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Instant water heater

singh Member Posts: 866
I would just remove old tank water heater and install a electric tankless water heater. Just make sure you have enough amps in the electric panel available.

Check out www.seisco.com

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  • Eileen Olive
    Eileen Olive Member Posts: 99
    Instant water heater

    Thinking of doing away with an old electric hot water heater (50 Gal). I would like to install a gas-fired instant gas heater, since I already have gas in the house. But how long do these heaters last? Are they reliable? What might be the "best" brand to look at? Any suggestions?
  • mark ransley
    mark ransley Member Posts: 155

    There are alot of variables you need to research and things to test before deciding on tankless. I did what you describe, removed a electric tank and have a Bosch 117000 tankless and my payback on the 500$ unit was 4-5 years. But, Ng tankless need a good gas supply and you need yours tested to be sure you have the flow with competing apliances on and calculate low winter pressure in to the figure. The 117000 btu Bosch is single use good for 1 person at a time. There are flow rates, temp rise, gas suply needed etc to figure if it right for you. The best may be a Takagi TH1 at ove 2000 but its condesing I think and 93% EF. Instal could be 1000 but it all depends on what you have. You need to do alot of research before jumping. First would be calculating what you pay per Btu for electric vs Ng to see if you might save.
  • Jim Wy.
    Jim Wy. Member Posts: 43

    If you dont have predictable clean water a tankless can give you alot of problems. If your incoming water supply is less than 60* I wouldn't go less than 180,000 btu because the gas unit will slow the cold water down so it has enough time to heat to the set temp you require.I've had success w/ Rinnai provided the mineral content in the water isn't high but use a cold weather vent kit if it ever gets below 0* in your area or the air intake will freeze shut .
  • Eileen Olive
    Eileen Olive Member Posts: 99
    Thanks, guys

    Had no idea it would be so involved. I have a brand new gas line running into the house, las year they re-piped the entire town. My water I cannot say for sure, but I "believe" it is good. We are in Neptune Township, NJ, and I have not heard any water complaints, as yet. Still in all, I didn't think the BTUs required would outweigh my home's boiler.
  • Shane_2
    Shane_2 Member Posts: 191

    I would suggest Rinnai, Takagi, or Noritz. Personally, I use Rinnai (availabilty, and I like their one piece vent). I would not recommend an electric unit in your area of the country.

    I was a little reluctant to use these units at first, but I think they are a great option for many homes. Just keep in mind; gas requirements, venting, unit location, electrical requirements.

    Also be advised there is a $300 rebate available through your gas company for installing a gas fired tankless water heater.

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  • Eileen Olive
    Eileen Olive Member Posts: 99
    Life span

    How long can one of these instant water heaters be expected to live? For the cost, I would expect it to have a life expectancy of much more than a HW tank. Yes?
  • Shane_2
    Shane_2 Member Posts: 191

    Rinnai claims 15-20 years, covers the heat exchanger for 12 years, parts for 5 years.

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  • singh
    singh Member Posts: 866

    why not electric?

    I have one in NY. Works great. 10 years now. operational cost low compared to tank.

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  • mark ransley
    mark ransley Member Posts: 155

    The coil on my bosch is copper and could last 30 years. The valves and electronics who knows. But I get a good hot water only shower without the unit set to high at maybe 2.5-3gpm with 40 f incomming on a 117000 btu unit. Key to success is testing with a manometer with competing apliances on in winters lower gas pressure, to be sure you get full BTUs. There are negatives but I save and the negatives are minimal.
  • Eileen Olive
    Eileen Olive Member Posts: 99
    And the negatives are?

    Since this is a big decision, I'd like to hear all the possibilities. Fortunately for me, the new gas lines, high pressure, run up to my new meter right outside the basement where I would mount the water heater.
  • Shane_2
    Shane_2 Member Posts: 191

    I personally have never used an electric whole house tankless heater, but given the electrical requirements for the largest electrical tankless(2 60 amp. or one 125 amp. breaker) vs. the medium gas tankless(1 3/4 gas line if less than 20' from meter), I just can't see any advantage going electric. Also, the GPM between the two is noticeable.

    If it were my house or my customer's house and they wanted better efficency, better recovery, and gas was available; I would install a tankless gas, standard gas, or replace existing electric. In that order, depending on available finances.

    Please don't get me wrong, I believe an electric tankless would be perfect for some jobs. I would not recommend one here.

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  • Erich_3
    Erich_3 Member Posts: 135
    Navien Water Heater

    Jim, I think the best solution for you is a Navien model "A" tankless water heater . It has a 98% efficiency. Nothing else comes close to the Navien. Here is a link so can can see their products.

  • singh
    singh Member Posts: 866

    just be careful with the reported gpm's.
    one gas model claims 9.2 gpm but at a 45*rise. so if incoming is 50* thats only 95* output, factor in piping losses and distance and luke warm water is now coming out.Then the cold water sandwich effect. This is why so many complain about after spending thousands on a gas unit and poor results. Pay back is long ways away.

    Electric has the elements directly in the water , so there is no efficiency loss unlike a gas HX. 200 -150 amp is all that is needed. Most homes have plenty of room.

    I increased the outputand effciency of my electric tankless by preheating it with a solar storage. The best way out of all !!

    I could think of better ways to utilize NG, pretty soon more and more LNG will be imported into the country. We could do better.

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  • Larry Weingarten
    Larry Weingarten Member Posts: 3,232

    ... A slightly different way of looking at the question is to ask what are you using hot water for, for how many people and how efficient are the appliances and fixtures using hot water? Also, how efficient is the piping at getting hot water to the points of use with minimal waste? You're talking a large enough investment that it could make sense to look at "structured plumbing", "GFX shower heat exchangers", "manifold plumbing" for a smaller home, or even old technology like a tempering tank.

    Simple, long lived and easy to live with are criteria I aim for. Also, there is some discussion on tankless at another site I play at, "waterheaterrescue.com".

    Yours, Larry
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562

    Water quality, water pressure, vent restrictions, gas availability and piping arrangements.

    If you have poor water quality you can plug up the HX and create hot spots that shorten life. Water pressure fluctuations have an impact on flow through an on demand. Unless you go with the new high efficient units you may have vent restrictions. You need proper sized gas meter and piping. The long runs in some houses may require a unit with a small buffer tank and recirc piping.

    If you do your home work and have a good application for tankless they are a great way to heat water. Rinnai, Noritz,Takagi and Navien have quality products. Make sure you factor in parts availability and service!

    Good luck!
  • Dave Larsen_11
    Dave Larsen_11 Member Posts: 39

    If you already have a boiler heating your home then you should consider an indirect heater tied into your boiler with a domestic priority control. More cost effective and will last a really long time.
  • Mainemike
    Mainemike Member Posts: 8

    I second the consideration of an indirect running with the existing boiler. I can say from first hand experience that a tankless may take a little getting used to. I currently have a small "single fixture" model in my home. As long as we are conscious of using only one fixture at a time it performs well. One other phenomenon we have noticed is the need to have a significant flow to trigger the burner. If I open a hot water faucet only slightly, chances are the heater will not fire. This is not an issue as long as you are aware of it and open the tap robustly. All in all, if I had a boiler I would choose an indirect, but since I do not, the tankless is a good alternative.
  • Lot to consider

    There are a lot of options out there and a lot of variables to make a decision that is right for you.

    Up front cost, product life, replacement cost, how long are you going to stay in your home, warranty, water quality, door and window locations, chimney size and condition, what type of heat you have in your home (Hot air or hot water/steam if considering inderect water heater), condition of old heating equipment, number of fixtures and how many multiple fixtures used at the same time, how comited you are to energy conservation and going green.

    Some times a standard gas water heater is the best choice. Not the most efficent but most effective for the price.

    I love indirect water heaters especially when tied to a high efficency boiler.

    On demand gas is great for the right applications and use patterns. I have used Noritz, Takagi, Rianni, Bosh, all nice. I prefer the Noritz due to vent price and ease of install. (On demands are not as efficent as everyone states IMO, no standby loss but the burner is not efficent, loose a lot of heat when you are making hot water that fast. They need better heat transfer)

    Electic is very efficent 100% in 100% out. Just cost a lot to run and most houses don't have near the electric service to run a whole house electic.

    I am in NJ call or e-mail if you have questions. 609.304.9749 / [email protected]

    Joseph A Landree
    JAL Co. Plumbing & Heating
    NJ Master Plumber Lic. #9718

  • singh
    singh Member Posts: 866
    sizing electric loads

    An accepted way to size electrical needs according to NEC codes is 100% load for the first 10,000 VA , then 40% for the rest. Water heaters, even tankless ones fall under the latter load requirements. This is why we can have coffee maker, microwaves, dishwahers, dryers, lights, etc in a house, because they won't be running all at once, if they did, they would trip the main breaker.
    A 150 amp -200 amp panel is all that is needed for a whole house electric tankless.
    I'd rather go with a 99.9% eff electric tankless vs . a 82% gas tankles that also draws electric.

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  • What happens.

    What happens when you are showering, someone is drying their hair, have a load in the electric dryer and trow a pot of Jo on.

    I am not an electrician by any means but look out.
  • singh
    singh Member Posts: 866

    Sounds like a typical morning in my house. BTW - I have a 150 amp main.

    p.s. The wife dries her hair, I have none : )

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  • Jalco,

    Published EF is true rated EF, on gas water heaters, no way to argue that.

  • 30 years on a Bosch copper heat exchanger, really?
    You should hope for 10-12 with a normal family/household, truly!
  • markotah
    markotah Member Posts: 36
    Instant Hot Water

    I have been using the RHEEM units. I like them for their warranty and brand name. If a Tankless won't work I can stay with the same brand and offer a tank model. But electric to gas in a tankless unit in a cold climate is a no brainer. Consider this, 180,000 btu unit will deliver about 4 gpm at about 120* supply temp with a 40*incoming temperature. This would require 52.75 KW to equal the flow rate with electric.
    52.75 x 1000= 52750/240 volt = 219 AMPS! How many homes could handle an electric unit?
  • bob eck
    bob eck Member Posts: 930
    tankless gas water heaters

    Tankless gas water heaters are great but there are some things that need to be addressed to make sure they are the right fit for your job.

    they shoud be located on a outside wall to cut down on the amount of vent pipe needed. must be able to vent according to code away from windows and doors plus not onto decks.
    you do need a large enough gas line 3/4" or 1" on most jobs all depending on the run of gas pipe plus all other gas appliances or just a direct run of gas pipe to the unit.
    if you have hard water you should have a water softner installed but if you do not wat a water softner you can install a aqua pure cuno filter model AP430 on the cold water inlet pipe and this filter will put a coating on the copper tubing and inside the heat exchanger that will not soften the water but will keep the unit from building up with hardness. if you use a water softner or the AP430 filter I would still have the contractor come back once a year and clean the heat exchanger as normal maintenance just like chainging the oil in you car. This will extend the life of your unit 10 to 20 years.
    if you want to save water and lower your water and sewer bills you also could change your shower heads to a lower flow like 1.85 gpm or 1.6 gpm. American Standard has a shower head called Flowise and this head flows at 1.5 gpm or can be turned to 2 gpm.
    there is a $300.00 federal tax credit for tankless gas models in 2009 and some states and local gas utilities also are giving tax breaks or rebates.
    look at using NORITZ look at their model N0751MDVC model. use the winter sizing to make sure the right model is installed. 12 year heat exchanger and 5 year parts warranty plus this unit vents with their stainless steel vent system.
    tankless gas water heater will give you endles gallons of hot water hour after hour plus these units only use energy when you need hot water. A tank type gas or electric water heater uses energy 24/7 to keep the water hot all the time so when you want hot water you will have it this is wasting energy. most tank type water heaters come with a 6 year tank warranty and 6 year parts warranty and these units need to be replaced about every 7 to 10 years and this adds to your cost to make hot water where the tankless gas ater with proper maintenance can last 10 to 20+ years.
    you can also put a grundfos domestic hot water recirculation system on the tankless gas water heater and you will have instant hot water in your bathroom as soon as you turn on your hot water faucet.

    If you get the right tankless gas water heater you will love it.

    Thanks Bob
  • markotah
    markotah Member Posts: 36

    I rep RHEEM Water Heaters and we are the only tank manufacturer to make make our own Tankless unit. At the end of the day all the units have proven to be very reliable and have a long history. The only new name to come up recently is Navien and we will have to see how these units life cycle. You have to remember that Tankless is not new technology and has more history than the standard power vented heaters we see today.
    In response to the maintainence that has been discussed with hard water you also have to remember that hard water will also shorten the life and reduce heat transfer on tank units as well.
    If you have a 30,40,50 gal heater now and you are not running out of hot water or you have a chimney issue Tankless is a great way to go. New construction or applications where a power vented heater is required could be great Tankless applications.
    The bottom line is as with any product how is the field support in your area.
  • hot_rod
    hot_rod Member Posts: 21,851
    The Viridian electric tankless

    look pretty nice. I like the spiral stainless and brass Hx better than the plastic versions. With the low wattage density elements, this looks like a long lasting product.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562

    Rheem is owned by Poloma a Japanese company that has had tankless for any years.Do not portray Rheem as it's own manufacturer of tankless. Their tankless is a Poloma.
  • markotah
    markotah Member Posts: 36


    I hate to burst your bubble but Paloma owns RHEEM Water Heater, Raypack, Rheem and RUUD HVAC, Solohart Solar Products. Go to www.rheem.com
    We don't buy others tankless units and label them as ours. The Rheem Supply Boilers are made in a Raypack facility and they use Rheem manufactured tanks. It is one big family that makes us one of the largest privately held companies in the world.
  • singh
    singh Member Posts: 866
    Do they modulate?

    Is there a gas tankless that can modulate.?
    Yes, a 180,000btu gas unit could give you a 4gpm (240gph) flow @ 80 rise.Factor in effciency. But what happens when there is only a 2 gpm demand.

    Seems like an awful waste of btu's. And why take a gas ignite it to thousands of degrees, just to make 80 degree water? Any sustained demand use and you'll find the savings are not there.

    There is not a 52kw electric unit, there is a 32kw unit and so amps are much less. And thank goodness I don't have 40* incoming. My well is 500' down in upstate NY and stays at 50* But I'd rather take that coupled with a solar pre heat and electric tankless any day.

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  • markotah
    markotah Member Posts: 36

    Yes! I believe that all Tankless gas units at this time modulate. The Rheem unit RTG66 w/180K BTU modulates from 11K to 180K BTU. Your 32KW x 3412btu = 109184 BTU. If your water is warmer you need to look at the temp rise you want from the manufacturers literature. Example 50*incoming to 110* (60* rise) supply would max out at 4.9 gpm. The lower the rise required the lower the BTU required.
    The RTG42 (118000 BTU unit) with the same parameters would give you 3.2 gpm.
  • Al Roethlisberger
    Al Roethlisberger Member Posts: 194
    What are the comparitive costs of a boiler system

    I've often wondered about how cost effective a domestic standby tank off of a boiler would be.

    1) It seems like it would be comparatively expensive to retrofit the tank, controller, valves, circulator, piping, etc. versus a new tank or even indirect/instant system.

    2) I also wondered how energy efficient it would be to fire the giant boiler to keep the storage tank temp up, versus a much smaller dedicated heater.

    I may be way off base here because I have no figures, but it is something I've wondered about since I DO have a gas boiler and expect that one day I'll have to replace my electric tank water heater *shrug*


    Just a DIY'er trying to learn, and improve and maintain his converted ca 1929 overhead gravity hot water system since there is no one local that can.
  • Ken Pakulski
    Ken Pakulski Member Posts: 3
    My personal experence

    This relates to my household your results may vary! Cool got that disclaimer stuff outa the way, lets start. I enjoy reading this column and deeply appreciate all info and help from all contributors. I am a service /installer and sales of residential and commercial comfort systems and I have installed quite a few water heaters, like all of you, from naturally vented, sidewall vented, to indirect and a few continuous supply water heaters. Now, I estimate a great deal of units and every once in a while I get to go back into the field to help install or troubleshoot a problem child.
    All info on this subject here is alot to comprehend for a home owner, so, this is how I help them to make the most educated buy that they will be "comfortable" with in years to come. Your significant other will remind you how comfortable you were making that decision to spend that dinero$$$ for a problem child.
    #1 is usage, how / what do you use the hot water for now? Jacuzzi tub, bathrooms, number of people V.S showers per day (oh and at the same time). Washer, dishwasher etc.
    #2 Energy savings expected/ payback time frame.
    #3 Installation site, can it be located for functionality building codes AND servicing? (told ya I am a service person)
    After we get thru all that we discuss pricing! Like a trip to a dentist,fun, fun, fun. Tankless $1,250. Service valves $90. Gas $150. Vent- outback$250. Day labor $720 Electric (hired out) $300 Permit $125 Total $2,682.00
    Indirect Amitrol wh-7 $850? Or a Peerless Stainless steel only $1,250. Pick one! Add Circ pump/Zone valve $125. Electrian $300. Piping parts $100 min. 6 hrs lab $540. Total $1,915 to $2,315 Add permit too! Tankless looks pretty darn good now!
    How about a sidewall vent, Heater $560. 3 hrs lab $270. Permit $125. Total $955.00. OK then a standard 40 gal. water heater use existing vent pipe (it is safe to use, isn't it?) Heater $386. Lab $270. Permit $125. Total $781.00. (Wow, look what time it is. You've spent 1 to 1-1/2 hours on a sales call and your not getting paid for it! cool eh?)Opps, apologize back to my story...
    These too were my choices when my used 52 gal "1966" vintage electric water heater(Dad got it from uncle Walt, for our old well water farm house in 1970.) It decided to leak around the lower element. Dang I thought dad said this will last a life time, Oh his life time. Here's how (I)fiscally decided, like everybody else does, what to do! 52 gal Elec water heater $266.00 Lab 3hrs (mine) electric service AND disconnect there, excellent shape & i installed a new updated whip from disconnect, i'm a big spender, like you. My electric is on a separate meter and interuptable (DTE shuts it down at night;) Now we have 4 people (2 of each gender) on a small farm. Yes we shower daily! In the summertime our bill to heat water only is $14-$17 mo. Winter it creeps up to $24.23 for my dec-jan bill. We take 10 gals of 100% hot water out twice a day, 20 gals total, for horse and lotsa rabbits. Yes, insert long(er) story here. Actually the "electrical charges" were $15.43 for dec-jan, the rest were tax/destination charges.
    Now there are times when the water pressure is not there,
    excelent water/low volume, so we kinda limit shower times 10-15 mins or hurry up if it gets spurtin alot of air, let settle 10 mins gives well time to recoup. Continue as normal.
    All the above mentioned water heaters are suitable to do a job depending on the job to do. This works for me as i said. If you do the homework and don't really "need" a Lamborghine when a Volvo will do, Well you get the idea. Hey we all know people that had to show the "Who's Bigger" I got me a...blah...blah...blah! Great i can have that installed for ya...
    Oh by the way EVERY JOB "is" different! Did you see the price of copper to install any of the above water heaters...? It wasn't included! I personally DO NOT quote a price to install until "I" see the job. There's no such thing as a standard installation when it comes to a Continous Supply water heater or a instant water heater. There is a difference. Jeez, almost forgot, Like it was mentioned a Rinnai will give you a code on the touch pad alerting you to when it "needs" to be descaled. (Maintenance is required, even on the standard vented units.) Surfaces over 140 Deg.F do scale depending on minerals in the water. Including "City" water- from wells. Can I set you up with a service contract to perform this for you? See sales. Or you want to bet the code goes unnoticed and then it fails, Yup seen it. "Whatda ya mean you never pay attention to those code things on the pad." Read all owners manuals that come with your purchase. And if you have any questions ask the installer if they are on site. Ask him to go over any maintenance you may be able to do. Sorry some maintenance is to be performed by trained people that have special tools for the task.
    The internet sites of the manufacturers have the manuals, if you want to read them, or does your clock on the vcr/dvd still flash 12:00? You too can be an educated consumer and with proper maintenance your heater will last "It's lifetime". Good luck with your purchase. Keep the faith."K"

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