Considering tankless water heater...anything I should look out for based on my situat

Discussion in 'Tankless Water Heater Forum' started by ken in nj, Jan 19, 2014.

  1. ken in nj

    ken in nj New Member

    Messages:
    1
    Location:
    NJ
    I need to replace a 40-gallon water heater (natural gas) and am leaning towards a tankless unit. I'm looking for recommendations on a sensible unit for what we have and have a number of questions. Here is the entire scenario with my thought process. Am I missing anything major?

    We have 1800 sq foot ranch with 4 people living in the house. We have 1 3/4 bathroom (one with standard size tub, the other with stand-up shower). Our living room was originally a two-car garage and a previous home owner converted it. The water heater and furnace are located in a small closet actually in the living room backing up to an exterior wall. The main circuit breaker is 200 amp and is located on an adjacent exterior wall in the living room. I have no idea how much the gas line draws and if it's already at adequate capacity for a tankless heater. The house is on a concrete slab, no basement, no crawl space below, there is a crawl space attic.

    The two showers are both at the opposite end of the house from the water heater and it takes a good minute--90 seconds to get warm water. I'm okay with that. I understand the physics behind it. Over the summer we completely remodeled the bathrooms and upon using the new showers the shower heads give a lot more flow, but the hot water now lasts about 15 minutes and then no one showers for at least 30 minutes. That's okay now with young kids, but with two daughters and teenage years rapidly approaching they won't want to shower at night so mom and dad can shower in the morning.

    My questions:

    What rate is a sensible gpm? Is 6.4 enough? How many BTU is enough? What does 199,000 BTU do for me as opposed to 150,000 BTU?

    Should I looking for a condensing unit?

    Being in the northeast, how do I need to address winter temperature concerns?

    What is a good model that has shown ability to hold up?

    What upgrades to the water line should I consider?

    What standard maintenance am I looking at?

    My general thought is that between the small closet space where the existing tank sits, it may pose challenges to install a larger tank. I also am hopeful I will get some return on the value of my home by "upgrading" to a tankless unit.
    Last edited: Jan 19, 2014
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,038
    Location:
    Bothell, Washington
    I installed a 199,000 tankless to see how that is like.
    My 15 year old gas water heater had failed, so it moved up my timeline to make the switch.
    I installed the tankless near the gas meter. The existing gas line, which shared with the furnace was too small for that much flame. I had two tankless units in boxes, and I was thinking of running them together. I haven't installed the second unit yet.
    It now takes quite a long time to get warm water. So long that I sometimes skip washing my hands with warm water, and just use cold. I need to either install a recirc line, or move the tankless near the bathrooms.
    Navien makes a nice tankless unit with recirc and buffer tank built in. In Northern climates, the 199,000 puts out about 5.0 gallons a minute. It may do a lot more in Florida, but I don't live there.

    I also use a tankless at Sue's. That tankless in in a corner between the two bathrooms. There is plenty of water for two showers at once, and since we're only talking a few feet, there is no time lag.
    One more reason I'm thinking of moving the gas line in my home and putting the tankless in the same location as my three bathrooms, which all share common walls.

    Many gas meters will handle a 80,000 and a 199,000 load, but your gas company will have records and be able to tell you.
    The longer a gas line is run, the larger the pipe needs to be. CSST needs to be larger than hard pipe.
    Last edited: Jan 19, 2014
  3. Soapm

    Soapm New Member

    Messages:
    50
    Location:
    Aurora, CO
    We've have this Paloma PH2-28RDVS for about 5 years now and am very happy with it. In your case, because it's a direct vent, I believe it can go right in your current closet because it more or less has a snorkel that sucks and vents to the outdoors. Sorry, I'm a layman so those are layman's terms.

    It also comes with a heater type thing that wraps around the where the water heats up and keeps it from freezing but I would think it's best to put it indoors in your climate. You're still going to have that 90 seconds to get hot water unless you install a recirc loop but you're used to that so I would live with it. Like Terry said, I've learned to wash my hands in cold water so the only thing you'll have to learn is to turn on the shower BEFORE you turn off the sink after shaving and brushing your teeth or you'll get a cold water sandwich for sure.

    Maintenance, you have to flush it out with vinegar periodically. In five years, I've flushed mines once but it's probably due since I just started getting an error code on the remote. Flushing is a piece of cake and takes about 45 minutes. Hopefully we can welcome you to the world of tankless.

    One last thing to consider, you have two girls on the way to record breaking showers each. A tank water heater has a built in timer since it runs out of hot water in 15 or 20 minutes. It gets you out whether you're finished or not since not many of us can take cold showers. With our tankless my daughter now takes 45 minutes showers for her 5 ft nothing, 100LB frame and insist every minute is needed. I couldn't imaging multiplying that times two...
  4. TheLex

    TheLex New Member

    I thoght I'd chime in with an issue regarding tankless water heaters, their warranties and how a recirculation system affects them. On most tankless units the warranty on the heat exchanger is something lie 13 years or longer. However, if you carefully look at their language, their use with a recirculation system shortens the warranty to 3 years on the heat exchanger. This may or may not be an issue for you.
  5. Reach4

    Reach4 Active Member

    Messages:
    2,296
    Location:
    IL
    That sounds as if you are referring to resale value. A real estate agent in your area could probably give a better estimate of that. My guess would be that most buyers won't see that as something worth paying up for. I may well be wrong.

    One thing to watch for is warranty gotchas. One brand posted recently said the warranty is void if used with water harder than 7 grains of hardness.
  6. Dana

    Dana In the trades

    Messages:
    2,862
    Location:
    01609
    In the NW corner of NJ wintertime incoming water temps can be as low as 40F. A 105F shower running 2.5gpm (pretty good flow, not a sipper, not a gusher) takes about 82,000BTU/hr of output, or ~100K of input (if non-condensing) or 85K of input (condensing.) For tub fills you want something on the order of 2x that, unless you consider waiting for the tub to fill an exercise in meditation.

    A 150K condensing unit will do, if you are never running both showers (or shower + tub) at the same time, but to have any chance at family harmony you'd like to be able to run two showers at the same time, which makes a 199K unit a safer bet.

    Given the distance between the bathrooms, if there is a place to install a single 199K unit that splits the difference, that would be a reasonable way to go. The plumbing is probably all in the attic? (Hopefully on the conditioned space side of the insulation?)

    Unless your furnace is UNGODLY oversized (some are), you aren't likely need a service upgrade. But be sure to pay attention to the BTU-requirements of the tankless. Very few are close enough to the meter/regulator to get away with 3/4" gas plumbing, and many or most will need 1-1/4" pipe, configured as a home-run to the regulator rather than a branch from the feed to the furnace. (Modulating burners can misbehave when there are rapid pressure changes, such as when your furnace burner kicks on or off.)

    A condensing tank heater like the smaller burner Vertex has enough burner to support one 2 gpm shower forever, and can fill a tub faster than a 199K tankless, if there is a place to install one of those near the mid-point.
  7. Jymer

    Jymer New Member

    Messages:
    3
    Location:
    Ontario Canada
    Install the Navien 240A model with the recirculation line output. If you do the recirculation loop to reduce the wait for hot water, Navien will not shorten the warranty. The warranty is in effect with the loop used! This unit will handle the most GPM you will ever need and with the built in buffer tank/recirculation line you can program when the loop is hot and works perfectly without the cold water sandwich!
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