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Hydronic Heat - Radiant Heating and Indirect Applications with the Takagi Tankless Water Heater T-KJr2
High Demand Water Heater Applications or Hydronic
and Radiant Heat Systems with the Takagi T-KJR

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High Volume Indirect Water Heating for Residential & Commercial Applications

The T-KJr2 Takagi Tankless Water Heater can be used as an indirect water heater in conjunction with a storage tank for high volume situations. The Storage tank should be 30 gallons or larger and must always be set at least 5 degrees below the T-KJr2. The T-KJr2 Takagi hot water heater is factory set at 120° so if you want to raise your tank temperature to 120° - you will have to purchase the T-KJR Temperature Remote Control or set the internal dip switches of the TKJr2.

The standby losses that are associated with typical gas water heaters are eliminated because there is no flue dumping the stored heat out of the storage tank. Recovery time can be over 5 to 6 times faster than a typical gas water heater due to the high recovery rate of the Takagi T-KJr2. Efficiency is also maintained over time, which is not the case with a storage tank water heater.

You should use a typical electric tank water heater for the storage tank - you disconnect the heating elements and use the lower aquastat to activate the circulator relay to turn the circulator so when the tank's aquastat calls for hot water - it activates the circulator that will pump water from the tank to the Takagi T-KJR tankless water heater and then back to the tank. You can use different size tanks to accommodate up to 5 bathrooms or more. For those of you using multi-shower heads - this is an excellent and efficient way to use multi-shower heads and still get the efficiency of a tankless water heater.

To use the T-KJr2 as a heat source for your heating system - you can heat your Radiant Floors, Hydronic Baseboards and Air Handlers with the T-KJr2. Just continue down the page to locate the info.

HouseNeeds Inc. sells all the components needed for these systems.

Legend for the Indirect Application with a Takagi T-KJr2
Components for an Indirect Water Heating System
All the below components can be found on the Heating Supply Page or by clicking here.
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You must use bronze parts for an all open loop system.
Example List of Hydronic Parts

1. Taco 0011 Bronze Pump (Circulator)
2. Bronze 3/4 inch flange set - for shut off flanges
3. Bronze 3/4 inch flow check (Check Valve)
4. Circulator Relay

Please Note: You should obtain the electric hot water storage tank from a local source as the cost to ship one of these is generally more than the cost of the tank itself.

How to set up a T-KJr2 for use as a Hydronic Radiant Heat Source

Below is a picture of a T-KJR hot water heater being used for 2 different temperatures.

We recommend that you purchase the TV-10 Direct Vent Kit for your TKJr as this can save you (On average) 15% on your heating bills vs a non-direct TKJr.

There are primary and secondary loops and the primary is the loop attached to the T-KJR. The secondary loops are the high and the low temperature heating loops.

To get one high temperature from the T-KJr2 you need to use a primary loop and then a secondary loop to feed your system.

To get one low temperature from the T-KJr2 you use a primary and secondary and wire as below.

There are various methods for wiring but the best method is to shut off the primary circulator based on the return of the low temperature water so as to not short cycle the T-KJr2.

To get your heat and your domestic hot water from the Takagi you can use many methods. The best method is to use an indirect water heating tank driven off the high temperature loop.

All the needed components can be found on the Heating Supply Page or by clicking here
The Takagi T-KJR used as a Heat Source

A Storage Tank (Indirect or Stand-Alone) for use as a Hydronic Radiant Heat Source

We do not recommend open loop heating systems as they can be dangerous and more and more local codes are not allowing them. So be careful if you decide to use an open loop heating system. For a few extra dollars you can add a flat plate heat exchanger to the system and get a good heat system and a safe potable water system with one heat source. The Example below illustrates this. You may not need all the components illustrated.

In the picture below we show a tank - but this could be any heat source that you want to isolate from the heating system. For example - a wood or gas boiler. (If you use non-oxygen barrier PEX with a boiler - then you would need to use something like this.)

Picture of all the parts needed to separate drinking water from your heating system
with a Brazed Flat Plate Heat Exchanger and more

Using a Flat Plate Heat Exchanger with any tank or heat source

All the needed components can be found on Hydronic Heating Site Supply Page by clicking here.

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