Navien NPE-240A2-NG wakes up every 5 minutes in the morning

[fredb]

Hi there!

We had a brand new Navien NPE-240A2-NG installed outside our house. We're using the internal recirculation and I have it scheduled to run during the day 7am-10:30pm. Everything works fine, I get hot water really fast. Haven't changed any other settings other than the schedule and max temp (139F). Starting at 7am, outside of the recirculation schedule it wakes up briefly (10secs maybe) every 5-10min. I was reading that some Navien units briefly fire up to keep the heat exchanger warm, even when idle, especially if the ambient temperature is cold. We're in the Bay Area and it gets to ~40F during the night, so not all that cold in my book. I haven't checked if it wakes up throughout the day or just early in the morning.

Is there something I can change on the settings (including installer settings) so it doesn't wake up so often? It's not a huge problem but still something we can hear.

Thank you for your help!

 

[Bannerman]

some Navien units briefly fire up to keep the heat exchanger warm, even when idle,

The Navien 'A' tankless models such as your 240-A2, in addition to being equipped with an internal circulator pump, is also equipped with an internal buffer tank.

Since water must be flowing through the heat exchanger before the burner will ignite, the initial flow from most if not all tankless units, will exit the heat exchanger, close to the incoming water temperature until the burner is fully ignited and supplying sufficient heat into the already flowing water.

Because hot water needs to continue flowing constantly for the burner to remain ignited, short hot water bursts such as turning the hot faucet ON/OFF/ON while rinsing dishes, will commonly result in a 'hot water sandwich' condition at the faucet due to the repeated initial cold flow from the heat exchanger each time a faucet is first opened, prior to the burner igniting each time.

The 'A' model internal buffer tank provides a small amount of hot water storage after the HE, so the initial cold water exiting from the heat exchanger, will mix with the hot water within the buffer tank, which will result in hot water more rapidly being supplied to fixtures with minimal 'hot water sandwich' effect.

The internal circulation mode, will cause the pump to periodically circulate water from the buffer tank, back through the HE, to ensure the water in the tank, will be continue to be maintained at the desired outlet temperature, ready for the next following hot water use.

 

[Sponsor]

 

[fredb]

Thanks for taking the time to answer! I think I follow what you're saying but the tank wakes up every 5 minutes or so every morning starting a 7am while everyone is sleeping. So there is no hot water bursts. I'm not sure if this is normal. During the day we get hot water super quickly so that part is great. I just don't understand why it wakes up every 5 minutes in the morning outside of the 30 minutes recycling schedule.

"The internal circulation mode, will cause the pump to periodically circulate water through the buffer tank, to ensure the water in the tank, will be continue to be maintained at the desired outlet temperature, ready for the next following hot water use." - Is this what's happening every 5 minutes? Is this a setting i could change? Would it be the "Recirculation Differential Temperature"? It is set at the default right now (9F).

Thank you for your help!

 

[Breplum]

I hope your unit is not outside a bedroom. That is not a place we ever recommend placement for the reason that it is not completely silent.
There may be parameter settings like the old A models had for 'exercise' timing, which controls how often it checks itself.
Call Navien if you dare try.

 

[GReynolds929]

Why do you need 139° water?

 

[fredb]

Why do you need 139° water?

I don't I need to lower it!

 

[Reach4]

Starting at 7am, outside of the recirculation schedule it wakes up briefly (10secs maybe) every 5-10min. I was reading that some Navien units briefly fire up to keep the heat exchanger warm,

If using an external recirculation line, I would think the purpose would be to keep the water in the hot water pipes warm.

Looking at https://million.requested-info.com/...heets/NPE-2_Installation_Manual_EN_210216.pdf I see "3.4.4 Navien HotButton Kit" starting on page 30. This would solve your noise problem, and it would save energy. The downside is that you would have to press the button as you enter the bathroom. You might be able to trigger it with a motion sensor instead of a button.

 

[fredb]

Trying to interact in this thread but all my messages are waiting for moderator approval for some reasons. Hard to get a conversation going

 

[GReynolds929]

I don't I need to lower it!

To lower the temperature use the down arrow key on the front panel till you get to the temperature you want.

 

[GReynolds929]

If you have the installation and operation manual, page 98-99 explain how to access advanced settings and adjust the recirculation pump settings and intervals if needed.
I would first lower the temperature, make sure the two-way valve is set to internal, verify the recirc settings. Are you getting any error messages?

 

[fredb]

If you have the installation and operation manual, page 98-99 explain how to access advanced settings and adjust the recirculation pump settings and intervals if needed.
I would first lower the temperature, make sure the two-way valve is set to internal, verify the recirc settings. Are you getting any error messages?

Yes I've lowered the temperature and monitoring in the morning. Will give update! Not error messages. Again, I'm happy about getting fast hot water in the house. Just don't understand why it wakes up so often in the morning.