need help to determine whats wrong with my a/c


  #1  
Old 05-14-12, 04:05 PM
L
Member
Thread Starter
Join Date: May 2012
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
need help to determine whats wrong with my a/c

my a/c wont shout off i can have it set at 73 and it never reaches it. it stays on constant. at night the oppiset it will reach it after all day being on than shouts off.they replaced the fan i knew it wasnt that please help is it the thermostat?
 
  #2  
Old 05-14-12, 04:49 PM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 5,491
Upvotes: 0
Received 4 Upvotes on 4 Posts
What temp does it reach in the home if the stat is set to 73? What type of system do you have? Make and model numbers? Is anything iced over? Is your filter clean? How long has it been since the unit was serviced?
 
  #3  
Old 05-15-12, 08:40 AM
HVAC RETIRED's Avatar
Member
Join Date: May 2008
Location: Wisconsin USA
Posts: 664
Upvotes: 0
Received 0 Upvotes on 0 Posts
Need more Information also U need to do some testing

my a/c wont shout off i can have it set at 73 and it never reaches it. it stays on constant. at night the oppiset it will reach it after all day being on than shuts off.they replaced the fan i knew it wasnt that please help is it the thermostat?
We need a lot more information: what state & large city do you live near so I can look up the summer design conditions?

I would have a Home Energy Efficiency Audit performed so you know what needs to be done to bring down the heatload requirements.

How does the airflow force feel coming from the diffusers, strong or weak? If weak, with power off, check blower wheel blades for lint build-up; if so, evaporator coil probably also needs cleaning.

Get a humidity gauge at an ace hardware store for under $10.
At 50% relative humidity the indoor temp-drop from the supply diffusers should be around 20-F below Return Air temp.

If the drop is higher, say, 24 or 25-F there is probably not enough air flow; with a high temp-drop the condenser discharge air rise above the outdoor air-temp will be less that the 20-F normal rise at 50% indoor humidity.
If appears dirty; Cut 230-volt power disconnect off to condenser & wash condenser; make absolutely that all the power is off even the the 24-volt furnace transformer power should be shut-off.

A high indoor humidity will raise the condenser temp-split but lower the indoor temp-split.

An A/C Tech should check the duct system for air leaks & seal them with mastic & then check air flow to the rooms with an anemometer.

Indoor blower Air flow should be around 400-CFM per ton of cooling.

There can be many reasons why it won't cool down to 73-F during the daytime! Normally we use 75-F as the indoor summer design temp that it should be able to reach at the outdoor design conditions.
 

Last edited by HVAC RETIRED; 05-15-12 at 08:50 AM. Reason: Clarity...
 

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