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  1. #1
    Join Date
    Jan 2007
    Location
    TN
    Posts
    49

    Best Dual Fuel system?

    Hello guys looking I am looking for some advice on the best Dual Fuel systems out on the market. I am currently utilizing a 14 year old Heil Gas Pack 5 ton cooling and 125,000 btu heat converted to propane (natural gas is unavailable) I live in the Middle TN area. I see that Rheem/Carrier/Trane and some others have units available. I am sure that there are some differences in these not sure other than a SS heat exchanger what would be the most important. I do not see a 90% package unit so far, most of these package units seem to be 80% not sure why that is maybe you guys do? Any information will be greatly appreciated the current unit is working fine but propane costs have risen dramatically in the last year or so and look to be pushing upward again. I think a nice efficient dual fuel unit might make sense for me maybe.

  2. #2
    Join Date
    Oct 2003
    Location
    las vegas
    Posts
    1,505
    have your contractor show you the heil pdx360 or pdx460 heil
    dual fuel gaspack this is what i have on our home
    very good unit when controlled with the iaq stat

  3. #3
    Join Date
    May 2000
    Location
    BENTON, KY 42025
    Posts
    339
    The Heil PDX4 has a lifetime warranty on the Heat exchanger and has a 10 year no hassle warranty, which means, if your heat exchanger or compressor fails in the first 10 years, the home owner get a new unit instead of just changing the part. The PDX3 has a 7 year no hassle warranty.

  4. #4
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,368
    The Rheem RQPW-B would probably be a good option for you. It is 14 SEER and 80% AFUE. It also uses R-410A refrigerant.

    Webpage: http://www.rheemac.com/products/Prod...icModel=RQPW-B

    Brochure: http://216.122.22.11/FetchDocument.a...6-578aa86ef5e2


    I like Trane and York rooftops also, but I don't think York offers dual fuel rooftop units. Trane's XL14c is a dual fuel rooftop unit with a good warranty and is 14 SEER and I think 80% AFUE (not sure on the AFUE): http://trane.com/Residential/Product...PDF_XL14c.aspx

  5. #5
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,142
    Tsubaki

    I don't care for package units and must assume that you are limited in this area.

    However with your reasonable electric rates, I think propane is a poor choice for backup if you are interested in operating savings.

    Run the numbers in the attached fuel comparison calculator. I suspect backup electric strip heat is cheaper than propane backup especially considering you will only have 80% efficiency on the propane.

    Definitely get a unit with var speed blower and the highest HSPF rating you can find. And insist upon a load calculation. Also ask what the BTUs produced by your system both cooling and heating on the HP side.

    IMO


    www.warmair.com/html/fuel_cost_comparisons.htm

  6. #6
    Join Date
    Jan 2007
    Location
    TN
    Posts
    49
    Yes Tiger I am limited by practicality and economics to a package unit and gas heat aux heat due to electrical supply and ductwork problems. It would be a major deal breaker to set up a split system and furnish power for electric aux coils plus I already have the propane tanks and lines in place. A dual fuel system looks to be the most economical install and from what I can see they are not much more expensive than a gas pack. I am curious as to why they do not manufacture a higher AFUE gas package unit for outdoor use, can someone explain please? I assume that the condensate freezing on a condesning unit might be part of the problem maybe? Also my local contractors are numb skulls when it comes to newer technology, its like pulling hens teeth to get any meaningful information. If I do my own research I will come out much better to let them know what to install for me LOL. They mean well, its just standard mode of operation in residential I guess. One guy told me yesterday that he had never installed a fully modulating economizer on a Rheem unit and that it was unavaliable, well shoot the rheemote site clearly shows the option LOL. I have not done a lot of studying yet but is there a duel fuel unit that utilizes gas auxilary heat similar to a standard electric backup coil heatpump where the gas can kick in on say low heat with the heat pump still running?? Then you would seem to have the most economical system. Maybe I misread the Heil and Rheem info do they in fact operate in that manner??

  7. #7
    Join Date
    Nov 2002
    Posts
    230
    None work with both gas and heat pump operating at the same time. On package units the heat pump coils are before the gas heat exchanger. The hot air off the heat pump will make safety switches trip on the gas furnace side. It's an either or thing.

  8. #8
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,142
    Tsubaki

    I would only go for propane if this was my only choice to keep myself and fam from freezing. Weigh the operating costs of propane vs updating your electrical service so that you could install a high eff heat pump package unit. With your area/climate and electric utility costs, this is a better choice than having dual fuel propane backup.

    IMO


    www.warmair.com/html/fuel_cost_comparisons.htm

  9. #9
    Join Date
    Oct 2003
    Location
    las vegas
    Posts
    1,505
    if the existing unit is a 5 ton icp gas pak & the
    electrical is ok why would the elec. upgrade be necessary
    i removed a pgad 60 & installed the pdx3 with no upgrades
    & before that had a pgf60 on same elec.& in march will
    be installing a pdx4 unless icp comes out with a pdx5
    do not plan on upgrading any of the elec.

  10. #10
    Join Date
    Jan 2007
    Location
    TN
    Posts
    49
    Guys I really appreciate the input it is very helpful I tryed out the fuel cost comparison calculator and it actually looks like backup electric coils and propane gas heat are not that much different, using the provided calculator, the heat pump numbers however are VERY attractive using the TVA electric rates.
    Marvin I only have #6 feed wire and a 50 amp disconnect for the existing unit I am not sure that it would carry the extra load of the heat pump running plus a minimum of 15kw auxiliary coils? I would think that a electrical upgrade will run up a big bill since my main is full and I will probably have to set a subpanel plus pull new wires a LONG way along with new disconnects etc etc.. Since the cost of electric coils versus propane gas seem to be reasonably close it would probably take a bunch of years to recover the cost of running the electrical feed with the the savings of propane gas versus electric coils (I am thinking over 20 years) especially since in a typical middle TN weather year there will not be that much annual run time for the backup heat. Kinda hard to guesstimate that though. Another big factor is the feel of that superheated (exaggeration but it does feel good) air when the gas heat is on, that will be sorely missed with the heat pump plus no way I am tossing my gas logs so I will still have the Propane tank in the back yard. The Rheem and Heil Dual fuel units look pretty good but I would still like to have a higher AFUE and I would also like to have a unit sophisticated enough to run the gas as auxiliary heat while the heat pump is running (cake and eat it too?). Maybe that is asking to much of the HVAC design engineers? I will keep searching, if anyone can help please post your comments thanks

  11. #11
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,142
    Tsubaki

    What is your electric rate? per KWH

    What is your propane cost? per gallon

  12. #12
    Join Date
    Nov 2002
    Posts
    230
    Basically there are two versions of gas heat. An 80% furnace and a 90+ furnace. The reason there is not a 85% furnace is the flue gasses start condensing at that range and the heat exchangers have to be able to resist the corrosion associated with the condensed flue gasses. If the heat exchanger is built to withstand the corrosion they might as well be 90+ for the construction would be the same. There is no package unit that I know of that has a 90+ heat exchanger and I would assume it has to do with the condensed flue gasses freezing up and ruining the heat exchanger because package unit are exposed to extreme outdoor conditions. If your looking for somthing signifiacntly higher than 80% AFUE it will be a long and fruitless search.
    Also as I previously posted, Dual Fuel units are designed to shift to gas heat completely at a given outdoor temperature for the reasons I previously posted. Good luck again.

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