How is this thing SUPPOSED to work?

Posted by DrYattz on January 10, 2009, 4:55 pm

I have a 7 year old Goodman 3 1/2 ton "split system" heat pump; the
compressor is about 40 feet from the air handler. The heat
occasionally blows hot (120 degree) air for a few minutes, but then
blows lukewarm (78 degree) air for hours, occasionally switching off
for about 5 minutes.

Last February I had a similar problem, and sought help here. Then,
the room temperature seldom reached the thermostat setting. A few
brilliant people made extraordinarily insightful criticisms of
Goodman, from which I could not afford to benefit by replacing the
unit. Finally, last February, I called a factory-certified HVAC
repair company which replaced the heating elements with higher wattage
ones, and things improved. The serviceman returned last week, checked
it out, and pronounced it "functioning properly."

But I still don't get it: why does the damned thing run all day long,
even after it reaches the set temperature on the thermostat? Why
doesn't it come on, blow hot air until it reaches the thermostat
setting, then turn off until the temperature drops below the setting
again?

I've got a graph that shows the pattern over an hour and a half:

http://img148.imageshack.us/my.php?image=hvac11009jm3.jpg

You can see that it only blows "hot" air for a couple of minutes - in
this sample from this morning, it never made it over 100 degrees,
although from time to time I find 125 degree air coming out.

I'm longing for the days of the old radiator systems. . .

Posted by Bubba on January 10, 2009, 7:19 pm

On Sat, 10 Jan 2009 13:55:05 -0800 (PST), DrYattz

>I have a 7 year old Goodman 3 1/2 ton "split system" heat pump; the
>compressor is about 40 feet from the air handler. The heat
>occasionally blows hot (120 degree) air for a few minutes, but then
>blows lukewarm (78 degree) air for hours, occasionally switching off
>for about 5 minutes.
>Last February I had a similar problem, and sought help here. Then,
>the room temperature seldom reached the thermostat setting. A few
>brilliant people made extraordinarily insightful criticisms of
>Goodman, from which I could not afford to benefit by replacing the
>unit. Finally, last February, I called a factory-certified HVAC
>repair company which replaced the heating elements with higher wattage
>ones, and things improved. The serviceman returned last week, checked
>it out, and pronounced it "functioning properly."
>But I still don't get it: why does the damned thing run all day long,
>even after it reaches the set temperature on the thermostat? Why
>doesn't it come on, blow hot air until it reaches the thermostat
>setting, then turn off until the temperature drops below the setting
>again?
>I've got a graph that shows the pattern over an hour and a half:
>http://img148.imageshack.us/my.php?image=hvac11009jm3.jpg
>You can see that it only blows "hot" air for a couple of minutes - in
>this sample from this morning, it never made it over 100 degrees,
>although from time to time I find 125 degree air coming out.
>I'm longing for the days of the old radiator systems. . .

You just havent been taught how a heat pump works. It extracts heat
from the outdoor air (when its cold outside). The colder outside it
gets, the less available heat there is for the heat pump to absorb
(but it does still extract heat.) It aint gas heat and it aint oil
heat but it DOES heat. The best way to figure it out is look at the
performance charts. I higher outdoor temps you have lots of btu's
available to heat with. When it gets to the 30's, 20's and lower,
there is less heat to absorb so it runs longer and longer. However, if
you were to look at the amp draw of the compressor you will see that
also drops as the outdoor temp drops. Thus, it uses less electricity
but runs longer. Eventually, it wont keep up and the supplemental heat
will kick in, the register temp rises and the house gets warm quicker.
The draw back is that your electric meter spins like a son of a bitch
during that extra warming process.
Just make sure the unit is properly charged, air flow is set correctly
and the unit is clean (all of which requires a pro).
If that dont work, move to a warm climate.
Bubba

Posted by KJPRO on January 11, 2009, 12:31 am

> On Sat, 10 Jan 2009 13:55:05 -0800 (PST), DrYattz

>>I have a 7 year old Goodman 3 1/2 ton "split system" heat pump; the
>>compressor is about 40 feet from the air handler. The heat
>>occasionally blows hot (120 degree) air for a few minutes, but then
>>blows lukewarm (78 degree) air for hours, occasionally switching off
>>for about 5 minutes.
>>Last February I had a similar problem, and sought help here. Then,
>>the room temperature seldom reached the thermostat setting. A few
>>brilliant people made extraordinarily insightful criticisms of
>>Goodman, from which I could not afford to benefit by replacing the
>>unit. Finally, last February, I called a factory-certified HVAC
>>repair company which replaced the heating elements with higher wattage
>>ones, and things improved. The serviceman returned last week, checked
>>it out, and pronounced it "functioning properly."
>>But I still don't get it: why does the damned thing run all day long,
>>even after it reaches the set temperature on the thermostat? Why
>>doesn't it come on, blow hot air until it reaches the thermostat
>>setting, then turn off until the temperature drops below the setting
>>again?
>>I've got a graph that shows the pattern over an hour and a half:
>>http://img148.imageshack.us/my.php?image=hvac11009jm3.jpg
>>You can see that it only blows "hot" air for a couple of minutes - in
>>this sample from this morning, it never made it over 100 degrees,
>>although from time to time I find 125 degree air coming out.
>>I'm longing for the days of the old radiator systems. . .

> You just havent been taught how a heat pump works. It extracts heat
> from the outdoor air (when its cold outside). The colder outside it
> gets, the less available heat there is for the heat pump to absorb
> (but it does still extract heat.) It aint gas heat and it aint oil
> heat but it DOES heat. The best way to figure it out is look at the
> performance charts. I higher outdoor temps you have lots of btu's
> available to heat with. When it gets to the 30's, 20's and lower,
> there is less heat to absorb so it runs longer and longer. However, if
> you were to look at the amp draw of the compressor you will see that
> also drops as the outdoor temp drops. Thus, it uses less electricity
> but runs longer. Eventually, it wont keep up and the supplemental heat
> will kick in, the register temp rises and the house gets warm quicker.
> The draw back is that your electric meter spins like a son of a bitch
> during that extra warming process.
> Just make sure the unit is properly charged, air flow is set correctly
> and the unit is clean (all of which requires a pro).
> If that dont work, move to a warm climate.
> Bubba

Bubba's my Hero... lol

Posted by on January 12, 2009, 10:46 am

x-no-archive:

> >>I have a 7 year old Goodman 3 1/2 ton "split system" heat pump; the
> >>compressor is about 40 feet from the air handler. =A0The heat
> >>occasionally blows hot (120 degree) air for a few minutes, but then
> >>blows lukewarm (78 degree) air for hours, occasionally switching off
> >>for about 5 minutes.

to the op

read about the "balance point" of heat pumps
http://www.arthurhewett.com/id26.htm
Mark

Posted by The King on January 12, 2009, 5:06 pm

On Mon, 12 Jan 2009 07:46:46 -0800 (PST), makolber@yahoo.com wrote:

>x-no-archive:

>> >>I have a 7 year old Goodman 3 1/2 ton "split system" heat pump; the
>> >>compressor is about 40 feet from the air handler. The heat
>> >>occasionally blows hot (120 degree) air for a few minutes, but then
>> >>blows lukewarm (78 degree) air for hours, occasionally switching off
>> >>for about 5 minutes.

>to the op
>read about the "balance point" of heat pumps
>http://www.arthurhewett.com/id26.htm
>Mark

There's not much to read about it. In a nutshell the balance point is
where the heat loss of the building is the same as the heat output of
the heat pump.

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