Need help choosing a water heater

Discussion in 'Water Heater Forum, Tanks' started by jestyr, Jan 20, 2010.

  1. jestyr

    jestyr New Member

    Messages:
    5
    Location:
    western kentucky
    I am building an addition on to a house and I need to install a new water heater. I know nothing about this stuff and I keep waffling back and forth on if I should go tankless or not...if I should get this water heater or that water heater...etc, etc, etc. So after some looking around on the internet I quickly realized that I am in no way qualified to determine this, and thus I find myself here seeking some help. Here is all the information I have about my installation.

    I need a water heater for a single bathroom that has a LARGE luxury shower. The shower is a multihead set up that "could" push out 8 gallons per minute if I wanted to blast everything. I like my long showers, so I'm looking at the 30 minute mark as a good starting point. It will be well water that has a bit of hardness to it. I haven't had it tested but it isn't horribly hard, but you can tell it. The water heater will be in a closet right next to the bathroom. I live in Western Kentucky and from what I have see for the region our water temp is around 57 degrees (this was from some map that I saw on a tankless water heater web page). Once again I don't know much about this stuff, but also from what I have read 120 degrees is good for a nice HOT shower??? So I'm looking at a 60 - 65 degree temperature rise I guess. The addition will be heated with propane. The guy I have installing my heating and air is putting in a Rheem unit, so if there is a decent Rheem water heater anyone can recommend that would be a plus there.

    So what is my best option? Tank, tankless, big, small, blue, red, round, square...:confused:

    If there is anything I have missed please let me know.
  2. Dana

    Dana In the trades

    Messages:
    2,785
    Location:
    01609
    60F rise at 8gpm is about 240KBTU/hr, well over the output of a "whole house" tankless. With a drainwater heat recovery unit as pre-heat for cold water feed to the heater & shower you could probably get there with a standard tankless, but it'd be a squeaker. (~160K from the tankless, ~60K in pre-heat.) Water hardness will also be a mainenance issue, more so with a tankless than a tank.

    8gpm for 30 minutes will also be tough. With a 100gallon tank you'd still need drainwater heat recovery to get anywhere near 30 minutes of full flow out of it.
  3. Dana

    Dana In the trades

    Messages:
    2,785
    Location:
    01609
    If the main showerhead is 2.5-3gpm, and you're only doing the sideshowers for 1-2 minute blasts at the end of a 30 minute shower a standard gas-fired 100 gallon tank might cut it, and a big-burner 50 gallon powervent like the Vertex™ 100 Power Direct-Vent surely would. It can deliver 164 first-hour gallons at a 80F rise, so figure ~180gallons/hr. At 3gpm you've used half of that in the first30 minutes, so you should have something to spare for the 8gpm gusher at the end. The smaller-burner version of the Vertex might make it too, but it'd be marginal if you went 35-40 minutes at 3gpm unless you had drainwater heat recovery heat exchanger in place (which would give you an extra ~ 30KBTU "burner" when the flow is 2.5-3gpm, which would nearly double it's apparent capacity at the lower flow rate.)

    A tankless is almost sure to come up short of flow in winter with all showerheads flowing. The Vertex 100 won't have that issue. A 100 gallon commercial tank with a 75K burner wouldn't have the flow issue either, but it's first-hour ratings would be even lower than the smallest Vertex due to lower combustion efficiency. Kicking it around in my head a bit it seems the Vertex 100 probably comes close to filling the bill (assuming 3gpm most of the time intersperse with 8gpm for only a few minutes at a time) where most other solutions don't.

    If you live in a large house heated by a large boiler (over 200KBTU/hr), an indirect-fired water heater running off the boiler might work for you too (and for less money than a Vertex.) The key there would be it's first-hour ratings at the boiler's full output, which is a function of the internal heat exchanger and the storage volume. If you want the full 8gpm for 30 minutes with capacity to spare , that's going to take something like a 300BTU/hr boiler or larger.
  4. jestyr

    jestyr New Member

    Messages:
    5
    Location:
    western kentucky
    ok, so this is certainly some info to chew on. i think you are correct about how the shower would likely progress. i doubt there would be a 30 minute shower at the full 8 gallons per minute. the 8 gal a minute would likely be more of a quick invigorating type of shower with the body jets. lets say a longer more relaxing shower will be just the two normal shower heads at 2.5 gallons each.

    so if im reading it right that vertex should be good for nice 30 minute shower @ 5 GPM if that is all i use.
    Last edited: Jan 20, 2010
  5. jestyr

    jestyr New Member

    Messages:
    5
    Location:
    western kentucky
    also looking at other water heaters that are recommended on this board i came across a bradford white (gx1-55) that delivers 200 gallons in the first hour and recovers 82 GPH. so what would the verdict be on a comparison between those two?
  6. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    I would go with an 75 gallon gas Rheem or Bradford White heater...set it on its highest heat setting and that should work for you....
  7. Dana

    Dana In the trades

    Messages:
    2,785
    Location:
    01609
    Maybe- even those with 75K/80% burners are only good for ~130-140 first-hour gallons, and cranking it up to "scald me pronto" might give you as much 160, but might not. At a 5gpm average due to occasional side-spritzing or a mega-flow main shower head you've burned through 150 gallons in the first 30 mintues-it has already run cold. The big-burner Vertex cranked up to a similar "scald me" level will give you ~15-20% more due to its ~95%+ efficiency heat exchanger (with the same 75K input burner rating) . To get more BTUs out takes either more storage, more burner, or higher efficiency. But at the standard setting a Vertex100 might be giving up the ghost at 30 minutes too if it's truly 5gpm.

    A 75 gallon 75K/80% Rheem with drainwater heat exchanger would probably do it though: A 4' long 4" diameter PowerPipe(tm) or similar will deliver slightly better than 50% of the heat back at 2.5 gpm, more than 40% back at 5gpm. 2.5gpm with a 60F rise is ~75KBTU/h, half of that is ~37K. 5gpm @ 60F rise is about 150K, 40% of which is ~60KBTU/hr. The output of a 75KBTU 80% burner is also 60KBTU/hr, so you're effectively doubling the burner size with drainwater heat recovery, which should give you some margin (and you'll use half the fuel doing it.) A Vertex 100's 95%-98% efficiency is only good for ~70KBTU/hr delivered to the water, compared to 120KBTU/hr with a Rheem + PowerPipe @ 5gpm, or ~95KBTU/hr @ 2.5gpm If you're truly using that much hot water, the payback on that will be WAY better than your 401K (especially since it's in after-tax dollars!) As a DIY you can install one for under a grand- but figure ~$1.2-1.5K to have licenced professional do it, depending on the complexity of the install. To get full-performance out of it, the output needs to feed both the cold water to the tank and the cold water to the shower, but if you have to pick one due to plumbing routing constraints feed the tank. That woud be a significant performance hit, from ~50% down to ~40%, but still worth doing at the volume you're guzzling hot water. If you have more headroom and can stuff a 5 or 6 footer in there, the extra cost is well worth the extra performance.

    A Vertex 100 is an expensive piece of hardware ($2K, which roughly 1.5-2x the price of a 75gallon Rheem or similar) and price/performance-wise you may do better with a 75gallon tank with a 75K/80% burner + PowerPipe than a Vertex 100 by itself. Even if it's $500 more in combined price than a Vertex 100 alone, the output capacity will be higher, and the fuel consumption lower. But it takes at least 5' of space on a vertical drain downstream of the shower to install one, and the complexity of getting the potable plumbing to/from the PowerPipe and the heater &/or the shower can be complicated (or impossible), depending on the layout.

    So, got all that? In tabular form the heat delivered ot the water is:

    75K/80% Rheem 75gal: 60kbtu/h

    75k/95% Vertex 100 : 71kbtu/h

    75K80% tank + DWHR: 95-120kbtu/h @ 3-5gpm (more at 8gpm)

    The storage capacity on all of them are the same- the performance differences will be in burner output + heat recovery. The higher the flow, the more heat is recovered in the DWHR scenario- not enough to COVER the difference, but well enough to MAKE a difference. My money sez you get better performance & value with the standard 75gallon tank + drainwater heat recovery, if you can jam it in there. At 3gpm the burner + heat-recovery output is greater than the heat being drawn- you can shower all day long at 3gpm, if you like! At 5gpm the rate of draw is ahead of the burner + DWHR , but by only ~30k, which should give you the performance & margin you seek with 75 gallons of buffer behind it.
  8. jestyr

    jestyr New Member

    Messages:
    5
    Location:
    western kentucky
    ...sigh...

    i dont really need to get into a pissing contest about who is "greener" here. but since my water consumption seems to be a big deal and since you have absolutely no clue about me or the rest of my life here you go.

    -my primary vehicle that i drive to work is a scooter...50+ mpg
    -my addition that i am building is going on my dad's house. instead of building a 1600 sq foot house for me to live in by myself, im putting on 800 sq feet to be less wasteful
    -bamboo and cork flooring throughout
    -cfl lighting
    -top notch energy efficient windows, insulation, etc...

    i'm sure there is more stuff i could come up with if i tried a bit but in all likelihood you think i'm just bs'ing you anyway. so, thanks for stopping by and playing. but really the one luxury item in my entire project here, i think ill keep it.

    --------------------------------------

    now, to the others that have stopped by, that you for the help. it has given me lots of info to mull around. currently i'm looking at that bradford white with the 200 gal first hour delivery. unfortunately i cant run that power pipe solution as my addition is a single story slab construction, but it was a good thought.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,263
    Location:
    Cave Creek, Arizona
    Without going through the tedious process of reading every previous answer, I don't know what "power pipe solution" is, but a 75 gas heater will give you about 1 1/2 to 2 gallons per minute of recovery plus the initial 75 gallons. Therefore in a 30 minute shower you will have access to between 115 and 130 gallons of "pure" hot water. If the heater's temperature setting is higher than the desired temperature so that you have to add cold water to the mix, which is usually the case, it will last even longer. And, these ratings are based on a 90 degree temperature rise, so that size heater should be more than adequate for your purpose. Forget about all the "you are not green enough" rants. They are probably doing their part to contribute to global warming.
  10. Runs with bison

    Runs with bison New Member

    Messages:
    891
    Location:
    Midwest
    It's hard to justify that sort of energy and water waste on a single person. At the stated rate and water temp is about three times what my family of four uses in a year. It's enough energy equivalent to cover 19,000 miles in our primary car...we get about the same mileage as the scooter. It would provide 2/3 of our home heating even though our home is several times larger than the addition mentioned and still could use some tightening as well as HVAC replacement and more insulation in a few spots (waiting for warm weather.)

    And operating the system as outlined will be expensive. For propane it'll likely run about $600-$700/year (add in any storage losses, though they will be very small in comparison). Here the additional water and sewer charges alone would run about $260/year.

    The problem in the U.S. is that we don't price energy or water resources appropriately. Market/price structure drive consumption and if things aren't priced according to their true costs then we get crazy bubbles. Energy is one of these ongoing bubbles, particularly in the U.S. unlike most places in the developed world.

    CFL's are great, pretty easy to justify the economics. Energy efficient windows and insulation are easy to do on new installations...an expensive PITA on existing homes where the builders appear to have had some undiagnosed insulation allergy But doing some things efficiently doesn't negate other extravagant wastes, particularly in the planning stages. Instead it makes them stand out that much more starkly.
  11. Dana

    Dana In the trades

    Messages:
    2,785
    Location:
    01609
    A: you never get 75 gallons of flow out of the storage due to mixing of the incoming water.

    B: He's figuring on an average flow of 5gpm

    C: The first-hour ratings in the manufacturer's spec are less than he's figuring on using in the first HALF-hour

    D: Bumping up the temperature 20-30 degrees doesn't come CLOSE to making up the difference. (Do the math- it has to add up or he'll run cold!)

    ...which tells me 75 gallons with a 75KBTU burner behind it just isn't gonna be enough.

    "powerpipe solution" refers to one manufacturer's line of drainwater heat recovery heat exchangers:




    By pre-heating the cold water feed to both the water heater and the cold feed to the shower with the substantial heat of the 95-105F water going down the drain more than 50% of the heat is recovered at 2.5-3gpm flows with a moderately sized heat exchanger. With a 75K burner in an 80% efficient water heater (which is where most tank heaters live), that's enough of a boost for the flow to run continuously for any period of time you like, much like a tankless. The transfer efficiency drops to ~40% at 8-10gpm, but it's 40% of a much bigger number- with 75 gallons of storage behind it it'll still run a good long while (but not 30minutes + at full flow.)

    Natural Resources Canada has developed a standardized test to be able to compare the performance of various vendors & models of drainwater heat recovery heat exchanger at 2.5gpm flow, available online here. There are other factors to consider too- some models have a single wrap of 1/2" or 3/4" potable plumbing, which can be quite restrictive at the higher flows we're talking. PowerPipe's versions have much less of an issue with this than some of their competitors due to their splitting the flow into 4 separate pipes for the wrap:



    Some of the others still get good flow by splitting it into upper/lower balanced flow sections:

    [​IMG]

    But if ever an application cried out for drainwater heat recovery for both enhanced capacity & efficiency, this one does. Getting the capacity may be the primary motivation in jesyr's case, but it will in fact use dramatically less fuel than a condensing hot water heater, and provide FAR more capacity.
    Last edited by a moderator: Apr 19, 2013
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    In general, this type of thing is good. As to how this compares with some others on the market, I do not know. One other one Dana seems to like divides the water flow into four channels (supply, not drain). This significantly increases the surface area and it is the surface area that determines the ultimate efficiency. I have not compared the stated test results.
  13. Dana

    Dana In the trades

    Messages:
    2,785
    Location:
    01609
    I've been bashed in online forums by the president Ecoinnovation of that company for relying on the NRCan third party tested & listed efficiencies, but his personal style and credibility didn't impress me. He seemed more interested in casting aspersions on the competition than documenting the actual performance of his own goods using impartial third party sources, and seemed to take fairly straightforward questions as insults. For that reason alone I would never buy from them, but clearly YMMV.

    The NRCan did extensive testing & measuring of some of the competitor's models, and in general the split-wrap PowerPipe designs tended to have lower pressure drop than models of similar efficiency. See figure 9, p24 (pdf pagination).

    Based on NRCan test data I ended up going with a 4" x 48" PowerPipe, and it's been delivering the expected peak-output performance that I needed to make my kludged-up heating/hot-water combi system work. The fuel savings were less important to me in the design than being able to run all space heating zones without impacting showering performance without cranking up the firing rate or temperature on the system, and I can guarantee from first-hand experience that the drainwater heat exchanger is doing quite a bit, without actually instrumenting and datalogging the system to verify it's precise efficiency. Without it I'd be taking cold shower in mid-winter mornings without it at the peak firing rates & temperature of the system set as-is, but it's possible to shower 24/7 with all zones calling for heat (and my kid sometimes even tries! :) )

    If you buy though EFI (the US disributor), they're quite competitive. EFI honors the listed wholesale price even on onesie-twosie quantities if you open an account with them, which costs nothing to open, and can be done over the phone with a credit card. EFI never marks up shipping or adds handling charges, they're a decent outfit to deal with. I've bought several things from them over the past half-dozen years, always with prompt & good service.

    With any of these gravity-film heat exchangers it's important to install them as vertically as possible to maximize the surface area used on the drain side. A 10 degree tilt will impact it's performance pretty severely, but a 3 degree tilt won't too much. Within any product line the fatter the pipe and the taller, the more heat exchange surface area is available, and the higher performance you can achieve. At 50%+ it effectively turns a gas-fired hot water heater into an "endless shower" at 1.5-2gpm. (Not so much with 4gpm gushers.) But it also increases the max showering capacity/time of even an electric tank to something like 2x whatever it is without it.

    From a return on investment point of view it's payback or net-present-value is maximized by going with the tallest and fattest that actually fits the available space, which limited me to the 48 inchers, but that proved to be good enough for my design goals, both on paper and in-situ. If you have more headroom, go bigger. (Even though the taller 4 inchers aren't listed on EFIs single-pager, they either have them or can get them, and it'll be cheaper than going direct through the manufacturer, Renewability.)

    But also from a strictly financial point of view, if you're a single-person household heating water with buck a therm natural gas the payback is pretty long. If heating with propane, heating oil, or electricity at 15cents/kwh, in a family of 3-4 the simple payback is typically sub-5 years.

    I'm heating with natural gas, but my goals were more about showering performance on the system than strictly NPV on fuel savings. From a family-harmony point of view never running out of showering water and having to wait for recovery has a real value in my book, but again, YMMV.
  14. Richard Bross

    Richard Bross New Member

    Messages:
    1
    Location:
    Ontario
    Thank you all for the feedback and advice. We just placed an order for the Thermodrain B 42 model. I will post pictures and feedback once we have it installed. Should arrive before Wednesday. Planning on installing it over the weekend. Anyone have any tips before we do our installation?
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    Surface area is the key to heat transfer. Dividing the flow into multiple smaller paths means more surface area, thus higher efficiency. Whether that increase is worth the extra cost of both materials and manufacture depends on your energy costs and expectations. IOW, you get what you pay for.
  16. Dana

    Dana In the trades

    Messages:
    2,785
    Location:
    01609
    Making it as close to vertical as possible is important for getting the rated performance out of it, since once its off-axis there is less total surface area of the water inside the drain in contact with the surface for the heat transfer to take place. A couple of degrees isn't an efficiency tragedy, but 5 degrees of tilt will make a measureable difference.

    Be sure to tee-off the output to feed BOTH the HW heater and the cold side of the shower, or it's a ~20% or greater hit in total peromance.

    Beyond that, installation isn't difficult- it' doen't take a master-plumber to get there.

    In most cases it's not worth bothering to insulate the output of the heat exchanger, since it's really tepid-water, not truly hot, and the losses even to unconditioned space is pretty low. I'd assume that in an Ontario location both the drain and HW heater would be located in a semi-conditioned basement(?).
  17. Dana

    Dana In the trades

    Messages:
    2,785
    Location:
    01609
    Buy from EFI, and you get a much lower price for any of their listed than Sears, Home Depot, or direct from Renewabilty.

    You have the link, their phone number is on it, and yes, the published prices are honored by EFI. The 3x48" is $471.50 + shipping-only, no handling charges and it's NRCan listed efficiency is 47.3%, about the same stated efficiency as the TD348B at about $115 more.

    It's your $115, spend it any way you like, just don't shoot the messenger when I tell you how to keep it in your pocket, eh?
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    FWIW, list prices on most things is not necessarily a good indication of street prices unless it's a monopoly (like say Apple products or Bose - you want to sell one of those, you sell it at the agreed price or you can't get the product!). Another FWIW, my house has LOTS of soldered joints in it...I don't use that as an indication of quality. If it doesn't leak when you first apply the water (and the things we're talking about are testing in the factory after being made), it's not likely to leak afterwards. Copper is a MUCH better conductor of heat, so breaking the water flow into smaller paths that are in more intimate contact with that heat exchanger has the potential to work better. In the smaller passageways, the water is never very far from the copper. In a flowing liquid stream, you don't get much of any convection, so it is conduction and temperature difference that make the thing work.
Similar Threads: Need help
Forum Title Date
Water Heater Forum, Tanks Need some real-time help - need to replace water heater today Mar 22, 2014
Water Heater Forum, Tanks Need help deciding between 3 gas water heater models Aug 4, 2013
Water Heater Forum, Tanks need water...help! Please.... Jun 29, 2013
Water Heater Forum, Tanks Need help! Leaking from lower element May 1, 2013
Water Heater Forum, Tanks I need Weil Mclain help in South Jersey Apr 4, 2013

Share This Page