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HVAC Discussions - Heating, ventilation and air conditioning.
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Posted by DrYattz on February 2, 2008, 6:09 pm
I have a 6 year old Goodman 3 1/2 ton "split system" heat pump; the
compressor is about 40 feet from the air handler. The heat comes on,
blows hot (108 degree) air off and on for a few minutes, then blows
lukewarm (78 degree) air for hours, seldom reaching the thermostat
setting.
I've got a graph that shows the pattern over a couple of hours:
http://img138.imageshack.us/img138/2423/hvac2ac5.jpg
So, with the thermostat at 70, the air in the vent starts at 64.
Within 10 minutes, its over 106.
Then at 25 minutes, it drops precariously to 76, then immediately
returns to 106/108.
It stays at 106/109 for another 25 minutes, then drops again to 74.
It spikes a time or two, then settles in at about 78 for hours, with
occasional spikes down to 74 and up to 88.
The temperature in the house never reaches the target of 70 degrees,
hovering around 67/68.
My repair guy (who first sold it to me) seems unable to remedy the
problem. About yearly, he checks/replaces heat strips, rewires and
replaces the thermostat, adjusts some differential, and declares it
working. But any meager improvement seldom lasts very long. He says
the drops and spikes are normal.
What's your take on it?
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Posted by Bobb on February 2, 2008, 6:27 pm
Do you have a digital thermostat or mercury bulb thermostat?
>I have a 6 year old Goodman 3 1/2 ton "split system" heat pump; the
> compressor is about 40 feet from the air handler. The heat comes on,
> blows hot (108 degree) air off and on for a few minutes, then blows
> lukewarm (78 degree) air for hours, seldom reaching the thermostat
> setting.
>
> I've got a graph that shows the pattern over a couple of hours:
>
> http://img138.imageshack.us/img138/2423/hvac2ac5.jpg
>
> So, with the thermostat at 70, the air in the vent starts at 64.
> Within 10 minutes, its over 106.
> Then at 25 minutes, it drops precariously to 76, then immediately
> returns to 106/108.
> It stays at 106/109 for another 25 minutes, then drops again to 74.
> It spikes a time or two, then settles in at about 78 for hours, with
> occasional spikes down to 74 and up to 88.
> The temperature in the house never reaches the target of 70 degrees,
> hovering around 67/68.
>
> My repair guy (who first sold it to me) seems unable to remedy the
> problem. About yearly, he checks/replaces heat strips, rewires and
> replaces the thermostat, adjusts some differential, and declares it
> working. But any meager improvement seldom lasts very long. He says
> the drops and spikes are normal.
>
> What's your take on it?
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Posted by Bubba on February 2, 2008, 7:27 pm
wrote:
>I have a 6 year old Goodman 3 1/2 ton "split system" heat pump; the
>compressor is about 40 feet from the air handler. The heat comes on,
>blows hot (108 degree) air off and on for a few minutes, then blows
>lukewarm (78 degree) air for hours, seldom reaching the thermostat
>setting.
>
>I've got a graph that shows the pattern over a couple of hours:
>
>http://img138.imageshack.us/img138/2423/hvac2ac5.jpg
>
>So, with the thermostat at 70, the air in the vent starts at 64.
>Within 10 minutes, its over 106.
>Then at 25 minutes, it drops precariously to 76, then immediately
>returns to 106/108.
>It stays at 106/109 for another 25 minutes, then drops again to 74.
>It spikes a time or two, then settles in at about 78 for hours, with
>occasional spikes down to 74 and up to 88.
>The temperature in the house never reaches the target of 70 degrees,
>hovering around 67/68.
>
>My repair guy (who first sold it to me) seems unable to remedy the
>problem. About yearly, he checks/replaces heat strips, rewires and
>replaces the thermostat, adjusts some differential, and declares it
>working. But any meager improvement seldom lasts very long. He says
>the drops and spikes are normal.
>
>What's your take on it?
Replace the stat. You've got a bad one.
"Its almost always the thermostat"
Bubba
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Posted by kool on February 2, 2008, 7:31 pm
>I have a 6 year old Goodman 3 1/2 ton "split system" heat pump; the
> compressor is about 40 feet from the air handler. The heat comes on,
> blows hot (108 degree) air off and on for a few minutes, then blows
> lukewarm (78 degree) air for hours, seldom reaching the thermostat
> setting.
>
> I've got a graph that shows the pattern over a couple of hours:
>
> http://img138.imageshack.us/img138/2423/hvac2ac5.jpg
>
> So, with the thermostat at 70, the air in the vent starts at 64.
> Within 10 minutes, its over 106.
> Then at 25 minutes, it drops precariously to 76, then immediately
> returns to 106/108.
> It stays at 106/109 for another 25 minutes, then drops again to 74.
> It spikes a time or two, then settles in at about 78 for hours, with
> occasional spikes down to 74 and up to 88.
> The temperature in the house never reaches the target of 70 degrees,
> hovering around 67/68.
>
> My repair guy (who first sold it to me) seems unable to remedy the
> problem. About yearly, he checks/replaces heat strips, rewires and
> replaces the thermostat, adjusts some differential, and declares it
> working. But any meager improvement seldom lasts very long. He says
> the drops and spikes are normal.
>
> What's your take on it?
If you could graph the refrigerant pressures and compressor amperage draw it
may indicate a refrigerant side problem such as leaking valves or overload
tripping intermittently.Even the temperatures in and out of the outdoor
unit, over time, may be helpful. Work with your " repair guy" only if he is
competent, qualified, certified, licensed, insured and all those other
things, if not, find one who is!
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Posted by DrYattz on February 2, 2008, 8:16 pm
> If you could graph the refrigerant pressures and compressor amperage draw it
> may indicate a refrigerant side problem such as leaking valves or overload
> tripping intermittently.
I have no idea how I'd measure these. Can the repairman?
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