Question about RTO Takagi Jr. TK-JR-N Tankless Water Heater - Natural Gas

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Takagi TK-JR vibrating noise

I have a takagi TK-JR that I use to heat a closed loop hydronic system in my garage. I use a grundfos three speed pump and run it on medium speed. It has worked great for two years and all of a sudden this year when I fired it up it vibrates like crazy. I cleaned the filter, added more air bleeds, flushed out the system and refilled with new 50% glycol and the thing still vibrates. I had the gas supply pressure checked, 8" of water and the takagi tech walked the gas guy through the process of dropping the manifold pressure but the next day when I fired it up, it vibrated again. If I stand there and nurse it through the first 15 minutes of operation by dropping the pump speed to low, I can get it to work without noise for as long as it is firing. Heater will not fire up with pump on low speed as there is not enough flow so I have to start it on medium speed and then switch to low speed so it does not vibrate itself to peices. I also had to up the pressure in the system to 30psi from 15psi and that seemed to help a bit. It acts like the water is boiling and that is causing it to vibrate. Pretty much same problem here. Sometimes when use kitchen sink or dishwasher water heater starts vibrating and quite loudly. If i open some cold/warm water it stops but as soon as i turn on all hot it starts again.

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  • Anonymous Mar 18, 2014

    Keep showing code 21water turn cold



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Remove your hydronic pump and replace the flexible impeller coupling that couples the impeller blades to the pump motor. make sure you don't do this on a sat or, sunday (i hate house calls then) and, be sure you have a new pump housing gasket before you start the job. Also check the unit for loose pipe brackets

Posted on May 20, 2009


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Why wont takagi tk jr doesnt heat

Flowmeter.....Gas Pressure.....Ignition?
I'm not psychic.
Tk-Jr is a dependable 140-145,000 BTU 2nd Gen Unit SS Vent , <.82 EF.
Failure is a Tech Service issue and the Tech may need Factory Support from California. This is probably a pre-A.O. Smith/Takagi unit
Does the igniter spark 3 times than shut down and fan purge HE? Can you smell gas tracer (remember NG/LP is odorless w/o mercapthan in it)? Tech will need a digital Manometer for Line and Manifold Pressure Test. And a Multi-Meter Toll Free # on Unit or in Manual

Sep 07, 2014 | RTO Takagi Jr. TK-JR-N Tankless Water...

1 Answer

Pump not working-delay in hot water delivery.In the past,a vibration occurred when cold water running above the pump.Can this be repaired.Power operating to pump. Thanks, mel ross

Question not 100% clear.

1) The pump is not working? Does the pump make a noise? if pump is not working full-time, it can cause delay in arrival.
If pump motor is suspect, and outlet has power, then check override switch located on timer. Set override to Timer, move some of the trippers outward, then manually rotate timer dial until pump turns ON.
If no noise is detected, or noise stops and starts, or seems strained, or if pump is hot, then pump motor may have burned out.

2) If pump is working, and makes noise like a humming sound, and pump motor is not hot, but hot water is not circulating, then unplug pump so it will not overheat and burn up.
Disassemble the pump and cross-over piece. Clean piping with white vinegar or CLR. Do not soak in CLR or it will damage seals. Rinse parts thoroughly. Reassemble and see if problem is resolved.
If pump is vibrating, then suspects include sediment and/or air inside line, and this can be resolved by cleaning as described. Also install air vent to increase life of pump.

3) Other causes for hot water delay at faucet are crossover.
Crossover can be caused by bad single-handled faucet cartridge, and/or by clogged-or-failed check valve on cross-over piece on grundfos.
This type of problem lets cold water enter hot line, and causes delay in arrival of hot water. Clean-or-replace the grundfos cross-over piece, and replace bad faucet cartridge.
Open following link for testing instructions:


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Sep 17, 2011 | Laing Thermotech Autocirc Undersink...

1 Answer

My Takagi T-K jr. keeps flashing an error code 21....the water turns cold and we shut it off ....wait a few...then turn it back for a little then wil flash again...have replaced the pressure...

In my case, the error code 21 was caused by the failure of the vent fan to run-on after shut off (easily verified by listening to the unit). The problem was not resolved by swapping either the fan or the control unit with another heater. I talked to a local service tech who had a couple of suggestions. One was to move DIP switch #6 to the upper position. After doing thisit will be necessary to re-initialize the controll by cycling power off and on. This fixed the problem. I emailed Takagi tech support to ask if I should consider this as permanent fix, or if there was something else I should do. Since I got no reply, I'll pass on the tech's other suggestion: buy a Rinnai.

Mar 27, 2011 | RTO Takagi Jr. TK-JR-N Tankless Water...

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Takagi Jr Flash Water Heater Problem

explain your problem.
Takagi is a great tankless heater, very few problems...

need more info

Aug 04, 2010 | Ultra Max Takagi Flash TH-1 Ultra High...

1 Answer

Tankless water heater not meeting the need

Yes the faucet could be a problem. Try changing for one which you know is ok.
The long run of pipework - each bend, elbow or joint all have a reducing effect on the flow, maybe enough to matter with a restricted outlet. none of this can be altered except by renewing with larger bore pipe - expensive!
Also there should be a dirt filter in the mains water input line/pipe. Try removing & cleaning. Try also removing , reconnecting and then the hot tap [faucet]

The boiler will have an actuator valve which fires it up when a certain flow of water is reached. If the flow is reduced AND the valve is worn, maybe a replacement. Not sure about it's USA construction but in the UK [it's called a diverter valve] many have a rubber diaphragm which is cheap to replace
Check also if it uses a flow sensor switch
Had a look at the Takagi web site and there are pdf's of manuals
Overall I am still thinking that the main prob is in the flow.
Hope I've helped - come back anytime

Feb 19, 2010 | RTO Takagi Jr. TK-JR-N Tankless Water...

1 Answer

We have a robbens underfloor heating system with a heatrae electric boiler on a floating floor system. The underflooe heating manifold has a grundfos Alpha + pump. What setting should this be at? Currently...

Venting of the system is when you re circulate the water or cooling fluid in higher speed to eliminate the air bubbles from the system.
If water circulate on a too higher rate does not have time to dissipate the heat so your floor is cold.
You need to go to 2 or even 1 depending on the length of the heating coil in the floor. Unfortunately the pump only has 2 speeds (setting 1 and setting 2) so whoever install your system had to calculate the length of the pipe for maximum efficiency. Try on 2 and if not satisfactory go to setting 1. If too hot on setting 1 then you can adjust the heat by reducing the amount of water from the shut-off volume control. It is a hit and miss situation, I know but unfortunately that is the only choice remaining now after the system is installed.

Jan 10, 2010 | Grundfos RCP-96 Recirculation Pump for...

1 Answer

Tankless on demand water heater.

Tankless water heaters normally take a little longer than a regular heater to provide hot water because they have to start and get warmed up. I'm guessing the heater uses a pilot light and that the short amount of hot water when you turn on the tap is hot because when the water is sitting still in the heater the heat from the pilot light is enough to get it hot. The tub faucet will get hot a lot faster than the shower because it lets a lot more water through and empties out the pipes faster than the shower. You could probably speed things up by letting the tub faucet run on completely hot for like 10-15 seconds and then turning on the shower.

Oct 24, 2009 | RTO Takagi Jr. TK-JR-N Tankless Water...

13 Answers

Takagi TK-JR vibrating noise

I have the same problem with a T-K3. The Takagi support site recommended cleaning the burner. When the plummer arrived to attempt the cleaning, he was not convinced that it would help. He called the Takagi 800 number and let them hear the problem over the phone. They had him set the fan speed dip switch (#4 on the upper left bank of switches) to the up ("on") position and reset the system. Problem resolved! Why they didn't recommend this when I contacted them, I haven't got a clue. Anyway, the system hasn't vibrated in several days of use.

Dec 23, 2008 | Ultra Max Takagi Flash TH-1 Ultra High...

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