Heating with tankless water heater vs boiler

[smarthat]

I'm considering heating an additional of a house (approx 1000 sq ft) by using radiators (like buderus type) and a supply of hot water from a tankless water system (like rinnai, takagi). Have any of you done something like that? Does it work? What are the up/ down issues when considering a boiler versus a tankless water heater in a heating system? I'm not considering any other options/ advantages (like having hot water).

Thanks
j

[Christheheatingdude]

Are tankless heaters approved for use as a boiler? Not sure about that one, cant sleep so my mind isnt working to fast at the moment. But I am not sure you can use them that way, code wise I mean.

[t527ed]

not sure but i doubt a tankless water heater is built for a closed loop system. look at the weil mclein ultra boiler. over 90% eff. only holds like a gallon of water.

[robertusa123]

iv seen it befor even had a job to bid on like that
with water coil in airhandler and a tankless water heater for each condo in a 30 unit bulding. they also wanted to provide domestic hot water off the same heater. insane set up, who would heat and drink the same water. we also had the bright idea of talking with the town inspector first. he said not leagle would have beed left holding the bag when we failed that inspection.
we sent a bid in for 90 direct vent furnace. dident get job fell sorry for who ever did get it

[beenthere]

There are water heaters made that do both heating, and domestic, it doesn't hurt the water.(they are ul rated and approved for that application.

[johnsp]

You might want to look at wall hung boilers: Baxi Luna, HTP Munchkin, Montior al make great units. You probably need under 50K BTU's. Most WH's (tank or tankless) do not have ASME rating ("H" stamp) so many towns/states (like MA) won't allow it.

[Jultzya]

There are many tankless units made for radient heat applications.

Closed loop has nothing to do with whether it's a boiler or water heater. That's why water systems have expansion tanks.

[smarthat]

I live in WA state. The link below is showing a house that was built with a heating system using a tankless water heater (Takagi). The winter temperatures here go around 30F, but not for long times (usually 40-55).

You can see that this was done professionally (I'm not talking about mixing drinking water with heating water). I already use a tankless system for kitchen/bathroom/utility needs. A 2nd unit would be dedicated to heating the rooms, separately from the 1st.

http://www.issaquahhighlands.com/ide...uildspecs.html

I'm planning to use the same concept, however, I do not like to have the air blown "in my face" when heating is required. Also, having the radiator units in the wall, might bring trouble and maintenance problems. I would rather use panel radiators, like http://www.buderus.net/Default.aspx?...purpose&mcid=9

These can be mounted with connection in floor, and the distribution lines can be in the crawlspace (easy to insulate and maintain).

I took some pictures of the system (basically, it has the following components: 1) tankless water heater 2) pump 3) control of temperature (usually it comes with the heater) 4) thermostat (some of the panel radiators have individual thermostat on them). Here are the links:
http://home.comcast.net/~topaz107/hydronic/system_1.jpg
http://home.comcast.net/~topaz107/hydronic/system_2.jpg
http://home.comcast.net/~topaz107/hydronic/temp_1.jpg
http://home.comcast.net/~topaz107/hydronic/temp_in.jpg
http://home.comcast.net/~topaz107/hydronic/temp_out.jpg
http://home.comcast.net/~topaz107/hy...mp_in_line.jpg
http://home.comcast.net/~topaz107/hydronic/flow.jpg
http://home.comcast.net/~topaz107/hy...l_radiator.jpg

On the other hand, I found this article http://www.radiantheat.net/faq_boilers/
which has some questions regarding the use of tankless water heaters instead of boilers.

Any thoughts, after seeing all these?

[johnsp]

Good article. It speaks for itself. Your Takagi is great for domestic hot water BUT it's not ASME rated and efficency is poor when reheated water is passed throught the HX. For a coupe of hundred more look at the Baxi Luna.

[thighway]

The "H" stamp is for BOILERS. A tankless water heater is a tankless water heater and not a boiler. It needs to be CSA approved for space heating, but in most cases cannot be used in a closed loop system. Check with your local codes to find out for sure.....as in some part of Ontario we have to separate the water even via heat exchanger (keeping domestic and heating water separate).

[Jultzya]

They are using this system to heat the home?

If so, does anyone see an Air Purger on, or in the piping?

[smarthat]

Yes, this system is used to heat the house. The house was in "dream of houses" (kind-of) last year (2004), and it was a model, open to public for more than a month. Probably, there are people living in right now.

I don't know where the air purger is, I was more interested at that time in the overall concept, especially in using the tankless water heater for (air) heating purposes.

[heatpumpguru]

BRADFORD WHITE MAKES A WATER HEATER THAT DOES RADIANT,we did a summer room with a 40 gallon gas that was not direct vent. Price was the driving force behind it,guy loves it.