Home Heating Tips to Save Money?

Discussion in 'Tankless Water Heater Forum' started by Robenco15, Mar 12, 2018.

  1. Robenco15

    Robenco15 New Member

    Joined:
    Mar 12, 2018
    Location:
    Connecticut
    Hi all,

    Bought my home this last July in CT. It came with a Navien CH-210 tankless water heater set up in the basement and running well. It does our hot water and heats our home (baseboard heating).

    I don’t know much about how it works, but I do know that for it being an efficient heating method, my propane gas prices this winter have been $600-700 a month, some worse than others.

    I have an 1888 home around 1400-1500 square feet. It is definitely leaky, and I’m sure that is the primary culprit of my high heating costs (along with this cold weather), but I would love any and all tips that I might be able to do to keep my Navien from using so much fuel so quickly. It really eats it up.

    Since I’ve had the Navien the heating supply has been set at 180F. Would turning it down to 160F or lower save me fuel costs?

    I tend to put the thermostat down to 62F at night and then 68-70F when I’m home. The thermostat always reads around 2-4 degrees lower, but it is an old thermostat. Is that large change in temperature working the Navien too hard and ruining it’s efficiency? Am I better off keeping it at 65F or at least going from 62F to 65F to 68F?

    Thank you for any insight. Cost of installation for the basement and first floor is almost $7k, so I can’t really entertain that any time soon. Appreciate any help!
     
  2. Dana

    Dana In the trades

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    Jan 14, 2009
    Location:
    01609
    Of course the biggest problem is the high expense of using propane as a heating fuel, but you can definitely do better. At 180F the thing is never in condensing mode, probably running 85-87% efficiency instead of 90-95%. Dropping it to 160F won't move the needle much.

    To get condensing efficiency out of the Navien the temperature has to be turned down to under 130F so that it delivers an entering water temperature at the boiler under 125F. If you have enough radiation to emit the full minimum-modulated output of the Navien with water temperatures that low without short cycling it into low efficiency and an early grave, that would the right place to start. If the boiler doesn't already have, it, installing the outdoor temperature sensor and tweaking in the "outdoor reset" curve can get the boiler to raise the water temperature as-needed to something higher.

    With outdoor reset adjusted perfectly it's more efficient to "set and forget" the thermostat, since recovering from setbacks requires higher temperatures (=lower efficiency.)

    Run the napkin math on the system/zone radiation against the 18-19,000 BTU/hr minimum fire output of the Navien as well as the fuel use heat load calculation on some wintertime fill-ups and report back. With the baseboard lengths (by zone, if multi-zoned) and load number it's possible to estimate the water temp needed at your 99% outside design temperature, and the lower water temperature at which it would likely exhibit short-cycling behavior.

    If you haven't already, download and archive a copy of the installation manual for future reference.

    At CT style propane & electricity prices better-class cold climate ductless mini-split heat pumps are cheaper heat than condensing propane. If you're considering adding air conditioning a mini-split or two can take a bite out of the heating costs, if sized correctly.
     
    Last edited: Mar 13, 2018
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  4. Robenco15

    Robenco15 New Member

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    So I should really turn the supply down to 125-130f? That won’t be too low to actually heat my home?

    I don’t think it has an outdoor temperature sensor.
     
  5. Dana

    Dana In the trades

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    Location:
    01609
    Yes you should turn the temperature down. Whether that's too low to actually heat your house is why you have to do at least the napkin math on the load & radiaiton. Click on the links in the previous post on how to do that, or post the total length of baseboard (zone by zone) here, and the exact dates & amounts of propane fill-ups (wintertime only), and your ZIP code (for weather data) and I'll run the numbers for you.

    A temp of 125F can almost certainly heat your house when it's a mild 45F outside, but maybe not when it's 0F out, which is why the outdoor temperature sensor and adjusting the outdoor reset curve would be useful.
     
  6. Ladiesman217

    Ladiesman217 Member

    Joined:
    Dec 31, 2010
    Location:
    MA
    Fiddling with the furnace will not save you any big money.

    How air tight are your doors and windows? Air does not leak through walls.

    How many floor levels are there in the house?

    Is your attic accessible? If so, you could start insulating the ceiling area of the house.
     
  7. Robenco15

    Robenco15 New Member

    Joined:
    Mar 12, 2018
    Location:
    Connecticut
    Thank you so much. This is so far above my head so I really, truly appreciate it.

    I have 4 zones:

    Zone 1 - 30.25'
    Zone 2 - 23.5'
    Zone 3 - 40'
    Zone 4 - 50.5'

    Propane Deliveries and Amounts:

    10/18/17 - 44.7 gallons
    11/10/17 - 67.6 gallons
    12/01/17 - 109.9 gallons
    12/19/17 - 121.9 gallons
    12/29/17 - 90.1 gallons
    1/05/18 - 87.9 gallons
    1/19/18 - 128.8 gallons
    2/01/18 - 95.6 gallons
    2/13/18 - 96.8 gallons
    2/27/18 - 69.5 gallons
    3/19/18 - 64.4 gallons

    Zip Code is - 06851

    Like I said, house was built in 1888 and probably pretty leaky and not that well insulated. Also, the LCD keypad things allows me to adjust the hot water temperature for the faucets and the heating supply for the baseboard heat. I don't seem to be able to adjust anything else through it.

    Thank you again!
     
  8. Robenco15

    Robenco15 New Member

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    Location:
    Connecticut
    Windows are new and not leaky. I have two doors that go to the outside that may be a little leaky and I will be addressing that come Spring/Summer.

    2 floors plus basement. 2nd floor was apparently where the attic was, but it is now the Master Bedroom and Bath. I'm assuming that because it was a recent addition it is well insulated compared to the lower level of the home.

    Maybe not big money, but if I have a nice efficient tankless water heater that I haven't been even been using correctly to maximize its performance, I'd like to fix that.
     
  9. Dana

    Dana In the trades

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    Location:
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    Right now the zone radiation isn't enough to emit the 17.5K (non-condensing) minimum fire output. At 180F out, 170F average water temperature (AWT) the fin-tube baseboard emits about 500 BTU/hr per running foot, so by zone even at high-temp it's emitting

    Zone 1: ~15,000 BTU/hr
    Zone 2: ~12,000 BTU/hr
    Zone 3: ~ 20,000 BTU/hr
    Zone 4: ~ 25,000 BTU/hr

    It won't short cycle on zones 3 & 4, but unless calls for heat overlap with other zones it's going to cycle bit on zone 1, and cycle a LOT on zone 2.

    At 120F AWT the baseboard puts out about 200 BTU/hr per running foot, so with 144' of baseboard it can run at 120AWT in condensing mode and not cycle, if operated as a single zone, or if all zones are calling for heat at the same time.

    If it's able to heat the house with 180F water, since your radiation is only emitting at most 72,000 BTU/hr (@ 170F AWT) with all zones calling for heat. From experience the odds are pretty good that the design load is actually about half that, at Norwalk's 99th percentile temperature bin of +9F. (Yes it gets colder than that, but only for ~87 hours in a typical year.)

    Looking at the period beginning 12/1 through 2/27 you used 690.6 gallons of propane. At a source fuel content of 91,600 BTU/gallon and a combustion efficiency of 87% that means you used

    690.6 x 91600 x 0.87= 55,035,295 BTU for heat (+ hot water, etc, but primarily heat)

    Station KBDR (Sikorsky Airport) logged 2816 HDD between 2 December and 27 February, and 2811 HDD between 1 December and 26 February. Averaging them together reduces the error related to the unknown time of day the fill ups occurred (but it's a small error over that large a period anyway.) So assume it's 2814 HDD.

    55,035,295 BTU/2814 HDD = 19,588 BTU/HDD

    In a 24 hour day that's 19,588/24= 815 BTU/ degree-hour.

    Load increases approximately linearly with temperature below the presumptive heating/cooling balance point of 65F (the HDD base, appropriate for an older, leaker less insulted home.) So the difference between the balance point and your 99% outside design temp of +9F is (65F - 9F=) 56 heating degrees...

    ...for an implied load of:

    815 BTU/ degree-hour x 56 degrees= 45,640 BTU/hr.

    So with 144' of baseboard that's 45,640/144= 317 BTU/hr per foot of baseboard.

    Typical baseboard will emit about that much at an AWT of about 140F (150F out, 130F return), so even at design condition you won't need water temperatures higher than 150F.

    But that's still above the condensing zone so it would take implementing the outdoor reset function to get it to run in condensing mode most of the time, breaking into the low 90s for average seasonal performance. But it will also take combining zones or dialing in the curve perfectly for it not to short cycle at low temp.

    A 45K heat load for a 1500' house is ridiculously high, twice that of a 2x4 framed INSULATED reasonably tight house with wood sash windows + storm windows. Air sealing is the lowest possible hanging fruit, but wall insulation comes next. If it's a bunch of leaky single panes, no storms, putting tight low-E storm windows over the exterior will bring the performance up close to current code-min for less money than a code-min replacement window.

    Harvey Tru-Channel is the tightest storm windows in the industry, and has a low-E glazing option. The low-E glass is an upcharge, but the "payback" is shorter than uncoated clear glass.

    If the foundation isn't air sealed & insulated, that could be as much as 20-25% of the total heat loss, depending on the air leakage and amount of above-grade exposure. The correct approach to insulating it depends on the foundation type & details.

    If it's a framed house with plank sheathing between the framing and siding it's usually possible to insulate the cavities with blown cellulose, which would also reduce air leakage, and could easily be another 20% or more of the heat loss.
     
  10. Dana

    Dana In the trades

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    Location:
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    If's a boiler, not a furnace. A furnace blows hot air.

    Air sealing the ceiling and basement is a first prerequisite to adding insulation. Insulation in the a leaky attic will get wet.

    Air absolutely DOES leak through walls, especially framed walls that have no insulation in the cavities, and BIG TIME through balloon framed walls with cavities that extend from the basement to the attic. The most important leaks are at the bottom and top of the house, since that's what defines the 24/365 stack effect pressures that drive infiltration even when there is no wind (rare, in coastal Norwalk.)
     
  11. Robenco15

    Robenco15 New Member

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    Location:
    Connecticut
    Alright, I’m going to read that a few times to really get a handle on it, but for right now should I raise the temp. from 125f to 140f or would just putting it back to 180f just be the same and cost me no more or less?
     
  12. Ladiesman217

    Ladiesman217 Member

    Joined:
    Dec 31, 2010
    Location:
    MA


    I knew that it was a boiler. Typo. I was thinking about my 60 year old gas furnace and instantaneous gas water heater fuel cost with a similar sized 1950's vintage house in MA. I estimate that I am around $1,200.00 annual for cost of ng. I would have to go through my bank statements to be sure.

    The temperatures in MA in and around January this year were much colder than a typical year. I am not sure how the heating cost will average out for the year.

    I assume that there is adequate "attic" insulation and wall insulation in the upper level. Windows are fine. I am not sure if the basement is finished and heated as a zone.

    If the basement is unfinished, drafts can easily be felt in the basement. Years ago I found a decent size draft in a single drain/vent pipe that went up an exterior wall to the roof through the attic. The draft froze a water pipe at one time during an extra cold weather period.


     
    Last edited: Mar 13, 2018
  13. Robenco15

    Robenco15 New Member

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    Location:
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    Would it be worthwhile to at least get my basement insulated? That was quoted at $1500, but we were told that would only make the first floor worse off and therefore if we were going to do the basement we should do the 1st floor as well.
     
  14. Dana

    Dana In the trades

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    Air sealing and insulating the basement walls doesn't make the first floor worse off, but it's not as high a priority as insulating the first floor walls. Both matter. The order in which you do it doesn't matter, but if you're only going to do one, insulate the first floor walls.

    Insulating the basement ceiling (first floor's floor) would be a mistake, especially if the boiler and pipes are in the basement where they might freeze. Insulating between the basement and first floor can increase energy use if there is heating system plumbing in the basement, since the distribution losses are then actually lost rather than staying inside the insulation boundary of the house.

    Insulating a basement has many pitfalls if not done correctly. Last thing you want is to turn it into a mold farm. That topic has been covered at length in multiple threads here, but with more information about your basement construction and foundation type I could go over in a more focused fashion.

    Installing the outdoor temperature sensor is low money, and worth doing. Take the time to figure out how to set up the reset curve, and pay attention to the boiler's behavior at low boiler output temperatures. If the burns are substantially less than 3 minutes and more than 10 burns per hour it's giving up quite a bit of the condensing efficiency and putting wear & tear on the boiler. Don't expect an HVAC tech to set up the outdoor reset curves correctly for you- that (almost) never happens. But it's not rocket science to play around with it until you find the right balance.

    Ladiesman217: Despite the early January bitter cold snap, the mean temperatures in January in eastern MA was slightly above the 25 year average. This has been a warmer than average heating season so far, with February WELL above average.
     
  15. Ladiesman217

    Ladiesman217 Member

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    Your charts are not valid for my location. Those charts apply to Boston at Logan Airport. Boston temperatures are moderated by the "warm" water of the Atlantic Ocean.

    Compare the the lows of the day between Boston and Framingham in late Dec and early Jan. Kind of a big difference in temperatures. Another 20 miles inland makes a big difference in temperature as well as snow fall.

    My gas bill runs from 20th to the 19th of each month.

    My monthly Dec and Feb therms used have been pretty steady for the last three years.

    My Jan 2018 therms used was more than 25% above the previous two years monthly therms used. I have not touched the thermostat for years except to change the battery.
     
    Last edited: Mar 13, 2018
  16. Dana

    Dana In the trades

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  17. Ladiesman217

    Ladiesman217 Member

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    Dec 31, 2010
    Location:
    MA
    Low temperatures were about 30° F below average late December 2017 thru early January 2018. Temperature hung around the lows most of the time. The low of -14°F on Jan 2nd was very unusual for this area.

    Total gas therms used were up over 25% when compared with previous two years for the Jan 2018 gas bill (12/20/17 - 1/19/2018). The gas therms used for Dec 2017 bill and Feb 2018 were normal.

    I suspect that the OP had higher than usual gas usage for the same reason.



    December 2017

    Framingham-Dec-2017.jpg


    January 2018

    Framingham-Jan-2018.jpg
     
  18. Ladiesman217

    Ladiesman217 Member

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    Dec 31, 2010
    Location:
    MA

    Does that mean you use 4 thermostats (aka 4 zones) to control your heat?
     
  19. Dana

    Dana In the trades

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    Four thermostats would be my interpretation.

    Zoning it floor by floor probably makes the most sense, especially if air tightness and insulation of the re-worked former attic second floor is a lot better than the first floor. In some houses it's possible to run it all as a single zone.

    Is the second floor have insulated kneewalls and vented mini-attic spaces?

    If yes, it's very common to have HUGE thermal bypass channels between the joists, moving outdoor air in the venting from one side of the house to the other under the floor and out the other side whenever the wind blows. Air sealing those joist bays as a retrofit is difficult to do well, often a fool's errand (speaking as one who has played the starring role of "fool" multiple times in those situations.)
     
  20. Robenco15

    Robenco15 New Member

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    Mar 12, 2018
    Location:
    Connecticut
    Yes, 4 thermostats.

    One is kitchen and living room, one is back sunroom, one is 1st floor bedrooms (2) and bathrooms (2), and one is upstairs bedroom and bath. Usually onlu adjust the living room and kitchen one. Only use 1st floor bedrooms when people visit.

    It’s been on 125f for over a day now and while I don’t hear the water heater basically at all (compared to when it was at 180F) When I’m in the living room above it, I’m not sure 125f is hot enough to actually heat my living room and kitchen (where I’ve been using the thermostat the most).

    Should I move it to 140F or would that just be no different in terms of efficiency as 180F?

    Also, January was terrible. Pipes froze and everything. Week long stretch of staying around and below zero.
     
  21. Ladiesman217

    Ladiesman217 Member

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    Dec 31, 2010
    Location:
    MA
    What was your propane use during the off heating season? That will give you an average monthly amount of propane used for hot water.

    Propane deliveries from August through Nov 2017.
     
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