Navien NPE 240A (NG)

[anh]

We are getting only cold water and if we are lucky, after 5-10min we would get warm water for a little while. I have cleaned the system with vinegar. I am about to replace the check valve. Please help me understand the following:

1. Per the front panel, at times, the temperature of the water going out is colder than the water coming in. Most of the time, the in/out temperatures are about the same. Is that normal?
2. The cold water intake, the pipe into the WH is feels warm and may be a bit hot at times. Would this be a check valve issue?
3. Is the 2-way valve the same part as the check valve?
4. The hot water out is connected to the condensation pipe, is that normal? There is no pipe going into the recirculation inlet as that was is capped.

Thank-you!

 

[anh]

Here is what they piping looks like. Thanks again.

 

[Sponsor]

 

[GReynolds929]

The 2-way valve is not the check valve. An easy way to isolate the check valve as the issue is to set the 2-way valve to external. If the temperature issue goes away you have a bad check valve. As an aside, you need to remove the condensation drain from your T&P drain line. Condensate from combustion will eat metal if not neutralized and you will have a leak.

 

[Fitter30]

Two way valve set to internal? What does flow sensor read? The in and out temperature sensors how far apart are they?

 

[Bannerman]

Below, is the flow diagram for the NPE-240A Internal Circulation setting.

If the internal Check-Valve remains stuck open, which is a fairly common issue with that tankless model, some or all incoming cold water flow will bypass the heat exchangers and instead, flow directly to the hot water outlet connection through the 2-way valve. As water flow will bypass the flow and temperature sensors, the water exiting from the unit could potentially be colder than the temperature sensor is reporting.

Further to GReynolds comment regarding the combined condensate and pressure relief valve drain lines, they require separate piping runs. Currently, if the pressure relief valve should release, the water being released under pressure will flow back-up into the gas burner's condensate drain pan and possibly also into the exhaust vent piping.

 

[Breplum]

Your checklist.
1. replace the check valve.
2. Have a plumber redo condensate in pvc to outdoors or add a neutralizer kit before joining to copper