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Replacing electric water heater

After about 30yrs, our 80 gal AO Smith electric has given up the ghost. My wife insists on a direct 80 gal replacement, so I'm thinking of using it as the basis for eventual upgrades. Therefore my current plans call for superinsulating the new tank by setting it on 2 or 3 inches of foamular 250 insulation, then fabricating a heavy jacket around the sides and top using glass fiber and a thin metal or PVC outer sheath. I also want to add thermal traps to the inlet/outlets, 3/4" wall Armaflex on the near piping, and tees above the service valves for add-ons at a later date [see below]. The drain will be replaced by an Apollo ball valve, suitably insulated, as I believe in their reliability and feel that a quick-on, quick-off action does the best job of flushing out the sediment.

ADD-ONS: We have an ancient oil-fired Am. Standard boiler [cobbler's kids going barefoot sort of thing] but feel with the heat-up in an un-air-conditioned house plus the cost of oil, poor condition of its DHW coil, etc. it's not currently an option to hook into it. However, we're keenly interested in putting solar collectors on the roof in the near term, and perhaps replacing the boiler sometime in the near future. Therefore, I would intend the bulk of our hot water to eventually be solar for 3 seasons and oil DHW for deep winter.

Any thoughts/feedback on this?


  • icesailor
    icesailor Member Posts: 7,265
    80 Gallon Electric:

    First of all, your 80 gallon electric water heater is way too big. Thirty  year old 80 Gallon electric has little insulation.

    On 1/1/15, new energy rules go into effect for electrics. If the tank is over 65 gallons, it has to meet higher energy standards. They put a heat pump on it.

    As far as your adding all kinds of additional insulation to slow down stand by losses, water heaters made for the last 10 years have foamed in insulation.

    There are far to many answers to your broad questions.

    IMO, you could replace the 30 YO 80 gallon heater with a 50 gallon modern and heavily insulated tank, with a thermostatic mixer, you would notice an immediate savings.
  • SWEI
    SWEI Member Posts: 7,356
    Fuel options?

    I'm assuming there's no natural gas in the area, but just in case...

    LPG prices vis-a-vis electricity vary widely.  http://www.eia.gov/tools/faqs/heatcalc.xls will help you make a reasonable comparison.

    If you are serious about solar, you should actually be using a tankless on the output of the solar system.  Tankless electric water heaters work fabulously when fed with 80ºF solar water on a winter day.  Not so good with 40ºF groundwater.  I'd push for the solar now rather than trying to graft it onto a tank style heater.  Parasitic losses from a two tank system can add up.
  • hot_rod
    hot_rod Member Posts: 22,257

    how much DHW your family actually uses. Also if you have a dump load like a bathtub, a 40 or 50 electric may not catch up quick enough for your needs.

    If a boiler replacement is in the future and solar, consider a dual coil 120 gallon tank with an upper element for back up. Upper element alone gives you the same as a 60 gallon electric tank. Solar into the bottom coil, and boiler into the upper.

    Now you have the choice of 3 fuel sources.

    Most anywhere in the US a properly sized SDHW will provide 60% of your HW need.

    3 collectors with a 120 gallon tank works well for medium to large residential DHW loads.

    Here is a 3 panel system, 120 tank, electric element back up, in MN.

    Consider the solar now as the tax credits may be gone next year,
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream