Seeking hot water replacement advice

Discussion in 'Water Heater Forum, Tanks' started by scooterman1, Nov 17, 2012.

  1. scooterman1

    scooterman1 New Member

    Messages:
    5
    Location:
    NYC suburb
    Need to replace a gas hot water heater with direct venting. Currently have a 15 year old 75 gallon unit. 4 in family (three baths). Never take more than 2 showers at a time or within an hour (unless we have guests). But have growing kids. My plumber uses AO Smith and thus I've been doing my research on their different options. He suggested a 75 gallon replacement. I started to look into more efficient units and identified two: XGV-50 and the vertex (highly efficient) models.

    The XGV-50 has 88 gallon first hour delivery but recovery of only 41 gallons. It has 40,000BTU input/hour and Energy factor of .62.

    The Vertex model (GPHE-50) has 127 gallon first hour delivery, 92 gallon recovery but uses 76,000BTU input. 90% thermal efficiency.

    The 75 gallon unit doesn't have a first hour delivery rating, recovers 81 gallons and uses 75,100BTU (model PCG75 or FCG75). No energy factor rating.


    I have no idea how best to make a decision. I want to be conscientious about energy usage but dont want to be in a situation where I'll regret having to take cold showers. Any thoughts on how to decide size/energy effeciency or experience with these (or brands) models?

    Thanks,

    Scott
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    Recovery, and thus first hour rating, is a function of btu input. The 75 gallon unit has a recovery of 81 gallons, which added to the 75 gallon storage gives a first hour rating of 156 gallons, but that is theroetical. Actual delivery would be less than that, because thermal cool down caused by the incoming cold water, and your usage would not be linear for 60 minutes, but if it were, that capacity would give you about 2.5 gallons per minute.
  3. scooterman1

    scooterman1 New Member

    Messages:
    5
    Location:
    NYC suburb
    HJ,

    I completely understand. My question is: will the two smaller WHs be sufficient or will I regret not getting a larger, but less efficient model?

    I worry that the vertex, while smaller, is overkill since I wont be using it for radiant heat. And the other 50 gallon unit, I fear will be too small.

    Thanks,

    scott
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,139
    Location:
    New England
    With children, at least early in life, you will often be taking baths. Running full tilt to fill a tub, you can get somewhere between 75-80% of the full capacity because the burner has little time to heat the incoming cold. The figures they show would be for something like say a shower where your gpm is lower and the burner running at full tilt will be able to warm that water more since you're draining it slower.

    AO Smith is not my first choice in WH.
  5. scooterman1

    scooterman1 New Member

    Messages:
    5
    Location:
    NYC suburb
    what would you recommend?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,139
    Location:
    New England
    Bradford White or Rheem (Rheem also makes the GE one sold at HD). Bradford White is not generally sold to consumers, only to professinals.
  7. scooterman1

    scooterman1 New Member

    Messages:
    5
    Location:
    NYC suburb
    Thanks for the advice. I'm inclined to go with BW as they have more options between 50 - 75 gallons. I think a conveniential 75 gallon tank is too much and not efficient but I worry that a highly effcienent 50 gallon unit won't produce enough hot water at peak times. I was intrigued with two models: M-4-60T6FBN and M-2-XR65T6FBN. The first is highly efficient and uses 40000 btu inputs but has lower first hour delivery of 96 gallons (and only recovery of 43 gallons first hour) vs. the second one that has 126 gallons first hour but uses 65000 btus and much higher first hour recovery.

    Any advice on how to think about the trade off of these two units?

    Thx
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    For a shower, you just have to be concerned with the heater' storage capacity. You will not be using the water long enough for the recovery to be a factor, other than how soon the heater refills for the next shower, if you drain it with the first one. Since you only heat the water you use, the vertex will operate for a shorter time period than the lower btu heater, but in the long run you will pay the same, before the efficiency rating is factored in.
  9. scooterman1

    scooterman1 New Member

    Messages:
    5
    Location:
    NYC suburb
    Agreed that storage size is the critical decision point. And therein lies my concern: 50; 60; or 75.

    Thanks for the input.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    My customers usually install a 50 gallon heater when their 75 gallon one fails.
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,139
    Location:
    New England
    Two thoughts...if you take marathon showers, bigger will allow you to do it, BUT, it means that you CAN take a marathon shower.
  12. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    50 gallons for a 3 bath house could be small, depending on usage of DW, WM, bath vs shower, etc. A high efficiency 50 might be good.
    75 gallon tanks will be quite a bit more $$$$.

    For "regular" gravity vented WH , recovery is approx. 1 gph per 1000 BTU. First hour for any unit is estimated at 70% of the gallon capacity. That is because you are mixing fresh cold water into the tank the minute you open a tap.

    Direct vent will limit your selections. AO Smith ( includes Lowes, Whirlpool, American, State, Sears, Reliant, and other brand names) has not had a good reputation for gas heaters in recent years. Majority on this forum favor Bradford White, and Rheem/Ruud. GE @ HD is made by Rheem, and other than a cheaper plastic drain valve should be same as a Rheem Fury.
  13. Dana

    Dana In the trades

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    2,921
    Location:
    01609
    Unless you're filling a large tub you don't need the extra capacity. A condensing hot water heater like the Vertex with 76KBTU/hr of input is delivering 70KBTU/hr to the water, which will run a single 2 gpm low-flow showerhead forever with 50F incoming water. Rather than two tanks, in a showering family you'd be better off with a a drainwater heat exchanger downstream of the shower drains as pre-heat to all cold water to the house, or at least to the tank & the bathrooms. That approach will double the showering capacity the tanke without using any more fuel, yielding an "apparent efficiency" of greater than 100% while in showering mode. (It has zero effect on tub-filling, since it's only recovering heat during simultaneous drain + water flows.)

    It would usually cheaper than installing 2 tanks as well.

    [​IMG]

    A 4" x 48" version or a 3" x 60" version typically returns more than half the heat of the outgoing drainwater to the incoming cold water at 2.5gpm flows according to Natural Resources Canada's third-party test data. It will be slightly less than half at two full shower flows, maybe 40-45% returned at 6gpm, but something like 60% return at 1.5gpm low-flow shower rates.

    I installed a 4x48 PowerPipe in my place 3 years ago to enhance water heating capacity with my kludgy heating system that heats hot water via a 48 gallon buffer-tank w/internal coil. The modulating burner heating the buffer never goes over 70KBTU/hr, even when all heating zones are calling for heat and someone is taking a shower. It makes all the difference in my case- I can keep the max temp on the buffer at ~130F and never run out of heat OR hot water (unless somebody forgets to pay the gas bill. :) )

    You may be able to eventually deplete a 76K Vertex + DWHX with two simultaneous 2.5gpm showers, but it would take the better part of an hour.

    With one shower it would ALWAYS keep up.
  14. wassermeister

    wassermeister New Member

    Messages:
    24
    Location:
    portland, OR
    You should get a gas water heater with minimum 0.67EF (energy factor). This is the requirement for ENERGY STAR. Rheem has a few good models around. The least expensive is an XR90 with first hour rating of 83 gallons. It is only a 29 gallon tank, but with a lot of power. It should cost about $750.

    Anything with 70+ gallons of first hour rating will do unless you are planning to have a hot tub and some other crazy water feature.
  15. Dana

    Dana In the trades

    Messages:
    2,921
    Location:
    01609
    If I misconstrued your initial posts as astroturfing, I apologize. And while it has seemed to me you were both advocating a bit too hard as well as protesting a wee bit too much at the mere suggestion, I've tended to qualify it with a "seems like", eh? I'm amazed it took you so long to actually deny it!

    The labeling issue squabbles and patent infighting are all VERY old news. I've long considered those to be just tiny tempests in a thimble-sized tea pots- mere footnotes in the history of this tiny industry. I'll continue to use NRCan verified efficiency is the gold-standard comparison of how different models perform, but I'm now (as always) far more interested in the price/performance point than the parochial infighting between competitors or their marketing faux pas.

    When ThermoDrain was first hitting the market 4 years ago they didn't have third party verification of performance, and now they do. Their NRCan listed EcoGFX model line was markedly underperforming PowerPipes of comparable size, which wasn't exactly confidence inspiring for the performance prospects of their second generation lineup. But with now verified numbers it's clear that the ThermoDrain line is at least meeting (but not exactly beating) the competition on apples-to-apples performance for heat exchangers of comparable size. So now it has come down to price.

    If EcoInnovation were to beat EFI's price/performance point by $100 I'm sure I'd be able to overcome any dis-taste for their web-forum & blog presence/style of 4 years ago.

    But in fact the price advantage is still $100 in the other direction when buying through EFI- so I'll continue to point that out that source when the subject comes up (just as I pointed it out to you.) As you've noticed, EFI pricing on Renewability's lineup is substantially lower than Home Depot & Sears pricing (or Renewability's buy-direct price) for the very same product. I don't know of any similar discounted or wholesale pricing availability for ThermoDrain, but I'd be curious to know if/when that happens.

    Ontario recently allowed savings from drainwater heat recovery efficiency to be included when demonstrating compliance with updated energy efficiency codes, which should give a boost to the industry a whole. I suspect all vendors have been suffering from low manufacturing volumes, and with higher volumes there will be a bit more wiggle room for competing on price. We'll see.
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