Temperature Difference ( Indoor Split)

 
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Old 09-02-2014, 03:52 PM   #1
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Temperature Difference ( Indoor Split)


One of My ac systems is not cooling right now. The fan works, air is blowing, condenser and evap coils are clean, filters are clean, evap drainage is clear.
Air temp. at first register is 57.6 while Tstat is 76 ( set point 73),
bottom register( bottom of stairwell) 55.8*!

Also there is condensation moisture at the first register. The duct inside is dry.

This stairwell used to stay at 73* all the time.
The last few days have been hotter that's true
Clearly I have to call in the HVAC technician, because I don't mess with refrigerants, but what is going on here?
Are temp differentials normal, or should the air coming out of vent be colder?
Just trying to learn.
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Old 09-02-2014, 05:33 PM   #2
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Re: Temperature Difference ( Indoor Split)


Should be approximately 20F difference between return and supply air. Ducts in attics may warm with the air warming as it goes through it. There will be temperature differentials in a house, those differentials will change with air leakage, sun angle, and open/closed doors.

condensation is about humidity, specifically the register is colder than the dew point. Dew point is a function of air temp and relative humidity.

You don't say which side of the blower the evaporator coil is on. If the coil is on the negative pressure side of the blower then you need water in the condensate trap to keep the system from sucking in outside (and probably humid) air through the condensate line.

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Last edited by thom; 09-02-2014 at 05:37 PM.
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Old 09-03-2014, 08:22 AM   #3
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Re: Temperature Difference ( Indoor Split)


This morning 9:00 am, the Tsat is back to 73*, same as set point.
I'll just keep an eye on it.
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Old 10-15-2014, 06:33 AM   #4
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Re: Temperature Difference ( Indoor Split)


As an hvac tech of 15 years I don't still understand the concept of a delta average (split) as any form of conglomerate.

I keep my home at 70 set point. supply air temp on average (r22, yeah, I know) is 61. are you telling me that my 9 degree delta means my system is not working properly? Overcharged? isn't that what a low delta means? And in case you didn't catch that, my return temp is average 70.

Well since this delta has no substance than I guess my relative humidity has no poignance either,correct?

Delta, return and supply, is not a truth. It's an excuse, a weak and impermissible bypass, for those thinking hvac is not truly rocket science..

delta means nothing. not in these considerations, at least.
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Old 11-01-2014, 07:11 AM   #5
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Re: Temperature Difference ( Indoor Split)


Quote:
Originally Posted by Peewee View Post
As an hvac tech of 15 years I don't still understand the concept of a delta average (split) as any form of conglomerate.

I keep my home at 70 set point. supply air temp on average (r22, yeah, I know) is 61. are you telling me that my 9 degree delta means my system is not working properly? Overcharged? isn't that what a low delta means? And in case you didn't catch that, my return temp is average 70.

Well since this delta has no substance than I guess my relative humidity has no poignance either,correct?

Delta, return and supply, is not a truth. It's an excuse, a weak and impermissible bypass, for those thinking hvac is not truly rocket science..

delta means nothing. not in these considerations, at least.
Depends on where you are measuring the delta at.
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Old 04-24-2017, 05:53 PM   #6
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Re: Temperature Difference ( Indoor Split)


There is a company that makes a nice delta T AC Monitoring box (hardware and software). See http://www.mhvacmonitor.com

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Old 04-24-2017, 06:10 PM   #7
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Re: Temperature Difference ( Indoor Split)


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Originally Posted by Ron R View Post
There is a company that makes a nice delta T AC Monitoring box (hardware and software). See http://www.mhvacmonitor.com

Did you pay for this add Dr Ron?
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Old 04-25-2017, 03:38 AM   #8
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Re: Temperature Difference ( Indoor Split)


For a hundred bucks less, you can get a Honeywell Thermostat that will monitor the temp delta.
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Old 04-25-2017, 09:05 AM   #9
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Re: Temperature Difference ( Indoor Split)


Quote:
Originally Posted by Peewee View Post
As an hvac tech of 15 years I don't still understand the concept of a delta average (split) as any form of conglomerate.

I keep my home at 70 set point. supply air temp on average (r22, yeah, I know) is 61. are you telling me that my 9 degree delta means my system is not working properly? Overcharged? isn't that what a low delta means? And in case you didn't catch that, my return temp is average 70.

Well since this delta has no substance than I guess my relative humidity has no poignance either,correct?

Delta, return and supply, is not a truth. It's an excuse, a weak and impermissible bypass, for those thinking hvac is not truly rocket science..

delta means nothing. not in these considerations, at least.
I would want more than a 9 degree split. But, we deal with dry / sensible heat, more than latent heat.

If you are happy, great.
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Old 04-25-2017, 09:13 AM   #10
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Re: Temperature Difference ( Indoor Split)


Quote:
Originally Posted by bhiggins View Post
One of My ac systems is not cooling right now. The fan works, air is blowing, condenser and evap coils are clean, filters are clean, evap drainage is clear.
Air temp. at first register is 57.6 while Tstat is 76 ( set point 73),
bottom register( bottom of stairwell) 55.8*!

Also there is condensation moisture at the first register. The duct inside is dry.

This stairwell used to stay at 73* all the time.
The last few days have been hotter that's true
Clearly I have to call in the HVAC technician, because I don't mess with refrigerants, but what is going on here?
Are temp differentials normal, or should the air coming out of vent be colder?
Just trying to learn.
Sometimes it takes a bit of time to figure out what is going on. We go to a house, and all is working fine. You can't just say "all is well, call us when the problem re-arises". Sometimes, one has to stay on site for an hour plus to catch the culprit.. Not there, but, as a betting man, I would go with either a blower motor, or condenser motor.
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Old 04-26-2017, 04:16 AM   #11
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Re: Temperature Difference ( Indoor Split)


Flash. This a 2.5 year old thread. That Ron R revived to spam his product.
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Old 04-26-2017, 09:19 AM   #12
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Re: Temperature Difference ( Indoor Split)


DoAH. I am losing it, man, losing it.
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Old 06-13-2017, 05:29 PM   #13
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Re: Temperature Difference ( Indoor Split)


Quote:
Originally Posted by beenthere View Post
For a hundred bucks less, you can get a Honeywell Thermostat that will monitor the temp delta.
I highly recommend the Honeywell, we have been using these for years and our customers love them.

Last edited by Jrock; 06-13-2017 at 05:33 PM. Reason: grammar error.
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Old 11-29-2017, 10:38 AM   #14
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Re: Temperature Difference ( Indoor Split)


Quote:
Originally Posted by beenthere View Post
For a hundred bucks less, you can get a Honeywell Thermostat that will monitor the temp delta.
Going to chime in here and say this is probably the most cost effective option!

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