BoilersGas
Conforto CH-299 Boiler Manual
Setup, everyday use, maintenance and troubleshooting for the 95% AFUE condensing gas boiler, with verified specifications.
- AFUE95%
- FuelNatural gas / LP
- DesignCondensing
- Example yearly gas cost$789
About the Conforto CH-299
The Conforto CH-299 is a 95% AFUE condensing gas boiler, certified under the ENERGY STAR program for residential hot-water heating.
With an AFUE of 95%, about 95% of the fuel it burns over a heating season becomes heat delivered to your radiators, baseboard or radiant floors. It is a condensing boiler: when the water returning from the heating system is cool enough — below roughly 130 °F with natural gas — water vapor in the exhaust condenses on the heat exchanger and releases extra heat. That is why condensing boilers are paired with outdoor-reset controls and work best with radiant floors or generously sized radiators that run at lower water temperatures.
ENERGY STAR lists it as able to integrate domestic hot-water heating — typically by supplying an indirect-fired storage tank or through a built-in combi module, depending on the exact model. Confirm which arrangement your configuration uses. It is certified for natural gas and propane (LP); conversion between fuels must follow the manufacturer's instructions and be done by a qualified technician.
Specifications
| Brand | Conforto |
|---|---|
| Model number | CH-299 |
| Fuel category | Gas |
| AFUE (heating efficiency) | 95.0% |
| Fuel type | Natural gas or propane (LP) |
| Condensing design | Yes |
| Listed as integrating domestic hot water | Yes |
Safety information
- Install UL-listed carbon monoxide (CO) alarms on every level of the home and outside each sleeping area. Test them monthly and replace them by the date printed on the alarm.
- If you smell gas, do not light anything or operate switches, phones or appliances inside. Leave immediately and call your gas utility or 911 from outside.
- The boiler must be installed by a licensed heating or hydronics contractor following the manufacturer's instructions and local codes; most jurisdictions require a permit and inspection.
- Every boiler has a pressure relief valve (residential hot-water systems commonly use a 30 psi valve). Never cap, plug or remove it, and keep its discharge pipe running to within a few inches of the floor or to a safe drain as code requires.
- If the pressure gauge reads zero or the boiler is overheating, turn it off and call a technician. Never add cold water to a hot boiler that has lost its water.
- Keep gasoline, solvents, paint and other flammables away from the boiler, and do not block combustion-air openings.
- Turn off the boiler's service switch or breaker before opening any panel. Pipes and the boiler jacket can be hot enough to burn.
- If the boiler supplies domestic hot water, install a thermostatic mixing valve and deliver no more than about 120 °F (49 °C) at fixtures to reduce scalding risk.
- Keep the outdoor vent and air-intake terminations clear of snow, ice, leaves and nests.
Installation and first-time setup
A boiler is the heart of a hydronic system, and the piping around it determines how well the Conforto CH-299 performs. Review these points with your installer.
- Size it to the heat loss
Ask for a room-by-room heat-loss calculation (such as ACCA Manual J) instead of copying the old boiler's rating — many older boilers are badly oversized. Also confirm that existing radiators or baseboard can heat each room at the water temperatures the new boiler will run.
- Near-boiler piping
Follow the manufacturer's piping diagrams exactly. Many modern boilers require primary/secondary piping or a hydraulic separator so the heat exchanger always gets the flow it needs, regardless of how many zones are calling.
- Clean the system and treat the water
Flush old systems thoroughly before connecting a new boiler; sludge and magnetite from old piping can foul a modern heat exchanger quickly. Fill with water that meets the manufacturer's limits for pH, hardness and chlorides, and use only approved inhibitors or antifreeze. A dirt or magnetic separator is cheap insurance.
- Expansion, air and fill
Size the expansion tank for the system volume, install an air separator, and connect the fill valve through a backflow preventer to protect your drinking water.
- Venting
Condensing boilers vent through PVC, CPVC, polypropylene or stainless pipe as the installation manual lists, usually as sealed-combustion direct vent. Pipe slope, maximum length and termination clearances from windows, doors and grade must follow the manual. The boiler must not share a chimney — and if a gas water heater used to share it with the old boiler, the chimney may need relining.
- Condensate
Pipe the condensate to a drain or condensate pump through a neutralizer if the manufacturer or local code calls for one; condensate is acidic. Protect drain lines from freezing.
- Outdoor reset
Install the outdoor temperature sensor and set the reset curve so supply water is only as hot as the weather requires. This keeps return water cool enough to condense for most of the season.
- Gas supply
Size the gas line for the boiler's full input, with a shut-off valve and sediment trap at the boiler, and leak-test every joint with an approved solution or detector. Propane operation requires the manufacturer's conversion procedure.
- Domestic hot water
An indirect tank is usually piped as a priority zone. Set the tank aquastat and boiler domestic-hot-water settings per the manual, and add a mixing valve at the tank outlet.
- Commissioning
Ask for a written start-up report with gas pressure and combustion analysis (CO and O2 or CO2) at high and low fire, system pressure, and the outdoor-reset and limit settings.
Using your boiler
Pressure and temperature gauge
Most residential hot-water systems are filled to about 12–15 psi cold and stay below about 25 psi when hot; your installer will note the correct cold-fill pressure for your building. A pressure that keeps climbing toward the 30 psi relief setting, or keeps dropping, needs attention (see Troubleshooting).
Water temperature and outdoor reset
Let the outdoor-reset control do its job. In mild weather supply water may be only 100–120 °F, rising toward the maximum only on the coldest days. Raising the maximum temperature "to heat faster" mostly raises return temperatures and stops the boiler from condensing, which costs efficiency.
Thermostats and zones
Hydronic systems respond more slowly than forced air, especially radiant floors. Use modest setbacks (a few degrees) on radiant zones and give each zone time to respond. Keep furniture and heavy drapes away from radiators and baseboard so heat can circulate.
Domestic hot water
When the boiler heats an indirect tank, domestic hot water normally takes priority, so space heating may pause briefly during long showers. Set the tank temperature at about 120 °F, or higher with a mixing valve if your installer recommends it.
Care and maintenance
| When | What to do |
|---|---|
| Every month in season | Check the pressure/temperature gauge, look for drips at the relief valve and fittings, and make sure vents and air intakes are unobstructed. |
| Start of heating season | Bleed air from radiators or baseboard with high-point vents if rooms heat unevenly or you hear gurgling. |
| Every month | Test CO and smoke alarms. |
| Every year | Professional service: combustion analysis, burner and ignitor/flame-sensor check, heat-exchanger cleaning, condensate trap and neutralizer service, vent inspection, gas pressure and safety-control tests. |
| Every year | Have the technician check expansion-tank pre-charge, relief-valve condition, circulator operation, low-water cutoff (if installed) and system water chemistry or inhibitor level. |
| Every 5–10 years | Replace CO alarms by the date printed on them. |
Troubleshooting
Use the table below to narrow down common problems. Anything involving gas, oil, combustion, venting or electrical components should be handled by a qualified technician.
| Problem | Possible cause | What to try |
|---|---|---|
| No heat anywhere | Thermostat setting; boiler switch or breaker off; gas supply off or ignition lockout; low system pressure. | Check thermostat, switch and breaker; note any code on the display and consult the manual's code table. Call a technician if the lockout returns. |
| Some rooms or zones cold | Air in radiators or baseboard; zone valve or zone circulator not opening; thermostat issue. | Bleed air at high points; confirm the zone thermostat calls for heat. A zone that never warms needs its valve or circulator checked. |
| Pressure rises toward 30 psi; relief valve drips | Waterlogged or failed expansion tank; fill valve letting water through; leaking domestic-water coil. | Call a technician; do not cap the relief valve. |
| Pressure keeps dropping | A leak in piping, a radiator valve or an automatic air vent; relief valve weeping. | Look for wet spots and drips. Frequent topping-up brings in fresh oxygen and minerals that damage the boiler — have leaks repaired. |
| Banging, kettling or gurgling | Air in the system; scale or sludge in the heat exchanger; low water flow. | Bleed air. Persistent kettling usually means the heat exchanger needs cleaning or flow needs correcting. |
| Boiler cycles on and off rapidly | Oversized boiler for small zones; supply temperature set too high; minimum firing rate above the load. | Ask your contractor to review the reset curve, anti-short-cycle settings and zoning; a buffer tank can help in some systems. |
| Error code on the display | The control has detected a fault or lockout condition. | Write down the code and look it up in the code table in your manufacturer's manual before resetting. |
| Water on the floor near the boiler | Clogged condensate trap or drain; failed condensate pump; relief valve discharge; leaking fitting. | Find the source: clear or replace the condensate drain components; relief-valve discharge or leaks need a technician. |
| Not enough hot water | Tank aquastat set low; domestic-hot-water priority disabled; scaled coil or tank. | Check the tank setting and boiler DHW settings; have the system checked if recovery is slow. |
Energy use and running costs
These examples assume a home that needs 50 million Btu of delivered heat per year — roughly a mid-size house in a cold northern climate. At 95% AFUE the Conforto CH-299 would burn about 526 therms of natural gas, roughly $789 a year at $1.50 per therm.
| Boiler | Gas used | Estimated cost |
|---|---|---|
| This model (95% AFUE) | 526 therms | $789 |
| Federal minimum (84% AFUE) | 595 therms | $893 |
| Older boiler (70% AFUE) | 714 therms | $1,071 |
On propane, the same heat would take about 575 gallons of LP gas (about 91,500 Btu per gallon); multiply by your local propane price to estimate cost.
A condensing boiler reaches its rated efficiency only when return water is cool enough to condense. Systems that run at high water temperatures all winter — common with undersized baseboard — will see lower real-world efficiency than the AFUE suggests. Circulator electricity is not included.
Frequently asked questions
What is the AFUE rating of the Conforto CH-299?
The Conforto CH-299 is rated at 95% AFUE and is a condensing boiler.
Can the Conforto CH-299 heat domestic hot water?
Yes. ENERGY STAR lists it as able to integrate domestic hot-water heating, typically by supplying an indirect storage tank or through a combi module depending on the exact model.
What venting does the Conforto CH-299 need?
As a condensing boiler it uses sealed vent pipe — PVC, CPVC, polypropylene or stainless as the manual lists — plus a condensate drain (often with a neutralizer). It cannot share a chimney with other appliances.
Can the Conforto CH-299 run on propane?
Yes. It is certified for both natural gas and propane (LP); a qualified technician must convert and set it up for the fuel you use.
How much gas will the Conforto CH-299 use?
To deliver 50 million Btu of heat in a year it would burn about 526 therms — roughly $789 at $1.50/therm.
When was the Conforto CH-299 ENERGY STAR certified?
It appears on the ENERGY STAR certified boiler list with a certification date of January 2025.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified boilers dataset published by the U.S. Environmental Protection Agency (record certified January 19, 2025), retrieved October 7, 2026.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with Conforto. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Conforto or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
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