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  1. #1

    Replacing new hybrid

    I live in the Pacific Northwest and have a 5 year-old hybrid, propane heating system that heats water to 165 deg and runs through a coil in an air handling unit to provide forced air heating. There are two air handlers (2 ton and 3 ton) with 3 zones on each one for a two story, 4300 sq ft. house with 10 ft and 9 ft ceilings. The heat / water source is a 100 gallon tank (A.B. White) that is heated with 199,000 BTU's. The system also provides domestic hot water by dumping cold water in the line to bring the temp down to an acceptable 120 deg. The problem is my monthly propane bills are typically around $1,000 per month in the winter and $800 to $900 in the summer to heat the water. (I set the tank temp down to 120 in the summer.)

    My wife and I will retire within four years and, although we are not happy to replace relatively new HVAC equipment, we don't want to pay this exorbitant monthly cost to heat our house and water on a fixed income. We intend to replace the system before winter sets in. Average winter temps here are in the 40's with occasional dips into the low 30's and high 20's. Summer temps are typically in the 80's and 90's with occasional spikes to 100 & 104 degrees. I have 2 ton and 3 ton A/C units for summer cooling that struggle in the higher temps.

    I received bids from three HVAC contractors to replace the system with 2 heat pumps and an alternative heat source as a backup. Two contractors (reps for Trane and Coleman) bid to install propane forced air units as the backup source. The third contractor (a Carrier rep) recommends a heat strip to replace the water coils in the existing air handlers. What are the pros and cons of each heat source system?

    I also intend to replace the hot water tank with 2 tankless units -- Rinnai 94LSI or Navien 240A. The Navien stats are the most impressive but the company web site represents the parent company as a 33 year-old boiler maker in Seoul, South Korea that has been licensed in the US since 2003 trying to establish a market share here. It does not have a track record in the US to determine if there are service issues to compare with Rinnai. My e-mail to Navien/US asking about service issues has gone unanswered. Does anyone have experience with the Navien product?

    Thank you for all information you may provide.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,750
    Whats your electric rate.
    And what is your current LP cost per gallon.(If you rent the tank, include the rent in LP cost)

    Basically, you have a commercial water heater, that you are using as a boiler.
    And those water heaters are not very efficient. They have a lot of stand by loss. As you found out.
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  3. #3
    Join Date
    Jan 2002
    Location
    Ft.Worth,Tx
    Posts
    4,584
    I would go with heat pumps with back-up propane heat, Rinnai would be a good choice for you domestic water needs but,I would not recommend it for heat.


    Carrier would also be my first choice in equipment , as long as it is installed properly.If you choose Trane it is also a good brand , but make sure it's installed properly.

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    "Everyday above ground, is a good day".
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  4. #4
    Thank you "aircooled53" and "beenthere" for your responses.

    The cost for LP is $2.75 per gallon and electric is 10 cents/KWH. I have other appliances (cooktop, BBQ, and fireplace log lighter) that require propane so I will not be getting rid of the tanks and will continue to lease them. (There are two 125 gal tanks because of code restrictions for their location.)

    The Carrier contractor provided an annual Operating Cost Estimate sheet that compares a propane FAU with other Carrier electric units. His estimate is based on gas at $3.08/gal. with 64,672 BTUh for heating costs and 41,588 BTUh cooling capacity. Adjusting for the lower LP cost, the estimated annual operating cost differential with the electric option for an Infinity 16 is almost $4,000 less per year than an LP unit. The installation cost of the electric system is also several thousand dollars less than propane.

    The decision of which system to purchase seems to be a no-brainer but when the information seems to be this good/significant I become suspicious and look for the "yes, but" clause -- like listening for what a politician or used car salesman is not saying. This is why ask for your comments about the pros and cons of each system.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,750
    At your current electric and LP rate. Electric strip heat is cheaper then LP.

    So a HP with electric aux will cost less then using LP as the aux.

    As for the water heater.An electric water heater would cost les to use also.
    Unless you go with a tankless as aircooled suggested.
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  6. #6
    Thanks for the info. Your comments lower my anxiety level and support the decision I have been leaning toward.

  7. #7
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    YES,but..

    You should have the duct system checked,any Variable speed motor,like Infinity will use more watts if the duct are too restrictive.Plus there can be other isuues,water leaks,fan failure,etc..

    The should test the static and compare the the fan chart for the current air handlers ,to be sure duct remediation is not needed.

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