Navien units in Tiburon, Belvedere and Mill Valley do one of two jobs: an NPE tankless water heater supplying the house’s hot water, or an NCB combi-boiler heating both the water and the house through radiant floors or other hot-water heating. Both are condensing, wall-hung and electronically controlled, and both reward regular care. We repair, flush and install Navien equipment as an independent company, not affiliated with Navien, and give you the price before the work.
NPE-A2, NPE-S2 and NCB
- NPE-A2 is a condensing tankless water heater with ComfortFlow: a built-in recirculation pump and a small buffer tank that shorten the wait for hot water and smooth out temperature swings.
- NPE-S2 has the same condensing design without the pump and buffer tank. Recirculation, if you want it, comes from an external pump.
- NCB combi-boilers heat the home through a hydronic loop and make domestic hot water on demand, all from one unit. While a hot tap is open, hot water gets priority and space heating pauses, then picks up again when the tap closes.
Combi-boilers and radiant floors
Some of the larger homes on the peninsula heat with radiant floors. When the floors stop warming, the problem is often in the heating loop rather than in the boiler itself:
- Low system pressure from a slow leak or a dripping relief valve, which the boiler reports with an error.
- Air in the loop, which causes gurgling pipes and cold zones.
- Zone valves or circulator pumps that stick, leaving one area cold while the others heat.
- An expansion tank that has lost its air charge, which causes pressure swings and relief valve discharge.
We check the loop and the boiler together, so you do not pay for boiler parts when a zone valve is the culprit. See heating repair for how a no-heat visit works.
Tankless care: scale, filters and condensate
Water heated in a small heat exchanger leaves mineral scale behind, and over time it shows up as fluctuating temperature, reduced flow or an error code. A yearly flush through the isolation valves, with a descaling solution pumped through the heat exchanger, keeps that in check. During the same visit we clean the cold-water inlet filter, check the condensate line and neutralizer, and inspect the vent run and its termination outside. On windy, exposed lots a damaged or blocked termination can cause ignition faults, so it gets a close look. Our HVAC maintenance visit can include the water heater or boiler.
NaviLink and recirculation settings
NaviLink adds Wi-Fi control: you can see the unit’s status, change the temperature and set recirculation schedules from your phone. Schedules matter in big houses with long pipe runs. Recirculation running all day burns gas for nothing, while a schedule built around mornings and evenings brings hot water to the far bathroom when people actually use it.
Short bursts of cold water between two showers, sometimes called a cold-water sandwich, come from water cooling in the pipes and the unit between uses. ComfortFlow on the NPE-A2 reduces it; on other setups, recirculation settings help.
When to call
Call if the display shows an error code, hot water stops or swings between hot and cold, the boiler’s pressure gauge keeps dropping, or water appears under the unit. No hot water in a full house, or no heat on a cold night, can go to our 24/7 emergency service. Our repairs carry a 90-day warranty, and parts carry the manufacturer’s warranty. If you have a Noritz instead, see the Noritz page.
Navien by town: Tiburon, Belvedere, Mill Valley.