Troubleshooting my tankless hot water heater
December 18, 2019 3:07 PM Subscribe
I'm trying to understand recirculating water and programming my tankless hot water heater. I finally realized that we get hot water in the taps when the heater is programmed to recirculate hot water (basically, keep hot water available) through the pipes. However, the water doesn't get hot at other times. My understanding is that it's better not to have hot water recirculating all the time. I don't know if I need to make a service call or if it's supposed to be like this.
I've had a Navien NR 180A in my old house for about nine years. I recently called for service when the water wasn't heating consistently and we had an error message, and the service person replaced the wick. That seemed to fix it... except sometimes not. After futzing with the programming and clock, I now have it programmed to recirculate hot water in the mornings and evenings.
At other times of day, if I run the hot water, it will get lukewarm (I can tell it's not tap cold), but not heat up enough for even a warm shower.
I didn't choose or install this system and don't know much about tankless hot water heaters--and I haven't been able to find a lot of information online--but it seems like the water heater should be able to heat up water on demand even when hot water isn't recirculating, if we wait long enough/run it long enough. Before I make a service call, I wanted to check and see if anyone knows enough about this kind of system to confirm my thinking.
I've had a Navien NR 180A in my old house for about nine years. I recently called for service when the water wasn't heating consistently and we had an error message, and the service person replaced the wick. That seemed to fix it... except sometimes not. After futzing with the programming and clock, I now have it programmed to recirculate hot water in the mornings and evenings.
At other times of day, if I run the hot water, it will get lukewarm (I can tell it's not tap cold), but not heat up enough for even a warm shower.
I didn't choose or install this system and don't know much about tankless hot water heaters--and I haven't been able to find a lot of information online--but it seems like the water heater should be able to heat up water on demand even when hot water isn't recirculating, if we wait long enough/run it long enough. Before I make a service call, I wanted to check and see if anyone knows enough about this kind of system to confirm my thinking.
Yes, you should get hot water at times when it isn't recirculating, but it can take a while (first the flow triggers the heater, then it starts heating the water, then the water makes its way to the faucet), which is why people put in recirculating pumps. If you aren't getting hot water even after waiting a reasonable amount of time, something is wrong.
posted by Dip Flash at 4:02 PM on December 18, 2019 [1 favorite]
posted by Dip Flash at 4:02 PM on December 18, 2019 [1 favorite]
That's not right. Are you flushing it once a year? You are supposed to. Have you installed any other gas appliances since you bought the place? They need a minimum amount of gas to run and there is a fair bit of planning to make sure that happens if all your appliances are gas.
posted by fshgrl at 5:20 PM on December 18, 2019
posted by fshgrl at 5:20 PM on December 18, 2019
One thing you should check is if the tankless system is running at all. Tankless systems have a minimum flow rate, below which they won't turn on. It's possible that the flow from your tap isn't enough to trigger it.
posted by It's Never Lurgi at 5:29 PM on December 18, 2019
posted by It's Never Lurgi at 5:29 PM on December 18, 2019
I have a Navien tankless heater but without a recirculator and it heats the water just fine. Yours should work too. What is the temperature set to on the heater?
posted by any portmanteau in a storm at 6:20 PM on December 18, 2019
posted by any portmanteau in a storm at 6:20 PM on December 18, 2019
Response by poster: To answer questions: I have a gas stove but haven’t added any additional gas appliances. Temperature is set to 120. No, I haven’t flushed it.
posted by bluedaisy at 11:26 PM on December 18, 2019
posted by bluedaisy at 11:26 PM on December 18, 2019
Do you know if it was always set to 120? I'm pretty sure I have mine set to 140.
posted by any portmanteau in a storm at 9:24 AM on December 19, 2019
posted by any portmanteau in a storm at 9:24 AM on December 19, 2019
Response by poster: Do you know if it was always set to 120? I'm pretty sure I have mine set to 140.
No, I don't know! It's definitely possible that with all the programming and button-mashing we did when it was having errors, I changed the temperature. I've just been reading around about this and it turns out that 140 is the default setting but recommended more for commercial settings, and many folks recommend 120 for homes. I'll raise it a bit and see if that helps (and I'm remembering we used to have to add cold water to the hot but not anymore, so maybe the setting changed at some point).
posted by bluedaisy at 11:23 AM on December 19, 2019
No, I don't know! It's definitely possible that with all the programming and button-mashing we did when it was having errors, I changed the temperature. I've just been reading around about this and it turns out that 140 is the default setting but recommended more for commercial settings, and many folks recommend 120 for homes. I'll raise it a bit and see if that helps (and I'm remembering we used to have to add cold water to the hot but not anymore, so maybe the setting changed at some point).
posted by bluedaisy at 11:23 AM on December 19, 2019
We've had it at 125 before and the benefit to that was that it was hot enough to have a decent shower with no chance of scalding yourself. But at 140 it is good for adding water to a mostly full bathtub and actually being able to change its temperature.
That being said while increasing the temperature may help, if 120 is fine when it is on recirculating mode then it should be fine when it isn't.
posted by any portmanteau in a storm at 11:34 AM on December 19, 2019
That being said while increasing the temperature may help, if 120 is fine when it is on recirculating mode then it should be fine when it isn't.
posted by any portmanteau in a storm at 11:34 AM on December 19, 2019
This thread is closed to new comments.
posted by bluedaisy at 3:28 PM on December 18, 2019