Can I add a tankless hot water heater to my existing furnace system?
December 6, 2014 10:44 AM Subscribe
I have an existing gas furnace system and a separate gas hot water heater. I'd like to get rid of the hot water heater because it is taking up too much room, and I want to use that space to fit in a washer and dryer. I have another house where the furnace and the hot water heater are all the same unit without a tank. Can someone modify my existing furnace to attach a tankless hot water unit to my existing furnace, or do I have to buy a whole new furnace to have one that integrates it?
Normally, a combined heat/hot water solution would use hot water heat rather than forced air; a single boiler unit (often tankless) can supply both hot water for heating and hot water for in-house use. A conventional forced air furnace can't be modified to heat water, and while theoretically possible it'd be pointless to put a hot water coil driven by a boiler on a conventional furnace.
That said, tankless hot water heaters are much smaller than tanks, and usually mount on the wall, so you don't need to necessarily replace the furnace to get the space savings. So I would suggest simply asking contractors if they could install a tankless such that there's space for your washer dryer. Suggesting integration will confuse matters and waste everyone's time.
posted by doomsey at 11:11 AM on December 6, 2014 [3 favorites]
That said, tankless hot water heaters are much smaller than tanks, and usually mount on the wall, so you don't need to necessarily replace the furnace to get the space savings. So I would suggest simply asking contractors if they could install a tankless such that there's space for your washer dryer. Suggesting integration will confuse matters and waste everyone's time.
posted by doomsey at 11:11 AM on December 6, 2014 [3 favorites]
Seconding that you just want to install a tankless gas hot water heater. They are quite small and wall mounted.
posted by ssg at 11:33 AM on December 6, 2014 [1 favorite]
posted by ssg at 11:33 AM on December 6, 2014 [1 favorite]
Just to be clear, when you say furnace do you mean an appliance that provides hot air delivered through ducts or do you mean an appliance that heats water which goes to radiators or baseboard? I ask because I have never heard of a combined furnace hot water heater.
posted by Pembquist at 12:01 PM on December 6, 2014 [2 favorites]
posted by Pembquist at 12:01 PM on December 6, 2014 [2 favorites]
2nding the questions above: do you have a forced-air gas furnace or a boiler that runs your baseboard heating? If the latter, then yes, you can get a combined tankless hot water heater/boiler--I've got one sitting in my basement at this very second. (As I discovered last winter, it starts to lose efficacy when the temperatures drop below 20 F for an extended period of time.)
posted by thomas j wise at 1:32 PM on December 6, 2014
posted by thomas j wise at 1:32 PM on December 6, 2014
Response by poster: To clarify - the heat in my house is hot water, not hot air.
posted by cmp4Meta at 1:43 PM on December 6, 2014
posted by cmp4Meta at 1:43 PM on December 6, 2014
Response by poster: I have a boiler for the hot water heating - my question is whether they have some kind of attachment for the existing boiler that will let it also take over the job of being the water heater. I don't want to buy a separate tankless hot water system - I am wondering if this is an add-on that could be attached to my existing boiler.
posted by cmp4Meta at 1:45 PM on December 6, 2014
posted by cmp4Meta at 1:45 PM on December 6, 2014
There is a difference between keeping the same water in your hot water heating system, and running your domestic hot water through it.
A domestic hot water system introduces oxygen and minerals into the heating circuit, and the minerals can be deposited on the inside of the boiler, reducing its efficiency ($), and the oxygen can rust any iron you might have in your heating system.
There might also be lead in in the boiler, in copper and brass fittings, making it inappropriate for domestic hot water.
An insulated water tank with a copper heat exchanger that you insert into your heater circuit to provide your domestic hot water will take up the same floor space as your existing domestic water heater, and have a slower recovery rate.
Like others have suggested, a tankless gas water heater might be your solution.
posted by the Real Dan at 2:37 PM on December 6, 2014
A domestic hot water system introduces oxygen and minerals into the heating circuit, and the minerals can be deposited on the inside of the boiler, reducing its efficiency ($), and the oxygen can rust any iron you might have in your heating system.
There might also be lead in in the boiler, in copper and brass fittings, making it inappropriate for domestic hot water.
An insulated water tank with a copper heat exchanger that you insert into your heater circuit to provide your domestic hot water will take up the same floor space as your existing domestic water heater, and have a slower recovery rate.
Like others have suggested, a tankless gas water heater might be your solution.
posted by the Real Dan at 2:37 PM on December 6, 2014
This thread is closed to new comments.
I think you'd need a local contractor to comment on the specifics of whether you have proper clearances and so on.
posted by treblemaker at 10:48 AM on December 6, 2014