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Tankless system to replace hot water tank and furnace?

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sadbttru
sadbttru Member Posts: 1
in THE MAIN WALL
Hi!

I have read through a page of topics and don’t know if this has been discussed or asked before so here we go...

My gas furnace and hot water tank (rental) and AC were all added to house when it was built 15 years ago. My hot water is a 75 gal tank and we are a family of 5. We have never had an issue with the tank or supply. Recently I was informed I might want to think about updating the tank as it had lived its life. In doing so we wanted to think about getting out of the hot water tank rental and buy a new efficient system.

We discussed with an recommended installer a tankless system that would also replace my furnace. I don’t know much about either and let him know that I did not want to notice a decline in heat or hot water.

Is there any sites anyone can recommend to learn more about this and is this a good way to go?

Thanks so much for any help.

I arrived here by searching and can’t seem to find the right key words. Started with tankless replacing furnace but mostly that leads to radiant heat. I want to use it to replace my forced air furnace.

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  • Ironman
    Ironman Member Posts: 7,376
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    A tankless (instantaneous) water heater won't replace a forced air gas furnace. They're two completely different animals.

    However, there are Hydronic Air Handling Units which can be paired with a tankless for space heating if certain conditions are met. The cost for replacing the gas furnace with the hydro AHU is usually greater than the furnace would cost and it could greatly limit your a/c options. Therefore, it's not something that I would generally recommend.

    Some caution about tankless even though we do them:
    1. Hard water is very detrimental to them and can require frequent de-scaling. This can be expensive and will more than out-weigh the amount of energy savings they purport.
    2. Pairing an AHU and tankless instead of a separate gas furnace means that if the tankless goes down, you have no space heating either.
    3. If you choose a tankless, make sure that isolation valves are installed so that it can be de-scaled when needed.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • JUGHNE
    JUGHNE Member Posts: 11,062
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    You mentioned concern about efficiency.
    What efficiency rating is the forced air furnace......the type of chimney connection would give an indication. Metal pipe or PVC plastic.

    Same question for the water heater.......

    If you are not sure pictures would help.

    Where are you located?
  • HVACNUT
    HVACNUT Member Posts: 5,841
    edited March 2020
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    @sadbttru , Metallica?
    You currently have a gas fired warm air furnace, with A/C, and a 75 gallon gas water heater?
    The water heater is direct fired? Meaning the tank has a chimney?

    I don't understand what "rental" and "supply" mean. You rent the water heater?

    If you feel the need to upgrade the heating and air conditioning, you still need a furnace, a new evaporator coil, new refrigerant lines, and new condenser.

    For domestic hot water, you can do a tankless or tank. Heat pump, power vent, atmospheric.

    Explain your situation a little more and in return you will receive a plethora of top notch information. Not from me, but other guys.

    NTI and others make a combi furnace. I make no claims. Just throwing it out there.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,306
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    Hello, Water heater rentals are not uncommon in Canada. If it were me, I'd be looking at the cost per delivered BTU for both gas and electricity and use that to help with a decision. If the furnace and AC are working properly and have more years in them, just looking at replacing the water heater might make sense. Drain-water heat exchangers are common there and could allow you to downsize your water heater, so could be worth looking into as well.

    Yours, Larry
  • mikeg2015
    mikeg2015 Member Posts: 1,194
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    Hydronic Air handlers cost as much as a 96% furnace, but realistically will only be 90% efficient on a tankless.

    It’s a kinda ok solution in a condo or highly insulated home where heating load is under 20-30k BTU. But still better to use a Combi boiler in that case. The internal pump can usually handle pumping directly to the AHU and all the interna controls are there already along with outdoor reset.

    But it;s still less efficient than a small 45k BTU furnace.

    The tankless and furnace will both vent in 2” PVC if near a wall or roof.

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