Navien 240 A installed, now questions

[tcangas]

Hello,
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

 

[havasu]

You are not using the recirc system which is built into the Navien unit. Instead, you have the Grundfos "recirc" system. it is not really a recirculation system, but rather it pushed hot water back into your cold side of the water, until the cold is tepid, and the hot is hot. If you want more faucets to have quasi-instant hot water, you can purchase more of the Grundfos thermostat end caps. As far as the cap on the recirc inlet, I can't remember, but the instructions will tell you which position to place the switches in to stop the Navien recirc system.

 

[RenewDave]

Not sure if the Navian set up to use the grundfos “transfer” recirc valve. I know Rinnai has in the instructions the use of that valve. Might give navian a call and ask if their unit will “fire” with that little flow.

 

[RenewDave]

Just checked the install manual. No instructions for the grundfos valve. Call navian before spending money on that.

 

[tcangas]

So I called Navien and they said in order for that set up to operate properly, I need to T off the supply line going into the unit, and run that into the recirc inlet (need a check valve in that run also) then set the 2 way valve to External. Tech said the way it is now there is no recirculation happening. I don't quite follow that since the valve at the farthest fixture creates a loop with the cold..unless I'm missing something. Appreciate the suggestions.

 

[havasu]

Yep, you do not have a true recirc system until you route that pipe back into the TWH recirc inlet, and eliminate the Grundfos pump.

 

[tcangas]

Yep, you do not have a true recirc system until you route that pipe back into the TWH recirc inlet, and eliminate the Grundfos pump.

Thanks again and to clarify, I'm not utilizing the Grundfos pump, only the bypass valve. Was told Navien's pump is sufficient and takes the place of any outside pump. I'm on hold w/ level 2 tech support now to get confirmation on a couple things.

 

[RenewDave]

What the navian tech is saying is that you are basically “fooling” the tankless computer so that it thinks that there is a loop. I think that might work though. How hard would it be to install a return line?

 

[tcangas]

Not hard to get a return line in there. It was put to me by my plumber that it was unnecessary and this new unit and valve would accomplish the same thing and save me the cost of the return line which was upwards of $1,500 so it seemed like an easy decision at the time.

 

[RenewDave]

That’s a little misunderstanding from the plumber of exactly that unit will do. Tankless companies try to make it sound like its a magic pill for “instant” hot water. It’s not. The pump is there, that’s all. A return loop will complete your system and you’ll be happy. It shouldn’t cost that much to pull a return loop, hook it to the unit and reprogram the computer.

 

[RenewDave]

The grundfos valve is part of the comfort series retro-recirc pump. I think only the Rinnai has their computer specifically acknowledge that that valve is in the system and will work. Right now...

 

[tcangas]

Yeah I'm thinking the return line and get it right. Thanks for all the insight, was very helpful.

 

[havasu]

I had the Navien wired remote where I could set the temperature quickly, the times the recirc system was active, flip it to vacation "off" quickly, and it displayed any fault codes. It was a great addition to my recirc system.

 

[tcangas]

I had the Navien wired remote where I could set the temperature quickly, the times the recirc system was active, flip it to vacation "off" quickly, and it displayed any fault codes. It was a great addition to my recirc system.

View attachment 17520

Mine is very accessible right inside my garage but I may rethink that one later too. Looks like I didn't do enough thinking in advance on this project

 

[breplum]

What did Navien level 2 customer service say?

 

[tcangas]

They confirmed I need to T off the supply line and into the recirc inlet then put a check valve after the T going up to the main inlet to prevent back flow. They sent me the Technical Bulletin and I attached it here. Am I wrong in assuming that if there is a Technical Bulletin on the Grundfos that it will operate "properly" with the 240A?

 

[RenewDave]

Sure looks that way. And, it won’t affect the warranty in any way, which is good. I think this will be an accepted installation method with all manufacturers, with this type of tankless.

 

[tcangas]

In your opinion, can this type of set up be comparable to have a dedicated return line?

 

[breplum]

tcangas,
Thanks for posting the Navien TSB.
The Grundfos device will get the distant fixture warm and make the cold line warm (briefly) also.
In no way is that like a dedicated return, because who likes warm water from the cold side tap?
There are undersink pump devices that will do the same thing, but at increased cost. I have mine set up under the kitchen sink with pushbutton activation.

 

[RenewDave]

I have the grundfos comfort series retro recirc in my House (too lazy to run a return line and install the full meal deal. I’m a plumber, go figure.) I put the valve under the kitchen sink and was prepared to hate it. I get about four to five seconds of warm water then I’m cold again. Well worth the time and money saved. You have have to decide if you want to roll the dice, but to save a grand, yeh, I’d try it.