Tankless Wtr Htr for Hydronic use

Riles

uses. I keep hearing contractors and manufacturers reps say use a Tankless Water for ANY hydronic use. I need some of your thoughts.

I believe from Alan Forbes comments that they work well on the Domestic side, although, I'm sure you need to supplement with storage tank when big soaker tubs and Cosmo Kramer type (12 GPM) showers are involved.

The unit I have a particular interest in is Takagi. I know the TK-2 lists modulating ranges from 20K to 185K.

I have heard the pressure drop across the heat exchanger is 27PSI, well, times 2.31, that equals 62.37 feet of head, WOW, that aint no 007, or even a 009 (high head). I understand if you pipe primary - secondary it will work. I'm confused.

Tell me if you would or if you wouldn't use them to handle a hydronic load, and why.

Even if you can, what about life expectancy?

Looking for reassurance or confirmation.

Thanks.

Joe_10

Tankless

I have not installed any in a hydronic system however I have serviced two in radiant floor settings. First is backup for radiant heat it works very well, pump used was a grundfos UP25-64f. The only problem was a buildup of something in the filter for the unit.Cleaned it and it runs well.It needed a replacement of water diagphram something Bosch recommends every 5 years. Once Is all that I know of.
Second was as the heat source for radiant floor with ethylene glycol.It has only had the replacement of the water diagphram.Using a Taco 007. It is Approx. 20 years old. The unit next to it was used for DHW and needed a new HX due to hard water.
All units are Bosch WR400K's.
Hope this helps
Joseph

Tom Bradd

Vitodens

You should try a Viessmann VitoDens they have a part called a low loss header that takes all the problems out of the job ..Good Luck

Alan(CaliforniaRadiant)Forbes

Takagi

We've never used them as a dedicated source for hydronics; always combined with DHW, run through a HX for radiant......and that was before I knew about the high pressure drop through the unit. We used a 007 and it worked fine since we were only pumping about 1 gpm (~ 2 ft. of head).

There are so many houses where there's no place to put the boiler...and not many boilers can be installed outdoors like the Takagi or Rinnai (I'd like to know of any). One day we'll get the chance to try one out. I'd sure like to know how they work. They can be real problem solvers.

You can get the pressure drop curve from your Takagi rep. although I remember it was like pulling teeth. You can also call me at (510)452-2844 and I'll FAX it to you. The one I'm looking at is for the TK-2, but I don't think the TM-1 is much different.

Takagi also puts out a 2 page letter called "Radiant Heating System Using the TK-1" and the only think that is an issue is making sure the Takagi doesn't fire when the return water temperatures is too high so that the high limit doesn't pop; they want you to install an aquastat that opens on temperature rise at 120*.

You don't have to worry about this on the TK-2 or TM-1 since these units are protected by proprietary limits; pretty slick.

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Riles

definately top shelf

> You should try a Viessmann VitoDens they have a

> part called a low loss header that takes all the

> problems out of the job ..Good Luck

Riles

definately top shelf

I have looked at and enjoyed seeing some pictures posted. No doubt Viessmann's Vitodens is outstanding. I'm just looking for thoughts on the Takagi, etc.

Yes that low loss header is slick.

THANKS