Tankless heating?

RojoHo_3

Has anyone tried using a tankless water heater for radiant heating and DHW? See: http://www.jlconline.com/cgi-bin/jlconline.storefront/45d33d700012f92a27177f0000010598/Product/View/0702heat

chris_86

There are,..

Right ways to do things and wrong ways to do things. Experience, application, longevity, and cost factors usually determine what goes into new construction. On the other hand you can get just about anything that heats water to warm a home if you don't take into account the other factors that make a good fit for the application. You could conceivably heat some homes with the heat from light bulbs and if this wasn’t such a ridiculous idea I'm sure many manufacturers of light bulbs would do all they can to convince you their product are better for the application than the next guys. But this example doesn’t stop some manufacturers from promoting their products in advertiser sponsored journals. Some heaters are excellent and because they sit on the wall much discussion and clarification is in order. It's just that some manufacturers are much more liberal with their claims than they ought to be! There will be more than a few posts on this subject and if you search the archives you will also find many opinions as well. Personally the link you posted could be considered helpful but because you will have to pay to find out I think it is of limited value.

jp_2

i doubt,

that article talks specific in heatloads, efficiency and operating costs......for one, the opening paragraph suggests only cast iron boilers or DHW tanks as alternatives, doubt it will talk of a mod/con boiler.

you certainly can say a systems works well, but if you guage it up against nothing, theres no comparision.

Rich Kontny_3

Have Two Test Sites

I have installed and am testing two different on demand water heaters for DHW and space heating.

I have a Takagi JR putting out about 185 degrees w/natural gas.Then I use the "Heating Box" by Navien America to give DHW priority and step down temps to both domestic and in floor needs.

I also have a Rinnai Continnum LP unit also putting out about 185 degrees. This too is sent to a "Heating Box" which gives priority DHW and provides infoor for a 975 sq. ft. garage.

Thus far both units are working great.I remind you that this arrangement is based on providing priority to your domestic hot water needs.

There are rumors that AO Smith and Navien America both have a condensing on demand heater that has about 94% efficiency.

This system is great for the right applications but not a whole house heat source by any means. There is always the option of a modular type arrangement to meet larger demands.

The key to this system is the "Heating Box" a product that was designed by a former Takagi engineer. The unit came out a year ago and there are probaly about 600 installations thus far.The Heating Box I use separates the domesic water from the hydronic system by using two flat plate HX's.

So far so good with the two systems I am involved with.
Contact me if you would like additional info and price info.

kontnyrichard@yahoo.com

Rich K.

David Woycio

Don't do it

Buy a boiler for heat and a water heater for heating water. PERIOD!

You can dance around this all you want and the bottom line is by the time you make the instantaneous safe (via heat exchanger) you could have installed a boiler that is designed for heating. We perform a lot of service on instantaneous heaters that need flushed, or high limits crap out, or flow rates aren't right or?????????

We are working on a job now that no HE was used. Potable water sat in lines all summer and this fall when unit went to fire in space heat mode all kind of nasty blue sludge went into potable lines. Homeowner has spent $$$$$ and unit is still misbehaving.

Lot of nice boilers out there that can do both.

my 2c

RojoHo_3

Sq ft & BTU per?

"I have installed and am testing two different on demand water heaters for DHW and space heating." How many square feet and how many BTU per sq. ft are you heating?

Mike.C

We have

installed a few of these and they work great. Small homes under 1500 SF Works great. Gas bill is low. Dosn't have a big boiler taking up space and it's compact. We also use Mod/cons on larger jobs.
On any system that is open loop we do pump exercise card to make sure that the water is circulated througout the system twice daily.

Plumdog_2

I agree with Metro Man

The tankless concept is cute, and the brochures are convincing, but in reality they are barely acceptable for their intended purpose (heating domestic hot water), and certainly not suited for space heating. I would pay a little more and get a mod-con and indirect storage if I were you.

Mike.C

I get a kick out of all the people that knock it because of the numbers or it dosn't fit their style or maybe your just scared it might work. I have 6 different jobs open loop heating and domestic that are working and have been working for the past few years perfectly. We use Rinnai because they seem to have the best flow @ certain GPM.
They are reliable and seem to be at the top of their class.
You don't like the idea maybe you should talk to someone who had one CORRECTLY installed.
Now I feel better.
Mike.C

David Woycio

Potable Poo Poo

Let me get this straight. Is a correctly installed instantaneous water heater for space heating mean that you are you running potable water through heating loops?

Whatever floats you boat I quess but sounds like something that can come back to haunt you. Too many "what ifs" for me. May bring a new meaning to scotch and water.

hr

The biggest issue

and the one that aticle failed to mention is what is a realistic GPM flow rate and expected output. Even with a high head circ the output for a pumped system is a bit, maybe quite a bite less than the listed output of the tankless.

Plus the code issues, plus the manufacturer approving closed loop installations, plus the actual efficiency when the thing is burning.

Not much high tech in that HX design. A small diameter coil with a large ball of fire inside it basically.

Cheap is the one and only reason they are used

What does that dual pump Heating Box sell for Rich? Seems to add that to the cost of the tankless gets you a nice mod con?? Plus those noise generating circs they chose to use

hot rod

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Plumdog_2

I agree with your points

and I have tried to help unfortunate users of these devices in applications where the loads are high and they just are not satisfactory. All those pumps and heat exchangers and cobbled-together piping arrangements are just as expensive as a mod-con with a tank; but not nearly as neat or efficient, nor as comfortable.

David Woycio

Ditto

Like reinventing the wheel when the wheel worked fine to begin with.

Best way to test....... take a shower (better to have volunteer) and start turning hot water on in the house. See how long it takes to hit high note!

Most of the instanteous units we sell are for cabin applicaions. They are perfect for this because when you want to shut down a cup of water is all these units hold.

Have you tried a Solo w/ a mini smart? Nice small package. The mini has a 3 gpm draw and you can adjust the contols on the solo for max output. We installed this unit on employees home and works well ....... plenty of hot water. Only issue he had was a shower mix valve ran a little cooler. But I think it's because it's pressure driven and with a little finangling should be good.

Best thing...... it's a boiler!

Rich Kontny_3

Energy Box

Retails for about $1995 add a Rinnai for about $1500 w/vent kit and you have a system that will heat up to 2,000 sq ft. Pumps do seem a little too noisy but overall it works fine. Water quality is an issue on domestic side due to close tolerances.

Currently they only have single wall XHs which can be a code issue.

The Energy Box saves alot of labor for those who have already pieced together systems like these! We have a wholesaler here in Milwaukee who loves the concept as he does a lot of design for high end bathroom and kitchen additions where they want there tile floors warmed with in-floor.

Rich K.