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indirect heat hot water tank vs. tankless coil heated on demand hot water - oil

gnagyg
gnagyg Member Posts: 15
edited August 2020 in Oil Heating
I am surprised that there is not an online tool out there, that helps you determine what is the smartest way to heat hot water, depending on your lifestyle. We are just two people who live in a house in New York. Four to six months out of the year we usually travel. We take showers in the morning and probably twice a week we do laundry. The dishwasher is run every other day. for every thing else we use cold tap water. we have a well. baseboard heat. 2600 sqft. should I really spend $ on an indirect heat water tank?

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 1,819
    edited August 2020
    Depends on your fuel bill.

    What are you currently using for Domestic Hot Water (DHW), the tankless in your oil fired boiler?

    While you are away, is the boiler needed to keep the pipes from freezing?

    I have a few simple inexpensive tricks to reduce your fuel bill without spending $$$ on an indirect. BTW we don't discuss price on the Wall. but your question has merit. the tankless water heater in a boiler is about 75% lower in cost than the Indirect. The operation cost of the tankelss is somewhat higher. The boiler is connected to a chimney that is removing heat from the boiler that is maintaining temperature for hot water. the burner might operate 5 to 7 times a day while you are away (not using any DHW) to maintain the temperature that is lost up the chimney.

    The indirect DHW tank is not connected to the chimney, so when the tank is hot and the burner shuts off and you are not home, the burner stays off and the boiler cools down. The water in the tank will loose about 10°F over a 20 or 25-hour period before the thermostat in the tank turns the boiler on to heat the tank up again. That can be a substantial saving.

    If you use 2000 gallons per year to heat and do hot water, there is a definite saving with the indirect tank. If you only use 500 gallons per year to heat and hot water then not so much!


    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    psb75
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 1,819
    edited August 2020
    Other considerations:
    *Well-water tends to have more build up on tankless coils.
    *Absentee owners away in the winter months should have some kind of monitor to protect from frozen pipes. A neighbor, the Honeywell Winter Watchman + a neighbor. or an internet thermostat.
    *Turn off the water when you are away for an extended time, even in the warm weather. A washing machine hose failure can happen at any time.
    * What is the reason for the Query? Are you changing boilers now? or just repairing the existing DHW system?
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • gnagyg
    gnagyg Member Posts: 15

    Depends on your fuel bill.

    What are you currently using for Domestic Hot Water (DHW), the tankless in your oil fired boiler?


    yes.

    While you are away, is the boiler needed to keep the pipes from freezing?

    i turn off the water at the pump, open the faucets and set the thermostat to 45F. there is antifreeze in the pipes ...

    I have a few simple inexpensive tricks to reduce your fuel bill without spending $$$ on an indirect. BTW we don't discuss price on the Wall. but your question has merit. the tankless water heater in a boiler is about 75% lower in cost than the Indirect. The operation cost of the tankelss is somewhat higher. The boiler is connected to a chimney that is removing heat from the boiler that is maintaining temperature for hot water. the burner might operate 5 to 7 times a day while you are away (not using any DHW) to maintain the temperature that is lost up the chimney.

    The indirect DHW tank is not connected to the chimney, so when the tank is hot and the burner shuts off and you are not home, the burner stays off and the boiler cools down. The water in the tank will loose about 10°F over a 20 or 25-hour period before the thermostat in the tank turns the boiler on to heat the tank up again. That can be a substantial saving.

    If you use 2000 gallons per year to heat and do hot water, there is a definite saving with the indirect tank. If you only use 500 gallons per year to heat and hot water then not so much!

    slightly less than 500 G a year.



  • gnagyg
    gnagyg Member Posts: 15

    Other considerations:
    *Well-water tends to have more build up on tankless coils.
    *Absentee owners away in the winter months should have some kind of monitor to protect from frozen pipes. A neighbor, the Honeywell Winter Watchman + a neighbor. or an internet thermostat.

    nest thermostat. antifreeze in the pipes. very nice and helpful neighbors :-)

    *Turn off the water when you are away for an extended time, even in the warm weather. A washing machine hose failure can happen at any time.
    * What is the reason for the Query? Are you changing boilers now? or just repairing the existing DHW system?

    We have to replace the existing boiler and I was surprised, how difficult the decision was. I got three bids, spent hours on the internet, talked to friends and still feel overwhelmed (admittedly, I started out totally clueless).

    I expected this to be pretty straight forward. lol!

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 1,819
    edited August 2020
    A 500 Gallon or less usage leads me to recommend a tankless coil. Also since you already use a coil, the well water must not be causing any problems.

    If you are away for an extended time during the cold weather, you can turn the DHW low limit to 110°F (or the lowest setting) while you are away. This will reduce the operating temperature and standby loss. If your control has the setting to set the low limit to OFF then that is even better. Most OEM Controls don't but an aftermarket control will.

    If you are absent during warmer weather then just shut off the switch and you won't be making hot water or heat at all. You won't be able to turn on the system by the WiFi if you do that, but you won't use any fuel oil either.

    If your new system is equipped with HydroStat MODEL Temperature Limit / LWCO Control with Thermal Targeting™ for Water Boilers, I believe that you can adjust the low limit by adjusting a dial inside the cover. Now, these dials are not designed to be operated regularly. That said, you will want to take care when making temperature adjustments from the 160° to the 110° or OFF position from the occupied to the unoccupied times.





    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 1,819
    edited August 2020
    On older analog aquastat controls, I was able to install a toggle switch to disable the DHW during unoccupied times. The homeowner would just flip the switch to turn on the hot water. upon leaving for extended times they switch off the hot water. That won't work on digital devices, however, there are other options using the ZR terminal on these newer digital controls

    I would need the model of the new boiler for a more detailed description.
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • "We have to replace the existing boiler and I was surprised, how difficult the decision was. I got three bids, spent hours on the internet, talked to friends and still feel overwhelmed (admittedly, I started out totally clueless)."

    Pretty normal.

    Personally, I try not to get hung up on DHW efficiency. My family spends about $25 per month for DHW and I don't see the point on spending thousands of dollars to reduce the cost to $20 or even $15 per month.

    @EdTheHeaterMan makes some excellent comments for winterizing and longevity.

    If you still want to go over boiler selection, let us know which ones have been recommended and some details of your house, i.e. how many square feet, what kind of emitters (baseboard, radiators, radiant, fan coils)?
    Often wrong, never in doubt.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,272
    edited August 2020
    To learn more about this professional, click here to visit their ad in Find A Contractor.
    STEVEusaPASuperTechszwedj
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 1,819
    I did not have a lot of experience with System 2000 or Energy Kinetics during my career in oil heat. However, I was impressed with the design. They were somewhat more costly back then but the lower operating cost was a reason to consider them. I did finally have the opportunity to install one several years ago... and was impressed.

    Their new Ascent Combi- boiler looks like a good choice if there is a servicing dealer near you. They advertise a competitive cost to install one.
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
    szwedj
  • gnagyg
    gnagyg Member Posts: 15

    A 500 Gallon or less usage leads me to recommend a tankless coil.

    :-) that’s what we decided on getting. But pretty much everybody I talked to told me: you have to get an indirect water heater tank.




  • gnagyg
    gnagyg Member Posts: 15
    :-) will be installed on August 13.
    HVACNUTSTEVEusaPAszwedj
  • SuperTech
    SuperTech Member Posts: 1,582
    gnagyg said:
    https://energykinetics.com/ascent-combi-boiler/ Most efficient oil fired DHW
    :-) will be installed on August 13.

    You will not be disappointed. Make sure the installed installs a scale stopper and sets up the burner with a digital combustion analyzer.  The fuel savings from going from a boiler with a tankless coil will be huge. This is a fantastic boiler in my opinion. 
    szwedj
  • HVACNUT
    HVACNUT Member Posts: 3,802
    Post before and after pics. 
    Robert O'Brien
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,272
    edited August 2020
    SuperTech said:


    gnagyg said:

    :-) will be installed on August 13.

    You will not be disappointed. Make sure the installed installs a scale stopper and sets up the burner with a digital combustion analyzer.  The fuel savings from going from a boiler with a tankless coil will be huge. This is a fantastic boiler in my opinion. 

    Never see a scale stopper on Long Island and have never had a scaled HX. Maybe that's why we have the best rolls, bagels and pizza? :)
    To learn more about this professional, click here to visit their ad in Find A Contractor.
    STEVEusaPAEdTheHeaterMan
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