Inside Temp VS Outside Temp


Old 08-20-03, 10:32 AM
Visiting Guest
Posts: n/a
Inside Temp VS Outside Temp

Could someone please indicate the (rule of thumb) the normal reachable difference between the outside temp and the inside temp? I have heard (from my building contractor supv.) that a 20 degree difference is normal but I am not sure I accept that.
If it is 100/105 deg. outside is it normal be unable to cool the inside temp below 80/85 deg?

We have had some hot days lately (central Texas) and 82deg feels good when you have been outside working in the yard @ 102 deg but my system and house is only 7 months old.

Just checking second opinions.

Last edited by Nemesis; 08-20-03 at 11:09 AM.
Sponsored Links
Old 08-20-03, 12:09 PM
Visiting Guest
Posts: n/a
You need to find out what the correct design temperature and humidity for your location is (usually a dry bulb wet bulb pair). If the outside temperature is significantly above this the AC will not hold the inside design temperature. If you are at or below the design temperature and you cannot hold inside at 72, the system was undersized. The ASHRAE handbooks have the design temperatures and humidities.
Old 08-20-03, 12:34 PM
Visiting Guest
Posts: n/a
Design Temputure

My problem is that the company and builder that would have the information that you say I need are the same that would have to replace/upgrade my system if it is found to be undersized. That being said, I am certain that they will deem the unit to be at the proper size. Design tempture is not very important to me since I had no input into the design.

As far as 72 degrees; I can not get the inside tempature down to 72 at any point during a normal summer day of mid 90s. I don't plan to run the system at 72 degrees but 76 would be nice.
Old 08-20-03, 02:09 PM
Visiting Guest
Posts: n/a
The design temperature is available at the library. It is the temperatre the system SHOULD have been designed to. They do not get to pick it from a hat. ASHRAE (American Society of Heating, Refrigeration, and Air Conditioning Engineers) publishes the baseline data. The system should have been sized to get at least 75F on the 90 or 97th percintile day. You do not need to ask the builder anything. If the system was sized correctly and the weather is outside the ASHRAE limits, the temperature will rise inside. If the system is smaller than it should be, the temperature will rise even when the outside temp is below the limits.
Old 08-20-03, 05:03 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Received 0 Votes on 0 Posts

I think here you can say your over a barrel. . The design temperature would be what ever they had set down in the contract. Most of the time it can be a 15o or 20o diff from out side I know we put it in the contracts all the time. That would be like you say you want 70o inside when its 105 out side. Ok you can have it ,but it will cost you more cause I will have to put in a bigger AC unit and most of the time its to big so it turns on and off a lot and dont get the humidity out of the home and you say it dont work worth a D--. Also you said the home was just 7 months old. The whole home is still damp and lets say wet inside from all the new wood drywall new cement ,on and on. When the AC get all this humidity out you will feel a lot cooler ED
Old 08-23-03, 05:31 PM
54regcab's Avatar
Join Date: Jul 2002
Location: Oklahoma City
Posts: 661
Received 0 Votes on 0 Posts
Thumbs up Leave it ON

You are leaving the unit set at the same temp all the time right ?
20 degrees is reasonable IMHO.
If you go too big you will haev a muggy house and high electric bills
As you said before, it feels good when you come out of 100 degree temps !!

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes
Ask a Question
Question Title:
Your question will be posted in: