High Efficiency gas furnace - return air temperature

Posted by on January 19, 2007, 12:12 am

The unit in question is Goodman GMV9509050XBA gas furnace (95% eff.,
90,000 BTU.)
It says in the Installation Instructions (page 7, Location Requirements
& Considerations) that the following must be observed:

"The temperature of the return air entering the furnace is between 55F
and 100F when the furnace is heating."

I am curious why the 55F requirement. I mean, when I'm not in the
house, I would like to set the temp as low as possible in order to save
on my heating bill. I think I could otherwise set it as low as 45-50F
and still keep the water pipes from freezing. But I wonder why I'm not
supposed to go below 55F. What could happen? Could the unit get damaged
and why?

Thanks

P.S. I'm in the Denver, CO area - 5,300 ft altitude, if that matters.

Posted by Tony Hwang on January 19, 2007, 12:59 am

bubbabubbs@yahoo.com wrote:

> The unit in question is Goodman GMV9509050XBA gas furnace (95% eff.,
> 90,000 BTU.)
> It says in the Installation Instructions (page 7, Location Requirements
> & Considerations) that the following must be observed:
>
> "The temperature of the return air entering the furnace is between 55F
> and 100F when the furnace is heating."
>
> I am curious why the 55F requirement. I mean, when I'm not in the
> house, I would like to set the temp as low as possible in order to save
> on my heating bill. I think I could otherwise set it as low as 45-50F
> and still keep the water pipes from freezing. But I wonder why I'm not
> supposed to go below 55F. What could happen? Could the unit get damaged
> and why?
>
> Thanks
>
> P.S. I'm in the Denver, CO area - 5,300 ft altitude, if that matters.
>

Hi,
I am just guessing. If return air temp. is to low it may not produce
warm enough air. Air is passing thru the heat exchanger at constant
speed and think law of physics.

Posted by on January 19, 2007, 2:11 am

>bubbabubbs@yahoo.com wrote:

>> The unit in question is Goodman GMV9509050XBA gas furnace (95% eff.,
>> 90,000 BTU.)
>> It says in the Installation Instructions (page 7, Location Requirements
>> & Considerations) that the following must be observed:
>>
>> "The temperature of the return air entering the furnace is between 55F
>> and 100F when the furnace is heating."
>>
>> I am curious why the 55F requirement. I mean, when I'm not in the
>> house, I would like to set the temp as low as possible in order to save
>> on my heating bill. I think I could otherwise set it as low as 45-50F
>> and still keep the water pipes from freezing. But I wonder why I'm not
>> supposed to go below 55F. What could happen? Could the unit get damaged
>> and why?
>>
>> Thanks
>>
>> P.S. I'm in the Denver, CO area - 5,300 ft altitude, if that matters.
>>

>Hi,
>I am just guessing. If return air temp. is to low it may not produce
>warm enough air. Air is passing thru the heat exchanger at constant
>speed and think law of physics.

Blow me.

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Posted by Bubba on January 19, 2007, 7:32 am

>bubbabubbs@yahoo.com wrote:

>Hi,
>I am just guessing. If return air temp. is to low it may not produce
>warm enough air. Air is passing thru the heat exchanger at constant
>speed and think law of physics.

Ertttttttt! Wrong answer Tony. Stick to what you do because it sure
isnt this.
Problem is possibility of condensation in the
furnace.......................in the PRIMARY!
Bubba

Posted by daytona° on January 23, 2007, 11:54 am

and runs out as waste water

>>bubbabubbs@yahoo.com wrote:

>>> The unit in question is Goodman GMV9509050XBA gas furnace (95% eff.,
>>> 90,000 BTU.)
>>> It says in the Installation Instructions (page 7, Location Requirements
>>> & Considerations) that the following must be observed:
>>> "The temperature of the return air entering the furnace is between 55F
>>> and 100F when the furnace is heating."
>>> I am curious why the 55F requirement. I mean, when I'm not in the
>>> house, I would like to set the temp as low as possible in order to save
>>> on my heating bill. I think I could otherwise set it as low as 45-50F
>>> and still keep the water pipes from freezing. But I wonder why I'm not
>>> supposed to go below 55F. What could happen? Could the unit get damaged
>>> and why?
>>> Thanks
>>> P.S. I'm in the Denver, CO area - 5,300 ft altitude, if that matters.

>>Hi,
>>I am just guessing. If return air temp. is to low it may not produce
>>warm enough air. Air is passing thru the heat exchanger at constant
>>speed and think law of physics.

> Ertttttttt! Wrong answer Tony. Stick to what you do because it sure
> isnt this.
> Problem is possibility of condensation in the
> furnace.......................in the PRIMARY!
> Bubba

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