Dradam
Member
Tech support is not open yet:
Just had installed a Navien 240a. Using the internal pump to set up an external re circulation line through the cold water system as return with a Grundfos comfort valve at the last fixture in the line. This seems relatively new for Navien and is in a recent Navien technical bulletin from 04/18/16.
The system is working as worked through by Navien tech support.
1) Two way valve set to external
2) Dip switch 1: on 2: off (making it look like internal recirculation)
3) Parameter 17 set to on- "Enable thermal bypass valve". (I am told by tech support that this lets the unit recirculate with much lower flows)
So here's my question:
The above system is working and sending warm water to may last fixture on schedule-- but it doesn't stay warm and I get a bit of a lukewarm sandwich until the full system kicks in.
How do I keep the water at the last fixture as hot as possible during scheduled recirculation times?
There is mention of :
Parameter 12 : Pump cycle interval time (20 is currently default)
Parameter 14: Return line sampling time (30 is currently default)
I am not sure how or if I should adjust these.
When the recirc schedule turns on it seems that my unit will then shut off when the cold water return to the unit is about 86 degrees. The water in the hot line then cools down (creating a sandwich) before recirc turns on again.
So what is the endpoint shutting off the recirc?:
Is it a temp parameter back at the unit?
Is it a flow sensor at the unit shutting off when the Grundfos valve closes at 99 degrees slowing return flow ?
Will changing parameters 12 or 14 resume recirc sooner ?
If anyone has a pdf of technical bulletian 2016-A-001 and 002 I would love to read them.
Thanks for your Input.
Just had installed a Navien 240a. Using the internal pump to set up an external re circulation line through the cold water system as return with a Grundfos comfort valve at the last fixture in the line. This seems relatively new for Navien and is in a recent Navien technical bulletin from 04/18/16.
The system is working as worked through by Navien tech support.
1) Two way valve set to external
2) Dip switch 1: on 2: off (making it look like internal recirculation)
3) Parameter 17 set to on- "Enable thermal bypass valve". (I am told by tech support that this lets the unit recirculate with much lower flows)
So here's my question:
The above system is working and sending warm water to may last fixture on schedule-- but it doesn't stay warm and I get a bit of a lukewarm sandwich until the full system kicks in.
How do I keep the water at the last fixture as hot as possible during scheduled recirculation times?
There is mention of :
Parameter 12 : Pump cycle interval time (20 is currently default)
Parameter 14: Return line sampling time (30 is currently default)
I am not sure how or if I should adjust these.
When the recirc schedule turns on it seems that my unit will then shut off when the cold water return to the unit is about 86 degrees. The water in the hot line then cools down (creating a sandwich) before recirc turns on again.
So what is the endpoint shutting off the recirc?:
Is it a temp parameter back at the unit?
Is it a flow sensor at the unit shutting off when the Grundfos valve closes at 99 degrees slowing return flow ?
Will changing parameters 12 or 14 resume recirc sooner ?
If anyone has a pdf of technical bulletian 2016-A-001 and 002 I would love to read them.
Thanks for your Input.