# Navien gas pressures



## highpoint

Installed the combi-navien in a house. It kept in faulting out. So my tech thought he would 'set' the gas pressure. Well naviens are a new ball game. I am stumped in how to get it to where it should be. The techs on the phone know nothing. They told me to fire it in high fire and if there 7 or so inches going into the unit , it's fine!
I'm not gonna sign this unit over without it being 3oo%.
Any help would be appreciated.


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## ZL700

What error code?

They were trying to get you to use a dip switch to force it into high fire and read the inlet gas pressure at that time with a manometer. Almost a standard test for tankless.

As with all high tech equipment, lack of proper tools, test equipment and product specific knowledge or training it will be a tough one to solve.


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## ZL700

On another note, I stopped in thier booth at the AHR show In Chicago a few weeks ago and they plan on releasing a new tankless line with a pressure assisted gas valve, in essence it will suck on the gas line to get the correct inlet pressure. Basically an on-board gas compressor. :thumbup:


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## pilot light

hmmm... go ahead....:laughing:


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## Gettinit

ZL700 said:


> On another note, I stopped in thier booth at the AHR show In Chicago a few weeks ago and they plan on releasing a new tankless line with a pressure assisted gas valve, in essence it will suck on the gas line to get the correct inlet pressure. Basically an on-board gas compressor. :thumbup:


Adding more problems on there end....so I guess we will be looking for a negative pressure at the burner then?


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## Gettinit

highpoint said:


> Installed the combi-navien in a house. It kept in faulting out. So my tech thought he would 'set' the gas pressure. Well naviens are a new ball game. I am stumped in how to get it to where it should be. The techs on the phone know nothing. They told me to fire it in high fire and if there 7 or so inches going into the unit , it's fine!
> I'm not gonna sign this unit over without it being 3oo%.
> Any help would be appreciated.


7 or so...that may be fine at high fire but what about the low end? Let me guess, they said it wasn't important?


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## OldSchool

Had the same problem with bureaus ....
They seem to suck the gas from the line
Gas pipe was sized right and pressure would drop to 4" on high fire.... Unit would shut down

I had gas company change main regulator on the meter and it had to be defective because it couldn't keep up with the demand

After the new reg it worked fine

Sent from my miniature laptop


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## GrumpyPlumber

OldSchool said:


> Had the same problem with bureaus ....
> They seem to suck the gas from the line
> Gas pipe was sized right and pressure would drop to 4" on high fire.... Unit would shut down


Holy cow, where normal MFP is set to 3.5" on most boilers, that would be cutting it close, maybe even create CO or rollout problems.


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## Gettinit

GrumpyPlumber said:


> Holy cow, where normal MFP is set to 3.5" on most boilers, that would be cutting it close, maybe even create CO or rollout problems.


Depends on the equipment now a days. Not everything is 3.5" anymore. It is also good to have an combustion analyzer along with a manometer anyway.


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## OldSchool

The pressure I was talking about was main line pressure not manifold

Sent from my miniature laptop


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## GrumpyPlumber

OldSchool said:


> The pressure I was talking about was main line pressure not manifold
> 
> Sent from my miniature laptop


I know, hence my reference to the closeness to 3.5" - scary....someone turns on a burner on the stove top and there's the difference.


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## GrumpyPlumber

Gettinit said:


> Depends on the equipment now a days. Not everything is 3.5" anymore. It is also good to have an combustion analyzer along with a manometer anyway.


Obviously a multi-stage GV for condensing will have differences, I was making a notation on the STD for 3.5" on traditional MFP's, with a main pressure @ 4" - cutting it real close.


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## OldSchool

The main pressure with nothing running was 7"

Then on start up it would drop to 4" and boiler would code out at 6a which is flame failure

The whole problem was the main reg

Sent from my miniature laptop


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## ZL700

Many tankless will run down as low as 4" inlet, many times with a reduced max BTU however, the majority cant handle the swings in inlet pressure caused by insufficient piping, reg and meter.


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## johnlewismcleod

Is this the NR-240 2K BTU Navien?


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## ZL700

johnlewismcleod said:


> Is this the NR-240 2K BTU Navien?


OP said it was a combi, so the CH series combi boiler


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## johnlewismcleod

ZL700 said:


> OP said it was a combi, so the CH series combi boiler


Thanks 

It sounds like you're starved for gas capacity. If this is a remodel install you may need to either up-size the gas line, get a higher yield meter, or go back to tank heater.

The Navien 240's need gas and lots of it. In some service areas of DFW they can't function period because of the antiquated service piping and demand during cold weather.

You need a minimum of 7" w.c. available _while_ firing at high burn. There is a port on the unit where you can connect your manometer and monitor what you've got while firing.


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## gtmechanic

*7" at inlet on high fire*

manual states 3.75" at high fire at boiler.


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## johnlewismcleod

gtmechanic said:


> manual states 3.75" at high fire at boiler.


Yep...that's the stated minimum, but it needs 7" regardless to actually run at high fire. 

It's possible that in the lab with zero friction loss and an unrealistic BTU capacity at the regulator it might work in theory, but in the real world you need 7" minimum.

I suspect with a manometer on the unit monitoring the high fire the OP will find his water column drops to or below 3.5".


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## pilot light

OldSchool said:


> Had the same problem with bureaus ....
> They seem to suck the gas from the line
> Gas pipe was sized right and pressure would drop to 4" on high fire.... Unit would shut down
> 
> I had gas company change main regulator on the meter and it had to be defective because it couldn't keep up with the demand
> 
> After the new reg it worked fine
> 
> Sent from my miniature laptop


No line pressure reg after the meter, so line pressure 7 to 14 wc after the meter ?


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## hanksplumbing

highpoint said:


> Installed the combi-navien in a house. It kept in faulting out. So my tech thought he would 'set' the gas pressure. Well naviens are a new ball game. I am stumped in how to get it to where it should be. The techs on the phone know nothing. They told me to fire it in high fire and if there 7 or so inches going into the unit , it's fine!
> I'm not gonna sign this unit over without it being 3oo%.
> Any help would be appreciated.


when it comes to naviens or any on demand you have to be sure to use a gas reg that reacts quickly like an appliance reg , because of the fast changes in demand a regular gas reg will fail . (thats my experience) of course it does depend on the error code , what i have also learned is that even though a 1/2 reg can handle the btu load , you must use a 3/4" reg no exceptions , and a 3/4" line . some people feel the maxitrol reg is the best and some say petrio regs are better . but really the error codes are the real starting point .
i have been on a jobsite where the unit fired perfect 7"wc , took the gauge off capped the line fired it back up , then the reg failed . if you can get me the error codes i maybe some help if not . i can get you in contact with someone that knows navien better than anyone else .


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## pilot light

hanksplumbing said:


> when it comes to naviens or any on demand you have to be sure to use a gas reg that reacts quickly like an appliance reg , because of the fast changes in demand a regular gas reg will fail . (thats my experience) of course it does depend on the error code , what i have also learned is that even though a 1/2 reg can handle the btu load , you must use a 3/4" reg no exceptions , and a 3/4" line . some people feel the maxitrol reg is the best and some say petrio regs are better . but really the error codes are the real starting point .
> i have been on a jobsite where the unit fired perfect 7"wc , took the gauge off capped the line fired it back up , then the reg failed . if you can get me the error codes i maybe some help if not . i can get you in contact with someone that knows navien better than anyone else .


 I have used a 5lbs to inches 1/2 pietro reg on a navien and its fine! No issues!


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## Gettinit

Who would ever put a Pietro and a Maxitrol in the same class? Maxitrol shouldn't be in the same country. I have never had a problem with those crap Maxitrols.


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## johnlewismcleod

Gettinit said:


> ... I have never had a problem with those crap Maxitrols.


Typo?


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## Gettinit

johnlewismcleod said:


> Typo?


No, just that they are crap compared to a Pietro and I have never had a problem with a Maxitrol on this application.


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## hanksplumbing

pilot light said:


> I have used a 5lbs to inches 1/2 pietro reg on a navien and its fine! No issues!


3/4" line after reg or before ? every issue i ever heard of was never with a pietro reg , i know that this brand was being used as a solution for alot of gas related issues .


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## pilot light

3/4 before and after always reduce regs pipe size if possible. It also is the closest when specing a reg for that application to a cr 240!


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## Surfing Plumber

I wouldn't go with Navien, check out their complaint

http://www.complaintsboard.com/comp...ny-does-not-stand-behind-product-c617997.html


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## Gettinit

Surfing Plumber said:


> I wouldn't go with Navien, check out their complaint
> 
> http://www.complaintsboard.com/comp...ny-does-not-stand-behind-product-c617997.html


They all have their problems. I wouldn't go by a HO assessment.


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## antiCon

not too familiar with navien but if there like noritz there should be a min./max. on the sticker on the cover.
min. burn on the manifold in the unit typically is around .65 ... on high 2.8ish and should never drop below 7in. at supply (FOR NORITZ) 
so should be on sticker with model/serial #


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## Widdershins

*You done now?*



Surfing Plumber said:


> I wouldn't go with Navien, check out their complaint
> 
> http://www.complaintsboard.com/comp...ny-does-not-stand-behind-product-c617997.html


I'm glad you got that out of your system.

Check back in when you have more than one complaint to register.


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## pilot light

It is wise to place the reg at specs!:no:


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