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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7836
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My 15 year old Trane bit the dust and I bought (for $7800!)

Customer Question

My 15 year old Trane bit the dust and I bought (for $7800!) a RUUD 5 ton 14 SEER with the attic equipment, too (what is that called). It's 100 degrees in Dallas and my brand new unit (installed yesterday) will not cool below 72 degrees during the day. Installer said this is correct that new industry regulations mandated this design for ALL brands. Disabled person in the house and needs it cooler than 72. Also told as temps lower outside, A/C will also go lower. Did I get ripped off and is all this true? My house is nearly 2600 sq ft and I have high ceilings in most rooms (one story, though).
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.
The installer is correct, however more than a few contractors will find legal reasons to fit larger equipment that will cool below 72F, for instance computer rooms and labs that need to be at 68F. The contractor simply designed the new system to meet code without considering the special needs of the disabled person. You have several options. Try closing 20 percent of the vents in the other rooms and see if the persons room goes lower than 72F... let me know how this goes. .
Customer: replied 1 year ago.
May try that....thanks. I am reading the code....seems like that degree split (between indoor and outdoor temp) is built in the equipment design. Installer coming back tomorrow to double check all setting done by the other guys yesterday. Just seems for the price, should be able to be a bit cooler indoors if I so chose.
Expert:  Phil replied 1 year ago.
Keep me posted, it will help if the thermostat is not in the disabled persons room...but closer to one of the warmer areas in the house.
Depending on the air duct size you can close up to 30% of the registers, that will move more of the cooling capacity to the room needing the extra cooling.
You can also try a sun shade on any windows in the room.
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Customer: replied 1 year ago.
Thanks. Tech came back yesterday and made a couple of adjustments that have seemed to help; I also closed 3 vents that also helped. Still unsure what's causing 47% humidity in the house. This morning it's 32%...but also 80 degrees outside.
Expert:  Phil replied 1 year ago.
Hello again,
Closing the 3 vents cuased the cooling oil to run colder, a colder coil removes more moisture from the air.
If you close too many vents and set the thermostat too low, the coil will develop a 40 pound ball of ice... we try to avoid that.
Close as few vents as possible, and set the thermostat as warm as possible to still be able to maintain you the persons room below 70F.
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We are on the honor system here. Please remember to rate my service before you leave today. It is how I earn a living, and does not increase your charges. If you need anything else, just let me know. You can continue asking follow-up questions at no additional cost.
Customer: replied 1 year ago.
The 47% humidity was before closing the 3 vents (2 in the great room and 1 in the den). The technician said it was caused by the high outdoor heat and that we had the thermostat set to 68 - but it was only cooling to 72. He said the humidity would decrease as the temperature outside dropped through the evening. When I left for work today, the thermostat was set at 68 and the inside temperature was also 68, but, again, the humidity showed 32%. I believe we will simply have to adapt to the changes an R14 mandates over what we have enjoyed for years with the R22. Thanks for your insight.
Expert:  Phil replied 1 year ago.
Hello again, the technician is not an engineer so that he has much of this sideways... not necessarily incorrect but a muddle of what is going on. If you attempt to sort things out on that basis it will not work. 32% relative humidity should generally please most people who need it to be cool in the house, the body cools by sweat evaporation... 32% will accelerate sweat evaporation. The technician is correct in pointing out that the hotter and more humid it gets outside, the less well the system will cool however... that is true with any system if it is not oversized. Most systems are designed to cool to 72F inside at 50% relative humidity until it gets above 95F outside... when it gets hotter than that, say 105 for example the system will not cool the house nearly as well because more heat is getting through the walls of course... the system is not sized for extreme conditions, so the temperature will rise inside----------We are on the honor system here. Please remember to rate my service before you leave today. It is how I earn a living, and does not increase your charges. If you need anything else, just let me know. You can continue asking follow-up questions at no additional cost.

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