All installations and services must be performed by qualified service personnel.

replacement parts for location identification). After the furnace is warmed up to a steady- state condition (about 15 minutes), the final burner adjustment should be made using combustion instrumentation for measuring carbon dioxide (CO2) or oxygen (O2), carbon monoxide (CO), smoke (for oil furnaces), and stack temperature. In order to achieve the most efficient combustion possible, the following steps must be taken.

IMPORTANT: To achieve proper combustion and efficiency instruments must be used to secure CO2, O2 and CO readings.

1.CARBON DIOXIDE (CO2) or OXYGEN (O2): Take a CO2 sample from the flue pipe or vent connector at a position close to the furnace. It is possible to achieve relatively high CO2 (or low O2) readings with low stack temperatures to produce maximum combustion efficiency. However, the CO2 and O2 values recommended are slightly less, though this means slightly lower efficiency, to allow the burner to better tolerate adverse operating conditions, such as a cold heat exchanger, downdraft conditions, heating content changes in the fuel. This working tolerance means less service and maintenance during heating seasons as well as a reduced chance of producing carbon monoxide under adverse conditions.

2.CARBON MONOXIDE (CO): As described above, take a flue gas sample from the flue pipe or vent connector at a position close to the furnace. The amount of CO generated by combustion ideally should be zero or only a trace. In all cases, it must be less than 50 PPM. Carbon monoxide is a colorless and odorless gas, but it is toxic compound. The production of significant quantities of CO is a strong indicator of incomplete combustion. Check the fuel supply and the burner for fuel leakage. Check for an inadequate supply of clean air for combustion. Also, check for a restricted or blocked flue, vent, or chimney.

3.SMOKE: (oil burners only) A smoke sample should be drawn from the flue pipe or vent connector at a position close to the furnace. For the greatest efficiency, if the first smoke reading is “0”, close the air shutter on the burner until a trace smoke reading is obtained.

4.FLUE GAS TEMPERATURE: The flue gas temperature will vary to some degree depending on the heating content of the fuel, the amount of combustion air, and airflow across heat exchanger. In general, the lower the stack temperature, the higher the efficiency. However, stack temperatures under 350°F may cause flue gases to condense, which in turn may cause excessive metal corrosion.

5.TEMPERATURE RISE: Supply air temperature (measured twelve inches into trunk, away from radiant heat from the furnace) minus (-) return air temperature, or

Temperature rise = Supply air temperature - Return air temperature.

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Thermo Products OMC-70, GMC-85 service manual
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GMC-85, OMC-70 specifications

Thermo Products has built a reputation for delivering top-notch heating and cooling solutions, and the GMC-85 and OMC-70 models are no exception. These high-efficiency gas furnaces are designed to meet the diverse needs of homeowners while prioritizing energy savings and comfort.

The GMC-85 model is known for its impressive efficiency ratings, operating at an AFUE (Annual Fuel Utilization Efficiency) of up to 85%. This means that a significant portion of the fuel consumed is converted into usable heat, making it an economically sensible option for heating your home. Additionally, it features a multi-speed blower motor, which allows for better air circulation and consistent heating throughout the living space. This model also includes a durable heat exchanger crafted from high-quality materials, ensuring longevity and reliability in performance.

On the other hand, the OMC-70 furnace offers a slightly lower AFUE rating of 70%, but it shines in certain areas such as cost-effectiveness and straightforward installation. Its reputation for reliability is bolstered by its rugged design and construction that can withstand the rigors of various climates. The OMC-70 also includes a standard efficiency motor, contributing to reduced energy consumption while delivering appropriate heating requirements for smaller spaces.

Both models utilize advanced technology aimed at improving user convenience and efficiency. Features such as electronic ignition systems enhance reliability by eliminating the need for a pilot light, while also providing a quick and efficient startup process. Furthermore, each unit can be easily integrated with smart thermostats, allowing homeowners to manage their heating needs remotely for optimized performance.

Noise reduction is another characteristic that sets these models apart. Both the GMC-85 and OMC-70 employ sound-dampening technologies to ensure quieter operation, providing a peaceful environment for families.

In summary, Thermo Products' GMC-85 and OMC-70 furnaces present excellent options for homeowners looking to achieve comfort and energy efficiency. With their durable construction, advanced technology, and features geared toward enhancing user experience, these models provide reliable heating solutions suitable for various needs and budgets. Investing in either of these products translates to improved energy savings and consistent warmth, making them popular choices in today's competitive market.
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