Navien Tankless Water Heaters, Boilers and Combi-Boilers for Chicago-Area Homes

Tankless water heater, boiler or combi-boiler: what each one does

A condensing tankless water heater heats water on demand as it flows through a heat exchanger. There is no storage tank keeping water hot around the clock, so the unit fires only when a fixture calls for hot water. Capacity is expressed as a flow rate at a given temperature rise, which matters a great deal here because incoming water is cold in a Chicago winter.

A boiler is a heating appliance. It heats water and circulates it through a hydronic distribution system — cast-iron radiators in an older Chicago bungalow, fin-tube baseboard in a post-war suburban home, or radiant tubing in a newer build or an addition. It is sized from the building's heat loss, not from how many showers run at once.

A combi-boiler does both. One wall-hung unit heats the home and produces domestic hot water, usually prioritizing the hot-water call over the heating call for the minute or two the tap is open. Combi units are popular where mechanical-room space is tight, but they have to be selected carefully: the same appliance must satisfy the building's heat loss and the household's simultaneous hot-water demand.

Our main Navien page covers equipment, service and sales in more detail: Navien installation and service.

Where the Navien lineup fits

Navien's condensing tankless water heaters — the NPE-A2 and NPE-S2 families — are domestic hot water appliances. The A2 series includes integrated recirculation features that suit homes with long runs to a distant bathroom; the S2 series is a straightforward condensing tankless unit where an external recirculation strategy or none at all is appropriate.

On the hydronic side, the NFB-H and NHB-H are boilers: heating appliances for radiators, baseboard or radiant. The NCB-H and NFC-H are combi-boilers, handling space heating and domestic hot water in a single wall-hung cabinet. Which family fits depends on the building's distribution system, its heat loss, and how much hot water the household actually uses at once.

Around that equipment sit the controls and accessories. NaviLink connectivity allows setpoint monitoring and adjustment from a phone and can make service conversations more precise. Recirculation options — internal on some models, external pump-and-return arrangements on others — address wait times at distant fixtures. Compatible Navien water-treatment products address water quality, which directly affects heat-exchanger life in the hard water common across Chicagoland.

This is not a model catalog, and the right answer is rarely the largest unit. Equipment selection follows the calculations, not the other way around.

For tankless installation, replacement and repair specifically, see our tankless water heater services page.

Manufacturer-qualified specifications worth knowing

The numbers below are manufacturer-published ratings for condensing equipment, tested under laboratory conditions. Real-world performance depends on sizing, installation, controls, water quality, the building and how the system is used.

• Condensing tankless water heaters rated up to .96 UEF, depending on model and configuration
• Boilers and combi-boilers rated up to 95% AFUE, depending on model
• Stainless-steel heat exchangers used across the condensing tankless and hydronic lines
• Compact wall-hung cabinets that free floor space in tight mechanical rooms and closets
• Boiler turndown ratios up to 15:1, allowing the unit to modulate down on mild days instead of cycling at full fire

What correct selection actually requires

Choosing equipment from a brochure is where most disappointing installations begin. A proper selection is an engineering exercise, and every one of the following inputs can change the answer:

• Simultaneous hot-water demand — how many fixtures realistically run at the same time, and at what flow rate
• Winter incoming-water temperature, which sets the temperature rise a tankless unit must deliver in January, not in July
• A building heat-loss calculation for any boiler or combi-boiler, based on the actual structure rather than square footage rules of thumb
• Gas capacity — meter size, pipe size and length, and the load of every other gas appliance in the building
• Venting — material, length, termination clearances and whether the existing chimney or sidewall arrangement can be used
• Condensate drainage and neutralization, including where the condensate can legally and practically go
• Electrical supply for the appliance and any pumps or controls
• Water quality, since hardness and sediment drive heat-exchanger scaling and service intervals
• Available space, service clearances and how the unit will be reached for maintenance
• Local code review and permitting, which differs between Chicago and the surrounding suburbs

If you want that review before spending money on equipment, our consulting service is built for exactly that conversation — heating, hot water and distribution looked at together.

Installation and tank-to-tankless conversion

Replacing a storage tank with a condensing tankless unit is rarely a straight swap. The gas supply frequently needs to be verified or upsized, new venting has to be routed and terminated correctly, condensate drainage must be provided, isolation valves belong on the unit so it can be serviced, and the electrical supply has to be in place. Done properly, the result is a wall-hung unit with no standby tank losses and hot water that does not run out; done carelessly, it becomes a unit that nuisance-faults and is impossible to service.

Boiler and combi-boiler replacements carry the same discipline plus the hydronic side: near-boiler piping, circulator selection, air and dirt separation, expansion, zoning and controls. Older Chicago-area systems are often converted from oversized cast-iron boilers, and the new equipment only delivers its rated efficiency if the distribution system and controls let it modulate and condense.

For replacement planning on the hydronic side, see boiler installation and replacement.

Maintenance, descaling and water quality

Annual service is the single biggest factor in how long this equipment lasts. On a tankless water heater, that means descaling the heat exchanger through the isolation valves, cleaning or replacing the inlet filter, inspecting the burner and venting, checking combustion and reviewing stored fault history. Chicago-area water is hard enough that skipping descaling shows up as reduced flow, temperature swings and eventually error codes.

Water treatment is part of the maintenance conversation rather than an upsell. Reducing hardness and sediment before the appliance slows scale formation in the heat exchanger and protects fixtures and other water-using appliances at the same time. Equipment should be matched to what a water test actually shows, not chosen generically.

Boilers and combi-boilers need their own annual attention: combustion testing, condensate trap and neutralizer service, system pressure and expansion checks, relief-valve inspection, circulator and air-separation checks, and cleaning of the heat exchanger where the manufacturer calls for it.

Water quality has its own page — see whole-house water filtration and treatment.

Common symptoms and error-code diagnosis

A displayed error code is a starting point, not a diagnosis. The code narrows the area; testing identifies the cause. Clearing a code without finding what triggered it usually means the same fault returns, sometimes with additional damage.

• Ignition problems — gas supply or pressure, ignition components, venting restriction, flame proving or control faults
• Scale buildup — reduced flow, longer heat-up, noise in the heat exchanger and efficiency loss
• Insufficient hot water — undersized equipment for winter temperature rise, scaling, a fouled filter or a distribution issue
• Fluctuating water temperature — flow below the activation threshold, mixing-valve problems, recirculation set up incorrectly or scaling
• Cold radiators or uneven heat — air in the system, circulator or zone-valve faults, distribution balance or control problems
• Boiler short cycling — oversizing, incorrect control settings, low flow through the heat exchanger or a limit tripping early

If the heat is the problem rather than the hot water, start with boiler repair and no-heat service.

Our full heating service list is on the heating services page.

Repair or replace, residential or commercial

Repair usually makes sense when the unit was correctly sized and installed, maintenance has been kept up, parts remain available and the failure is a discrete component. Replacement becomes the honest recommendation when the appliance was wrong for the building from the start, when the heat exchanger is compromised, when repeated faults trace back to an installation problem that cannot be corrected economically, or when repair costs begin approaching the cost of correct new equipment. We give you the findings and the numbers and let you decide; there is no sales pressure attached to a diagnosis.

The same equipment families appear in light commercial work — small multi-unit buildings, salons, restaurants and offices — where simultaneous demand and recovery matter even more than they do in a single-family home. Commercial selection follows the same calculations, with cascade or multi-unit arrangements where a single appliance cannot cover the load.

What we are certified for, and what we are not claiming

Right Away Plumbing & HVAC is certified specifically for Navien tankless water heater installation, service and maintenance. That certification is limited to tankless water heaters and we do not extend it to the rest of the lineup.

Navien boilers, combi-boilers and other Navien equipment are installed and serviced by our licensed plumbing and HVAC technicians following the manufacturer's published specifications. We are licensed, bonded and insured, and we work from 2093 Rand Rd, Des Plaines, IL 60016.

Warranties vary by product, application, installation and maintenance. The applicable written Navien warranty governs coverage on the equipment, so review it for your specific unit — we do not promise coverage on your behalf. Qualifying installations may include our lifetime product, labor and parts warranty program; terms and eligibility apply.

Frequently asked questions