Heating, Air Conditioning, Fridge, HVAC/New Lux Furnace - 80,000 95% Eff


QUESTION: A Luxaire Gas Furnace LX Series TM9E single stage furnace was installed a week ago.  Since this was installed, it runs for 20 minutes stops of 5 and then runs for 20 more minutes.  The house is 1600 square feet and the new thermostat is set at 70 degrees.  This is much noisier than the Tempstar 100,000 gas furnace that they took out.  My question is can this be fixed, if so how, if not what can I get to replace this piece of crap that will get my home heating needs back to what they were prior to this Luxaire mess?

ANSWER: Hi Karla, Luxaire is made by York and is a good unit. I wouldn't replace your piece of crap till I can get some more details. The output on the new furnace is 76K and on the old furnace was 80K. So we are only talking about 4K difference. Not enough to worry about.

I am in NW Missouri and temp have been in the 30's, so assuming the temps in Iowa are about the same. That being said 20 min. seems to be a long run time.

Let me know what the model number on the furnace is. Should be in your paper work and/or in the burner compartment.


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Below is the information on the invoice.  The unit that was previously in place was a 100,000 vs 80,000 - does this have something to do with why it is running all the time?  Am I mistaken that single stage furnaces - they turn on, bring it to temp and then turns off.  Why is this running 20, off 5 and then back on 20, is this newer habit of "single-stage"? Is there a way to cut the noise?  Our temps here have been in the 20s.  Thanks!

Luxaire - LX Series TM9E part number TM9E080c16MPll,
Pleated filter OCO16251P
Liquid Line Drive - SP0401022
Filter Rak - FR1625
AC Pad - E130303
Lux AC - TLJF3654153
Lineset - Mal 30-20
2" PVC - 2 Pcs
Adp Coil - YE81936E210 B2005 AP

ANSWER: Karla, Your new furnace delivers 4000 BTU less than the old furnace. I think it's time to call the installer back out. Here are some question you can ask him.

Did he do a Manual J ( heat load calculation)?

What is the delta T (temperature rise) of the furnace?

What is the CFM when running in heat mode?

Let me know.

---------- FOLLOW-UP ----------


Below are the answers to the questions from our last e-mail exchange.

Did he do a Manual J ( heat load calculation)? No

What is the delta T (temperature rise) of the furnace?
Measured at the heat vent 15 feet from the furnace, 108 deg F.  Return temperature 69 deg F.  Delta T is 39 deg F.  Specifications say a 40 deg – 70 deg rise in the furnace before it reaches the duct. See the installation guide referenced in the next question page 13.

What is the CFM when running in heat mode? CFM from the installation guide for a TM9E080C16MP11 is 1380 CFM at 0.1 in. static pressure.  The setting is “medium”.  Per the tech who reviewed the install, any faster will increase noise – any lower will affect performance (ie: insufficient airflow).  Install guide available at:

House is still cold, the PVC Pipe to outside is still popping and the unit now runs for 30 minutes off 15 and then back on 30 minutes.  The sound will not change unless we "consider" replacing with a 2 stage instead of the single stage unit.  Please let me know what you think.  Thanks!!!!

Hey Karla, Without doing a manual J they were just guessing. Could be slightly under sized. The delta T should be measured right at the furnace. I'm a little disappointed in that tech. Did he offer any solutions other putting in a 2 stage furnace? Which is not the solution.

I do want you to do a couple of thing for me. Remove the furnace filter for a few hours and let it run. See if the run time changes. Before you do that turn the power off to the furnace and remove the bottom cover. There will be a furnace control board in there. In the upper right there will be a terminal marked " heat" let me know what color of wire is attached to the terminal.

BTW where are you hearing the popping noise?

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Jim S.


I can answer questions on gas or electric furnaces, ac units and heat pumps. I don't work on boilers,chillers,or home appliances.


I have been in the HVAC trade for over 35 years. For the past 15 years I have owned my own business. I am semi-retired so I can answer questions in a timely manner.

I attended trade school for 5 years on weekends and evenings. This was very hard to do, but well worth it!

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