# Navien 240a issues



## Jeremy26 (Aug 13, 2013)

I have a Navien 240a unit installed in external circulation mode. There is a complete 3/4 loop to all fixtures. Every fixture has hot water almost instantly except for the master shower. It is a Moen positemp valve. not sure if that makes any difference. Any Ideas?


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## PlungerJockey (Feb 19, 2010)

Go post an intro and I'll tell you about my similar experience.


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## Jeremy26 (Aug 13, 2013)

My name is Jeremy Im a master plumber in Lubbock TX. I have been in the field for 15 years. Sorry I didnt give an intro initially. Im new to this whole networking thing.


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## PlungerJockey (Feb 19, 2010)

Sorry Bud

You ahve to do it in the intro section. Go over and read a couple to get an idea of what we are looking for. We take that pretty serious here, it's about the only thing.

Better hurry before the others see you, they will throw rocks at both of us


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## PlungerJockey (Feb 19, 2010)

How big is the house?

I would change the Moen cartridge first, just to make sure its not mixing there.

I installed a Navien NPE-210 and I've had the same problem. It has a Delta shower valve. I changed the cartridge, did not fix.

The house I installed mine in is a pretty good sized house. Water is pretty much instant to most of the house, but nobody really notices anything other than the master shower.

As you probaly know, that recirc pump does not run continious. It runs till the water in the recirc line reaches the coefficent temp. The shower that is giving me all the trouble is at the end of the recirc line.

The Navien is in the basement, the recirc line runs east from the Navien to the kitchen then up to the 2nd floor, then west across the 2nd floor, then back down to the master bath shower.

I have 2 theories, the water is cooling down in the loop causing the temp in the recirc line to cause fluctuations at the master shower.

or the water is mixing from the recirc line and the shower supply coming from the Navien.

I've talked to Navien, they were not much help. The homeowner has a Navien certified warranty tech showing up Thursday. I hope to know what the problem is then.

I thought about running a direct line from the Navien to the shower, or opening it up and installing a check valve at the shower recirc and supply lines.

The homeowner complaint has been that is takes along time to get there and the temp flucuates. It is very inconsistant with the problems. I have checked the temp at the shower with a temp probe and it showed a 10 degree fluctuation. I also got a severe flutuation at the master bath lav.
The temp at the kitchen sink was pretty consistant. The temp at the Navien out the hot side service valve has no fluctuation.

There you know everthing I know. I doubt the problem is with the unit. It is either a long recirc line or cold water mixing near the problem shower.

In the future, if it is a residential application I will not install the Navien recirc system. I will run the recirc line thru a small electric W/H with a recirc pump I can control when it comes on and goes off.

I should also mention I have not had any trouble with their products till now, but it has been a bid pain in the butt.

Hope this helps, if it does not check back Thursday or friday and I should now more.


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## Jeremy26 (Aug 13, 2013)

Any word on what the navien rep had to say Mr.jockey?


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## PlungerJockey (Feb 19, 2010)

Recirc loop is too long. Navien with the internal tank and pump was a poor choice for the application. Next time I'll use a standard tankless with a external pump and tank.


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## rzp 06 (Mar 21, 2012)

Just out of curiosity, did the guy from Navien tell you what the max recirc loop length on the 240 is?


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## PlungerJockey (Feb 19, 2010)

Anything over 100 feet and you are SOL, issues develope on anything over 70 feet. With the long lines, the parasitic heat loss is too great for the unit to compensate for it.


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## Drewp311 (Sep 17, 2011)

If the house was looped for the recirc line going to each manifold then all the hot lines should have been insulated. Were they? I can't imagine if they were all wrapped sufficiently why you couldn't exceed 100' easily. My theory is that there could be a hot and cold line crossing/touching somewhere as it comes into the master bath.


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## PlumbDumber (Aug 7, 2013)

PlungerJockey said:


> How big is the house?
> 
> I would change the Moen cartridge first, just to make sure its not mixing there.
> 
> ...


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## PlungerJockey (Feb 19, 2010)

Drewp311 said:


> If the house was looped for the recirc line going to each manifold then all the hot lines should have been insulated. Were they? I can't imagine if they were all wrapped sufficiently why you couldn't exceed 100' easily. My theory is that there could be a hot and cold line crossing/touching somewhere as it comes into the master bath.


On my project, to the best of my knowledge the pipes are not insulated. It never was a problem with the old 75 gal and constant recirculating pump. The problem with the Navien is it controls the recirculating pump. It may not kick on for 12 hours. I'm not going to stand there and time it. 

I can force the pump on by resetting the unit and check the temp at the fixtures and everything is prefect. If I could change the parameters on the Navien and make the pump run more often it would not be an issue. 

I'm going back over next week and I'm going to run a pex from the W/H to the master shower. The line will be about 25' long, the wait for hot water won't be a issue and it will take care of the fluctuation.


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