The Intertherm M3RL gas furnace, a product with a 90-plus AFUE rating, is a high-efficiency direct vent condensing furnace. This discontinued downflow unit designed specifically for modular homes can use a vertical or horizontal two-pipe venting system. The M3RL is LP convertible.
Several features of the M3RL are meant to ensure a long life of the furnace. For example, the M3RL has a hot surface ignitor, a 30-second blower delay that also delivers warm air at the start-up and a 30-second post-purge that protects the heat exchanger’s longevity. The tubular aluminized primary heat exchanger is made from heavy gauge aluminized steel while the secondary heat exchanger is stainless steel.
When the M3RL is matched with a compatible coil, the blower-off delay and multi-speed direct drive blower reportedly provide an improved cooling capacity. Furthermore, this product is equipped with a diagnostic system that uses light flashes to indicate problems and help troubleshoot.
Our furnace is 11 years old and we have had a pressure switch replaced 1 time and that’s it. The furnace has worked flawlessly since new in 2004.
"Frustrated Beyond Belief"
Intertherm Furnace is 6 yrs old. I have spent hundreds of dollars on repairs & servicing several times each winter. Always the limit switches. This should not need to be replaced several times each heating season. I bought furnace because it was supposed to me more efficient. What a joke! My bills are higher than ever since we have to keep space heaters running throughout the house 24/7. Pretty sad when you wake up in the morning and you can see your breath. Will never purchase another Intertherm product and have nothing good to say about company that installed it.
Eau Claire, WI
Other M3RL Reviews
A few minor problems with the M3RL are posted on online discussion forums. For example, a homeowner writes to an HVAC discussion board with the complaint that the vent safety switch on the inducer is continuously “popping” on a 6-year old unit. Technicians on the forum suggest there may be a vent blockage or the unit may simply need a replacement safety switch.
Another consumer posting on justanswer.com asks a technician to help decipher the diagnostic flashing codes. Using the codes and their description located on the furnace, it is determined that this consumer’s problem is a build-up in pressure, and the pressure switch needs cleaning. After cleaning the switch, the furnace works properly.
Intertherm M3RL Model Numbers
The M3RL is available in different models which vary in efficiency and capacity.
BTUs per Hour
Intertherm offers a 1-year parts, labor and technician mileage warranty on its HVAC products. In addition, consumers have the option of purchasing an extended coverage plan.
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