Navien NPE-240A tankless - low initial pressure when 2+ faucets open

[steve80]

Hi,

Lately I've had the following issue. when 1 hot faucet is open, no problem, but when I open a 2nd hot faucet, both faucets drop in pressure, then after about 5 seconds, it gets to normal hot pressure.

I've descaled it 3 times in 2022 (we have soft water) and the water coming out was not dirty at all. I clean the water/air intake filter, etc... all the usual maintenance stuff.

I replaced the Check Valve as it had a broken gasket and caused cold water mixing into the hot water (that was a different issue), the plumber replaced the Flow Sensor and Water Adjustment Valve.

Any thoughts as to what the issue could be?

I'm hesitant to get another plumber because I've already had 3 in (1 was the installer, 2 were other companies as I was hoping they'd be better than the installer).


Thank-you in advance!

 

[havasu]

Have you tried contacting Navien Customer Support?

 

[steve80]

Have you tried contacting Navien Customer Support?

Yeah, they told me to get a plumber to call

 

[havasu]

Sorry, sounds like horrible customer service. When I installed my Navien 240 in 2009, they actually sent one of their techs to help properly install it. How time/money changes things!

 

[Twowaxhack]

Maybe the tankless isn’t getting enough cold water Until the pressure equalizes in the system when turning on another faucet.

Some heaters modulate flow until the heater can reach the outlet set point. Maybe that’s just the way Navien is within your special set of parameters it’s installed in. I hate Navien

I would install a pressure gauge and have people recreate the scenario while I watch the gauge. Install the gauge on any hose Bibb on the cold side.

 

[Twowaxhack]

If you have a pressure reducing valve, check your pressure. You might can bump it up to around 75-80 psi and get rid of your problem. Maybe……

Make sure all your valves are fully open.

 

[breplum]

What happens when you trip the relief valve. Do you have the similar problem with flow low, then high?
If you do, then for sure there is an issue within the unit or something problematic with the bypass valve ports maybe.
If not, then it must be piping or faucet ...

 

[aldridgeplbg]

Hi,

Lately I've had the following issue. when 1 hot faucet is open, no problem, but when I open a 2nd hot faucet, both faucets drop in pressure, then after about 5 seconds, it gets to normal hot pressure.

I've descaled it 3 times (we have soft water) and the water coming out was not dirty at all. I clean the water/air intake filter, etc... all the usual maintenance stuff.

I replaced the Check Valve as it had a broken gasket and caused cold water mixing into the hot water (that was a different issue), the plumber replaced the Flow Sensor and Water Adjustment Valve.

Any thoughts as to what the issue could be?

I'm hesitant to get another plumber because I've already had 3 in (1 was the installer, 2 were other companies as I was hoping they'd be better than the installer).


Thank-you in advance!

Are you on a well pump you could be experiencing the pressure fluctuate when the well pump finally kicks on when pressure drops. Could be a bad expansion tank on your well pump if that is what you have.

 

[CT18]

Yeah, they told me to get a plumber to call

Navien should get you in touch with a certified Navien company. Back in the day they were the only ones that could do warranty work on the units.

 

[Twowaxhack]

Replace the Navien when it craps out with a better brand.

You couldn’t “ gift “ me a Navien.

 

[steve80]

Thanks for the many replies.

I'll get a pressure valve and put it on an outside hose bib and test and adust the PRV as needed to get to 80 psi. All valves are fully open, I closed them off 1 at a time to see if there was any broken faucet cartridges.

Trip the relief valve, as in open it fully and leave it open?

I'm on city water.

I'll call Navien again today, see if a different rep can help me.

I'd replace this, but it's only 3-4 years old

 

[SHEPLMBR]

When was the last time it was flushed?

 

[steve80]

When was the last time it was flushed?

april 2022

 

[SHEPLMBR]

april 2022

I would say flush it now for starters and see if that helps.

 

[steve80]

I spoke with a plumber and he said to hook a garden hose to the hot service valve, so I did that and ran it for 10 minutes @ 125F and it was a solid 5 GPM the entire time. I know the navien should make more GPM, but I guess it's 5 due to the garden hose restriction (it's a 1/2").

Is this a normal GPM for this test? I read the nav can do 11.2 GPM.

I called Navien again, explained the pressure issue, and they said "please have a certified technician call back when they're infront of the unit".

 

[Twowaxhack]

The units are rated by rate of rise based off your cold water temp that you feed the heater.

Lower the incoming temp, the less hot water you’ll get out of the unit.

So you’ll need to know the incoming cold water temp and the water heater set point…..then refer to the specs to see how much hot water the unit will produce.

 

[CT18]

I spoke with a plumber and he said to hook a garden hose to the hot service valve, so I did that and ran it for 10 minutes @ 125F and it was a solid 5 GPM the entire time. I know the navien should make more GPM, but I guess it's 5 due to the garden hose restriction (it's a 1/2").

Is this a normal GPM for this test? I read the nav can do 11.2 GPM.

I called Navien again, explained the pressure issue, and they said "please have a certified technician call back when they're infront of the unit".

I would bet a large chunk of money that Navien is not getting 11GPM. That might be in a perfect setting with maybe a 20 degree temp rise. You need to look at the temp rise and then see what they say for GPM. I bet you need close to a 60 degree temp rise living in O Canada.

 

[steve80]

I found this in the manual.

I have mine set to 125F output and the input is 45F so that's an 80F temp rise... wow that's crazy.

So I guess it will get less than 5.6 GPM in the winter based on the table above?

It's weird how this was never and issue for the past 3-4 years, and it's warmer this winter than last.

 

[steve80]

After some testing with a 1/2" garden hose, I found the following:

42F in
5.0 gpm @ 125F out (83F rise)
5.8 gpm @ 115F out (73F rise)
6.2 gpm @ 110F out (68F rise)
6.6 gpm @ 105F out (63F rise)

So I guess the Navien is working as intended, just that the water coming in is too cold but we never had the issue before. So frustrating.

 

[Twowaxhack]

Use lower flow shower heads innthe guest baths