Unreasonable expectations?

[pendragon1998]

It has been in the 90-100 degree range here for about 2 weeks. We don't have any shade on our house, which is a 1 story, 1200 sq ft, factory-built with central air. We set the AC to 68 but it is maintaining the house at 75 in the day and reaching 68 after midnight. AC guy came out and said freon was at max capacity, vents were blowing 67.5, he cleaned it, and basically said there was nothing he could do. Filter is new, outside unit is clean and unobstructed. It wasn't so hot inside last two summers we were here. What do I tell our property manager, now? Am I being unreasonable about wanting lower temps?

 

[Heatdr]

Set up a sprinkler to spray on the condenser coil,that will lower your ambient temp which will inturn lower you discharge temp inside.Just a light spray not a fire hose

 

[bczygan]

Did you know that the standard way to design AC systems is for them to be able to cool up to 80% of the high temperature for your area? They are not designed for worst case or even the highest typical temperatures.

 

[Bobhdus]

I see you have a property manager, is this a lease or rental? If this was "your" home, here are some things you could try... You might get a decent window unit for the area you want to feel the coolest. Keep doors and vents closed in unoccupied areas.

If you were going to own the home I would have insulation added to walls, cavities and attic. Insulation board installed on your garage doors. Window film helps increase R value too... Plant some trees...

I could never get my wife to understand that just because you can set the thermostat to 70, its doesn't mean it's capable of getting there when its 90 degrees outside.

 

[J.A.Varela]

First off ebay up some seeds.

OOPS. Reread it. You don't find 75 degrees of very low humidity air comfortable.
I'll either suggest Atkins or a move to Nova Scotia.

 

[CWO4GUNNER]

Nothing new..One of my new tenants in a 1600SF home was complaining that last summer in her apartment (500SF) she never had electric bills so high ($219) in summer and that even though the temprtue inside the home thermostat reads 75F (112F outside) she can't understand why when she stands in front of the large 48x60 windows the sun feels hot on her skin....My explanation...SIGH

 

[Beemer533]

I'd say you need to look at your insulation, windows and doors first. You could also do a blower test to see where all your air infiltration is.

I don't know what the condition or age of the home is, but you need to sort these things out to get the most out of your Ac...

 

[pendragon1998]

It is a rental, about 4 years old. I am sure this POS house is under-insulated and has air leaks. We keep the doors closed and curtains drawn as much as possible. The build quality is truly poor. I just don't recall it being so hot inside last summer when it was in the 100s. My wife was pregnant last summer, so I would have heard about it if the AC wasn't working. Shouldn't the air coming out of the vents be more than 8 degrees cooler than the air going in the return? I thought it should be more like a 20 degree difference.

 

[Rockhead261]

Typical ASHRAE standards call for an air cooled A/C system to be capable of cooling the interior to 20F below outdoor ambient temperatures. A 75 degree house on a 95 degree day is the best you can expect. Anything more is a bonus.

 

[over40pirate]

An 8 degree temp difference, is a sign something is wrong. Close to 20 is what you want from everything I have read.
Can you inspect all of the duct work?

 

[phansen39]

What size/tonnage is the ac? Is house multi-story, How about windows, how much house faces south?

 

[ambenz]

I would cut a round inspection hole in the plenum, on the furnace, where the coil is situated and silicone a piece of round plexiglass over the hole.
See if the chiller coil has frost on it or if it is freezing up like a block of ice.
10 to 1, your problem is that the "coil fins" on the chiller coil, inside the furnace plenum, is clogged with dust and dirt from previously cheap filters used during construction or even by yourself!
It also maybe clogged from dirt finding a way around the filter.
Furnace filters are the most important thing to properly install and use...they keep the fins on the chiller coil free from obstruction and allows air to pass through the coils and fins, transferring the cold into the air and the humidity onto the coil, to drip off into the pan and out the drain!!!!
To clean the coil, back flushing pressurized water through the fins should dislodge all the dust and junk the coil caught throughout these past years!

 

[CWO4GUNNER]

I was taught that the your delta-T should be a minimum of 12F up to 25F. When my personal home AC delta-T got down to 13F after 6 years use, adding 2 pounds maid all the difference jumping up to 22F that was 2010. Now I notice the delta-T dropping about 1 degrees a year now about 18F. So next fall Ill let my gauge set (Sman3) do superheat and sub-cooling calcs against the manufacturers recommendations along with delta-T and probubly weigh in 1 pound at a time max 2, bringing the tamp back up to 25F. 15% loss of refrigerant per year is normal and acceptable for residential, 30% for commercial. Remember that percentage against your units labeled amount (mine 7.5 Lbs) when the technician insist on doing leak assessment for only $500 or they cannot grantee the added refrigerant at $200 per pound loss.

 

[phansen39]

back flushing pressurized water through the fins should dislodge all the dust and junk

And flood the furnace and floor with water.

Don't do this.

 

[sourdough]

Bobhdus says:

I see you have a property manager, is this a lease or rental? If this was "your" home, here are some things you could try... You might get a decent window unit for the area you want to feel the coolest. Keep doors and vents closed in unoccupied areas.

If your property manager will allow it, temp install an 5-8K BTU window unit (less than $200 at HD or Lowe's) in a central area window (and use a Duck heat-shrink clear window plastic film [or similar for about $15:will cover about 20 windows] and the 2-sided tape inside the window to block any outside air if the curtains don't seal). The outside unit supports need not be heavily attached to the outside of the house. Run it at a higher t-stat setting (about 2*-3*) in conjunction with the central unit so it cuts out before the central unit during the cooler parts of the day. The central unit will distribute the cool air equitably from both units if the fan and ductwork are in good shape.

I have posted before (ad nauseum to regular members of this forum) that I have an LG 15K BTU 120v window unit used in conjunction with the forced-air furnace fan on manual to cool a 2100' ranch house. Today we had shopping to do and came home (to a closed-up well-insulated house) at 2 PM to 92* OSA, turned the window unit/fan on, and it pulled the house down 2* (from 76 to 74*) in an hour and it's holding at the same temp.

You can always take the window unit with you when you vacate the premises.

 

[meathooker]

Typical ASHRAE standards call for an air cooled A/C system to be capable of cooling the interior to 20F below outdoor ambient temperatures. A 75 degree house on a 95 degree day is the best you can expect. Anything more is a bonus.

Exactly! (Well there's more to it then simply 20 below ambient but your on the right track)

In idaho our ASHRAE design temp is 95deg and inside is 72. We get to 100-105 regularly and customers call in bc its 80 in their house. I explain them and let them know their system is doing exactly what it's supposed to.

 

[Rayver]

Only number I have in this area is that A/C should be dropping air by 20+ F⁰ from ambient. You post says you're getting 8-9. Bigger A/C?

 

[LS6 Tommy]

15% loss of refrigerant per year is normal and acceptable for residential, 30% for commercial.

There is no leak repair requirement for any equipment with a charge of less than 50# and the requirement for commercial/industrial refrigeration or process cooling is 35% of the charge in 12 months. All other equipment is 15% in 12 months. All discovered leaks at or above those ranges must be repaired in 30 days.

Tommy

 

[LS6 Tommy]

Typical ASHRAE standards call for an air cooled A/C system to be capable of cooling the interior to 20F below outdoor ambient temperatures. A 75 degree house on a 95 degree day is the best you can expect. Anything more is a bonus.

Only number I have in this area is that A/C should be dropping air by 20+ F⁰ from ambient. You post says you're getting 8-9. Bigger A/C?

I believe that's wrong. IIRC, the standard is a 20* Delta from return to supply, not from outside air to supply. Even if I'm remembering it wrong, in my area of NJ the design temp is 91*, so according to you, I should only be only getting a 70* discharge on a 90* day. Most properly operating systems I've worked on over the last 30 years will do 65* or better on a 90* day. It doesn't drop off much until we break 95.


Tommy

 

[Jagmandave]

We get high temps and humidity in our area in the summer too, and my house has no trouble staying at 74-76 on 100+ days, but to make it feel more comfortable I do ran a fan in the den to circulate the air....that way when the A/C unit kicks off it doesn't feel stuffy. My house was built in the 60's and is not energy efficient, it still has the original windows and doors and it's a multi-level....

I have heard that 20* delta thing for years, but I agree that I think they mean the difference between the air into the plenum and the air out, cause I can't imagine getting the house comfortable if you could only get 20* below outside temps, it would NOT be comfortable if it was 80+ inside on a 100+ humid Kansas day.

As to the OP, I think the other poster is right that you've got something keeping you from getting good temp exchange from the A coil - dirt or ice on it. You can buy a chemical that you spray on the coil, it's slightly acidic but it smells nice, with the A/C off and the coil defrosted, you use a pump sprayer to coat it and let it drip off, you might have to do it several times but it will get it clean. I agree cleaning up any excessive drippings is a good idea. That and a good clean filter might be all it needs......however if it's icing up you're probably low on Freon....

Also make sure your outside coil is clean and the fan is running properly...if you can shade the outside unit it will help it too.....

 

[bazar01]

It is a rental, about 4 years old. I am sure this POS house is under-insulated and has air leaks. We keep the doors closed and curtains drawn as much as possible. The build quality is truly poor. I just don't recall it being so hot inside last summer when it was in the 100s. My wife was pregnant last summer, so I would have heard about it if the AC wasn't working. Shouldn't the air coming out of the vents be more than 8 degrees cooler than the air going in the return? I thought it should be more like a 20 degree difference.

8 degrees delta T across the coil is too low.
Is this electric heat strip?
I would suggest hooking up an ammeter on one leg of the 230V supply.
If the system is pulling >20 amps in cooling mode, the heat sequencer contact is welded close.

 

[pseudorealityx]

8 degrees delta T across the coil is too low.
Is this electric heat strip?
I would suggest hooking up an ammeter on one leg of the 230V supply.
If the system is pulling >20 amps in cooling mode, the heat sequencer contact is welded close.

This is solid idea. Discharging air at 67 degrees is a huge "this is wrong!" thing.

The unit should be discharging air in the mid to high 50's.