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Navien NB-150 DHW Priority
Afternoon. Just would like to know if anyone else experienced this item. New Navien NB-150 boiler installed. The default setting for the outdoor reset I changed from finned tube baseboard to Low mass setting. Essentially it was changed to wood flooring with the temperature range for supply from 80-140 F and the return set point range at 70-116 F. This is good for the house and the floors. What I noticed was that the indirect DHW storage tanks' aqustat was calling for hot water five times an hour. What was happening is that the cooler wood floor water was being pumped through the indirect tank and cooling the water down to the point that the aquastat called for more hot water to be pumped through. There is a parameter setting on the boiler that has the default "ON" that the DHW circ pump will be on when there is a call for heat. That parameter was changed to off. The DHW circulator pump still runs when there is a call for heat. I called Navien countless times with their response it is the wiring. I traced all of the wiring and it was done correctly. One of the third level fellas said it was time for the multimeter. I gave them all of the readings. When there is a call for DHW only the DHW circulator pump runs and the supply pump and the return (boiler) pump shuts off. That is how the parameters were set at the factory. When there is call for DHW the two main pumps have continuity but they do not run as factory set. The call for heat all three pumps run. The intresting part is on the zone control and the aqua stat. When there is a call for heat the zone control on the boiler is showing continuity and the aquastat is showing 26AC. With that piece of information Navien decided to ship a new board and the installer swapped out the old one for the new one. The end result is no difference. I decided to do a custom outdoor reset with a minimum temperature of 120. I am matching the hot water so the indirect does not cool down. The lowest I can go for the max range was 157 degrees. So the outdoor reset has a range of 120 to 157 degrees. At this time the calls for hot water has stopped. I am keeping an eye on the floors to ensure they are in the 80 degree range and not getting too hot. At this time its ok. I dont think this is ideal and boiler is not working as designed. Wanted to know if anyone else had this and what they had to do to get around this and also does anyone have any other ideas? Also what was done with the custom outdoor reset would there be issues with that? Appreciate the help.