a/c overwhelmed by heat

[zafdor]

The obvious question is: How cold is the air coming out of the vents? Also, is your attic properly vented (or have an exhaulst fan)?

[barry]

The heat load on the AC is the sum of the conduction loss through walls, windows, etc. and that incurred in cooling (and dehumidifying- no small challenge in SE VA) infiltration from leakage.

Can we assume the system was running non-stop?

Not knowing what energy-conservation measures are in place, it's a SWAG as to what measures would benefit you most. SWAG taken.

Suggestions:

1) Replace filter- too cheap to quibble unless it's new. See that all air-movers are moving air. Probs- see 5. 2) See that all windows, including storms are closed. Tightly. 3) Look for the obvious air-leaks, like all door-seals, especially at top and bottom of enclosed volume of house. Chimney-effect thing. 4) Close shades, especially facing S & SW. No shades? Good investment. 5) If A/C has not been checked/serviced within a year, schedule it now. Better techs will be busy, and you don't want a hack/salesman. Ask what checks or basic servicing you should do regularly.

Vaulted ceilings will make it difficult to retrofit proper ventilation, but you might check that you've sufficient soffit vents if there's a ridge vent. Which I'm assuming. (There really should be a "channel" for air-flow from soffit vents, between insulation and roof-deck, out ridge vent. To reduce heating of house and frying of shingles.)

Ceiling fan in "great room" mainly mixes hot air above with cooler below. Sub-optimum. You'd get better perceived cooling with small circulators moving only air down at human-level. "Vornado" comes to mind- works for me.

OTHO, 84 vice 102 is good. :')

HTH, J

[badgolferman]

Yesterday in SE VA the heat was so oppressive my home AC was overwhelmed. At 4 PM when I came home the temperature outside was 102. My AC is set to 78 and the inside of the house was 84. By the time I went to bed at 11 PM it had come down to 81 inside the house. This morning it is at 78 again.

Is this a function of the poor insulation of my house or is it likely my system needs to be serviced? My house is 1650 sq ft with vaulted ceilings and one ceiling fan in the great room and ceiling fans in the bedrooms. I also have two skylights in the great room that I hate which contribute to heat in there too. I believe the system is 2 or

2.5 tons; the original barely adequate system installed by the builder.

[Lou]

Yes to both. BTW fans do not cool your house they cool the people in the house. You might get free advice from the electric company. They come to the house in NJ.

Lou

[udarrell]

It could be both!

SE VA Norfolk summer design: 91-DB, 76-WB 48% Relative Humidity; near a lot of water. Don't use the ceiling fans in a vaulted room; hot air rises, don't bring it down or mix it with the cooler lower level air! Leave the hot air stratified a few feet above the occupant space level.

Where are the Return Air inlets and Supply Air outlets located; high or low, ceiling or walls? I don't like vaulted ceilings for cooling or heating!

Can you close off or cover the skylights?

Also, the A/C system may not be working properly! Provide us with the make and model number of the condenser!

Check the air discharge temp rise off the condenser!

- udarrell

[Slumlord]

An A/C system should be sized for the design point in your area. If it was sized for the max temp (100F+), the system would be oversized, causing a humidity problem in your home during evenings and cooler days.

Normally, a system has a swing of 3 F. Meaning, if you set the thermostat at 75 F, it could go up as high as 78 F during the peak heat gain hours (normally 3:00 to 6:00 pm).

If your A/C is only having a problem during this unusually hot weather, the system is probably working fine. The hotter it gets outside, the lower the cooling capacity/efficiency goes for the system. High SEER systems especially see a sharp drop in efficiency (compared to a 10 SEER).

What you need to do is reduce the heat gain going into your home. Most designers assume that you have shades on your windows that you can close during hot days. In well insulated homes, light through windows/skylites can account for 40% to 50% of the heat gain in the home. Blocking out that light, especially east and west facing windows will help a lot.

Also during really hot weather, utilities will reduce voltage about 5%. This will result in a further capacity drop in your A/C system.

badgolferman wrote:

[Jeff Wisnia]

Must be tat global warming I keep hearing about.

Too many cattle belching up methane.

Jeff

[Joseph Meehan]

You have been given some good advice and information. I will only add a few thoughts.

A/C should be sized based on the home's construction, including insulation. There for if you A/C is not keeping you cool under "normal" conditions, it may not be functioning as it should or it may be undersized. Of course in large parts of the world right now, temperature is not normal and it is much hotter than normal.

If you are unsure of the insulation, have it checked and consider adding more. More is always better.

[PipeDown]

Assuming the A/C is working properly and that you were just temporarily overwelmed, you could on those really hot days, close off a few rooms by closing the doors and vents (just not the room with the thermostat) and cool less of the house if that is paractcal.

[~^Johnny^~]

[~^Johnny^~]

[~^Johnny^~]

[Carolina Breeze HVAC]

#1 complaint in VA and NC, SC the past week has been this one.

Normally, no one took the time to explain something called design temp to the homeowner, and prob 50% of the calls were based upon that.

[TURTLE]

This is Turtle.

Well you need to get some one to explain to you what design temperature is and why the contractor did not put a unit sized to take care of any temperature over

95ºF and when it get 102ºF outdoors your going to get hot. Maybe it will make you feel better while your hot in your home.

I would have your unit serviced to see if it is anything wrong there.

TURTLE

[Slumlord]

Its not an urban legend. If you check out PJM's website (thats the grid for the mid Atlantic states), part of their emergency procedures, during periods of very high load, is to drop the voltage on the system by 5%. Its the last step before they initiate rolling blackouts

[~^Johnny^~]