Heating, Air Conditioning, Fridge, HVAC/Furnace Blower


Hi, Joe.

I have a couple questions regarding my furnace blower and possible replacement of it.

I have a carrier 52mcb100-1 gas furnace. According to what I can find out it has a 1/2hp 4 speed 115v 1075rpm motor. It is a single stage furnace with a PSC motor.

I was looking at a couple things. I want to leave my blower motor on continuous to help balance the temperatures between the 1st and 2nd floor, however with the current motor it uses a bunch of electricity.

Looking on the net I found the evergreen motor. It is a ECM motor that claims it can replace older PSC motors, and save a good amount of electricity. Here is a link; http://www.genteqcomfort.com/EnergyEfficient/theMotorMatters.aspx

Also, the motor I was looking at to replace my current motor; http://www.comfortgurus.com/product_info.php/products_id/3645

Last question; I have been experimenting with leaving my furnace blower fan "ON" continuous instead of "AUTO" and the strange thing is, when ever the furnace calls for heat the fan shuts off for about 1 minute and furnace ramps up comes on with heat, then when the furnace no longer calls for heat the fan stays on. Is this normal?

Thank You and have a great day,


I have not personally installed one of these motors, but it looks doable with any 24 volt ac t-stat. Briefly looked at the sequence of operation, when nothing is calling , ( heat or cool )your running on low fan operation, minimal amperage draw, when you call for cool or heat , the blower fan ramps to high speed,or what ever speed you select ( medium high etc. ) ( your probably not saving anything while on high speed or very minimal ) I looked at the web site you sent for the model you want to buy :


The above web site you provided shows it's a ONE HP ECM @ 11 AMPS. not a 1/2 HP motor. The amperage is high. Only guessing at this , but your standard 1/2 HP run at less than 11 amp.FLA,( as it's a smaller rated motor HP wise ) now If the page you sent was for a general description and they make a 1/2 HP ECM ( and that was the one you were planning on buying ) then you need to compare the FLA of your current PSC to the ECM FLA and more important the amprege while running at low speed. It did not list the amperage draw when it was running on low speed.It gave a aprox. watt reading. You should find what the amperage draw is on the ECM motor at low speed ,The brochere says typically 95 WATTS at low speed which converts to .80 amprege ( which is excellent ) then compare to the FLA of your current motor.Website does  not say exactly as voltages vary in homes,and a dirty air filter affects amprege draw also. You would have to put an amp. probe to check before and after installing ECM motor.If it's somewhat close , to me the saving may be miniscule vs the purchase price and install of the motor.Then check with an amp. probe the ECM at full speed and compare to your current PSC at full speed to see if your saving anything also.

2nd Question :

Typically anytime when you put the fan switch to ON at the stat, independant or run either heat or cool ,your fan is not suppose to slow down ,or stop and restart, it suppose to run at the constant ON fan speed.  ( the ON fan speed certainly can be a different fan speed than if it was in AUTO for the heat/cool ) Typically when you select ON at the stat,the fan relay opens a set of heat contacts/cool contacts that go to a different fan speed, and closes a set of contacts at the same fan relay to energies a high speed tap of the motor. So to me you have some type of wiring issue. If you plan on buying this ECM motor you still may have the same issue with the fan shutting off/on as you explained I do not know that for sure, you may be OK. You can only troubleshoot so much via the Internet.  

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40+ years diversified experience.An HVAC/Refrigeration Self Employed Contractor since 1986. NATE Certifield. Answer questions pertaining to Residential and Commercial Air Conditioning , Warm Air Heating, Heat Pump systems.Mechanical and Electrical troubleshooting of these systems.Be as detailed as possible when describing problem.Packaged unit or split systems.No appliance questions.


Installation and Troubleshooting, Mechanical and Electrical, in following areas, Refrigeration ( Walk In and Reach In Coolers and Freezers ) Commercial Roof Top and Packaged Heating/Cooling ( Natural Gas,Propane, Electric, and Heat Pumps ) Computer Room Air Conditoning Systems,Commercial Residential Packaged and Split Systems Air Conditoning and Heat Pumps.Warm Air Oil , Natural and Propane Gas Heating systems.

Graduated from Private Technical School in 1975. An HVAC/Refrigeration Contractor . Have Unlimited Heating/Piping and Cooling Contractor License.Limited Sheetmetal Contractors License.NATE Certifield. York Certifield Master Heat Pump Technician 1986. Served 33 years combination Active Duty Air Force , Air Force Reserves and Air National Guard in the HVAC/Refrigeration Shop/Mechanical Shop. Troubleshooting/Installing HVAC/Refrigeration Equiptment Worldwide. Retiring in 2003 as a Senior NCO ,and a Mechanical Superintendent.

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