The Navien NPE tankless water heater is available in two models, the S (Standard) and the A (Advanced). The difference between the two is the inclusion of a buffer tank and recirculation pump on the A model.
Some contractors believe they do not need to purchase an A unit simply because there is no recirculation loop in the application they are working on. However, there are still advantages that the A unit provides without the external loop. Some advantages include:
Using the circulator to do internal recirculation - which does not require an external loop. This will provide hot water to the fixtures faster because the unit will not have to go through start up.
Better control of the “cold water sandwich” or “cold water stacking”. By maintaining the buffer tank, the outlet water temperature will be more consistent during flow changes.
Providing hot water at a lower flow rate. Having the buffer tank and heat exchanger pre-heated will provide hot water at a very low flow rate, eliminating some of the issues seen with units that require a 0.5 GPM minimum flow rate to heat water.
The recirculation pump in the A model can be programed to only run when the unit reaches certain temperatures or at specific times throughout the day so that it does not run continuously and waste energy.
For more information about our NPE-A and NPE-S units, please visit tanklessmadesimple.com.