Takagi tankless nightmare

[ThomSF]

Hi all. Been lurking on the forum for a while and created an account just to post this since it seems like others have had issues with Takagi tankless water heaters. I would appreciate any advice since I'm running out of ideas here

The situation: Renovated our home and the contractor installed a Takagi tankless water heater (AT-H3P-OS-N) a little under a year ago. Water was not heating up to temp with and without the recirculation pump on. Turns out cold water was going into the hot water return line, so we installed a check valve on the return line. Problem fixed? Not really

With the recirculation pump on: we are now getting hot water to all of the fixtures & shower located on the side of the house closest to the water heater. The fixtures/shower on the opposite house would get hot, but only briefly, then would only be warm. After a while, the heater will throw an error code 441 "flow sensor failure". After calling the Takagi tech, he walked me through removing the sensor, cleaning, inspecting, then reinstalling it. The error code will go away, but would come back if the above steps are repeated. (we have sufficient sized gas lines, so that shouldn't be the issue). The tech is saying the flow sensor is working, and there must be something in the water pipes or fixtures (air and/or debris) that might be causing the sensor to throw the error code. Anyways, they are sending a new sensor to me to replace. Will update this thread once I do

With the recirculation pump off: We are getting hot water to all of the fixtures & shower located on the side of the house closest to the water heater. The showers/fixtures on the side of the house opposite the water heater would only get warm, not hot.

We're out of ideas. Filters on the cold and return lines have been cleaned. The tank is only a year old and I don't think it needs to be descaled (the issue of water not heating up has been going on since the tank was brand new!) The Takagi rep recommended we install a check valve on the cold line too, but I don't see how that would help because we don't have any issues with hot water getting into the cold line. That might be our next step though since I don't know what else to do

Does anyone have any advice? This is becoming a nightmare, and I regret not just getting a standard tank water heater.

 

[I Plumb]

Hi all. Been lurking on the forum for a while and created an account just to post this since it seems like others have had issues with Takagi tankless water heaters. I would appreciate any advice since I'm running out of ideas here

The situation: Renovated our home and the contractor installed a Takagi tankless water heater (AT-H3P-OS-N) a little under a year ago. Water was not heating up to temp with and without the recirculation pump on. Turns out cold water was going into the hot water return line, so we installed a check valve on the return line. Problem fixed? Not really

With the recirculation pump on: we are now getting hot water to all of the fixtures & shower located on the side of the house closest to the water heater. The fixtures/shower on the opposite house would get hot, but only briefly, then would only be warm. After a while, the heater will throw an error code 441 "flow sensor failure". After calling the Takagi tech, he walked me through removing the sensor, cleaning, inspecting, then reinstalling it. The error code will go away, but would come back if the above steps are repeated. (we have sufficient sized gas lines, so that shouldn't be the issue). The tech is saying the flow sensor is working, and there must be something in the water pipes or fixtures (air and/or debris) that might be causing the sensor to throw the error code. Anyways, they are sending a new sensor to me to replace. Will update this thread once I do

With the recirculation pump off: We are getting hot water to all of the fixtures & shower located on the side of the house closest to the water heater. The showers/fixtures on the side of the house opposite the water heater would only get warm, not hot.

We're out of ideas. Filters on the cold and return lines have been cleaned. The tank is only a year old and I don't think it needs to be descaled (the issue of water not heating up has been going on since the tank was brand new!) The Takagi rep recommended we install a check valve on the cold line too, but I don't see how that would help because we don't have any issues with hot water getting into the cold line. That might be our next step though since I don't know what else to do

Does anyone have any advice? This is becoming a nightmare, and I regret not just getting a standard tank water heater.

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It seems to be all Tankless models with built in pumps are problematic thats been my experience. The better way is to buy the tankless with out the built in pump then go to a website called faster hot water order there recirc pump set up. Then you have an A+ set up. I’m a plumber and I’ve been called out to a house with the exact same model you have with the same issue. Called tech support got the whole run around. the original plumber installed it perfect to the manufactures directions. I’m about to pull it off the wall install new Takagi with external pump. Takagi is a great brand I install 90% of the time. Just not the one with the built in pump.
so back to your question, I think it has something to do with the pump activating flow switch/ thermastate activating the burner or not activating the burner. Not sure, I’ve spent sometime trying to figure it out. Nothing yet.

 

[Sponsor]

 

[Bannerman]

The showers/fixtures on the side of the house opposite the water heater would only get warm, not hot.

I suspect the fixtures on that side of the house are being suplied cooler water from within the circulation return line, not from the hot supply line. There should be a check-valve located at each location where the hot supply line is connected to the circulation return line.

 

[Bannerman]

Turns out cold water was going into the hot water return line, so we installed a check valve on the return line.

How is cold water entering the return line? Depending on where the cold water is entering, a check valve in the return line is likely to be insufficient.

 

[Breplum]

always check to see if there is some bypass leak in the hot system: shut cold valve at water heater and turn power off at the WH, then open a hot faucet and confirm the water flow eventually stops completely.
I only install and service Navien, but did have one less than a year old with a defective flow sensor...Navien smart board makes diagnosis easy, now with multi line display on the front of the unit. NPE A series with the built in pump is a dream unit.
I've had Takagi and Noritz field training but they are too much trouble if the situation like yours arises.
Good luck.
P.S. I would probably add a check valve and expansion tank after the check valve.

 

[Fitter30]

Brand and model of pump. Pipe size , length and number of 90s (ells).

 

[Jandro11]

Did you ever find a resolution with this? I’m running into the same issue. Original water heater was two years old and I ended up replacing with a new unit only to have the same issue.

 

[John Gayewski]

Did you ever find a resolution with this? I’m running into the same issue. Original water heater was two years old and I ended up replacing with a new unit only to have the same issue.

I skipped the reading but the issue sounded to be with the recirc and balancing or bleeding.

Do you have a diagram of your piping layout?