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Problem with preheated water and Navien Tankless System
I have a Navien 240 A NG Tankless hot water heater. The unit dip switches are set for internal recirculating pump which I need to circulate the water to the back of my house. I have the unit set at 130 degrees. The unit works fine during milder weather.
To complicate matters, I have a geo thermal heat pump that generates hot water as a by product when it is operating. The hot water is pumped into a hot water storage tank. That storage tank is connected to the Navien. During colder days, it produces about 110-115 degree water that then feeds the Navien. This is where I run into problems. During colder days the Navien is receiving pre heated water at 110 - 115 degrees. For some reason, it will not fire and will not reach the 130 degree set point, when the source water is that high. The Navien works fine when the source water is less that 105ish.
I do not have the DIP switch # 6 set for storage tank use because if you have #6 on, it will not allow the recirculating pump to work. I need the recirculating for the back of my house.