Backup Heat Source Necessary?

Discussion in 'General Discussions' started by JackA, Nov 6, 2009.

  1. JackA

    JackA New Member

    We live in N. Virginia and are considering installing a geothermal system to replace our existing LP furnace. Is it necessary to have a backup system as we would like to get off of the LP all together? We have an LP fireplace that could be used if everything failed. We also have an electric heat pump for the upstairs of the home that will remain until it dies. Any advice would really be appreciated.
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome,
    Most building codes require the installation of emergancy(electric resistance) heat as part of the heat pump install. Wheather you ever use it or not is a subject for the design phase of your project.
    To answer your question directly no. The seperate system upstairs as well as an lp fireplace will be more than enough.
  3. teetech

    teetech Member Forum Leader

    You should not oversize your unit to handle 100% of your heating load. If the fireplace will carry you through the coldest days that would be fine. As waterpirate said you would not have to use electric heat if you don,t want to.
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I have never heard of code requiring back up. Not saying it isn't so, just surprised.

    Any body else run into this?
  5. gabby

    gabby Member Industry Professional Forum Leader

    Local building codes take precedence over state and federal minimum requirements; therefore, "who knows what lurks in the mind's of men."
  6. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I would ignorantly suggest that any codes such as that may be referring to air source heat pumps?
  7. JackA

    JackA New Member

    I failed to mention that the reason for the LP backup is that my 200amp panel is very close to being maxed out and therefore they quoted me an LP backup so as not have to upgrade my panel ($$$) to handle electric backup.
  8. ciws14

    ciws14 Member

    Really? How about 95%?
  9. gabby

    gabby Member Industry Professional Forum Leader

    I don't believe any heat dominated region would have an aux heat source. I know I can't find anything in Texas code, and I heard Florida has no such requirement.
    Ohio has no such requirement that I am aware of since long before heat pumps, all electric homes had only one source of heat. Now that doesn't mean that an all electric resistance furnace didn't have a fireplace in the structure, but mostly a choice of whomever was building the structure.

    It is common to design homes with a 95% load for cooling or heating, which is based on what region one lives. My design is 97% for cooling and the heating is whatever it happens to be since heat is really not a big deal for Houston. It is not uncommon to design for 99% cooling for Dallas homes since they may have 20-40 days of 100+ temperatures with high humidity. Houston is normally designed for 75-77 degrees as an upper limit. My design is 73 degrees for both winter and summer. I don't like heat. Here the design is met with a unit that has higher outputs in stage two compared to other brands, plus it has an extra coax for dehumidifying which gives a little extra without jumping another ton. It is all about balance. I believe that the unit will run in stage 1 about 70% of the time until the temperature breaks 93 degrees, then it is stage two. Winter operation should never move into stage two unless it snows at the Alamo.
  10. gabby

    gabby Member Industry Professional Forum Leader


    Your electric load would change if you got one or two Geos to handle both loads. Removing the air source heat pump may be all that is required, or switching to a single source heat source zoned for the two loads.
    In either case a load assessment would need to be taken prior to choosing which route to pursue.
  11. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Many local codes in my area make no differance between air source and geo, it's just a heat pump. Everyone remembers the black eye air source took when it first got popular, so resistance is futile, I mean mandatory for new installs.

    How does everyone feel about starting a seperate thread to argue about what % of the load should be covered and why?
  12. gabby

    gabby Member Industry Professional Forum Leader

    Well, you opened that door so I figure anyone who wrestles in the mud subsidizing implementation of these units is qualified to open a multinational/regional thread where differences in opinion may be fruitful.
  13. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Not so much wrestling in the mud, as trying to find a definitive answer. It has been disscussed to stale mate, or pissed off as a part of other threads with no clear vision for anyone.
    If it truly is contractor preferance only, then lets once and for all write the thread with all views represented so it is available to newbies for a resource.
    I can make a good argument for both sides but prefer one over the other.
  14. gabby

    gabby Member Industry Professional Forum Leader

    I agree.
    My suggestion is that anyone who contributes should specify the region of the country they are most experienced so we don't have Long Island geothermal properties being mixed with geothermal properties in Utah..............hmmm, you think anyone does geo in Utah?

    Like it or not, these are the characteristics that shape the design criteria of a system install, and one of the major reasons we have an apples to oranges comparison from one location to another in overall design, and in designing for load percentage.

    Point of reference:

    Rotary Mud Drilling = mud wrestling---not arguments, which is another way to look at it.
  15. JackA

    JackA New Member

    So, just to confuse things a little more. I have an existing LP furnace that is 5 years old and functioning without issue. Can I install a geo heat pump and keep my existing furnace for backup heat? The contractor would like me to install a geo heat pump with a new higher efficiency LP furnace for backup heat.
  16. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Last time I checked, people in Utah were still using buffalo chips for home heating.

    Dewayne Dean from Salt Lake City, Utah
  17. mseifert

    mseifert Member

    When I maxed out my 200 amp panel, they just installed a sub-panel - which connect to the original panel through one of the breaker slots. Not a huge expense. Since you don't use 200 amps at once, it isn't an issue adding more breakers / loads.
  18. gabby

    gabby Member Industry Professional Forum Leader

    If you have a furnace about 10 years old, then it would make sense to update to a higher efficiency model; however, if the furnace is working well and will be a standby device with the major heating done by a geo, then it becomes a more difficult choice to make. If their is ductwork mods with the installation of the new system, it makes sense to upgrade your furnace rather than doing it twice.

    Dewayne I like the buffalo chips reply.
    Just seeing if you were paying attention to this thread...rotflmas.
  19. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    RE the code question, I'm not going to grab the book but I think the verbage in the IMC is along the lines of a system with the ability to maintain 68* in occupied space. This does not require aux heat if you are a 100% loader or in cooling dominated climates. If you are a 92-98% loader as I am it would suggest that aux is a code requirement depending on design (if I achieve 98% for folks who want 72* in the winter, I might be at 100% for 68* and therefore not require aux. per IMC). Local codes of course vary.
    Wether or not you wire it, I would get the aux coil now when it is essentially a throw in (it will be marked up more later).
    If you wish propane auxiliary (I wouldn't support that choice) get the new furnace now.
    good luck,
  20. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    That code requirement to maintain 68 rings a bell with me as well - I'm sure I read that somewhere in Florida codes

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