Looking for an HVAC specialist to answer a question I have. | GTAMotorcycle.com

Looking for an HVAC specialist to answer a question I have.

GateKeeper

GateKeeper

Well-known member
Not knocking anyone’s knowledge, life experience, or google searching capabilities, but I am looking for someone who is in the business of Heating/Air Conditioning that really knows their stuff and can possibly provide a proper answer, not a guess, or a generalized answer, but a conclusive answer.

not looking for a debate, speculation, and so on….

Question: Why does my A/C run for 3-5 hours at a time non stop, to drop the temperature by just 1-1.5 degrees in the house. It will typically not run all day, house will warm up to 24 degrees, then at 10:30 p.m. Ecobbe is set to bring the temp down to 23 degrees, and the A/C will now run for the next 3-5 hours to drop temp 1-1.5 degrees.

I even have just the fan running for 20 minutes at a time just to circulate the air in the house, the Ecobee does this automatically it’s set to run 20min/hour

this is a brand new unit installed 2019, 1.5 ton unit, for a 2500 sq foot home, windows, doors are all brand new, attic is full of insulation, done 3-4 years ago, no leaks, drafts and so on. Ducts were cleaned when A/C was put in, new 5 inch filter is changed or cleaned every 6 to 12 months, it’s not dirty I can always see through it, also note, the furnace/ac, hot water tank were all replaced at the same time it’s all new equipment, yes the coils/condenser as well, if I got the terminology correct.

now in the winter furnace works as I would expect, it turns on, runs for 15-30 minutes give or take, warms up the house, a few hours later temp drops and furnace kicks in again, runs for a nominal time, raises the temp and this goes on throughout the entire day/night, it does not run for 3-5 hours like the A/C, it’s behaviour is what I call normal

i can provide more info, but this really has me stumped, and the guys from the company the equipment was purchased from.

Thanks……
 
GateKeeper said:
I am looking for someone who is in the business of Heating/Air Conditioning that really knows their stuff and can possibly provide a proper answer, not a guess, or a generalized answer, but a conclusive answer.
Click to expand...
unless a tech is on-site, this is the only kind of answer you're going to find on the internet.

I was into HVACR, there are a few possible scenarios, based on the info given:

It seems like it takes longer to cool your place than to heat it? (sounds like your cooling unit might be undersized for the space)

Maybe the temperature sensing device is faulty?


I know @Iceman was a pro for many years, maybe he can chime in
 
GateKeeper said:
Not knocking anyone’s knowledge, life experience, or google searching capabilities, but I am looking for someone who is in the business of Heating/Air Conditioning that really knows their stuff and can possibly provide a proper answer, not a guess, or a generalized answer, but a conclusive answer.

not looking for a debate, speculation, and so on….

Question: Why does my A/C run for 3-5 hours at a time non stop, to drop the temperature by just 1-1.5 degrees in the house. It will typically not run all day, house will warm up to 24 degrees, then at 10:30 p.m. Ecobbe is set to bring the temp down to 23 degrees, and the A/C will now run for the next 3-5 hours to drop temp 1-1.5 degrees.

I even have just the fan running for 20 minutes at a time just to circulate the air in the house, the Ecobee does this automatically it’s set to run 20min/hour

this is a brand new unit installed 2019, 1.5 ton unit, for a 2500 sq foot home, windows, doors are all brand new, attic is full of insulation, done 3-4 years ago, no leaks, drafts and so on. Ducts were cleaned when A/C was put in, new 5 inch filter is changed or cleaned every 6 to 12 months, it’s not dirty I can always see through it, also note, the furnace/ac, hot water tank were all replaced at the same time it’s all new equipment, yes the coils/condenser as well, if I got the terminology correct.

now in the winter furnace works as I would expect, it turns on, runs for 15-30 minutes give or take, warms up the house, a few hours later temp drops and furnace kicks in again, runs for a nominal time, raises the temp and this goes on throughout the entire day/night, it does not run for 3-5 hours like the A/C, it’s behaviour is what I call normal

i can provide more info, but this really has me stumped, and the guys from the company the equipment was purchased from.

Thanks……
Click to expand...
1.5 tons is 18,000 btu. Not sure what size furnace you installed but it will be a hell of a lot more btu than that (and should therefore have a much shorter cycle to satisfy). FWIW, I expect 1.5 ton for 2500 sq ft to be undersized. That leads to long run times, slow temp changes but great dehumidification. How did the 1.5 ton get selected? Did they run manual J or just wing it? You say the house is sealed tight but did they do a blower door test? Low E windows? High solar heat gain would mean the heater runs less and the A/C has to run harder.
 
I don't think I've ever installed a 1.5t in a 2500 sq ft home ever. It likely needs a 2t at minimum. An undersized unit may work somewhat fine in "normal" heat, but it'll seriously struggle under heat/humidity loads like we're currently seeing.
It also sounds as though the unit may be low on charge and this is very easy to check for a tech with a set of gauges.
If it is really low on refrigerant you will see ice build up around the lines entering the plenum on top of the furnace and also around the lines/valves on the outdoor unit.

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1. Undersized unit.
2. Normally they're not sized to bring the temp down in a hurry. It's better for them to run constantly than to cycle on and off ... but the consequence is that a temperature change takes a long time, and it won't keep up in really hot conditions.
2. Dehumidification takes a lot of energy.
 
Brian P said:
2. Dehumidification takes a lot of energy.
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True story. By having it off during the day and then on, he has many hours of water that needs to come out. He may be less annoyed by the run-time if he was watching enthalpy drop instead of temperature. On that note, you can change indoor blower speed to get more temp change and less latent heat removal if you wanted to.
 
We just had our unit adjusted yesterday. It wasn't running properly during the day...the pressure was too high due to full sun hitting the outdoor unit and some fins were blocked with dust and it was shutting off more often than it should as a safety feature due to building pressure in the unit. Technician adjusted the charge of the refrigerant (lowered it a little) and cleaned the fins and vents. All AOK now, back to icy cold. No idea if that's your issue but the past couple of days have been a bit soupy and so that exacerbates the problem. It's pricey but we get the AC and Furnace looked at nearly every year to head off problems like this. The cycling issue lasted all of a few hours before it was fixed.
 
Can you close off some vents in the basement to re-direct the cool air higher in the house?
I do this in my house as it was built with undersized ductwork.


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Robbo said:
Can you close off some vents in the basement to re-direct the cool air higher in the house?
I do this in my house as it was built with undersized ductwork.


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Be careful doing that. If your ductwork is already undersize, closing off vents increases the SP (harder on the fan) and reduces the cfm through the indoor coil. Go to far and you can sometimes ice up your coil. My returns are inadequate and the only real option without tearing the house apart is increasing the return size in the basement which will send more air to the basement but allow higher cfm through the coil. I don't need temp reduction in the basement, but dehumidification never hurts.
 
GreyGhost said:
Be careful doing that. If your ductwork is already undersize, closing off vents increases the SP (harder on the fan) and reduces the cfm through the indoor coil. Go to far and you can sometimes ice up your coil. My returns are inadequate and the only real option without tearing the house apart is increasing the return size in the basement which will send more air to the basement but allow higher cfm through the coil. I don't need temp reduction in the basement, but dehumidification never hurts.
Click to expand...

Yep…that’s why I said some vents not all. Trial and error.


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Ok, thanks for the input, in order of responses I will answer some of the questions or comments

bigpoppa - 1.5 ton for 2500 sq feet undersized perhaps, however I might be wrong on the size, it might be bigger, thermostat Ecobee has been changed 2 times with brand new units, still the same problem

greyghost - furnace carrier 59tp6a BTU output 39,000 to 117,000 2 stage. AC carrier infinity 16 central air model 24anb630a300, web sites say it’s between a 1.5 ton to 5 ton unit, I don’t know how to tell what mine is but it might be a 2 or 2.5 ton and not the 1.5 I said earlier, NO blower door test, and YES to low E windows

iceman - tech was her 2 days ago all in top working order, no ice buildup at all

brianp - undersized, maybe….but to have to run 3-5 hours to drop 1 to 1.5 degrees is crazy, and house is more or less closed all day long no in and out of persons

jc - no direct sunlight on unit, all clean, 1 year old, annual checkup done 2 days ago, no issues found

robbo - 4 vents in basement 2 are always open one in the front of base,ent one in the back, vent in bathroom is closed it does not get hot or cold to keep it open and door is open unless being used, I open or close one vent where I am sitting depends on how cold I get, but it’s a open concept finished basement

Thanks…
 
GateKeeper said:
greyghost - furnace carrier 59tp6a BTU output 39,000 to 117,000 2 stage. AC carrier infinity 16 central air model 24anb630a300, web sites say it’s between a 1.5 ton to 5 ton unit, I don’t know how to tell what mine is but it might be a 2 or 2.5 ton and not the 1.5 I said earlier, NO blower door test, and YES to low E windows


brianp - undersized, maybe….but to have to run 3-5 hours to drop 1 to 1.5 degrees is crazy, and house is more or less closed all day long no in and out of persons\
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2.5 ton. That makes more sense for sizing. I bolded the part that shows the size. That makes your long cool off period more suspicious.

Furnace BTU unknown, you need a longer model number to determine size but it doesn't matter too much in this context.

For reference, I have a 15 yo 3 ton that is likely low on charge. On really hot days, the A/C can run from dawn to dusk and the house temp keeps rising. I normally drop the house to 73 at 7 pm (which takes until about midnight) and then turn it up to 80 at 11 am to avoid the expensive tou. House is normally 78 to 80 by 7 pm and the whole cycle repeats itself. If it's cool at night I will open windows instead of running a/c.
 
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GateKeeper said:
Furnace 59tp6a080
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78,000 btu @97% efficiency. A/C is 30,000 BTU. Therefore you expect A/C cycle times to be more than double furnace cycle times You have 3/4 or 1 hp blower so that should be sufficient airflow for 2.5 tons (assuming no duct disaster). Furnace has ECM motor so it should be doing it's damndest to hit the flow rates regardless of SP.

When you say the tech came out and gave it a clean bill of health, any idea what they actually measured? Ideally airflow but I have never ever seen one do that. Should do static pressure at various locations but I almost never see them do that either. Temp delta across coil? Refrig pressure/temp/superheat/subcool?
 
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