Navien 240 A install question

[tcangas]

Hello experts,
Just had this unit installed and the plumber suggested going with a Grundfos bypass valve at the farthest fixture to avoid the cost putting in a return line. Said it would work just as good. We're getting hot water quicker than before but still over a minute at some fixtures.

What doesn't seem right to my simple mind is how the recirc inlet can be left capped off/unused and this still work-see pic. I also saw some pics of a similar unit but it had a T in the cold water inlet that fed into this recirc inlet. Is this necessary for the Navien to recirculate property? Could this be why we still have to a good while for hot water? The DIP switch are currently set to 1 and 2 On and 3 Off and Int on the 2 way valve. Thanks in advance for any help

 

[Breplum]

Hi tcangas...I see you posted the same issue on Plumbing forums site.
What did level 2 at Navien say?
I would guess that settting the valve for "external" bypass and there are parameter settings that you can invoke without changing any piping.
Of course with the Grundfos bypass valve, the resulting warm water on the cold side should be a deal killer anyway.
But doing aftermarket dedicated recirculation on and existing copper piping system, with typical short sweep 90 degree elbows, is not a great idea -though it is done all the time, erosion will eventually likely take its toll.
Please update us?

 

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[tcangas]

Hi tcangas...I see you posted the same issue on Plumbing forums site.
What did level 2 at Navien say?
I would guess that settting the valve for "external" bypass and there are parameter settings that you can invoke without changing any piping.
Of course with the Grundfos bypass valve, the resulting warm water on the cold side should be a deal killer anyway.
But doing aftermarket dedicated recirculation on and existing copper piping system, with typical short sweep 90 degree elbows, is not a great idea -though it is done all the time, erosion will eventually likely take its toll.
Please update us?

They confirmed that in order for the bypass valve to have any effect, we have to T off the supply line into the recirc inlet. They sent me the Technical Bulletin on it that shows the set up-I tried to upload it here but saying file is too big but it's only 459KB. Stupid question, if they have a Technical Bulletin on this then is not safe to assume that this set up actually works albeit maybe not as good a dedicated return line?

 

[CPTJOE]

They confirmed that in order for the bypass valve to have any effect, we have to T off the supply line into the recirc inlet. They sent me the Technical Bulletin on it that shows the set up-I tried to upload it here but saying file is too big but it's only 459KB. Stupid question, if they have a Technical Bulletin on this then is not safe to assume that this set up actually works albeit maybe not as good a dedicated return line?

I've got the setup you're asking about. I have an NPE-240A installed without a dedicated re-circulation line. Instead it uses the existing cold water line back to the water heater with a bypass valve from the hot to the cold at the furthest fixture. At the heater itself the cold branches with a line going into the cold water-in and another into the recirculate-in. The DIPs are set to 1-ON and 2-OFF with the two-way valve set to EXT - this seems to be incorrect according to the manual with the DIPs set for internal re-circulation and the valve set to external, but it does work.

Unless you like warm water coming out your cold fixtures, especially the one where the bypass valve is (happens to be my master bath sink), I wouldn't recommend this setup. The bypass valve (Grundfos) is loud and seems to open about every 20 minutes regardless of the demand for hot water. I'm also not sure what controls when the re-circulation kicks in, if it's the water heater or the bypass valve?

Keep in mind if you drink water from the tap, filtered or not, there's a good chance it's been through the heater. Ever since our tankless was installed I've been suspicious about drinking water that recirculated through the water heater for who knows how many times.

Lastly the jury is still out for us as to if the Navien and associated setup is actually any more cost-effective than my old tank heater. I haven't noticed any appreciable decrease in my gas bill (probably because the re-circulation is running every 20 minutes), but I have noticed an increase in my water bill - likely due to having to run the water enough to get the hot out of the cold line when we want to get any cold water.

For the heck of it I tested switching the two-way valve to INT (the DIPs were already set for internal re-circulation). This resulted in no hot water at all, even after running it for several minutes. I'm guessing the flow sensor didn't detect the demand for hot water based on the current piping configuration.

If I had to do it over again, I would have opted for the dedicated external re-circulation line (since my walls were opened up anyway, but my plumber didn't offer it I guess to keep the costs down). Internal re-circulation seems like it would have been the next best option instead of the 'use the cold line as the -recirc' setup I have now. Yes, I don't have to wait a long time for hot water with the current setup - it's lukewarm until the heater kicks in, but the downsides outweigh the benefit in my opinion.

 

[tcangas]

I've got the setup you're asking about. I have an NPE-240A installed without a dedicated re-circulation line. Instead it uses the existing cold water line back to the water heater with a bypass valve from the hot to the cold at the furthest fixture. At the heater itself the cold branches with a line going into the cold water-in and another into the recirculate-in. The DIPs are set to 1-ON and 2-OFF with the two-way valve set to EXT - this seems to be incorrect according to the manual with the DIPs set for internal re-circulation and the valve set to external, but it does work.

Unless you like warm water coming out your cold fixtures, especially the one where the bypass valve is (happens to be my master bath sink), I wouldn't recommend this setup. The bypass valve (Grundfos) is loud and seems to open about every 20 minutes regardless of the demand for hot water. I'm also not sure what controls when the re-circulation kicks in, if it's the water heater or the bypass valve?

Keep in mind if you drink water from the tap, filtered or not, there's a good chance it's been through the heater. Ever since our tankless was installed I've been suspicious about drinking water that recirculated through the water heater for who knows how many times.

Lastly the jury is still out for us as to if the Navien and associated setup is actually any more cost-effective than my old tank heater. I haven't noticed any appreciable decrease in my gas bill (probably because the re-circulation is running every 20 minutes), but I have noticed an increase in my water bill - likely due to having to run the water enough to get the hot out of the cold line when we want to get any cold water.

For the heck of it I tested switching the two-way valve to INT (the DIPs were already set for internal re-circulation). This resulted in no hot water at all, even after running it for several minutes. I'm guessing the flow sensor didn't detect the demand for hot water based on the current piping configuration.

If I had to do it over again, I would have opted for the dedicated external re-circulation line (since my walls were opened up anyway, but my plumber didn't offer it I guess to keep the costs down). Internal re-circulation seems like it would have been the next best option instead of the 'use the cold line as the -recirc' setup I have now. Yes, I don't have to wait a long time for hot water with the current setup - it's lukewarm until the heater kicks in, but the downsides outweigh the benefit in my opinion.

Check this TSB out. Your DIP settings are wrong and you also need to change the Parameter settings. It's working good for me. I have my Navien set to 130 F and I get warm water quickly which we can work with because we don't have to wait 2.5 minutes to get any warm water before we step in the shower so it reduces the wasted cold water. But using the cold water pipe for recirc is still going to leave you waiting for the hottest water if you need it to say do dishes-our Grundfos vale is at the kitchen sink. So I'm sure it's not as ideal as a dedicated recirc line would be but it's definitely saving us time and water waiting for the all cold water to purge the lines like we were before.

This site is not letting me upload the pdf saying it's too big so if you want me to send you the pdf email me at tony@american-california.com and I'll send it to you.