening time.

    What's interesting is the furnace engages the propane auxiliary heat for the recovery. So until the temp gets back up to 70, the propane furnace is running those 2 times a day. It takes about a half hour depending out outside temps.

    My question is...

    Now that we are theoretically heating more efficiently with the geothermal system, should we just leave the temperature set to 70 all day long so the propane backup never runs? Or is there some way to disengage the propane backup for normal temperature recovery?

    I don't get enough info from our system to tell me how much energy it's using during the night to keep up the temp. So it's hard to calculate it. Is there some kind of software I can use with the water furnace system that would give me the hour by hour breakdown of the usage?
  2. gsmith22

    gsmith22 Active Member Forum Leader

    keep the temp at the same temperature night and day and don't do a setback and your propane furnace won't come on at the jump in thermostat temperature. heat pumps are much better at maintaining a temperature then they are at jumping 4 degrees instantly.
  3. SShaw

    SShaw Active Member Forum Leader

    Many thermostats that support dual-fuel and that have an outdoor temperature sensor will allow you to disable the AUX heat if the outside temperature is above a chosen temperature. You could disable the propane backup if you had such a thermostat.

    If you don't have that option, WF thermostats have a differential setting between stages that affects when the AUX comes on. If you set the differential for the highest stage to be more than 4 degrees, then the AUX shouldn't come on with a 4-degree setback.

    Those settings might be in a hidden "installer" section of the thermostat.

    If your 5 series units include the energy monitoring package, and the appropriate Symphony thermostat, you would be able to look at instant and daily energy use and maybe estimate the savings of the setback, both with and without the use of propane to recover.
  4. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    I have two units, one in my in-law apartment. Mom was insistent that night time temperature be cooler. My solution was to set back to 66 at 7 or 8 pm so it coasts down by bedtime. I scheduled mornings to 68 at 5 AM, then 70 at 7 AM.
  5. cfergu22

    cfergu22 New Member

    Ok, thanks a lot for your responses.

    The first thing i'll look into is the thermostat differential settings.

    I'll also lessen the setback and try to program a small ramp up. Maybe go 2 degrees, then bring it back one degree at a time.

    I'll look into the energy monitoring package. I'm assuming that is a feature I don't have because they didn't' tell me about it. So I'll reach out to my HVAC contractor and see if they have any options for me. It seems like you need the information to really run your house efficiently.
  6. SShaw

    SShaw Active Member Forum Leader

    The link below is to an old document, so some details may have changed, but it looks consistent with what I just installed in October. The document describes the options for the 5 and 7 series. The kits can be field installed.

    w w w

    You will need to fix the www at the front of the above "link"

    Basically, you need the advanced AXB control board, various sensors, and the thermostat.

    You can tell what you have factory installed by looking at the model number of your units. This is listed on page 2.

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