Pilot-only operation of a water heater???

Discussion in 'Water Heater Forum, Tanks' started by Montalvo, Sep 2, 2010.

  1. Montalvo

    Montalvo New Member

    Messages:
    77
    Location:
    California
    While my wife was away on a trip, I turned the water heater setting to "Pilot" to save gas, since I was the only one in the house, the summers have been hot and I enjoy cool showers. Much to my surprise, the water was PLENTY hot...from just the pilot! Granted, it wouldn't likely support filling a soaker tub but it was more than enough for a ten minute shower (five minutes is our norm). Now...here's my question:

    Can I operate the water heater indefinitely, or perhaps at least during the warm winter months, using only the pilot?

    Here's some additional background. Except when we have guests, this 75 gallon water heater is used ONLY for hot water in the master bath and warm water in the laundry room, where clothes are washed in a front-loader (i.e., low water usage). Another water heater serves the rest of the house. It was sized so large to accommodate a large soaker tub which my wife uses very infrequently and only during the winter. The water heater has a timer circulation pump to eliminate hot water delays and is stored in an unheated room that stays quite warm in the summer.

    Additionally, will leaving the water heater setting on pilot shorten the water heater's lifespan? And will the savings in natural gas be sufficient to even justify this practice?

    Not sure if this practice will "save the planet" but perhaps it'll save me a few bucks! Thanks for any insights you can offer.

    Bob
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Normally, you can use up to about 75% or a little more of its capacity before you notice it cooling off. So, you were using only about 25 gallons in a shower for 10-minutes unless you have multiple heads. Not sure how many BTU's the pilot produces. My guess is it's not that many, so I'm somewhat surprised it heats things up much...maintain, I could understand with the lower losses on the newer tanks (better insulation), maybe it could heat things up, but it would be slowly.

    WHen I lived in Kuwait, the storage tank on the roof got hot enough so we used the cold for hot. If where the tank is regularly gets hot during the summer, the incoming water would at least reach ambient there, and might go up a little. How hot is it in the area where the heater is located?
  3. jimbo

    jimbo Plumber

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    There is one problem. Keeping a water heater at less than 125º is potentially dangerous....allows legionaires to grow. I don't know really how widespread the problem is...but there are some areas we hear that the code requires water heater to be at minimum 140, with tempering valve.

    [video=youtube;9E-u5YNi8B4]http://www.youtube.com/watch?v=9E-u5YNi8B4[/video]
    Last edited by a moderator: Jan 28, 2011
  4. Montalvo

    Montalvo New Member

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    77
    Location:
    California
    Thanks for the feedback...

    Jim, the water heater is in a south-facing equipment room that is vented and the door is frequently open. In Sacramento, that makes for a warm room all summer! But I realized that since I usually shower in the evening, the water temperature might well be much lower in the morning, since we often have 40 degree swings between high and low temperatures. Sure enough, the temp this morning was only 95 degrees, while it was over 110 last night.

    And Jimbo, you raise a good point about the Legionnaire's risk. These temperatures are just perfect for growing Legionnaire's and my retired wife and I are at higher risk due to our age. In addition, from what I read, it's spread by water mist...like what you get in SHOWERS!

    Oh well, I guess I'm not gonna be able to save the planet after all. Sorry folks...

    Bob
  5. Dana

    Dana In the trades

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    In Sacramento you can "save the planet" by putting in a relatively cheap "no-pumps required" low-maintenance in-line batch solar heater like Harparis Sun Cache:

    http://www.harpiris.com/

    In CA there are probably pretty good subsidies for stuff like this. They're much cheaper to buy & simpler to install/maintain than active solar hot water, and in your case, would deliver at least 3/4 of the benefit of a bigger-deal system: For an evening-showerer like you the incoming water to the tank from the batch heater would be hotter than 125F most of the year. And since that design has an internal heat exchanger rather than storing the heat in potable water, even when it's at tepid temps the potable water in the thing is fully purged on every significant draw, not stagnating.

    The other thing you can do (on a much smaller budget) is to insulate all of the near-tank plumbing (including the cold water feed and temperature & pressure outflow stuff) as well as any accessible hot water distribution plumbing with 3/4" walled closed cell stuff (2x as thick as what's generally available in box-stores.) If your plumbing supply sources don't carry it, you can buy it online. R4+ is what you're looking for. In a study of CA homes done by PG & E a handful of years ago the average amount of source-heat abandoned in distribution plumbing was something like 17%, and insulating cuts that in half. A good chunk of the standby losses of tanks like yours is the near-tank plumbing, also fixiable with a bit of pipe insulation. This is very cost effective (pays for the material in less than two years) and will save high-single-digit to low double-digit percentages of hot water heating fuel in most CA houses.

    With a batch heater and insulated plumbing you'll likely cut your water heating fuel use by more than half.

    For a mid-cost project (and still not cheap), putting a drainwater heat exchanger downstream of the main shower will cut energy used in showers by about half (but won't do squat on the tub-fill end.) They're a bit hard to find in the US, but the distributor for one vendor is EFI (in Westboro, MA), and it's easy to open a commercial account with them to get the wholesale price on even onesie-twosie purchases. Bigger (both diameter and length) is always better, from See: http://www.efi.org/wholesale/pdfs/power_pipe.pdf For performance info comparing model-to-model, see: http://oee.nrcan.gc.ca/residential/personal/retrofit-homes/drain.cfm?attr=4 In a "typical" house hold water use pattern where most bathing is showers, this would be good for a ~20-25% reduction in hot water fuel use.

    But that's all a lot more trouble & expense than just putting the water heater in pilot mode, eh? :)
  6. Montalvo

    Montalvo New Member

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    77
    Location:
    California
    Solar's not an economic solution yet.

    Thanks for the comprehensive ideas on saving the planet, Dana. But I was a finance major in college and have a much more negative take on the economics of solar systems than those who promote/sell them. Vendors like Harpiris and greenies invariably base their cost-savings potential for solar on something called "payback", i.e., how many years it will take for the system's savings to repay the cost of purchase/installation. But while such a calculation is simple and generates sales, it's simply wrong; it denies the "time value of money". When you take out a thirty year loan on your house, you're actually repaying maybe three times the amount of the loan...because you're making payments over time and being charged interest, which represents risk and the time value of money. Instead, prospective solar buyers should utilize either a calculation called "net present value" or discount the cost-savings by the owner's cost of capital. For me, that's 5% and it would take 17 years to recoup my investment, AFTER incentives, using my utility's marginal rate for natural gas. That's almost certainly beyond the useful life of the unit.

    While solar has become the darling of the save-the-planet crowd, the economics for individuals, even with government (AKA taxpayer-paid) and utility company (AKA consumer-paid) incentives, just don't pencil out for the vast majority of consumers when the calculations are done correctly. Besides, China's currently building more than one coal-fired power plant EACH WEEK. I'm guessing it'd take one of these units on every house in America to offset just three months worth of new Chinese power plants!

    However, I will double-check the pipe insulation that you suggested. While even that may be difficult to justify economically beyond what's already in place, the expense is minimal.

    Bob
    Last edited: Sep 4, 2010
  7. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    THANK YOU! You are absolutely correct in your calculation and also your assessment that most solar installations are not economically viable in the short term. On the other hand some people (bliss ninnies or people with more money than sense?) don't care about the economics of a project as long as it makes them feel good.

    I have a really dark corner in my kitchen and have sometimes wondered about having a solotube skylight installed. When I run the numbers, and I mean a very simple cost of installation vs. cost of electricity for the existing lights it would take a minimum of TEN YEARS before seeing ANY economic return. I've also been toying with the idea of a small photovoltaic system to power my Internet connection (FiOS) and a few LED night lights. This one is far worse than the skylight. I may go ahead with the PV experiment but I know it will be for the fun of the project and not in any way an economy move.

    And don't even get me started on the replacement windows fad. That one is probably the BIGGEST non-economic return craze to ever hit the homeowner.
  8. Dana

    Dana In the trades

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    While I share your distain for the misplaced popularity of solar for the most part, with cheap plastic batch heaters they usually CAN be NPV+ in reasonable time frames as a DIY project. "Reasonable time frame" is clearly not a 3 year to NPV+ deal in any installation, whether heating hot water with cheap natural gas or even 20 cents/kwh electricity, but it usually makes it on total lifecycle costs (unlike many copper flat panel or evacuated tube systems.) You must have RIDICULOUSLY cheap natural gas to come up with 17 years to NPV+ on a DIY Harparis installaion with 5% money- I'd be curious to see the assumed numbers for HW use, solar fraction, fuel cost, & fuel price inflation you used to come up with a 17 year number. (Which probably IS within the typial lifecyle of a batch heater, in any case, mere 10 year warranty period notwithstanding.)

    Drainwater heat recovery is a similarly a long term investment, but easier to make the number work when it's 5 people taking showers/day vs. 2. But it can work fairly easily with 7.5cent electricity a 5% discount rate and a presumtion of 4% energy cost inflation. See: http://www.renewability.com/uploads/documents/en/analysis_dwhr_minnesota.pdf Whether it works for you depends on what you think natural gas is going to do over the next decade or two, and the volume of shower water is going down the drain daily, and the average incoming water temp (which is clearly warmer in Sacamento than Duluth).

    Whether either batch solar or drainwater heat recovery is the best investment in efficiency for any indivitual home depends a lot on the particulars, but in most cases I'd hazard that it is not. Drainwater heat recovery is WAY ahead of stuff like replacement windows though. Active solar thermal tends to be in the same class as window replacement- dismally NPV- on lifecycle cost when viewed solely from an energy cost POV. (But from a creature comfort POV windows can sometimes be "worth it" though.) For most houses the money is far better spent on air-sealing to reduce the infiltraion rates, & spot insulating to fix gaps & thermal bridges.

    Even when not cost effective on fuel use, drainwater heat recovery pays back in a single day if it avoids having to hear from an irate spouse from a cold shower, eh? (Have you priced divorce lately? ;-) ) With Sacramento CA incoming water temps a standard 40 gallon gas fired HW heater becomes an "endless shower" situtation when coupled with drainwater heat recovery- it'll never run out of HW at standard single-shower flow rates. It gives you the means to waste as much hot water as you like in the shower, but with the water heating at only half-price. For a showering application it's much higher efficiency at much lower capital & maintenance costs than any tankless on-demand HW heater. (Even in cold-water Canuckistan it more than doubles the showering time before it falls below a comfortable shower temp.)

    Pipe insulation is usually short years to NPV+, even with cheap natural gas, even if it's hard to measure on the billing statements. Going higher than R4 only works if your fuel prices are 2-3x the national average, which can still be the case in places with high-priced propane, or heating water at very low efficiency with embedded coils in hydronic heating boilers. I see very few installations where even near-tank plumbing was already insulated as part of the installation, but I don't live in CA (and I'm not in the biz, so I'm not seeing 100 HW tank installations per year). In fact the only ones I've seen have been DIY. I'd be curious to know how "...what's already in place" at the heaters in your house!?! (Is it required under CA Title 24 regs or something?)

    I'm not quite seeing how Chinese power plants factor into your financial analysis, but I'm educable- try me! :)

    I only rose to your "save the planet" bait with what might actually make sense in ANY time frame, should you choose to pursue it (even at a cash loss, if spending it that way it made you feel better.) If you dig up some of my posts on the solar & geothermal forum on this site you'll read what I truly think about the cost-effectiveness & efficacy of most solar thermal installations. (I'm definitely not a fan.)

    Furd: Electronically ballasted T5 or T8 fluorescents with occupancy sensor switches will provide more light and save far more grid-power than any LED or PV solution. (Which would probably be a better investment for most homes than solar hot-water.) Small scale PV is only cost effective in comparison to ridiculously overprices daylighting fixtures & such.
  9. Montalvo

    Montalvo New Member

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    77
    Location:
    California
    Solar still doesn't add up...

    Actually, Dana, I used the Harpiris' website's numbers (http://www.harpiris.com/multiunitandcommercial/economics.html) but when I re-ran the calculations just now, the number of years to achieve positive NPV comes up as 20 years, not 17. That's based on $1470 cost (double the post-incentive $735 cost/bedroom for a two-bedroom installation), $119/year cost savings/year (double the 48 therms saved/bedroom at my marginal cost of NG of only $1.28) and a 5%/year discount rate.

    Now in my situation, a positive NPV would actually take much longer. As I mentioned, this water heater serves only the MBR, laundry room and one guest room. With lower-than-average hot water consumption, I would save even fewer therms than Harpiris suggests, extending the period to achieve a positive NPV even farther. And I'd have an eye-sore on my roof...or a badge of honor if I was trying to trumpet my sacrifice in battling global warming!

    BTW, my comment about China's power plants is based on the arguments against US compliance with the Kyoto Agreements, a treaty that would significantly (and painfully) curtail US GHG but, because it's not signed by China and India, would do very little to reduce the growth in worldwide anthropomorphic CO2. In other words, spending ANYTHING on the reduction of GHG absent a commitment from the biggest users with the fastest growth rates is not going to have a significant impact in the judgment of most scientists.
    Last edited: Sep 6, 2010
  10. Dana

    Dana In the trades

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    Fair enough- most of your costs are standby in a low use situation, and breaking- even with even the cheapest of solar would be tough. (Most solar thermal installations are just that- roof ornament/banners for a point of view, IMHO.) The installed-cost estimates on the Harparis site are probably close to 2x what a DIY installation would be, and your PM showing habits will likely give you a higher solar-fraction than their boilerplate estimate, but it's still a losing proposition @ $1.28 NG assuming zero/low fuel price inflation, and lower than average HW use.

    Holding it to a standard of cost-effectiveness relative to avoided fuel costs isn't necessarily the correct metric for a "save the planet" goal. The more relevant question would be whether it was the best deal in terms of $/ton of CO2 avoided. But here again solar domestic hot water usually fails- there are usually much better places to spend the money in a typical home.

    Spending what's clearly cost-effective in fuel-cost terms on GHG reduction is OF COURSE worth it, independent of what happens in Asia (and generally isn't done.) Most homeowners won't touch anything that isn't clearly NPV+ in under 3 years, even though they'd still reap a financial benefit of longer term energy investments. Energy costs are not typically a primary cost for most businesses or families, and just doesn't get the attention. As fossil-fuel prices rise with Asian development, the break even point on efficiency investments become ever shorter. Oil is cheap right now (due to the worldwide recession), but it probably won't be 10 years from now. NG in the US market may stay cheap for awhile though, due to vast previously untapped shale-gas reserves just now coming on line when there's already something of glut of coal-seam gas. But if/when carbon gets taxed a lot of that gas will get vacuumed up by electric utilites. (Some of that is already happening, since the marginal cost per kwh delivered burning NG in a state of the art 50%+ combined-cycle plant is so much lower than the typical 30% thermal efficiency coal plant, along with the anticipation of future carbon taxation.) The next decade will be an "interesting" ride in energy markets, to be sure, and it would be tough to project zero-inflation over that period on any fuel, including NG.
  11. Montalvo

    Montalvo New Member

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    77
    Location:
    California
    All good points, Dana.

    The biggest question mark is what the future will bring on supply/demand relationships for energy and taxation. I remember hearing a virtually unanimous chorus of doomsayers during the energy crisis of the late 70's proclaiming that the price of oil could ONLY go up, since the world's supply was finite and demand was skyrocketing. Despite that, 30 years later, the inflation-adjusted price of oil is LOWER than it was then. As my econ professor used to point out, you begin to realize the capacity of the marketplace to increase supply when you discover that the number of Rembrandt paintings in museums around the world is substantially higher than the number of paintings that the artist actually painted in his lifetime!

    On another subject, Consumer Reports magazine's latest issue has an interesting article on high-efficiency water heaters and suggests that hybrid heaters are a good solution. At eight years old, my existing heater probably has no more than two more years of life. Based on how I described my low usage, would replacing it with a hybrid be worth considering when the time comes?

    Thanks again for your insights.

    Bob
  12. Dana

    Dana In the trades

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    In 1980 the US essentially WAS the oil market, consuming some ridiculous fraction of the world output, and US energy policy essentially drove the world price. That will not be the case in 2020. With the deregulation of oil prices and the unprecedented & massive shift toward higher-fuel economy cars in the US in the early 80s the prices crashed and stayed low until the fleet of econo-boxes got replaced by SUVs & pickups. The US consumer was the tail wagging the oil dog. In 2000 the US was still consuming about 25% of world production, China & India combined were consuming barely 10%. But by 2020 we'll be less than 20% of the total oil market, and the emerging Asian tigers will be matching or exceeding our consumption- US energy policy will still have an effect on world oil pricing, but not nearly as much as it did in 1980. (Past performance is not a guarantee of future returns.)

    While clever methods have been developed to squeeze the last bits out of aging oil fields, exentending their useful life (and expanding the known reserves), the days of just poking a hole in the ground and pumping are long gone. Maybe we should start burning Rembrandts instead... :) (The deep water stuff has yet to be exploited but it's not cheap to develop.) Experts will differ on "by how much", but nobody I know of in the industry is expecting oil production to keep pace with increased world demand (predominantly from increases in Asian consumption) at even $150/bbl of a coupla summers ago, let alone at a sufficient pace to keep it trading in the $70-80/bbl range. Even if the US & Europe embark on a massive electrification of the transport sector it can probably only change the slope, not the average direction of the oil price curve over the next decade. Inflation-adjusted oil prices have never fallen back to 1970 levels- being at-parity or slighly lower than 1980 is nothing to crow about. The near doubling of oil-price between 1979 & 1981 was about OPEC price-fixing. The price spike of 2008 was driven by anxiety about pumping capacity vs. world consumption rate. World consumption rate has (temporarily) fallen, storage tanks everywere are near capacity, keeping a lid on prices. But the pumping capacity hasn't changed appreciably, nor will it in the forseeable future. As the world economy picks up, so will world demand- the problem hasn't exactly gone away.

    The warranty on your heater may be up in a coupla years, but if you replace the sacrificial anode and don't have ridiculously hard or acidic water there's plenty of reason to believe it'll last another decade or more.

    Whether a hybrid HW heater makes sense to you depends a lot on what you pay for electricity, gas, and how you heat your home in winter. They all totally suck for recovery time and first-hour gallon ratings (compared to gas fired tanks.) Since they pull the heat from the surrounding room as well as from the compressor's motor, they represent a net heating load during the heating season, but reduce the cooling load slightly during the cooling season (albeit at lower efficiency than your central AC.) Odds of it ever being cheaper to operate than a standard efficiency gas-fired tank are low unless you have very cheap electricity. They have COPs of ~2.0 -2.2-ish, but if you're paying many times the price per source BTU with electricity as you do for gas, it may not exactly be cheaper to run. Standby losses will be lower though. eg: 15 cents/kwh electricity is the same as $4.40/therm natural gas. (29.3kwh ==1 therm). If you can truly get a 2x efficiency out of the hybrid at your low usage (maybe, you can, but it's probably lower) the hybrid would then be like $2.20/therm source fuel, and if a pretty-good gas-fired tank delivers 50% efficiency in your app you'll about break even on operating cost with $1.10/therm gas. If you have 10cent electricity it might be a good deal, if yours (like mine) hits 20 cents during economic good-times, maybe not.

    If you heat your home hydronically (pumped hot water, whether radiant floor, fin-tube baseboard, or radiators) you'll get better average overall efficiency with an "indirect" tank running as a zone off the boiler. With a low-mass boiler the summertime efficiency will be somewhat better than your existing tank (lower standby losses, since there isn't a center-flue convecting heat out of the tank, or a pilot light.) During the heating season it improves the overall AFUE of the system by giving the boiler a higher, more efficient duty-cycle. But if you're heating with heat pumps/force-hot air, steam, etc. fuggedaboudit.

    The CU isn't exactly the best source on this sort of stuff (the hack-job they did on the tankless-on-demands a few years back depended a lot on high-volume use, and exaggerated some of the quirks of tankless units.) The high standby loss of gas-fired tanks makes them far less efficient for low-volume users such as yourself. With low-volume use, atmospheric-drafted tanks with pilot ignition only pull ~ 40-45% efficiency. See:

    http://old.aceee.org/conf/08whforum/presentations/1a_davis.pdf

    Mind you, the test setup is less than ideal- they didn't fix the standby loss of the uninsulated plumbing, but perhaps that was intended to mimic the typical "as installed" situation. You may find the effect of R2 insulation on solar fraction in the system tested here an interesting datapoint (see the discussion on page 3)

    http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1856-10.pdf

    The effect of pipe insulation is significant in any stored-heat situation, but still counts for tankless units.

    If you can tolerate the quirks of tankless on-demands, they'll have the lowest operating cost, but the bigger-deal units cost quite a bit, and still have a not-insubstantial electricity standby cost, but their efficiency doesn't fall straight off a cliff at low volume use the way tank heaters do. The unit I keep recommending for off-gridders is the Bosch 1600H, since it has no standby loss, no standing pilot and decent (but not rebate-worthy) 0.80EF efficiency (below the 0.82EF cutoff for subsidy), doesn't require expensive venting (cheap galvanized B-vent will do), and you don't need to run electrical circuit to run it. It'll come in at half the installed cost of it's microprocessor-controlled cousins, if still 50% more than a 50 gallon tank, but by going from 40-45% to 70% (real-world efficiency) it'll use dramatically less fuel. If you have very hard water you'll need to de-scale the thing on a schedule (probably annually- more often for high volume users.)

    The quirky bits about on-demands in general is that there's a hesitation on ignition, so a slug of cold water gets through between the warm-ish water from the previous draw before the newly heated hot water shows up (the "coldwater sandwich".) Much is made of this, but in relatively warm-water areas (like Sacramento, as opposed to Winnipeg) it's not very jarring. The other issue to watch out for with a unit like the 1600H is that it's lowest-modulated fire isn't super-low, so in summer when the incoming water from the street is warm and the flow out the tap is low the heater itself may have a hard time regulating the temp or even flame-out to keep from overheating (you have to run the flow stronger than you might normally do for hand washing or warm-rinsing.) When used with very short-draw appliances like many new front-loading washers that pull a pint at a time, the ignition delay can even be long enough that very little hot water actually makes it to the appliance, etc. But for things like showers, filling large tubs, you'll never run out (as long as you pay your gas bill.) Many of the more expensive tankless heaters modulate down low enough that some of these issues won't be a big deal, but some might. While the high-fire output of something like the 1600H isn't going to support 2 showers and a clotheswashing draw simultaneously, it'll be plenty for your application, at least until you install a 4-sidespray 12gpm shower (at which point the raw BTU-boost of drainwater heat recovery becomes more important than NPV.)

    If you replace it with another gas-fired tank, going with a forced-draft & electronic ignition unit that scores over 0.65 on an EF test is still worth it. The convection losses at the flue are lower, and you don't have a pilot burning 24/365, and you may go from 40-45% as-used efficiency to ~50%. Still low efficiency, but a 15-25% fuel savings.
  13. Montalvo

    Montalvo New Member

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    77
    Location:
    California
    Thanks for some very complete information, Dana. Whoa, you clearly know a heckuva lot about this stuff! Of the things you covered, perhaps the most important part was that my existing WH could last another decade or more. You see, I have a 7,200 square foot house and that WH serves just the MBR, laundry room and a guest bedroom. The rest of the house AND the house's hydronic heating system is served by a Phoenix water heater boiler, which I installed with advice from this site three years ago, replacing a commercial WH that failed just after its five year warranty expired.

    And as for the hybrid WH, with a marginal cost of electricity of 49 cents/kwh, it's clear from your kwh-to-therm cost example that that's out of the question even if I did need to replace my WH. As for the quality of my water, I'm in the Sierra Nevada foothills and our water comes straight off the mountains, with very low mineral content so it appears that my WH has gotta good deal more life in it. And by the time it does crap out, the various options for replacement and the energy cost profile will likely be vastly different from today.

    In summary, I guess I should stop whining about saving a few bucks on energy when I've gone and built a 7,200 square foot house for two people!

    Bob
  14. Dana

    Dana In the trades

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    :) :) :) :) :)

    Methinks yer onto something there!

    Drain the sludge off the bottom every year or two, replace the sacrificial anode every 5-6years (whether it needs it or not) and simple-minded beasts like tank HW heaters can go a very long time. Most of them die from neglect- rusting out due to a depleted anode. (Maintenance? What maintenance?) As a DIY you're looking at ~$30 (give or take $10) for the anode. Just be sure to put a date tag on it to remember when it was last replaced or a "replace by..." note or something to keep track.

    If it croaks before the Phoenix does, (or if NG prices soar) it'd not rocket science to set up an indirect tank as a zone running of the Phoenix (through a heat exchanger) which would probably close to double your HW heating efficiency compared to the standalone tank(s), provided you're running the Phoenix at anything near domestic-hot-water temps. (If you're running it at 100F or lower it may not very good tradeoff between space heating efficiency & HW heating efficiency to raise the temp a few 10s of degrees though.) There are many combi-systems built around condensing (and other) tank HW heaters. The Phoenix has a burner big enough to handle endless showers & filling big tubs as well.
  15. Montalvo

    Montalvo New Member

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    77
    Location:
    California
    Thanks for the advice, Dana. But the prospects of utilizing the Phoenix to serve the needs of both water heaters would be more costly than it's worth. My house is U-shaped, about 300' from one end to the other, and the water heaters are widely separated specifically to deal with the distance challenges of supplying hot water.

    But I'm happy to know that, with the right maintenance, I can squeeze an extra decade out of my WH. Many thanks!
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