My Rinnai tankless water heater cycles up and down when we turn on the hot water. The water gets hot and then cold, hot and then cold. What is the problem?
You need to first make sure is the tankless who do the “up and down”! .If the problem manifest on more then one faucet then the problem is the unit. Have a thermometer (we use a infrared gun wich we train on Hot water pipe !) and see if actually the unit is the culprit. If the problem is only on one shower It is possible also to be a “antyscalding valve” If the trigger valve on your shower is being adjusted too low then it trigger a splash of cold water now and then on regulate intervals.Try to adjust the temperature lower at the unit (say 110F ) and see if the problem change. If it does, then the problem is for sure in the faucet. If it does not change , then you have a problem with the water flow sensor.It is simply getting stuck. Bad bearing or even a piece of Teflon tape. I believe you will need a certified technician for that so no issues with your warranty will appear.
Answers & Comments
You need to first make sure is the tankless who do the “up and down”! . If the problem manifest on more then one faucet then the problem is the unit. Have a thermometer (we use a infrared gun wich we train on Hot water pipe !) and see if actually the unit is the culprit.
If the problem is only on one shower It is possible also to be a “antyscalding valve” If the trigger valve on your shower is being adjusted too low then it trigger a splash of cold water now and then on regulate intervals. Try to adjust the temperature lower at the unit (say 110F ) and see if the problem change. If it does, then the problem is for sure in the faucet. If it does not change , then you have a problem with the water flow sensor . It is simply getting stuck. Bad bearing or even a piece of Teflon tape. I believe you will need a certified technician for that so no issues with your warranty will appear.