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OK to downsize water heater?

malex
malex Member Posts: 106
Time to replace 10+ year old Rheem gas water heater. It's a 50 gal 40K BTU unit and it's never given any problem for our 3 person hh. Recently, after all 3 took showers back to back it did run out of hot water and out came rusty water - hence the kick in the butt to replace the aging heater...

I've been looking at the Rheem Platinum 40 gal 38K BTU unit - I assume efficiency has gone up in the past 10 years and I am not one to want to heat an extra 10 gal on standby but wonder if it will match the old heaters delivery. The spec sheet says it will work for 2-4 person hh and 50 gal is for 5 people+...

Thoughts? Also, are there any better alternatives to the Rheem Platinum 40 gal/38K BTU unit in the same price range?

Thank!

Comments

  • george_42
    george_42 Member Posts: 97
    use either a 40 or 50 gal and set output temp to about 150 or so to kill legionnaires bacteria and put a mixing vale to deliver 120 deg water and you will have all the hot safe water you need
    HVACNUT
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 8,853
    @malex

    40 gallon should be fine for three people. Back to back showers or showers and washing machine could be an issue but if usage is reasonable you will have no issues. They have the same size burners so not much difference
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,129
    edited March 2020
    Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out. B)

    Yours. Larry
  • Steamhead
    Steamhead Member Posts: 14,424
    With the lower burner input, you may run out of hot water more often.

    You are correct that water heaters are more efficient now. If that were my house, I'd stick with a 50-gallon unit.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • ChrisJ
    ChrisJ Member Posts: 11,549

    Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out. B)

    Yours. Larry


    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    mattmia2icy78
  • hot_rod
    hot_rod Member Posts: 14,753
    ChrisJ said:

    Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out. B)

    Yours. Larry


    Cast iron radiator behind Jerry :)

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    ChrisJSuperTech
  • ChrisJ
    ChrisJ Member Posts: 11,549
    hot_rod said:

    ChrisJ said:

    Hi, You might test flow from the shower head and if it’s over 2.5 gpm consider getting a 1.5 gpm head that has the Water Sense certification. If you switch to a lower flow head, you can go to the smaller heater with very little concern about running out. B)

    Yours. Larry


    Cast iron radiator behind Jerry :)

    Clow gas steam my friend.
    That's got a built in boiler.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    mattmia2
  • malex
    malex Member Posts: 106
    Thanks all - i'll consider sticking with 50 gal or suffer Kramer hair with the lo flow head... only on the wall will a Seinfeld meme turn into a conversation about Jerry's cast iron radiator...
  • mattmia2
    mattmia2 Member Posts: 2,869
    There is a thread about them on here somewhere from about 10 years ago.
  • mikeg2015
    mikeg2015 Member Posts: 1,181
    Basic atmospheric Tank water heaters have a little more insulation now but the basic burners haven’t changed in 20 years. About 75-80% efficient. But why are cheap. So no payback for fancy ones.
  • ChrisJ
    ChrisJ Member Posts: 11,549
    > @mikeg2015 said:
    > Basic atmospheric Tank water heaters have a little more insulation now but the basic burners haven’t changed in 20 years. About 75-80% efficient. But why are cheap. So no payback for fancy ones.

    I'd be more concerned about the heat going up the chimney than the tank insulation or burner design. There's a ton of heat going up that pipe when the burner is off.

    My power vented 50 gallon stayed impressively hot without power for 3 days
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 2,869
    My power vented 50 gallon had a ton of standby loss compared to my Superstore.

    Conventional gas and electric water heaters used to be cheap, but between the price of metals and oil skyrocketing and requirements to suppress ignition of vapors they are about triple the cost of what they were 20 years ago and making alternatives competitive.
  • mikeg2015
    mikeg2015 Member Posts: 1,181
    We replace a lot of parts on power vents. The increase in installed cost probably results in about a 8-10 year payback or longer. Not really worth it in my opinion. A good option for new construction or if you are avoiding reclining a chimney however.
  • hot_rod
    hot_rod Member Posts: 14,753
    Hopefully those power venters are not PVC vented. The high temperature that migrates up after a burner off cycle can really cook the PVC. Perhaps the worse application of PVC for venting flue gas.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    mattmia2
  • ChrisJ
    ChrisJ Member Posts: 11,549
    edited March 2020
    > @hot_rod said:
    > Hopefully those power venters are not PVC vented. The high temperature that migrates up after a burner off cycle can really cook the PVC. Perhaps the worse application of PVC for venting flue gas.

    Both mine and my parents are done in PVC exactly as Bradford White said to in the manual and there's no signs of overheating.

    I'm also almost positive the blower continues after the burner shuts down for some set period.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    mattmia2
  • hot_rod
    hot_rod Member Posts: 14,753
    ChrisJ said:

    > @hot_rod said:

    > Hopefully those power venters are not PVC vented. The high temperature that migrates up after a burner off cycle can really cook the PVC. Perhaps the worse application of PVC for venting flue gas.



    Both mine and my parents are done in PVC exactly as Bradford White said to in the manual and there's no signs of overheating.



    I'm also almost positive the blower continues after the burner shuts down for some set period.

    Sure a post purge helps, may as well send more of your heating dollars up the flue.
    It's the glue joint that can fail, hard to see and predict that. The flue gas temperature in that center flue water heater is well, well beyond the 140F PVC temperature rating. Mod cons don't generally produce much over the operating temperature of the boiler. If and when they do, time to clean the HX

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ChrisJ
    ChrisJ Member Posts: 11,549
    edited March 2020
    > @hot_rod said:
    > (Quote)
    > Sure a post purge helps, may as well send more of your heating dollars up the flue.
    > It's the glue joint that can fail, hard to see and predict that. The flue gas temperature in that center flue water heater is well, well beyond the 140F PVC temperature rating. Mod cons don't generally produce much over the operating temperature of the boiler. If and when they do, time to clean the HX


    The blower mixes cool air in to cool the exhaust.

    The joints are solvent welded. Why would they fail before the pipe?

    Regardless in my case and my parents I'm not concerned. We both keep an eye on things and would likely catch it early.

    When I replace my heater if they call for a different material I'll use it otherwise it's staying.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • mattmia2
    mattmia2 Member Posts: 2,869
    The power vent part outlasted the tank at about 18 years although it was starting to sometimes go out for reasons i didn't want to figure out. Everything looked ok with the burner and the connections and solder joints on the control. i decided it was time to work on the boiler project more quickly when that started happening.

    The PVC did not look so great.




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