Tempstar IIS 90 Two Stage Gas Furnace Review

The Tempstar IIS 90 Two Stage Gas Furnace in model series T9MPT Tempstar gas furnace line up offers up to efficiency up to 92% and is listed as an Energy Star rated gas furnace. The key feature of the Tempstar IIS 90 Two Stage gas furnace aside from the efficiency of the furnace is the lifetime warranty on the heat exchanger. The 7 year no hassle replacement warranty is okay but I have reservations about it. In my experience heat exchangers fail, if a heat exchanger is going to fail, heat exchangers will fail around 9 to 11 years for the average failure in my experience and career as an HVAC service technician. So the 7 year no hassle replacement warranty, while being a good thing, will proably never be used but it is good it is a part of the purchase. One thing missing from the Tempstar IIS 90 gas furnace is a variable speed motor which will likely not affect heating as much as it effects cooling and dehumidification for summer use if the system will be matched with an air conditioning system. As with any two-stage gas furnace High Performance HVAC urges caution about efficiency claims by manufacturers because the test for two-stage gas furnaces is the same test manufacturers use for single stage gas furnaces and is subject to question about accuracy of efficiency according to ASHRAE. Put short, HVAC manufacturers will have to restest all their equipment when the new DOE test (recommeded by ASHRAE) is put into effect. Some of the features for the Tempstar IIS 90 gas furnace are:

• Rated about 90% for AFUE which is good but subject to question as stated above


• Two-Stage operation which allows a lower firing rate for milder days and 100% firing rate for the coldest days. For this feature to work properly a two-stage heating thermostat is necessary


• 7 year no hassle replacement warranty if the heat exchanger fails for the Tempstar IIS 90 gas furnace


• Lifetime Limited Warranty for the heat exchanger in the Tempstar IIS 90 gas furnace


• 5 year limited parts warranty for the Tempstar IIS 90 gas furnace


• Energy Star rated gas furnace

There is not much history about Tempstar except the fact they are owned by United Technologies.