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AC Register Discharge Temperature MLD 06-28-2007
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Posted by =?ISO-8859-1?Q?Tekkie=AE?= on July 3, 2007, 8:24 pm
.p.jm@see_my_sig_for_address.com wrote:

>>
>> Yes, she's getting a snow job.
>
>         Then it should be nice and cold in thre. What's the problem ?
>
She's frosted

PexSupply Save 10 468x60
Posted by MLD on June 28, 2007, 3:36 pm

>
> >
> > >
> > > > I have a Central AC system that's been around since '73. The air
> > > > temperature coming out of the last register in line has consistently
> > been
> > > > 54-56F year to year even with an OAT of 90F.. My daughter has a new
> > system
> > > > and initially the register air temp was 70F. Service Tech says he
> found
> > a
> > > > leak. Now, after the repair, the air temp doesn't get lower than
67F
> > and
> > > > the Tech says that's normal and everything is working OK. OAT is in
> the
> > > > high 80's low 90's--Is she getting a line of bullshit??
> > > > MLD
> > >
> > >
> > > You would normally get a minimum of 12-15 degree drop. It's all going
to
> > > depend on a lot of data.
> > >
> > > So what's her temp differential?
> > >
> >
> > Don't have the exact numbers but for a ballpark evaluation--Return Air
> Temp
> > (room temp)=73F with a register discharge=67F. That low a differential
(6
> > deg ) would seem to indicate that the unit still is in trouble and needs
> > help.
> > One possible explanation and it's a BIG reach-- is the fact that the AC
> air
> > has to travel from basement to a second level and is being heated as it
> > makes its way up the line--It's not that long a run, however, and the
> ducts
> > that are visible are well insulated --no negative comment from the
Service
> > Tech as to this being a possible explanation. Using my own system as
> > previously noted--return air temp=77F with a register air temp=56F.
giving
> a
> > differential of 21F which seems consistent with a good working system.
> .She
> > is dealing with the people that installed the system and based on this
> > information do you think that she is being given a snow job when they
tell
> > her everything is working normally?
> > MLD
>
>
> Yes, she's getting a snow job.
> Is it the air conditioners fault? Don't know, it could be a ducting issue
> (heat gain). Either way, it's not operating correctly!
>
> In order to get to the root of the problem you need to take measurements
at
> the furnace or air handler. Measure the inlet and discharge air as close
to
> the evaporator coils as possible and see if your differential is still 6
> degrees. If so, this points you to the air conditioning system. If it's
> 12-15 degrees, then this points you to the poorly designed ducting system.
> Another possibility is that the air handler is moving an extreme amount of
> air by the evaporator. Do you have the model numbers of the equipment.
Lets
> see if it's a matched system or something that's been cobbled together.
>
> It's best to get a second diagnosis from a service company that can
actually
> see and test this system. They should be able to diagnose the system
rather
> quickly after they gather all the required data.
>
>
Your comments are extremely helpful and appreciated. Being on the East
coast with the AC unit in the mid-west it's beyond my following through on
your suggestions. However, based on your remarks it's time for the AC
company to be brought back in to do a more professional diagnosis and
troubleshooting job. Again--thanks for your input.
MLD



Posted by udarrell on June 28, 2007, 4:43 pm
MLD wrote:

>
>
>>
>>
>>>
>>>
>>>>
>>>>
>>>>>I have a Central AC system that's been around since '73. The air
>>>>>temperature coming out of the last register in line has consistently
>>>>>
>>>>>
>>>been
>>>
>>>
>>>>>54-56F year to year even with an OAT of 90F.. My daughter has a new
>>>>>
>>>>>
>>>system
>>>
>>>
>>>>>and initially the register air temp was 70F. Service Tech says he
>>>>>
>>>>>
>>found
>>
>>
>>>a
>>>
>>>
>>>>>leak. Now, after the repair, the air temp doesn't get lower than
>>>>>
>>>>>
>67F
>
>
>>>and
>>>
>>>
>>>>>the Tech says that's normal and everything is working OK. OAT is in
>>>>>
>>>>>
>>the
>>
>>
>>>>>high 80's low 90's--Is she getting a line of bullshit??
>>>>>MLD
>>>>>
>>>>>
>>>>You would normally get a minimum of 12-15 degree drop. It's all going
>>>>
>>>>
>to
>
>
>>>>depend on a lot of data.
>>>>
>>>>So what's her temp differential?
>>>>
>>>>
>>>>
>>>Don't have the exact numbers but for a ballpark evaluation--Return Air
>>>
>>>
>>Temp
>>
>>
>>>(room temp)=73F with a register discharge=67F. That low a differential
>>>
>>>
>(6
>
>
>>>deg ) would seem to indicate that the unit still is in trouble and needs
>>>help.
>>>One possible explanation and it's a BIG reach-- is the fact that the AC
>>>
>>>
>>air
>>
>>
>>>has to travel from basement to a second level and is being heated as it
>>>makes its way up the line--It's not that long a run, however, and the
>>>
>>>
>>ducts
>>
>>
>>>that are visible are well insulated --no negative comment from the
>>>
>>>
>Service
>
>
>>>Tech as to this being a possible explanation. Using my own system as
>>>previously noted--return air temp=77F with a register air temp=56F.
>>>
>>>
>giving
>
>
>>a
>>
>>
>>>differential of 21F which seems consistent with a good working system.
>>>
>>>
>>.She
>>
>>
>>>is dealing with the people that installed the system and based on this
>>>information do you think that she is being given a snow job when they
>>>
>>>
>tell
>
>
>>>her everything is working normally?
>>>MLD
>>>
>>>
>>Yes, she's getting a snow job.
>>Is it the air conditioners fault? Don't know, it could be a ducting issue
>>(heat gain). Either way, it's not operating correctly!
>>
>>In order to get to the root of the problem you need to take measurements
>>
>>
>at
>
>
>>the furnace or air handler. Measure the inlet and discharge air as close
>>
>>
>to
>
>
>>the evaporator coils as possible and see if your differential is still 6
>>degrees. If so, this points you to the air conditioning system. If it's
>>12-15 degrees, then this points you to the poorly designed ducting system.
>>Another possibility is that the air handler is moving an extreme amount of
>>air by the evaporator. Do you have the model numbers of the equipment.
>>
>>
>Lets
>
>
>>see if it's a matched system or something that's been cobbled together.
>>
>>It's best to get a second diagnosis from a service company that can
>>
>>
>actually
>
>
>>see and test this system. They should be able to diagnose the system
>>
>>
>rather
>
>
>>quickly after they gather all the required data.
>>
>>
>Your comments are extremely helpful and appreciated. Being on the East
>coast with the AC unit in the mid-west it's beyond my following through on
>your suggestions. However, based on your remarks it's time for the AC
>company to be brought back in to do a more professional diagnosis and
>troubleshooting job. Again--thanks for your input.
>MLD
>
>
A 6 degree split is unacceptable!
There could be hot air from a non conditioned area being sucked into the
indoor blower downstream of your temp check point. It is important to
determine whether there is a light or heavy heatload on the evaporator &
condenser, therefore go outdoors, if it is a round condenser, take a
reading of the discharge air temperature split as compared to the
surrounding outdoor ambient temp. Find out if it is a single speed
condenser fan motor or two speed then ask the tech, contractor or go to
the condenser company's website, then if possible, look up the Expanded
Data on that condenser.

http://www.udarrell.com/airconditioning-excessive-airflow.html
- udarrell

--
WISDOM PRINCIPLE DIRECTED EMPOWERMENT COMMUNICATIONS -
THE REAL POLITICAL ISSUES and WISDOM BASED PEOPLE EMPOWERMENT

http://www.udarrell.com/

http://www.udarrell.com/my_pages2.htm

http://www.udarrell.com/principled_adjudication_disputes_administration_justice.html
(Needs Editing ASAP)

http://www.udarrell.com/recognizing_real_enemies.html

http://jesuschristsavior.net/Beatitudes.html

http://www.antiwar.com/ ***

Reality Is Not An Easy Thing To Be Confronted With, or to Accept!

Posted by on June 28, 2007, 6:46 pm


> A 6 degree split is unacceptable!
> There could be hot air from a non conditioned area being sucked into the
> indoor blower downstream of your temp check point. It is important to
> determine whether there is a light or heavy heatload on the evaporator


He stated: Return Air Temp (room temp)=73F


> &
> condenser


He stated: OAT is in the high 80's low 90's


>, therefore go outdoors, if it is a round condenser, take a
> reading of the discharge air temperature split as compared to the
> surrounding outdoor ambient temp. Find out if it is a single speed
> condenser fan motor or two speed then ask the tech, contractor or go to
> the condenser company's website, then if possible, look up the Expanded
> Data on that condenser.


His posted temps pretty much tell you the load conditions.
And just what do you think the expanded data is going to tell this
homeowner?



Posted by udarrell on June 28, 2007, 9:43 pm
kjpro @ usenet.com wrote:

>
>
>>A 6 degree split is unacceptable!
>>There could be hot air from a non conditioned area being sucked into the
>>indoor blower downstream of your temp check point. It is important to
>>determine whether there is a light or heavy heatload on the evaporator
>>
>>
>He stated: Return Air Temp (room temp)=73F
>
>
That depends on where he is taking the return air temp, if the furnace
sits over a return air chamber he may not get the mix of the hot air
entering the blower.
That is a common occurrence when the chamber under the airhandler is not
properly sealed off from the attic where it comes down the interior of
the walls, etc.

>>& condenser
>>
>>
>He stated: OAT is in the high 80's low 90's
>
>
>>, therefore go outdoors, if it is a round condenser, take a
>>reading of the discharge air temperature split as compared to the
>>surrounding outdoor ambient temp. Find out if it is a single speed
>>condenser fan motor or two speed then ask the tech, contractor or go to
>>the condenser company's website, then if possible, look up the Expanded
>>Data on that condenser.
>>
>>
>
>
>His posted temps pretty much tell you the load conditions.
>And just what do you think the expanded data is going to tell this
>homeowner?
>
>
I assure you the condenser split will provide some information that may
be helpful. He did not check the condenser split, I only view the unread
posts & don't recall that he posted the head pressure(?) The Outdoor
Ambient Temp (OAT) does not indicate the actual amount of load that the
condenser is discharging, the condenser delta-T (Split) provides an
indication of it.
If he did the saturation temp on the gage would give a good indication
of the split.
Goodman Expanded Data tells me everything I need to know concerning
whether the unit is delivering the mfg’ers specs.
- udarrell

--
WISDOM PRINCIPLE DIRECTED EMPOWERMENT COMMUNICATIONS -
THE REAL POLITICAL ISSUES and WISDOM BASED PEOPLE EMPOWERMENT

http://www.udarrell.com/

http://www.udarrell.com/my_pages2.htm (AC Links)

http://www.udarrell.com/principled_adjudication_disputes_administration_justice.html
(Needs Editing ASAP)

http://www.udarrell.com/recognizing_real_enemies.html

http://jesuschristsavior.net/Beatitudes.html

http://www.antiwar.com/ ***

Reality Is Not An Easy Thing To Be Confronted With, or to Accept!

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