If install cost wasn't an issue...

Discussion in 'Tankless Water Heater Forum' started by Eusibius2, Nov 12, 2009.

?

Tank or tankless?

  1. Tankless

    14 vote(s)
    48.3%
  2. Tank

    10 vote(s)
    34.5%
  3. Combination (please post if 'combo')

    4 vote(s)
    13.8%
  4. Other (please post if 'other')

    1 vote(s)
    3.4%
  1. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    You can get 170F out of 10 square foot panel, if you crank the flow down to nuthin'. It's all about total net BTUs delivered, not the temperature at which it's delivered. The average efficiency of flat panels at 170F in a coastal New England winter will be ~50% best-case. If you run it a lot cooler you can probably hit 70% or more in the shoulder-seasons.

    I don't know how many therms you expect to reap from ~100sf of low-temp solar in a heating season, but I'd hazard in Rockland MA it's under 200therms (20MBTU), but for the sake of argument say it's 200 (even if 100 is more likely), and lets assume against all likihood that it'll collect it all in the coolest 100 days (or 2400 hours) of the heating season. Is the average heat load on your basement all winter, at 65F interior temp going to be under 20,000,000/2400=8333BTUs/hr? Is it less than half that? Maybe...

    If it's well sealed from infiltration, with an insulated slab and R20 on the walls, or you run the collectors at under 100F to get 65-70% efficiency out of 'em, maybe you'll get a noticable midwinter boost out of it. In the shoulder seasons with somewhat warmer outdoor temps you'll get more.

    The dirty little not-so-secret about solar heating is that most existing standard-construction homes will lose heat far faster than you can collect it with an array that fits within the footprint of the house. If you don't have whole-wall R-values over R25 above grade, and over R15 below grade including R10 under the slab) don't expect too much. 100sf of collector may be measurable in the heating bill, but unless you're already under 700gallons/oil or 1000therms/gas in a season you'll need a sharp pencil to see it. If you're burning only 300gallons or 400 therms/year it'll be dead-obvious.
     
  2. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Joined:
    Jan 5, 2009
    Occupation:
    Used to be in IT
    Location:
    South of Boston, MA
    When we 1st moved in we went thru 3 tanks of oil the 1st year
    We used about 1.25 tanks of oil last year, it was 10% colder then average & I was heating 10% more space
    The new sunroom off the back is not fully sealed, so once that is done it will be even warmer
    I heat with wood in fall & Spring, supplement with wood in the winter
    I'd like to get it under 1 tank of oil a year

    I built a greenhouse against one part of the back of the house
    On a sunny 30 degree day it goes up to 60 or so
    That keeps part of the house much warmer
    In the Spring It was going up to 107 in the greenhouse
    Hate to see what it would go to if I didn't take the storm windows off in the Spring
    So another plan is to heat my hot tub with a solar collector in the good weather

    Other option is to heat the garage...even up to 60 would be nice
    Better then leaving the panels "idle" in the winter

    and by solar setup I actually meant a 6-9kw or better photovoltaic/wind system to offset my electric WH :D
     
  3. AAnderson

    AAnderson In the Trades

    Joined:
    Oct 25, 2009
    Location:
    Aptos, CA
    Absolutely tankless! Bare in mind this is still new territory for a lot of plumbers and home owners. I've sent clients to this site to get a slightly more objective opinion on the subject than other sites
    . There are two type of plumbers here, those that are stuck in the tank ages and those that have evolved and adapted to new technologies.
    Heat exchanger replacement? It depends, indoor Rinnai; 1 1/2 hours, exterior 30 minutes. Navien HX replacement (yes it can happen and did), 2 hours, Tagaki, 2 hours, Bosch 250, 635, 2400 and 2700, 1 1/2 hour.
    Navien board replacement of the V1.50 with an upgrade to the new V2.0; 15 minutes, Rinnai, same, Bosch, 30 minutes. We've had a number of Takaki ground fault circuits cook in lightning strikes as have Rinnai
    Water valve replacement on a Rinnai 2532, R 85 or R 94LS 30 minutes, gas valve replacement on same with high / low fire adjustment; 45 minutes
    Bosch gas valve replacement 250, 635, 45 minutes CO2 adjustment; 15 minutes with a combustion gas analyzer.

    So far in 30 plus years we've installed about 1,500+ tankless WH. the over whelming have been Rinnai in the last 11 years and they have the best technical service. Navien well, as i've told reps, if you want to try and be #1 you have to start with support.
    You can't expect a home owner to work on a tankless and as we all know, home owners don't call until it's broke at 4:30 PM on Friday.
    We used to be the go to people for Bosch in central California but we parted ways with them and if you've dealt with Bosch very often, you can imagine why. We focus on service for Paloma/ Rheem, Rinnai, Tagaki, Noritz and Navien.
    The problem is never in the box, its either gas, venting, application and mis-installation that give us 30 plus hours a week in tankless service calls alone and these result in either failed systems or very expensive re-installations.
    We just swapped out a Rinnai R 85 LP and installed a Navien RR 240 A because the water quality and lack of condensate collection ate the HX on the R85 after it was installed 18 months ago. The owners had paid $9,900 for the Rinnai installation where we charged $3,400 to installed the Navien, The original contractor installed a recirc pump with a 28 gpm flow (way over sized). Judging by the amount of couples and capped tee's, i'd say they really didn't know what they were doing. Gas was taken off from a 3/4" line to the FAU.
     
  4. ChuckS

    ChuckS New Member

    Joined:
    Mar 17, 2009
    Location:
    Aurora, CO
    What do you think of Paloma? We've had one a few months now and it seems to keep up. Are they reliable? Do they last?
     
  5. AAnderson

    AAnderson In the Trades

    Joined:
    Oct 25, 2009
    Location:
    Aptos, CA
    Paloma

    For the life of me, I have no idea why Paloma and Rheem have tech support in Alabama. Getting through to them is difficult and they want you in front of the uit if there is a problem. I like like their WH but not the support. I had a customer the had one in a sealed room and the oxygen sensor did it's job. I told the customer that if the O2 drops below 17% the unit will shut down. I also told them to either keep the door open or get a carpenter to install 2 large vents in the doors. they didn't and I go the same call again... the new Paloma line is pretty robust and if they move into the commercial market, they will do well. Selling them at Lowe's and Home Depot is not the best market move I've seen.
     
  6. AAnderson

    AAnderson In the Trades

    Joined:
    Oct 25, 2009
    Location:
    Aptos, CA
    The bottom line on any tankless is after market support. The only one right now is Rinnai that has been consistent. After servicing a Navien on thanksgiving eve, I had hopes Navien would step up to the plate but so far after nearly a month, zero response from them.
    Regardless of the brand and model you choose, carefully look at who is going to service this once it is in place and who is going to support those that do service this. This is the area most manufactures have failed to recognize, support and training of field service personnel. I had attended a trade show and talked to one manufacture who stated their product would never need service and if there were a problem, their sales people would take care of it. Funny thing, no one picked this product up to distribute.
     
  7. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Sunrooms & passive solar tends to be significantly more efficient than water heating panels due to the ultra-low operating temp. You lose a lot less heat to the 30F outdoors per square foot of glazing with a 60F sunroom (a 30F delta-T) than you lose with a 120-170F panel (a 90-140F delta-T), eh?) You simply can't get the same performance out of a panel.

    To get useful space heating out of 100' of panel, you need to be able to deliver the heat at sub-90F water. (As in a radiant slab), not 120-150F baseboard. With baseboard use at least double (triple, if you have the space) the linear feet that you'd use with 150F water to get something reasonable. Low temps to keep the collector efficiency up is everything.

    If your hot tub is decently insulated you would likely be able to keep it hot all winter long with a single 48' panel. Unlike DHW situations, you're keeping it under 110F, and never drawing off the hot water while introducing volumes of sub-55F water. Solar hot tubs are easy- it's just a lot less energy required.
     
  8. zl700

    zl700 DIY Senior Member

    Joined:
    Aug 26, 2009
    Location:
    Western NY
    A Anderson once wrote- Did you delete?-

    "After servicing a Navien on thanksgiving eve, I had hopes Navien would step up to the plate but so far after nearly a month, zero response from them."

    I'm curious what you are expecting from Navien?

    When servicing a unit, if you fill out their labor form with a valid claim (screens are normal maint), they send you a check.

    What service did you do and are they aware of it?
     
    Last edited: Dec 21, 2009
  9. AAnderson

    AAnderson In the Trades

    Joined:
    Oct 25, 2009
    Location:
    Aptos, CA
    Navien still has yet to send the service agreement after 18 months of promises. At this point, I really don't expect a thing as they've failed to follow through and don't respond to phone calls or email. I should have known better. What I have begun doing is collecting labor on service charges and informing the customers, they can attempt to collect from Navien.
    This particular service was an emergency called out through Navien to Action Sales, the central California distributor to my office.
    I know two other companies who's claims for labor have been declined, they no longer install or service Navien. This is how a product disappears from the market.
     
  10. Runs with bison

    Runs with bison Member

    Joined:
    Aug 23, 2009
    Location:
    Midwest
    This is one of the major problems with tankless compared to tanks. With a tank the service aspect isn't an important consideration. I've generally serviced my own. Even this Whirlpool I have with a major known design defect and a major controls defect (ECO failure) is something that I can replace parts on for free. A properly made and designed tank should be DIY-only throughout its life.

    The homeowner has a lower probability of finding someone who is competent to handle a tankless install and configuration, prevent cold water sandwiches and other problems. Not all of this is the installers fault. Home pipe routing and existing plumbing problems contribute. Plus users can have very different hot water requirements (flow and temperature) that vary by over an order of magnitude.
     
  11. Scott D. Plumber

    Scott D. Plumber In the Trades

    Joined:
    Jun 30, 2009
    no brainer

    Tankless by Rinnai or noritz only. (I'm a Rinnai guy)

    Repairs = Easy if you take a little time and get trained up a bit. No it's not a DIY job.

    Boiler/Indirect? Ok, great if I'm in the NE, but what about when it's summer and I have to run a hot BOILER all day to keep my Indirect hot ALL DAY? how about the HEAT GAIN that now my A/C has to overcome from the boiler and the tank to keep the house cool? Nobody ever thinks about that one.

    Yes, The DHW is almost free in the winter, but I think you get to pay it back in the summer from several different directions.
     
  12. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609

    Sure they do- all the time! (The efficiency nerds behind CA Title 24 are all over this one, and gawwwll-leee, the subsidies for indirects in oh-so-cold CA are the same as for a tankless.)

    But the keeping the boiler hot all summer is why internal coils in boilers SUCK, and indirects are GREAT. You don't have to keep the boiler hot all summer with an indirect- you fire it when the indirect calls for heat, then let it cool off. With a high-mass boiler it pays to have a higher-mass indirect and set it up for a very large hysteresis to keep the fractional heat abandoned in the boiler small, and guarantee long enough burns that you're not murdering the boiler with cold cycles. But overall it's not much worse than a standalone tank heater in summer, even with a monster-sized cast iron beast. With smaller cast iron boilers it'll beat a standalone tank in summer. Even oil-fired beasts are cold-start tolerant these days.

    But if it's a low-mass boiler like a mod-con the boiler itself is usually smaller burner-wise than a whole-house tankless, better INSULATED than a tankless, and spends far less time idling at temp since it's not being brought up to temp every time somebody washes their hands or rinses out a washcloth. That increased efficiency translates into a LOWER load on your AC than with a tankless (provided the standby loss on your indirect is well controlled. Some is, some ain't... but all can be easily brought up to snuff with additional insulation if need be.)

    The air conditioning load of a 1/2 degree/hr 30 gallon indirect tank by itself is 125BTU/hr or 3000BTUs/day (and then only if it's maintained at 180F! It's half that if kept at 130F). Call it 4K/day for a 40 gallon indirect.

    Care to take a stab at the daily air conditioning load of a single square foot of south facing glazing is in your neighborhood? How about a square foot of skylight? If your neighbor's house is painted white, THAT could represent a higher AC load on YOUR house than a mod-con + indirect!

    It wouldn't surprise me if a tankless + indirect combi beats a standalone tankless on minimizing AC load in summer, provided the indirect & plumbing is well insulated.

    If you want to really get picky, measure the AC load difference between direct-vented sealed combustion tankless is vs. a tankless that uses room air for combustion. (I'd bet that's the same order of magnitude air-conditioning load as the standby loss of a good indirect.) All mod-cons are sealed combustion/direct vented, which would not be true for standard-efficiency tankless units (if true for condensing versions.)

    Don't get me wrong- I have nothing against tankless hot water heaters, but the whole air conditioning load thing with indirects is completely out to lunch. Methinks you're being misled by the issues surrounding tankless coils in boilers, which are a whole other animal, and run at roughly half the summertime efficiency of the same high-mass boiler with an indirect.

    For a comparison of indirects vs. internal coils, see:

    http://www.nora-oilheat.org/site20/uploads/FullReportBrookhavenEfficiencyTest.pdf

    This study models mostly oil-fired WAY oversized cast-iron boilers, which are way less efficient in summer than the oversized gas-fired mod-con they tested (system #11). Smaller units will uniformly test better in water heating mode than bigger units, all other factors being the same. The smallest (90KBTU-in) cast iron oil-fired boiler was tested in both indirect mode and tankless coil mode (systems 12a & 12b) had more than twice the efficiency in indirect-mode than when using it's internal coil for the hot water (24% vs. 51%) , and comparable to a standalone gas-fired tank. (51% vs 57%). The oversized mod-con + indirect made 59%.

    In the real world an 0.82-0.84EF Noritz only runs ~70-75% water-heating efficiency due to the short cycling. And while tankless standby losses are low, they're not lower than a mod-con's. Both are zero during long periods between firings, but the time between firings is longer for the mod-con, and the mod-con is better insulated. If you add the AC load of a non-condensing Noritz's combustion-air infiltration aspect to it's inter-draw losses on hand-washing cycles, etc, are you REALLY sure it's less of an air conditioning load in summer than a right-sized 83% AFUE cast iron boiler + indirect? Less than a sealed-combustion & right sized mod-con + indirect?

    Maybe so, but I'd need a measurement to verify that.

    And they're all a lower AC load than a 10 square feet (one window) of south facing glazing (even the low-E stuff) in most of the US.
     
  13. AAnderson

    AAnderson In the Trades

    Joined:
    Oct 25, 2009
    Location:
    Aptos, CA
    They've taken care of the invoice even though it's taken longer than it should have.
    the service I performed was to replace the unit as it had a leaking heat exchanger and this was not available at the time. Yes they were aware of the problem and David Mills was in on this too.
     
  14. zl700

    zl700 DIY Senior Member

    Joined:
    Aug 26, 2009
    Location:
    Western NY
    Good to hear-

    I suspect they don't cut checks instantly as most companies only run checks once a month, and that only happens if requests are in.
     
  15. Daltex

    Daltex New Member

    Joined:
    Jan 31, 2008
    Location:
    Texas
    One thing that I haven't seen addressed is the disaster potential of the tank type HWH. I have 5 HWH's and 3 are upstairs over living areas. To relocate isn't possible or at least practical. 2 have had massive leaks destroying the lower level. Both were less than 10 yrs. old.

    I have the ability to replace 2 or the 3 upstairs/attic units with gas fired tankless. The 3rd would have to be electric so not interested in tankless there.

    Has anyone heard of tankess blowouts?
     
  16. Dunbar Plumbing

    Dunbar Plumbing Master Plumber

    Joined:
    Apr 18, 2005
    Occupation:
    Service Plumber, Outdoor Temperature Relief Owner
    Location:
    Northern Kentucky/Greater Cincinnati Area

    Both tanks and tankless units, especially in areas where a wood structure is involved counting numerous floors would require a pan. To me, a pan for a tankless is crazy, but those compartments can leak.


    Did those water heaters that blew, did you have them in code approved pans with 1" drains, or area floor drains in the area where they was installed?
     
  17. zl700

    zl700 DIY Senior Member

    Joined:
    Aug 26, 2009
    Location:
    Western NY
    Absolutely!
    Pans and water sensing electronic water shuttoff valves are the way to go
     
  18. Scott D. Plumber

    Scott D. Plumber In the Trades

    Joined:
    Jun 30, 2009
    yep!

    Blowouts?..not exactly. HX failures Sure, plenty of them. Senn them fail from freezing, incorrect instalation and even just plain worn out! Guess what heppens? THEY LEAK! Water pours out of every hole on the bottom at a little over about 1 GPM sometimes...endlessly.

    In fact a certain electric model had so many Chamber failures that they got tossed out of Ferguson Enterprises and are in a big fat lawsuit.

    Everything dies eventually...except old plumbers, we just smell that way.

    this is why The WAll SAver drain pan exists. www.thewallsaver.com
     
Similar Threads: install cost
Forum Title Date
Tankless Water Heater Forum Cost of install for Navien NPE-210A Feb 28, 2017
Tankless Water Heater Forum Opinion on installation for Rinnai Tankless? May 17, 2019
Tankless Water Heater Forum Help with sizing / installing Rinnai RU180in Tankless water heater? Feb 26, 2019
Tankless Water Heater Forum Tankless installation positioning Aug 16, 2018
Tankless Water Heater Forum Navien 240 A install question Jun 6, 2018

Share This Page