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Advice on repl DWH + bb WH, in Illinois

tc60045 Member Posts: 31

Situation - Equipment:

- I have a 75 gallon DWH that takes 75K BTU and has a recovery of 74 gallons.

- Still works, decently efficient, nearing EOL Set to 125 degrees.

- I also have an ELECTRIC WH for a supplemental baseboard hydronic system in our basement. 9k Watts, temperature set to 140 degrees. No problems, except $$$ to run

- Great programmable thermostat for baseboard unit; happy to stagger it to ensure showers take priority in the mornings if I am supply limited.

Situation - Usage:

- DHW is a challenge now that those kids shower in the morning (and wife does laundry)

- Water temperature step-up is brutal during winter time -- I swear I've seen incoming water at 40 degrees, so getting that to 125 in our current WH takes forever.

Request for Your Advice and Counsel: Replacing one or both units...

- Would be great to get rid of both WHs with one, very efficient unit.

- Don't want a full-fledged "boiler" as we only use the baseboard system 5 months a year

- In other words, want a unit big enough to handle winter loads, but not so big it costs us a fortune during warmer months from heat loss

- Seems like a tankless system would be really stretched to handle the morning loads without some storage inline, either warming water on intake or holding HW...

- Condensing storage heaters like the Versa series from HTP look pretty good to me, but I wonder whether these are beasts that will cost a fortune when we aren't using baseboard system.

- Current baseboard hydronic system is closed; converting to potable likely will take some cleaning; I will ask about this in another thread

Appreciate any insights on equipment I should consider, either by class or by brand name / model -- to ensure there aren't any "commercial" endorsements, please feel free to recommend "similar to" and I'll get your meaning.




  • SWEI
    SWEI Member Posts: 7,356
    more info

    about how many kWH do you burn in a year for heating, and what does that cost you per year?

    Do you have a heat loss calculation for the building?  This is critical in order size the boiler correctly.

    What kind of shower heads are in use?  How many at one time?  75k 75 gallon is quite large for a residence.  I'm guessing its performance has dropped a bit over the years.
  • tc60045
    tc60045 Member Posts: 31
    More data for you...


    Thanks for your quick reply. A few notes:

    - the baseboard system is supplemental / secondary...

    - the house is heated with a separate forced air system.

    - why run a supplemental system? forced air through ceilings in finished basement leaves little kids freezing as they play at floor level. Very happy with this setup.

    - baseboard system draws 9KW, which equates to approx 30,000 BTU of heat to our basement, keeping it plenty toasty on cold Chicagoland Winter nights. This system has worked well for years, so 30,000 BTU is a solid number (provided my calc of 9KW to 30K BTUs is solid).

    - three showers @ 2.5gpm can be on in the morning

    That 75 gallon WH has always been a dog -- seems like at 5 minutes into first shower of the day, the temp starts dropping... and dropping... It is lucky to be at 100 degrees by the third shower, and takes an hour to re-heat the tank, despite 75k BTUs. I won't impugn the brand here but I curse it, often. It is supposed to have a dip tube to prevent this from happening. I also drain the tank out annually and have a filter to prevent sediment build-up, btw.

    Also, you said the b-word: boiler. I'm going to be open-minded as I'm a novice to this world, but the thought of a full-fledged boiler for my 125 degree DHW and 140 degree baseboard system makes me nervous... Boiler in concept is different than boiler in name. Staying open-minded....

    Thanks! TC
  • SWEI
    SWEI Member Posts: 7,356
    annual usage

    for that baseboard, in kWH and dollars?

    Thanks for mentioning the forced air primary.  Once we get some numbers on this, I suspect it may make sense to reverse this - using a high efficiency boiler to feed the baseboard as your primary heat source and supplementing that with forced air.  You may need the services of a professional to get this right, but I suspect it will be well worth your time and money.  Proper controls (two stage thermostat at a minimum, possibly something more sophisticated depending on the furnace type, baseboard sizing, room layout, etc.) will be key.

    Before you get much further on a design, please do try out a couple of lower flow showerheads.  I'm partial to the Kohler Forte (K-10240 in chrome) but we see good reports here on both the Delta/Alsons and the High Sierra.  Don't let bad experiences with older low-flow designs color your decision -- a lot has been learned over the past 30 years and the latest crop is quite useable.  Reducing three simultaneous showers from 7.5 GPM to 5.25 (or even 4.5) will make a significant impact on system sizing.
  • tc60045
    tc60045 Member Posts: 31
    moving afield...


    Estimate for you: 9,000 watts times 8 hours of pure heating time during a winter day * 30 days @ 5 cents / kwh is $108 a month for 5 - 6 months. My rough estimate is that gas would cost 1/3 of that, thus we would save $72 / month or $400 - $450 a year in heating just the basement over those few months with a highly efficient gas WH.

    This is a 4,000 square foot house INCLUDING the finished basement -- about 1,000 ft2 basement, 1,600 first floor, 1,400 2nd floor.

    There are zero baseboards on the main floor and zero baseboards on the 2nd floor, thus heating the entire house via the basement baseboards seems implausible and highly inefficient to me: we save energy by letting the basement drop to 64 degrees overnight while the warm air heats (mainly) the 2nd floor.

    The baseboard system, given my estimate above, would require 30,000 BTU for 8 hours of the day during the winter months. Yes an average and yes a guesstimate.

    Thanks for tips on the showerheads -- happy to try some.
  • SWEI
    SWEI Member Posts: 7,356

    Did not realize you had only partial coverage with baseboard.

    The vast majority of domestic water heating appliances are not code approved for space heating.   On top of that, at least 95% of those with an "H" stamp which I have seen are installed in a manner which either delivers poor comfort, damages the heater, or is dangerous -- or several of the above.
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