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Takagi temperature fluctuations
David Meiland
Member Posts: 12
with one 2.5 GPM Speakman AnyStream shower head (a personal fave).
Water pressure is from a 120-gallon bladder tank that produces 60PSI when full and kicks on the well pump at 40PSI. It takes quite a lot of water to get from 60 to 40. There would not appear to be *any* chance that this shower would be capable of kicking on the well after running for 90 seconds, and doubtless the tank is never actually full when the shower starts anyway. Regardless, the timing of the temperature drop is so consistent that I think it's coming from the unit itself, not anything external.
Water pressure is from a 120-gallon bladder tank that produces 60PSI when full and kicks on the well pump at 40PSI. It takes quite a lot of water to get from 60 to 40. There would not appear to be *any* chance that this shower would be capable of kicking on the well after running for 90 seconds, and doubtless the tank is never actually full when the shower starts anyway. Regardless, the timing of the temperature drop is so consistent that I think it's coming from the unit itself, not anything external.
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Comments
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New Takagi TK1s installed for DHW only, replacing a tank unit. LPG piped thru about 35 LF of 3/4" black iron pipe. Water supply is from a 120-gallon pressure tank. After about 90 seconds in the shower, the water temp drops by several degrees, enough to require an adjustment of the shower valve. Then another couple of minutes later is goes back up, requiring a second adjustment. From there on it's usually stable.
There's plenty of gas and plenty of water flow. This occurs every time regardless of water use at other fixtures, well pump cycling, etc.
Anyone dealt with this, or have thoughts on it?0 -
Couple things
The Takagi ramps up to high fire until it reaches the operating temp set on the unit, then ramps down and modulates to the set point. During this time your hot water pipe is also coming up to the temp of the water now going through it. In other words, some of the heat is being lost to the pipe until the water has run for a minute or two. Once the pipe has acclimated, you don't have that heat loss hitting your faucet and the temp stabilizes.
This is pretty common to all brands of tankless units I have been around, Bosch, Rinnai, Takagi, whatever. It's just the way they work. The length of your run from the heater to the shower/bath plays a large part in this variation.0 -
That would cause
the opposite of what we experience. I understand that the unit can only control the temperature of the water leaving it. It appears to do this correctly, for the most part. It is a relatively short run of insulated 1/2" copper pipe to the shower, and the pipe comes to temp fairly quickly.
The problem is that the temp suddenly drops after a stable level has been reached, as though the unit suddenly modulates down for some reason. No changes to flow rate, incoming water temp, pressure, etc., are happening. I'm guessing that there is something going on in the Takagi's internal controller, but not sure what it might be.
Needless to say, I was hoping this would be an easy one!0 -
Tis the nature of the beast...
You'll get used to it. Just start the shower a few minutes earlier than you normally would and it will be stablized by the time you get in. I used to have one of these in my own home, so I speak from first hand experience.
ME0 -
Dave
Is this a standard shower or does it have multiply heads ?
Does the preasure fluxuate during the shower ? If the preasure drops alittle the unit would adjust and then change again as the water preasure ( from the well ) came back to high preasure.
This units are different from the tank types that America is used to and customers need to know it dosn't the same way.
Scott
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
It is coming from the unit itself...
and as stated, it is the nature of the beast. It assumes maximum flow is going through the unit, and fires to maximum burn rate. Once it realizes that it is overshooting, it backs off. It takes it a minute to realize actual load and stablaize around the flow. Once it locks into the load, provided that nothing changes quickly, you are at a point of stability.
You'll get used to it.
ME0
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