Replies

1. 
   Shacko | Jul 05, 2005 11:27pm | #1

   I can't figure it out, there is too much missing information.  The tankless water that you are talking about I am not familiar with.  What is the btu rating of the heater?.  What is the domestic load?  What is the heating load?.  If I had this information, I might have a possible answer.  [I think at this time you are overloading the heater]. [I have never heard of a tankless heater supplying both domestic  and heating water].  I may be wrong!.  I hope that someone comes up with a better answer.  Lots of luck.

1. 
   Flatfive | Jul 06, 2005 05:28am | #5

   The TK-2 is 20,000 to 185,000 BTU input. I am only running the one water-saver shower head, the heaters are not turned on. I get up at 5:30 AM. No one else is up then, so no flushing or sprinklers coming on either. (Nothing on a timer) It's gotta be either the mixing valve or the Takagi.

1. 
   Shacko | Jul 06, 2005 10:54pm | #7

   What you say about the input of the water heater seems to be large enought for your installation. [Out-put is what I really wanted; don't worry about that].  Most mixing valves that I am familiar with require periodic maintenance.  they go out of wack easily. If you have the papers that came with the valve, check them out.  If you have a pressure, temperature control valve in your shower, that is another thing to look at.  Thats the best I can do.  Its hard to do this long distance. I would look at the shower valve first.  Lots of luck.

1. 
   Flatfive | Jul 13, 2005 09:47pm | #8

   I called Takagi. First, they suggested that I had the dip-switch settings wrong. I checked them and they are correct. Then, they said the flow may be too low. The heater may be shutting off momentarily. Since I live in Southern California, the water temperature is pretty warm. I have the heater set to 180 degrees and then run it through a mixer valve before it goes to the bathroom. So, there is less of the hot water used. I have a low-flow shower head, too. This morning, I took a shower with the hot water in the sink running too. I had no fluxuations in temperature! So, I guess that's the problem. I will try a different shower head or try to  modify that one somewhat.

1. 
   Shacko | Jul 13, 2005 11:04pm | #9

   Without being there I'm still leaning toward your shower valve.  You didn't say if it is a temperature, pressure valve.  The shower head should not cause this problem. For a test, try taking the shower head off, with your sink off, see if there is a fluxuation in the water temp. if there is,try it with the sink running, if that changes the temperature [with the shower head off] then the problem is not in the shower head.  I still lean toward the shower valve.  Lots of luck.

2. 
   Flatfive | Jul 14, 2005 08:05am | #10

   The shower valve is a pressure-sensitive device. However, I have disabled the movement of the diaphragm with a screw. The shower head is not the problem but could be the solution. I just need to increase the flow through the heater so it doesn't shut down.

3. 
   Flatfive | Jul 14, 2005 08:54pm | #11

   Well, maybe not. This morning I again took a shower with the lavatory sink running hot only. There was some fluctuation in the temperature of the shower. I'll call Takagi again.

4. 
   davidmeiland | Mar 29, 2006 05:14pm | #12

   I have the same issue with a TK1s. The temp variations are not large, maybe a drop of 3-5 degrees after getting in the shower, and it's not sudden but somewhat gradual. Still, it's annoying. What did you ever find out about yours?

2. 
   jtm | Jul 06, 2005 12:39am | #2

   I have a TK-1, and have the same problem you've described.

   I tracked down the cause to my yard sprinkler system.  Every time the sprinkler goes on, my pipe system looses water pressure for just a few seconds and TK-1 senses it and drops the hot water output to compensate for the lack of water input.   Otherwise, overheated water (steam?) exist inside the unit and it would go to safety and dump. (explode?)

   TK-1 is slow to ramp back up as water pressure is stabilized but it's as steady as the feed water's pressure/temperature/hot water demand is steady.  Does it do the same thing if a toilet is flushed or a fixture goes on anywhere in the house? 

    I just reset my sprinkler timers as not to interfere with my shower.  Perhaps a small holding tank of constant 140 degree water,say 5 gal size may smooth out the swing for you.

    

3. 
   IMERC | Jul 06, 2005 01:18am | #3

   somebody flushed or turned on the water some place else in the house and the reaction curve is slow.

   bad or sticking mixing valve.

    

4. 
   myriad | Jul 06, 2005 02:46am | #4

   We have a TK1 that had the exact same problem.  Is yours new by any chance?  We called the Takagi rep., and when he came over, he found out that someone at the factory had accidentally left a 'test' lead on the heater circuit board. The lead is used on the assy line for making sure the emergency shut off works. It basically turns the heater on full blast until the shut off kicks in and turns the heater off. As a result you get fluctuating temperature... most annoying!  Anyway, after he pulled the test lead off, it has worked flawlessly ever since with NO fluctuation, even when the hose or other water using devices are on.

   The men may be the head of the house, but the women are the neck and they can turn the head anyway they want.

1. 
   Flatfive | Jul 06, 2005 05:29am | #6

   Well, mine is new, but it's a TK-2 not a TK-1, but it could have the same thing, I guess. I'll contact Takagi.

   Edited 7/5/2005 10:30 pm ET by Flatfive

2. 
   woodway | Mar 29, 2006 07:17pm | #13

   I personally like the Tagagi units but I didn't know they will send out a factory rep to solve problems in installed home units. If they do, then I'm even more pleased with them and I haven't even bought one of their units yet.

1. 
   Flatfive | Mar 29, 2006 09:27pm | #15

   They sent out a factory rep, but I paid $60 for his time. Plus, I had to take a half day off work to meet him. He recomended increasing the size of the gas line and ball valve, which I have done. It didn't improve things. Now, he thinks I have a plumbing screw-up where cold water is getting into the hot line. I don't see how that makes the TK-2 "flame out" but I'll look into it.

1. 
   sandalboy | Mar 30, 2006 04:47pm | #16

   Does this sound like what is going on with your unit?I have a NTI Trinity boiler that does my domestic hot water on demand. I have had a problem similar to the cold water sandwich that you describe, and it only happens in the summer when the boiler is not heating our floors also. I spent a lot of time tracing the events that cause this on my machine. I have not changed anything yet, so this is just my theory.This occurrs when the shower is on only. Very hot water for about 3 minutes, cold water for about 2 and the hot for a while. Seems like it gets hot enough to shut down. This unit is capable of making too much hot water, and has trouble with too small quantities.Take a shower while running the hot on the sink also. No hot / cold cycling.I've gone in the basement and felt the temp of the pipes while someone takes a shower.I think that the boiler gets hot enough to cut out. The mixing valve is mixing plenty of cold in, needing very little hot to make the desired temp. Due to the little hot flow, the flow sensor in the unit thinks there is no call for hot water, and the unit stays off. It only comes back on once cold water has gone all the way through the unit to the mixing valve. At that point the mixing valve starts pulling enough from the hot side to turn on the boiler again.I think that moving the flow sensor to the point after the mixing valve would solve this.The other solutions are to use more hot water when showering, or to install a small storage tank and pump.I'm going to try moving the flow sensor first, and if that doesn't do it, I'll do the storage tank.

5. 
   whoover | Mar 29, 2006 07:41pm | #14

   It sounds like a problem which is typical of tankless water heaters.  Anything which causes the water heater to stop heating...changes in flow or pressure...even momentarily, can cause a slug of unheated or under-heater water to enter the hot water line...hence you see the temperature drop.  This is known in the industry as the cold water sandwich...not mentioned in all the advertising hype.  If you had a storage water heater, such a thing would not happen....one of the benifits of having a buffer of hot water.

   Bill

    

1. 
   MikeFitz | Mar 31, 2006 06:38am | #17

   It may be common with certain manufacturers or certain types of plumbing, but certainly not an endemic problem- I have a Rinnai unit which never does this.  It may be more of an isue if your plumbing is run as a branched system as opposed to a home run system.  Mine is a home run, separate feeds from a monoblock for all fixtures.  Just a thought.