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

: The furnace and its gas valve must be disconnected from the gas supply during pressure testing of the gas supply system at pressures in excess of 1/2 PSIG (13.9 inches W.G.). The furnace can be isolated from the gas supply by closing the manual gas shutoff valve serving the appliance at test pressures equal to, or less than, 1/2 PSIG or (13.9 inches W.G.).

: Copper and brass tubing and fittings (except tin lined) shall not be used if the gas contains more than a trace (0.3 grains per 100 cubic ft.) of hydrogen sulfide gas. Check with your gas supplier.

For natural gas, the maximum supply pressure is 13.9 in. W.G. and the minimum supply pressure, for purposes of input adjustment, is 4.5 in. W.G.

For propane gas, the maximum supply pressure is 13.9 in. W.G. and the minimum supply pressure, for purposes of input adjustment, is 11.5 in. W.G.

2. Oil Tank and Piping (OMC-70)

: All local codes and ordinances take precedence with regard to tank and oil lines. All lines must have oil shutoff valves, a good pipe joint compound approved for use with oil on all pipe threads, no kinks; no sharp bends and be properly tested for leaks. Flare fittings are recommended for tubing.

: Do not run the oil pump dry for more than five minutes.

Your furnace is factory equipped to operate on No. 2 distillate fuel (domestic heating) oil. In very cold weather, No. 1 distillate fuel oil may be used. Your oil supplier should be contacted for recommendations.

: Do not use motor oil or any fuel other than No. 1 or No. 2 fuel oil in this furnace.

Burners are most commonly installed with a single stage fuel pump (refer to Figure 7). This type of fuel pump, when connected with a supply line only, is satisfactory where the fuel supply is level with, or above, the burner. This type of installation permits gravity flow of oil to the burner. When it is necessary to “lift” (raise) oil to the burner, a return line should be connected between the fuel pump and tank. This requires insertion of the “by-pass” plug into the fuel pump. If the lift exceeds approximately 10 feet, a two-stage pump should be installed with a return line. When a return line is used with either single or two-stage pumps, air is automatically returned to the tank, making the unit self-purging.

Use of continuous runs of heavy wall copper tubing is recommended. Always use flare fittings. Avoid use of fittings in inaccessible locations. Avoid running tubing against any type of heating unit and across ceiling or floor joists.

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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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