OT: Anybody bought a new central A-C unit lately? We're being told . . .

[OldWiseCock]

Hi,
Where are you located? What you’re asking is not way out of line. I am not a contractor. I’m an hvac design engineer. I do residential and commercial load calcs duct design, ventilation, fresh air makeup, exhaust systems, etc all over the country. For local projects I can come out for a site visit and collect all the data and create the load and design, select equipment, and then you can have that design bid. I know a couple contractors I would recommend for the work but I don’t price their work. I just avoid the folks that use grandpas thumb to size equipment. I think you may be on the right path with separating the up and downstairs. Without seeing the home it’s hard to say if their pricing is decent.

I typically work for other contractors on a design for their project or directly for builders who want a good design before they involve an hvac company. I do sometimes work for home owners in your situation who need help and can’t find good support out there.
I’m happy to talk and see if I can help. I’m the owner so I’m pretty much able to do as I wish. .

give me a call or email this week. 803-216-1959. Michael.rhodes@relativeheatingandair.com

Forest Acres. I'll give you a call later this week.

The house faces exactly SE so the front of the house gets the morning sun.

 

[Rhizzlebop]

Forest Acres. I'll give you a call later this week.

The house faces exactly SE so the front of the house gets the morning sun.

Hi, just dawned on me that I never heard from. Give me a call and let’s see if I can help you out. 803-216-1959

 

[cocks rule]

Third HVAC guy came in yesterday and did an estimate for an upstairs unit. $14,000 for a 15 SEER Trane, 2 ton unit. He he would NOT do a Manual J calculation. When I pressed him he said, I'll do it for $1200, but I just use the rule of thumb - 1 ton per 600 sq. feet. The upstairs is 900 square feet. When I asked him about his rule of thumb he said, "I'd rather oversize than undersize."

All 3 have refused to install a mini split with 3 blowers/cassettes. Last guy said that would cost me $2,000 more than installing a regular heat pump in the attic, and the result will not be as good. The problem is that we use the attic for storage, and with an attic installation we would lose the storage. Plus, the rafters are not insulated so it gets hot up there. When I asked if I should have someone blow foam insulation into the underside of the roof in the attic he said, "yeah, that will help the unit." That will be another $2,000.

My estimates for a heat pump in the attic start at $10,000 and go up to $15,000. That seems like a big range.

12,000 btu window unit. 319.99 done!

 

[byrdman#]

Thanks guys for the help and input. Now, if we can just settle down to 'cool' summer temps in the Midlands, say 91-93!

Santa can’t work miracles.

 

[byrdman#]

I have a mister spraying on my unit and I'm thinking of misting my roof.

If you mist your roof, you will take away about 1/3 of the roof life in a best case scenario.

 

[cockyferg]

Heat Pump 101 and Thermostats 101 should be required credits for HS graduation! LOL!

Bolded is an exchange I have with my wife CONSTANTLY!!

I leave mine at 72 year round and my system never had trouble. For years I used a programmable thermostat and set it higher in the day and cooler in the evening. An HVAC tech tips me it would be cheaper to set it and forget it and he was right. My bill has gone down considerably since doing that.

 

[Conway Gamecock]

As others have stated, get some ceiling fans for your home. Remember that hot air rises, cold air stays at the floor level. Turn fans to run clockwise for winter months (they push the warmer air downwards from the ceiling), and counter-clockwise for summer months. Clockwise more for pushing warmer air that nestles on the ceiling where we don't habitate down to where we do, counterclockwise more for just circulating the air and getting the cooler air more throughout the room, instead of keeping your floors cool.

Also a REAL good trick for enjoying the coolness of your AC: go outside and work in the yard for an hour or so in the heat of the day. When you come back inside, your home will almost feel chilly to you, guaranteed.......

 

[Conway Gamecock]

12,000 btu window unit. 319.99 done!

My family used to own apartment buildings until we sold them. They were built in the late 60s/early 70s. Used to have radiators for heat, and no central AC, so they all had window units.

I cannot for the life of me understand why the manufacturers cannot develop condensation drains that won't leak the water onto the wooden window sills or down the side of the walls, or side screens for adjusting to the width of windows that do a better job of weather-proofing those areas on each side of the unit, or that keeps the outside bugs from coming into the homes....

 

[Garnet chicken]

I leave mine at 72 year round and my system never had trouble. For years I used a programmable thermostat and set it higher in the day and cooler in the evening. An HVAC tech tips me it would be cheaper to set it and forget it and he was right. My bill has gone down considerably since doing that.

Somehow the physics of that don't add up. If it's 95 outside and when you leave the home you say set it on 80 and you're gone 9 hours, it will run considerably less during that time. If you leave it on 72, it will have substantial more run time. A programmable t stat will know your get home time and bring the temp down gradually. The same for heat.

 

[cockyferg]

Somehow the physics of that don't add up. If it's 95 outside and when you leave the home you say set it on 80 and you're gone 9 hours, it will run considerably less during that time. If you leave it on 72, it will have substantial more run time. A programmable t stat will know your get home time and bring the temp down gradually. The same for heat.

There's more to it than what you're saying. Also, remember, it's not like you're cooling the air outside that's 95 degrees. You're pulling air from inside your home, which is already cooler. It takes a lot more energy to bring something up or down a degree than it does to keep it constant

 

[cockyferg]

Somehow the physics of that don't add up. If it's 95 outside and when you leave the home you say set it on 80 and you're gone 9 hours, it will run considerably less during that time. If you leave it on 72, it will have substantial more run time. A programmable t stat will know your get home time and bring the temp down gradually. The same for heat.

Either way, whether my physics are right or wrong, my energy bill says keeping it constant is cheaper

 

[CockofEarle]

that, with the new energy efficient ratings, when for example, you set the thermostat at, say 75, and then in the middle of a 100 degree + day you set it down to, say 72, the units today are not designed to pull down 3 degrees or more until evening or when it cools off later - 8PM or so. Can anybody confirm this? Just asking.

Sounds about right, our components have been bought overseas since early 90’s …..designed to fail & can’t handle loads.

 

[andypants]

If you mist your roof, you will take away about 1/3 of the roof life in a best case scenario.

Thanks! Is that due to grit washing off?

 

[Rhizzlebop]

There's more to it than what you're saying. Also, remember, it's not like you're cooling the air outside that's 95 degrees. You're pulling air from inside your home, which is already cooler. It takes a lot more energy to bring something up or down a degree than it does to keep it constant

Agreed. It’s a much more complicated matter involving mass and duration along with whether we are talking about a heatpump in winter intelligently recovering vs using strip heat, how the defrost cycles are handled (whether time based or demand based). Much more complex.

furthermore the ene4gy billing you have makes a difference. My company charges demand billing for taxing their grid during peak hours. So during the summer (peak hours being 4-7) I set my upstairs bedroom system to only r7n half of each of those hours. The reason being they look at those 3 hours of use for each of the 30 days of a month (90 hours) and the single largest use hour they charge almost $13 per KWH used. Then for each of of the other 1600-2500 kWh I use in a month they charge me 5.5 cents per kw. So by knocking off about 2kw off those peak hours I save about $26 plus the 2x30x5.5 cents each month vs letting it run.

same for winter except 6-9 am.

 

[Gamecock Lifer]

that, with the new energy efficient ratings, when for example, you set the thermostat at, say 75, and then in the middle of a 100 degree + day you set it down to, say 72, the units today are not designed to pull down 3 degrees or more until evening or when it cools off later - 8PM or so. Can anybody confirm this? Just asking.

For YEARS most A/C units have been unable to lower the temperature more than 20-25 degrees when it is very sunny and warm. That is just how it is. Even with models that were made prior to current efficiency regulations that is the case.
If you want it icy cold you can add a window unit to a specific room in your house 🤷‍♂️

 

[gamecox4982]

I purchased a window unit a few years ago just in case the HVAC went out, best buy I ever made. Now when it gets hot upstairs I shut the door at night and put in the window unit - takes 2 minutes and we sleep very comfortable

 

[Six Million Dollar Man]

Installing/using ceiling fans constantly helps too.
Ceiling fans don't actually cool a room, but makes a room feel a few degrees cooler at less cost than setting the thermostat those few degrees lower.

This. Spinning ceiling fans augment what the AC us trying to do. I can't sleep without mine going. Also, we added a 14,000 BTU window unit for the bedroom and you can hang meat in there in the July. Then we cut the 3 ton central air unit up to about 78 overnight. Its on a timer so it doesn't kick back on until dawn the next morning. These digital thermostats really help.

 

[cocks rule]

This. Spinning ceiling fans augment what the AC us trying to do. I can't sleep without mine going. Also, we added a 14,000 BTU window unit for the bedroom and you can hang meat in there in the July. Then we cut the 3 ton central air unit up to about 78 overnight. Its on a timer so it doesn't kick back on until dawn the next morning. These digital thermostats really help.

Window unit in the bedroom is the only way to go. 66 degrees every night while the rest of house is 78.

 

[Rhizzlebop]

For YEARS most A/C units have been unable to lower the temperature more than 20-25 degrees when it is very sunny and warm. That is just how it is. Even with models that were made prior to current efficiency regulations that is the case.
If you want it icy cold you can add a window unit to a specific room in your house 🤷‍♂️

This is a fact. The only way to get a whole house super cold like that on a hot day but yet keep humidity down other times is to install a packaged chiller and fan coils. Big $$$

 

[OldFlaCock]

I love my wife, but physics is not her bag. When we get in the car in the summertime, she turns the thermostat as low as it goes. I have told her a thousand times, if you want the car to be 70 degrees, all you have to do is set it at 70. If you set it at 60, it won't get to 70 any faster. She pays me no attention and does it anyway.

What do they say about fixing stupid?????

 

[titaniumspur]

What do they say about fixing stupid?????

Wife might be right if the car has a variable displacement compressor and depending on how the controls are programmed.

 

[TheReelEss]

Wife might be right if the car has a variable displacement compressor and depending on how the controls are programmed.

It doesn't.

 

[Garnet chicken]

My HVAC person had said a while back that a residential variable speed compressor was downplayed for just a 2 speed compressor because of mechanical failures. It may have changed since then.

 

[Bftboy]

The homes we rent on St. John have large wall units. We go to the beach turn them off and when we get back it takes no time to cool any room. I’m surprised I haven’t seen them anywhere around here.

 

[yemacock]

As others have stated, get some ceiling fans for your home. Remember that hot air rises, cold air stays at the floor level. Turn fans to run clockwise for winter months (they push the warmer air downwards from the ceiling), and counter-clockwise for summer months. Clockwise more for pushing warmer air that nestles on the ceiling where we don't habitate down to where we do, counterclockwise more for just circulating the air and getting the cooler air more throughout the room, instead of keeping your floors cool.

Also a REAL good trick for enjoying the coolness of your AC: go outside and work in the yard for an hour or so in the heat of the day. When you come back inside, your home will almost feel chilly to you, guaranteed.......

I wish and pray that my brother and sister-in-law would agree with you. They say they cannot live without the house being 70 degrees or below. They are overweight and have diabetes and freeze me in my own house. They think I'm being unreasonable saying that 72 degrees is the norm and they've never heard such crap.

 

[jedi_mike]

I have tried to explain to my wife that if the unit is on it is cooling as much as it can doesn't matter if therm is set 5 degrees below current temp or 20. I have been married for 25 yrs. We have this talk every yr, lol

I have this talk practically every day with mine.I normally leave mine on 77,she or my daughter starts doing something in the house and complains that’s it’s hot in the house,I tell them your hot not the house,there’s a difference,I tell them to outside for a few minutes and come back in.I catch them turning the temperature down to 72 or lower,I tell them “why don’t y’all just cut it down to the lowest if you think it make the air colder?they don’t reply back.I also told them if they paid the light bill,they can run it at whatever they want.

 

[jedi_mike]

For YEARS most A/C units have been unable to lower the temperature more than 20-25 degrees when it is very sunny and warm. That is just how it is. Even with models that were made prior to current efficiency regulations that is the case.
If you want it icy cold you can add a window unit to a specific room in your house 🤷‍♂️

It was atleast 15-20 years ago at my old job I was talking to a electrician and we was talking ac temperature,he told me the same thing,he said to tell if I needed Freon/working right was to get the temperature at my return and then check it at my register and see what the difference was,he said I should see a 20-25 difference.he said the air can’t get no colder than around that temperature difference.

 

[CockSure]

I just built a new home 3 years ago. I built 2x6 instead of 2x4 so I could get extra insulation in the walls. And I put a lot of insulation i the attic. I told the AC guy I wanted my house to stay at 70 degrees even if it's a 100 degree day. He told me that building 2x6 is the way to if you want a cool house in the summer and a warm house in the winter. I've got no problems staying cool on the hottest days of the year.

 

[chief2791]

I just built a new home 3 years ago. I built 2x6 instead of 2x4 so I could get extra insulation in the walls. And I put a lot of insulation i the attic. I told the AC guy I wanted my house to stay at 70 degrees even if it's a 100 degree day. He told me that building 2x6 is the way to if you want a cool house in the summer and a warm house in the winter. I've got no problems staying cool on the hottest days of the year.

Yep, that's the way to go, combined with the spray foam insulation.

Will most likely be building in the next year or two, and it will be our forever home (time to downsize). I couldn't care less about the finishes, etc. inside the home, will let my wife deal with that, but I will definitely be the one making the call on the structure itself, which is going to be energy efficient. 2x6 outside walls and spray insulation are definites, and geothermal is likely.

My wife and I like it cool, so the summer months are brutal on the power bill, we keep it at 70 during the day and 68 at night. However, in the winter months we set the thermostat to 62, so it's somewhat offset, the heat rarely comes on unless it's really cold outside.

 

[Gamecock80SC]

I lived in an apartment where the a/c could be set at 69 and could only cool to 75 to 83 to 84 during day. At night it mayyyyy have caught up and gotten into the low 70 range. And it ran CONSTANTLY racking up huge bills.
The management tried telling me that it’s normal for an a/c to not cool within 20 degrees of what you have it set to in the SC summer.
I reminded them that I have lived in SC for 40 years and every a/c unit I have ever had cooled to what it was set at without a problem. I complained enough to where they finally replaced the unit and it solved the problem.

 

[Garnet chicken]

Yep, that's the way to go, combined with the spray foam insulation.

Will most likely be building in the next year or two, and it will be our forever home (time to downsize). I couldn't care less about the finishes, etc. inside the home, will let my wife deal with that, but I will definitely be the one making the call on the structure itself, which is going to be energy efficient. 2x6 outside walls and spray insulation are definites, and geothermal is likely.

My wife and I like it cool, so the summer months are brutal on the power bill, we keep it at 70 during the day and 68 at night. However, in the winter months we set the thermostat to 62, so it's somewhat offset, the heat rarely comes on unless it's really cold outside.

Make sure the a/c equipment is sized for those temperature variables. Normal sizing for SC used to be using a 75° indoor temp with using an outdoor of 95°. In a really tight home that seals everything, you want to make sure you get over 3 air changes an hour or you will have terrible indoor problems. Some have to have preconditioned outside air piped into that home. Inside humidity level also determines comfort, if your dwelling has over 60 Rh, it will not feel comfortable and too much removal of moisture will also not be good.

 

[chief2791]

Make sure the a/c equipment is sized for those temperature variables. Normal sizing for SC used to be using a 75° indoor temp with using an outdoor of 95°. In a really tight home that seals everything, you want to make sure you get over 3 air changes an hour or you will have terrible indoor problems. Some have to have preconditioned outside air piped into that home. Inside humidity level also determines comfort, if your dwelling has over 60 Rh, it will not feel comfortable and too much removal of moisture will also not be good.

Good information, appreciate it!

I'm in the the building industry on the manufacturing side, so I know plenty of builders/contractors. I remember one of my builders telling me almost exactly what you said. IIRC he had to install some type of extra air handler (don't know if that's the correct term), but he said it was an incredibly tight and energy efficient home, just have to make sure that you do it right.

 

[USCLaw85]

I love my wife, but physics is not her bag. When we get in the car in the summertime, she turns the thermostat as low as it goes. I have told her a thousand times, if you want the car to be 70 degrees, all you have to do is set it at 70. If you set it at 60, it won't get to 70 any faster. She pays me no attention and does it anyway.

i do the same thing your wife does and my wife tells me the same thing you tell your wife. Damn.

 

[BattleshipTexas]

Don't set the Tstat below 22 degrees differential of outside. It can't do it and will just run constantly doing nothing for you but spending your money. If you don't have some ceiling fans, get some, they work.

So when it is 112 in Texas, I should set i on 90? Really? While an A/C can't lower the temp inside from 112 to 73, if you start out the day in your house at 73, it can keep the temp there even if outside goes to 112. At least my AC always could.

 

[TheReelEss]

i do the same thing your wife does and my wife tells me the same thing you tell your wife. Damn.

I always tell her to think of it as a number line. You can't get below 70 degrees without going thru 70. She's a math teacher so she gets it. Just doesn't care.

 

[cockyferg]

Agreed. It’s a much more complicated matter involving mass and duration along with whether we are talking about a heatpump in winter intelligently recovering vs using strip heat, how the defrost cycles are handled (whether time based or demand based). Much more complex.

furthermore the ene4gy billing you have makes a difference. My company charges demand billing for taxing their grid during peak hours. So during the summer (peak hours being 4-7) I set my upstairs bedroom system to only r7n half of each of those hours. The reason being they look at those 3 hours of use for each of the 30 days of a month (90 hours) and the single largest use hour they charge almost $13 per KWH used. Then for each of of the other 1600-2500 kWh I use in a month they charge me 5.5 cents per kw. So by knocking off about 2kw off those peak hours I save about $26 plus the 2x30x5.5 cents each month vs letting it run.

same for winter except 6-9 am.

True, I have Duke power in my house now, but I used to be in the city where they bought power from duke and then tacked on a few extra cents per kilowatt hour