Navien NPE-240A hot water takes a long time to reach faucet

[jhawk89]

We recently moved into a new build 3 floor townhouse that is using the Navien NPE-240A for the water heater and have been experience many issues related to water.

1. Water pressure is very low at the shower faucet (ie. it was measured at about half the PSI it usually should be).
2. Water takes a long time to get to a hot temperature at any faucet.
3. Water doesn't get as hot as we were hoping (I tried bumping the temp up and it's still just "mildly" hot at the faucets).
4. Some faucets like in the kitchen, don't really get hot nor cold.

This post I wanted to narrow in on the 2nd issue where the water is taking a long time to get to a hot temperature. I outlined the other issues in case it would provide any additional clues on what might be going on.

From my quick research, it seems like the recirculation settings may be incorrect but I've been struggling to understand whether this is an external/internal recirculation loop and what to set the int/ext valve to and what to set the dip switches to.

I was hoping some of y'all could take a look at these photos to help guide me in at least setting the right recirculation settings and maybe helping to alleviate this slow hot water issue we've been experiencing.

Thanks!

 

[Bannerman]

Your system is utilizing an external recirculation loop so the 2-way valve should be set to Ext and Dip switch 1=Off & #2=ON. With appropriate settings, the recirculation loop should cause hot water to circulate so as to rapidly arrive at fixtures throughout the home. The diagram below shows the flow path for an external recirculation loop.

You didn't specify the current temperature setting. I anticipate the WH will be set to provide hot water exceeding 120F as the outgoing flow appears to be routed through an adjustable thermostatic mixing valve that will mix cold water with higher temp hot water directly from the WH to supply a specific lower temperature, usually 120F to the home's hot faucets. As there is an additional hot water line that is Tee'd before the tempering valve, I suspect that line will supply hotter water directly from the WH, likely to the dishwasher.

One issue that is common with that WH is the failure of the internal check-valve to reliably close fully. When this occurs, cold water can flow backwards through the circulation pump and out through the recirculation water supply connection (recirculation loop return), causing cold water to flow in reverse to fixtures through the return line so as to reduce the temperature at each faucet. See the diagram directly below for the location of the internal check valve.

If the check valve is remaining stuck open, replacing it is the usual remedy. While the repair for your fairly new WH is likely covered by warranty, because the original check valve is prone to repeated failure, I anticipate you could also/instead install a common inline check valve in the return line before the WH to provide a more reliable and permanent method to prevent reverse flow to fixtures. The link below shows an example of an inline check valve.

Diagram showing appropriate DIP switch settings for External Circulation loop.

Two-way valve setting.

https://www.homedepot.com/p/SharkBi...ect-Brass-Check-Valve-U2016-0000LFA/202721920

 

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[jhawk89]

Your system is utilizing an external recirculation loop so the 2-way valve should be set to Ext and Dip switch 1=Off & #2=ON. With appropriate settings, the recirculation loop should cause hot water to circulate so as to rapidly arrive at fixtures throughout the home. The diagram below shows the flow path for an external recirculation loop.

This is what I determined was the settings initially from my research, so I configured the valve and dip switches like you mentioned but the time to hot water seemed to be significantly worse than setting the recirculation to be internal. I'll re-configure it back to what it is supposed to be.

You didn't specify the current temperature setting. I anticipate the WH will be set to provide hot water exceeding 120F as the outgoing flow appears to be routed through an adjustable thermostatic mixing valve that will mix cold water with higher temp hot water directly from the WH to supply a specific lower temperature, usually 120F to the home's hot faucets. As there is an additional hot water line that is Tee'd before the tempering valve, I suspect that line will supply hotter water directly from the WH, likely to the dishwasher.

That did it to raise the temperature reaching the faucets! I've always lived in a condo building so all this has been new to me. Thank you so much for this information!

One issue that is common with that WH is the failure of the internal check-valve to reliably close fully. When this occurs, cold water can flow backwards through the circulation pump and out through the recirculation water supply connection (recirculation loop return), causing cold water to flow in reverse to fixtures through the return line so as to reduce the temperature at each faucet.

If the check valve is remaining stuck open, replacing it is the usual remedy. While the repair for your fairly new WH is likely covered by warranty, because the original check valve is prone to repeated failure, I anticipate you could also/instead install a common inline check valve in the return line before the WH to provide a more reliable and permanent method to prevent reverse flow to fixtures. The link below shows an example of an inline check valve.

I've heard about the check valve failing on this unit but it is brand new by months. I read on this forum that you could feel one of the cold water lines to determine if it feels hotter which might indicate a failing check valve. But maybe there's a better way to check if this is the problem?

I think the information you provided is enough for me to go off of. I can probably reach out to Navien about the check valve and then maybe toy with installing the inline check valve in the future. We've been living with lukewarm showers for several months, greatly appreciate your help and information!

 

[Bannerman]

I read on this forum that you could feel one of the cold water lines to determine if it feels hotter which might indicate a failing check valve.

If cold water is flowing out from the WH through the recirculation loop return line due to the stuck open check valve, then that line will become cooler, not hotter.

 

[Fitter30]

Theres a hot water mixing valve not 2' from the heater. Follow the red line off the bottom left side runs into a valve with a black knob right side white line on bottom. Look on the knob see if has hotter or colder on it and adjust it with water running with a thermometer. Run the heater temp to 140*

 

[jhawk89]

If cold water is flowing out from the WH through the recirculation loop return line due to the stuck open check valve, then that line will become cooler, not hotter.

So after not running water for a few hours, I checked the line leading to the "recirc" label on the WH and it feels cool while the "hot" line feels warm-ish. Could this indicate a bad check valve? I'm curious, it seems like the pipes are colour coded for temp and the pipe leading out of the "recirc" is white.

Theres a hot water mixing valve not 2' from the heater. Follow the red line off the bottom left side runs into a valve with a black knob right side white line on bottom. Look on the knob see if has hotter or colder on it and adjust it with water running with a thermometer. Run the heater temp to 140*

Yes, as Bannerman mentioned, this did the trick for the hot water temp! Thanks for the tip

 

[Bannerman]

pipe leading out of the "recirc" is white.

The recirc connection is for the return from the circulation loop within the home. As the hot water will loose heat energy while it is being circulated, particularly if the pipes are not sufficiently insulated, then the hot water that is returning to that connection will be substantially cooler, but should be at least warm while circulation is occuring. If it is cold/cool, it will indicate cold water is leaking in reverse through the check valve into the return line.

If the return line becomes even cooler while hot water is flowing to a faucet, that would further prove cold water is leaking in reverse through the check valve.

while the "hot" line feels warm-ish

If the circulation pump is running, the outgoing hot line should be close to the temperature setting for the WH. Circulation is not necessarily continuous as the WH uses a sensor to measure the return water temperature, so when the return temperature meets or exceeds the return temp setting, the pump will be shut down for some time until the circulation loop cools whereby the pump will be reactivated. Recirculation maybe also programmed to only run at certain times of day when hot water is likely to be utilized, with no circulation occuring when hot water is not likely to be needed, so as to reduce fuel consumption.

A defective check valve will usually result in the hot line to be cooler when the 2-way valve is set for Internal Circulation as cold water flowing in reverse through the check valve and pump, will mix with hot water exiting the heat exchanger and buffer tank, resulting in hot water exiting the WH that is substantially cooler than the temperature setting. See flow path shown below.