Eemax TankBuddy -- Opinions Sought

Discussion in 'Water Heater Forum, Tanks' started by Mark Alhadeff, Jan 19, 2017.

  1. Mark Alhadeff

    Mark Alhadeff New Member

    Joined:
    Jan 19, 2017
    Location:
    New York
    I'm wondering if anybody has an opinion on (or experience with) Eemax's TankBuddy. The TankBuddy is a small tankless heater that is designed to work with a typical tank heater. They claim to get you close to 2x the effective hot water from your tank. As far as I can tell it is only sold through Lowes and all the reviews there are from people who received the unit for free. https://www.lowes.com/pd/Eemax-TankBuddy-Water-Heater-Tank-Booster/1000072073

    I'm interested but suspicious about this thing. I get how it is supposed to work but what makes me doubt Eemax's claims is simple physics. Hot water rises so I suspect it won't engage until your tank is almost completely full of cold water, and it can't work against cold water. It only works with warm water.

    This is my first post here, so please excuse me if I am violating any rules/traditions of this forum.

    Thanks in advance for any information you can share.
     
  2. Mark Alhadeff

    Mark Alhadeff New Member

    Joined:
    Jan 19, 2017
    Location:
    New York
    To be clear, my experience with our tank running out of hot water has been a very quick change from hot to freezing -- it seems to me that this would only help during the in-between time when the water is no longer hot, but not cold either. For me that is a very short time. But maybe I'm missing something (or maybe what I consider freezing is not objectively that cold -- just subjectively cold because I'm in the shower).
     
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Joined:
    Jan 5, 2008
    Occupation:
    Test, Don't Guess!
    Location:
    Land of Cheese
    A standard 40 gallon tank should provide enough hot water for a comfortable 15-20 minute shower using a standard shower head. Some people are installing larger tanks or duel tanks if they have a need for more hot water.

    What is the problem that you are trying to resolve?
     
  5. Mark Alhadeff

    Mark Alhadeff New Member

    Joined:
    Jan 19, 2017
    Location:
    New York
    Our newer (to us) home has a heater that is undersized for us, but of a relative young age. We were about to upgrade to a larger tank (we don't want to put in a second tank) and I stumbled upon this new product. Honestly, I am also interested in the concept on a pure "geek" level and would love to hear about the opinion/experience of others. When it comes down to it, I suspect we'll just go with a bigger water heater. Still, this would be less expensive.
     
  6. cacher_chick

    cacher_chick Test, Don't Guess!

    Joined:
    Jan 5, 2008
    Occupation:
    Test, Don't Guess!
    Location:
    Land of Cheese
    I have never heard of the device in question.

    If the water heater is working properly, it would not instantly turn cold while you are taking a shower. As you use hot water from the tank, cold water is flowing in, but the overall temperature will taper down over time. If that is not the case, the heater has an issue.

    If the heater is working properly, one method to get longer periods of hot water is to turn the tank temperature up to 140F, but to do that safely you need to have a tempering valve installed to eliminate the danger of people getting scalded at the fixtures.
     
  7. Mark Alhadeff

    Mark Alhadeff New Member

    Joined:
    Jan 19, 2017
    Location:
    New York
    Thanks for the suggestion, but we've already got the temperature cranked up (but without a tempering valve). We are pretty careful with the hot water and basically temper at the time of use using the faucets. I've got a feeling that the reason we don't get a slow taper down from hot to warm to cold is because we have an old water guzzling shower head (and pretty high water pressure). The combo means we are emptying our very small tank (30 gallons) extremely quickly -- there's no chance for the water to reheat. And I do like our water guzzling shower head! This is a weekend home, but I think I'm just going to get an 80 gallon tank and enjoy a luxurious long shower. I think we'll get one of the Westinghouse Stainless Steel models (I think they are made by HTP). I like the idea of tankless, but I worry about our electrical service being stretched to the limit (200AMP service).

    Also, I found that the TankBuddy thing is also available branded as the SmartBoost by EcoSmart. There are more reviews available for it, but still nothing very inspirational. Most seem like fake reviews to my skeptical eye.
     
  8. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    It's possible that the dip tube on your water heater is corroding away, giving the water heater a lower "apparent capacity".

    Unless you have competent electrician & pluming skills, it will cost more to install the dedicated power wiring & breaker installation for the than the $300 for the TankBuddy itself. You're probably looking at about a grand all-in to have it professionally installed, possibly more (do you have sufficient space in the breaker panel? Does the wiring need to go through finished walls/ceilings?)

    If it's showering performance you're after (rather than tub-filling), putting the grand toward a drainwater heat exchanger would be better than up-sizing the tank or adding a TankBuddy. A drainwater heat exchanger doesn't use more power, but can recover ~50% or more of the heat that's literally going down the drain, returning it to the incoming stream of cold water prior to the water heater & shower, roughly doubling the showering time for a 40 gallon electric tank with a 130-140F storage tank, and turning a typical 40 gallon gas burner into a "never ending shower" experience at a 2 gpm or slower flow.

    [​IMG]

    [​IMG]

    With plastic drain pipe it's a pretty easy DIY. The fattest and tallest that fits is the "right" one, since the additional marginal cost is small compared to the additional recovery efficiency. The ~50% return efficiency starts at 3" x 60" or 4" x 48", but if have more head room to work with, taller is better.

    It won't do a thing for tub-filling capacity, since the heat recovery can only take place if the drain is flowing at the same time as the water is being drawn.
     
    Last edited by a moderator: Feb 4, 2021
  9. Mark Alhadeff

    Mark Alhadeff New Member

    Joined:
    Jan 19, 2017
    Location:
    New York
    Thanks again for the continued responses.

    As far as installing the TankBuddy, it would be a cinch for me. I have decent plumbing skills -- having done a ton of plumbing on a house we restored a decade ago. I made all the really bad mistakes already! I can solder pretty well but lately I have been lazy and started using sharkbite connectors (possibly a new mistake). As for electrical, I think I'm pretty darn good. A friend who is an electrician gave me lots of lessons and hands-on training during the previously mentioned remodel. I'm very comfortable working in the panel, but I wouldn't need to. The TankBuddy works off a shared 240V/30Amp circuit when used with an electric water heater. Basically it turns off the water heater when it is doing its thing.

    The drain water heat exchanger has got my attention. I've been interested in energy harvesting since my son won a bunch of awards for an energy generating piezo tile he designed and built. Plus, my house is a late 70's "solar tech" house. While all the systems have been turned off, it previously had what I can only describe as a passive-active solar energy collector that harvested the sun's energy for heat and hot water (it has a large masonry thermal mass behind a glass wall with all kinds of ductwork, fans, and electronics to facilitate moving the heat energy where it is needed). All the infrastructure for the harvesting is still in place, but the previous owners said it never functioned to their liking and had it mothballed (the glass is behind vinyl siding). I was actually crawling around in the sealed room with all the equipment just yesterday and for the first time noticed the heat exchanger for the hot water. It's a finned design (air to water). The entire room is a real museum piece. At some point it will be repurposed for living space -- but until then it could be a exhibit in the Museum of Carter Era Green Energy.

    I'm thinking about the heat exchanger. I'll be googling now. Again, thank you.
     
  10. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Wow, an 70's vintage trombe wall house- I remember those! (Got any pictures to share? Do document the mechanicals before gutting that room!) Hopefully they put an insulated curtain wall between the glass and the vinyl siding! I'm very curious as to how the finned air-to-water pre-heater was supposed to work- could it actually by a water-to-air hydronic coil taking stored solar heat from a tank for space heating purposes?

    Gravity film type drainwater heat exchangers have been around since the early to mid 1980s, but had/have a low net-present-value if installed solely for the energy savings in low energy price markets. At NY electricity pricing the financial payback is quite reasonable if heating hot water with electricity. The showering-capacity performance has a different payback since it can also reduce the size & cost of the other mechanical systems up front.

    National Resources Canada has established a test protocol to be able to compare apples-to-apples on the return efficiency of different makes & models, independently tested by third parties (not just the manufacturers.) A downloadable spreadsheet for making those comparisons lives here. Most vendors will sell them at retail pricing from their websites, but they can also be ordered from the big orange box store. Renewability often has a discount priced unit (the model varies) up on Amazon.
     
  11. Mark Alhadeff

    Mark Alhadeff New Member

    Joined:
    Jan 19, 2017
    Location:
    New York
    Thanks for the comments Dana. I keep hearing myself say (in a Brooklyn/Long Island accent), "Hey, who knew I had a Trombe Wall House?" Considering we named the house "Casa de Hunu" maybe it shouldn't be surprising. I sent you an email with a link to a Facebook post with photos of the "solar furnace" (that's what the old marketing material we inherited from the original owners called the system). The heat exchanger is definitely for hot water. I'm attaching a photo of it along with a page from the brochure.
    IMG_0315.jpg image006.jpg
     
  12. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Plumbed correctly a drainwater heat exchanger helps all the time during a shower, not just at the end, giving the tank an "apparent capacity" boost.

    The heat exchanger should be plumbed to feed it's room-temperature or higher potable water to both the cold side of the shower AND the hot water heater. The shower's mixer then uses hot water out of the tank at a slower rate, since it's mixing the 125-130F or whatever hot water with 70-75F water rather than 35-45F water to come up with a ~105F shower head temp. Additionally, the water in the tank is being diluted with room temperature water rather than truly cold water, thus taking longer to drop to an unacceptable showering temperature.

    Even when the tank's temp has dropped to the tepid 90sF at the output, the recovery time is much quicker than if the tank had been fed cold water rather than pre-heated water dropping to the 90s at the top, since the bottom of the tank is ~70F instead of ~40F.

    A typical 2 gpm shower with a 70F rise (35F up to 105F) is a heat rate of ~70,000 BTU/hr, or ~20,000 watts. If half the heat is recovered from the drain (again, a 4" x 48" or 3" x 60" or taller) it's only pulling heat out of the water heater at 35,000 BTU/hr, or ~10,000 watts. A typical 40 gallon electric hot water heater delivers 4500 watts, so without the drainwater heat exchanger the shortfall is a whopping 15,500 watts, with no chance of keeping up and with a sharp rate of temperature decline. WITH the heat exchanger the shortfall is about 5500 watts- the average temp in the tank is dropping at only about 1/3 the rate.

    The heat exchangers are tested at 2.5 gpm, and the efficiency at lower flows is a bit higher than specified. Most 2.5 gpm shower heads (the current max legal maximum for shower heads sold in theUS) aren't really flowing that fast, since that is tested at 80 psi water pressure. If you have lower house pressure (which you do) the flow is less. A low-flow showerhead might be rated at less than 2 gpm, and deliver less than 1.5 gpm in a house where the pressure is only 30-40 psi. Bucket-test the flow rate on your shower against a watch or stopwatch. The rate at which the tank is depleted can be gauged by your actual flow rates, and the return efficiency of a drainwater heat exchanger can be estimated at the lower-than-tested flow rate too. A gravity film type heat exchanger that tested 50% @ 2.5 gpm will deliver about 57-58% efficiency at 1.5 gpm.
     
    Last edited: Jan 24, 2017
Similar Threads: Eemax TankBuddy
Forum Title Date
Water Heater Forum, Tanks Eemax 2.5 Gal.Electric. Anode Jan 11, 2019

Share This Page