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Mark Henley
Mark Henley, Journeyman Technician
Category: HVAC
Satisfied Customers: 3217
Experience:  UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential
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I have a forced air lennox pulse furnace 20 yrs. old that

Resolved Question:

I have a forced air lennox pulse furnace 20 yrs. old that makes a loud noise on starting . Sort of a growling noise , what is that ?. We just bought the house in the summer and now the heat is on it works ok but the noise on start up is very noticeable.
Submitted: 7 years ago.
Category: HVAC
Expert:  Mark Henley replied 7 years ago.

Hi,

 

Ok, I need to determine if its a combustion noise or a blower noise, when the furnace is off and then it starts the burners which will light about a minute before the blower starts do you hear the noise then or does it come when the blower starts, if you don;t know please run a cycle like that and try to note that info.

 

Thanks

 

Mark

Customer: replied 7 years ago.
the noise is brief and is before the air fan comes on so it must be combustion
Expert:  Mark Henley replied 7 years ago.

Hi,

 

It sounds like it is , and its not uncommon for the pulse furnace, you will need to have a service out to replace the flapper and check the heat exchanger , its probably just the flapper and a tune-up. Not really a DIY project , I don't think there is any danger in running it but always have a CO detector just in case.

 

Thanks

 

Mark

Customer: replied 7 years ago.
what is a flapper ? and is it normal to make a noise ? We have co detecters. You didn`t mention that lennox has a recall on these furnaces and to test the heat exchanger is $400. My question is the noise on start up that is a growling , vibrating noise that lasts about 10 seconds and goes away. Does that mean the flapper is worn out ? What is it, a gas regulating valve ?
Expert:  Mark Henley replied 7 years ago.

Hi,

 

Its part of the burner air intake like a diaphragm , being 20 years I guess I didn't think about the warranty or recall, was just answering the noise question. Usually its the source of a noise when it is failing but I also said to have it tuned up and heat exchanger checked, they should be able to do this in one call in less than an hour.

 

Thanks

 

Mark

 

 

 

 

Customer: replied 7 years ago.
I know it`s hard for you to coment on a noise that you can`t hear, but I accept your discription of the cause of the noise , the question then would be is it normal, or is it worn out , will it last the winter ? what do you think . It is our intention to replace the furnace in the spring .Is this an expensive part, should we have changed now Thanks for your input
Expert:  Mark Henley replied 7 years ago.

Hi,

 

The part cost is very low on this, I would figure this whole service being done on regular time rates should be less that 250 dollars, in my opinion it is money wasted though unless you can get another year out of it besides this year.

 

More than likely it will last especially if it has just started, I can not guarantee it will not leave you without heat and in need of emergency service one day but if the noise is going away after start up its probably going to last for a while yet. If it's me , I run it and replace it in spring or before next heating season.

 

Thanks

 

Mark

 

 

 

 

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