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Updated over 3 years ago, 07/18/2021
AC cannot cool below 78F
Hi BPers,
We have a house that was built in 1984 in Texas. The tenant claims that the AC cannot cool down below 78 F. The outside temperature was around 100 F when they claim this. The AC is running all the time. The AC man says that its common for this type of house and it only cools down to 78% of outside temperature. The tenant claims that because the AC cannot cool below 78 F, its a safety issue for the tenant. The tenant age is in their 70s.How do i handle the tenant's complain ?
James and Shanti
sittin here on the top floor in NYC it is often 85 F - but thanks for starting this thread - I learned a lot!
As several have explained, as a rule of thumb in the industry, units are sized to cool a home approximately 20 degrees below outside temperature.
It's not as easy to just say "get a bigger unit". Bigger is not better, its actually worse. Air conditioning is actually the process of dehumidification. Too large of a unit doesn't run long enough to properly dehumidify.
You can properly size a unit, and it not cool a house. That means you have other issues, insulation, windows etc etc.
As others have suggested, get a couple window units to supplement for hotter days.
HVAC is about even pressure. The A/C blower (furnace) needs to get air back as much as it is putting it out. Ensure none of the returns are blocked. In some homes, I have seen one large air return located in a central hallway. If a bedroom has its door shut, the air can't get back to the main return vent and be cycled back through.
Yes, get a new A/C guy, as it could be pressure, undersized unit, or just that you need a new unit with better and more updated refrigerant.
@James Kandasamy, I didn't read all the comments so I apologize if I'm repeating what anyone else has said. If you have or can get one of the little laser thermometers they have at Lowe's, etc, test the temp right at the return (the great big vent where the air is sucked into the unit) and a nearby supply register (the little ones that blow the air). The differential should be approximately 15-20 degrees between the readings. If not, that's an indication that it's not working correctly. If it's a very old outside unit, it may require replacement. If the return air filter is filthy, that can affect things as well. If the differential between the two vent readings is within the correct range, you may have a horrendous insulation issue; it happens, and attics are the worst, since that's where all the hot air goes and generally stays. If this happens to be in SA, let me know, I know a great AC guy. Good luck, and let me know if I can help with anything.
Have Granny sit closer to the unit
OR
Stick in an window unit to provide additional cooling.
#5 Wholesaling Contributor
- Real Estate Broker
- Naples, FL
I have a rental where the A/C never shut off. The tenant complained of utility bills running over $500 per month and they were not able to get the temperature to a comfortable level.. The house is about 2100 SF. The first A/C company came out and could not find a problem but they were kind enough to bill me for the trip:) I got another opinion: the A/C unit was not large enough to cool that SF of house. I replaced the unit and the utility bills dropped quite a bit and the tenant was able to get the temperature down to a comfortable level. Sounds like you need a new and possibly larger unit along with the other suggestions of ventilation and insulation. Help your tenant ASAP!
Hey James, let me give you my professional opinion. I am a N.A.T.E Certified technician who actually got licensed in Dallas at Lenox. The machine are only designed to cool 30 degrees below outside temperature in laboratory conditions. So it sounds to me like you have an insulation problem. That could be the ductwork, the attic/walls or even the doors and windows. A bigger unit can actually make the condition worse. The units are designed for a certain "tonage". I would start with a company that's does full service.
Check the condensate drain line(s). This could be just one of many problems, but one I just now encountered.
At my own house, the A/C system has a single condensate drain line and a back-up kill switch. The drain line was plugged, water was backing up and triggering the kill switch, which shuts off the outside condenser to prevent more condensate from collecting and overflowing the pan (single story house, inside unit is in a closet and the pan is inside the unit). When I was inside the house, the fan was still running so it sounded like the unit was running just fine, but outside the condenser was off, so the temp just kept going up inside. The unit ran fine at night and in the morning, but had trouble from around 3 pm to 9 pm.
Once I figured this out, I cleared the drain line and it seems to be working just fine.
Andy
I had a similar problem....took a bit to figure out they were turning it off when they left for work. As others have stated, make sure they are leaving the thermostat at a comfortable temp.
there is no one size fits all for what an ac unit is able to do. I have worked on units that have a greater than 30 degree delta between supply and return. There are several great responses above, but the one thing you should do right away is to resolve this for the tenant.
Originally posted by @James Kandasamy:
Hi BPers,
We have a house that was built in 1984 in Texas. The tenant claims that the AC cannot cool down below 78 F. The outside temperature was around 100 F when they claim this. The AC is running all the time. The AC man says that its common for this type of house and it only cools down to 78% of outside temperature. The tenant claims that because the AC cannot cool below 78 F, its a safety issue for the tenant. The tenant age is in their 70s.How do i handle the tenant's complain ?
James and Shanti
Its not that expensive because you have the ventilation in place and the electricity. Get someone that advertises they have a reputation to protect and a lot of them won't charge for an inspection. Pumps good too. Keep your tenants happy. They cover your expense It's just a matter of simply hooking a new one up. Another thing is your probably experiencing energy loss also a house that age due to expansion and contraction or just simply the build. Relocating a thermostat into a different part of the house. Usually they install those in the cooler parts. Like upstairs if it has an upstairs. Then you may have to offset heating so then you might try zoned heating and air thermostats.
Do you have a home warranty? If so, can you make a claim? If not, can you purchase a window or portable AC unit from the hardware store then ask the tenants if they can use this so that you can save money to replace the AC unit in winter. During the winter season, the AC repair companies slash the price margins.
There's a scientific way to determine the what size HVAC system. Its called "Manual J", and it's backed by the industry trade association. Most companies don't bother doing it, they use a rule of thumb like 1 ton per 600 sqft, or something. There's also a "Manual S" for equipment selection, and a "Manual D" for ductwork calculations.
If you talk to a company that knows what these are and how to do them properly you're probably talking to one of the elite companies. The rules of thumb don't account for many factors that influence HVAC system design.
Maybe the air filter is dirty.
Frank
get new ac unit (more powerful ?), perhaps new windows/insulation.....or, just give them some window units and tell them to shut up.
Interesting array of responses here. Good information.
Great thread! Had the same issue with my own home when I was renting before I bought from the landlord a few years ago. She tried the window unit solution until a new outside unit could be sourced. And I'm considering one now for my living room b/c it's an older home and not well insulated.
I did replace all the old windows with new double-paned ones after the last hurricane and it made a HUGE difference in my electric bills - cut in half for the summer. A few other things to help are: blackout curtains, those mister systems that go over the outside condenser to help cool the area around them and also some shade for the outside unit. A well placed tree or other shade source to cover the outside unit without blocking air flow can really help it work. Good luck!
I've had this same issue and it was a problem with not enough intake. If the intake vent is in a poor location or in my case, if there is only 1 vent, then you have poor circulation. You can extend the vent that your have or cut a new one.
Lots of older return air vents can end up in small hallways, etc where all the doors end up closed and isolating the vent itself. @Brian Rockwell hit it; it's another possibility anyhow. I think in the end a good HVAC guy is probably not a bad idea.
Thanks for continuous response. My actions would be to check the ventilation of the house specifically in the attic. I don't believe a bigger unit would make a difference as I changed to a bigger condenser unit last year (sorry..the bigger units suggestions). Will keep you guys posted.
James and Shanti.
I work for an HVAC company (besides being a property manager) and I concur with the others who said get a second opinion. There could be a problem with the equipment compatibility or the stat. Also, blown in insulation is a cheap solution for these kinds of problems. Less than $1.50 a square foot here in California. But it makes old houses feel so much better.
Many good suggestions here...
78F is not good enough.
I hope your AC guy did a comprehensive look at the system. I would want to know the following and if it was in range:
Subcooling
Superheat
Air Flow of Evaporator (should be 400 CFM per ton of AC)
Good air flow at condenser unit? Yes/No
Condenser Unit dirty or clean?
Evaporator coils clean or dirty?
Squirrel Cage clean or dirty?
Suction Pressure
Discharge Pressure
Duct leakage?
Attic Infiltration?
Humidity of Supply and Returns (may be expressed as Wet Bulb)
Amp Draw of Compressor (and what it is supposed to be)
Temperature Difference of Supply/Return
There are many more items to check, but this should be the minimum on your report/invoice. "It's good" or "it's just hot outside" is not a satisfactory answer on how the unit is running.
It is disturbing that the outside unit i.e. the condenser was replaced with a larger size but not the evaporator/air handler. You may have a mismatch. It is best to match equipment. If it is mismatched, did the AC company modify the piston size or TXV? You may be flooding the evaporator coil and that will show up with the above information on your unit.
As stated earlier, insulation and duct leakage (both supply and return) should be checked. You may be sucking in attic air or blowing nice cold air into the attic.
A Manual J calculation, as also mentioned, is the best way to size a unit. But a good rule of thumb in the deep South is 400 to 450 square feet per ton of air conditioning. So, for a 2000 square foot house with moderate insulation and no duct issues, a 5 ton would work. You can check this now yourself if you know the tonnage and square feet. If you have the AC company replace the equipment, see if they can do the Manual J calculation.
Also, how is the insulation/weather stripping?
Coils are dirty.
I've read the posts and most of them are bunk.
The size of the AC unit is based not just on the square foot of the house, but its age. An older house may not have as much insulation as a newer one and a larger unit will be needed to keep up with the convection heating during really warm weather.
An AC unit is proper working order can an will cool a property well below a 20 degree exterior/interior difference. The only exception to this is if it is very poorly insulated.
1) Insulate the property, especially the attic. You can use blown insulation or you can get a 2 lbs. closed cell polyurethane froth pack from Foam it Green spray foam insulation and spray the underside of the roof. I've used this on several properties, usually the crawl space for keeping the cold out in KS, and have loved the insulation it gives.
2) Hire a reputable HVAC contractor to get your correct AC size.
Here in Kansas, we can get below zero in the winter and over 100 in the summer. So anyone saying their HVAC doesn't keep up with the heat, need to look at their units. Our hardest time here actually, is the winter.