Hobby_Man22
Well-known member
Is it normal for it to kick back on after only 9 minutes or so of being off and then run for about a 35 minute cycle when it's 100 degrees outside?
How long should the ac shutoff for when its 100 outside?
- Thread starter Hobby_Man22
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Hobby_Man22
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This is in my shop so sometimes it will run none stop for 3hrs straight in the afternoon.
depends a lot on your insulation . but 9 mins is not terrible
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Hobby_Man22
Well-known member
I think it has a 6 minute compressor lockout to allow the pressures to drop before it restarts.
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Hobby_Man22
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I bet the bill would be $500 if I left it running all month.
danski0224
Well-known member
If the outdoor design temperature is 100, and the equipment is sized perfectly to the load calculation, it would not shut off.
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Hobby_Man22
Well-known member
Is this only a heat pump thing? The reason it doesn't shutoff is because it doesn't get below the threshold to shutoff.
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Hobby_Man22
Well-known member
Unless it does that on purpose, but my guess based on a digital thermometer is that it's cooling about the same amount the building is heating up.
danski0224
Well-known member
Heating or cooling, it doesn't matter.
If the equipment is sized to meet the load, then the equipment will not shut off when those conditions are met.
It also means that if the outside temperature rises/falls outside of design temperature and/or the desired indoor set point is outside of the design temperature, the space will warm up in cooling operation or get cooler in heating operation.
Equipment "off" times between cycles may be related to time limits for compressor protection or defrost, high/low limit/pressure trip... or coincidence.
If you do not know your load calculation and design limits, any issues/problems/solutions are just guesses.
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Hobby_Man22
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Many variables to take into account.
The main thing would be your insulation. If you get the room to your desired temp and then switch off the unit how fast does it take for the temp to climb a few degrees? Most thermostats are designed to come on when the desired temp rises a half of a degree so it can keep the area the same temp.
Where is your thermostat located? If its right by a register you may be getting a false reading of the room. Using fans to circulate the air can help to make sure you don't have a dead spot but is really a band-aid. Place a digital thermometer by your thermostat and confirm the temp is the same, then move to various areas of the shop and see if the temp rises which will confirm a weaker zone and relocation of the thermostat or additional ducting may be needed.
The main thing would be your insulation. If you get the room to your desired temp and then switch off the unit how fast does it take for the temp to climb a few degrees? Most thermostats are designed to come on when the desired temp rises a half of a degree so it can keep the area the same temp.
Where is your thermostat located? If its right by a register you may be getting a false reading of the room. Using fans to circulate the air can help to make sure you don't have a dead spot but is really a band-aid. Place a digital thermometer by your thermostat and confirm the temp is the same, then move to various areas of the shop and see if the temp rises which will confirm a weaker zone and relocation of the thermostat or additional ducting may be needed.
Jeepster04
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Pretty much impossible to say either way, but typically heat pumps will run near non stop when the temps are at their extremes if the unit is sized appropriately. If it short cycles (oversized), it wont remove the moisture and its hard on the unit. If its undersized, it will run constantly and not cool the space.
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Hobby_Man22
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It cools about 2.5 degrees below set temp and kicks back on when it is 2.5 degrees above set temp confirmed by a field piece temp meter. It's just a basic thermostat. Luckily it's not the kind that keeps it within 1 degree of set temp the system would never shut off. I think it is oversized a bit because the installer said he has a 3.5 ton in his shop and it doesn't keep up so I think he just didn't want me coming back and complaining that the system didn't keep up. Looks like I just need more insulation to increase the length in between shut off time. I just hope it's not going to shorten up the run cycle when the temp isn't 100 outside its already at about a 9-12 minute cycle unless the temp is above 90 outside then it's more like 20-25
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Hobby_Man22
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I also have a 3 degree offset because it was cooling way below the set temp so the thermostat is in a bit of a dead area. My main concern is that it restarts after a short time like 8 minutes. That was the point of my thread
Sounds about right, Texas can get awful hot...
Once my garage is cool to 72, I bump the T-stat up to 76 and even at 103 degrees/100% humidity OS it stays comfortable in garage.
My son lives in San Antonio and his power shuts off 3X daily for 30 minutes, he's not home during the day, last friday night he got home late as he had business in Port Victoria. Came in at 2000 hours to no air in the Condo. Took management til monday to sort it out.
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Hobby_Man22
Well-known member
I did but the r30 isn't enough. It needs another layer.
Jim greengo
Well-known member
When was the last time it was serviced?
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Hobby_Man22
Well-known member
The question is is it okay that it kicks back on after 6 minutes?
danski0224
Well-known member
Maybe, or maybe not.
Yankeefarmer
Well-known member
If this is the new unit in your shop, it most likely has an internal protection circuit to keep it from restarting sooner than the manufacturer considers “okay.” Check with the manufacturer or the company you bought it from (if you trust them) to be sure.
Sure, if it needs too.
5-6 minute time delay between runs should be enough to equalize the system.
If it has a 5 degree swing and rises enough to kick on in less than 10 minutes id be looking at air leakage. Just posted about it in another thread. No amount of insulation will help if the controlled air is getting sucked out and replaced with hot air.
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Denwad
Well-known member
here's an anecdote
Our house in San Tan Valley AZ struggled with A/C bills. In July of 2020 the bill was 550$. Old 5 ton A/C unit.
At the beginning of last year I dumped a pallet of insulation into the attic , that cut the bill approximately 200$. The catch here is i don't think the insulation was the biggest help, it was the fact that I found many many rips and tears in the ductwork that i sealed up. Holes big enough to put my fist through.
We were running the AC at about 72-75 degrees.
Our house in San Tan Valley AZ struggled with A/C bills. In July of 2020 the bill was 550$. Old 5 ton A/C unit.
At the beginning of last year I dumped a pallet of insulation into the attic , that cut the bill approximately 200$. The catch here is i don't think the insulation was the biggest help, it was the fact that I found many many rips and tears in the ductwork that i sealed up. Holes big enough to put my fist through.
We were running the AC at about 72-75 degrees.
danski0224
Well-known member
Attic is the worst place for HVAC.
Duct leakage is a big thing.
The attic may have R38 insulation, but the ductwork, depending on when it was installed, may have R4.2, R6, R8 or R10. If the insulation is installed properly.
Duct leakage is a big thing.
The attic may have R38 insulation, but the ductwork, depending on when it was installed, may have R4.2, R6, R8 or R10. If the insulation is installed properly.
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Hobby_Man22
Well-known member
I've measured mine. It comes out the vent at 52 degrees
danski0224
Well-known member
Go measure it at the evaporator coil.
You can also measure the return air temperature at the register and at the equipment.
Air leaks are bad, especially at the returns. This includes the boot to structure interface on the ceiling or in the wall, flex duct to boot or other duct connections, duct collars to the ductwork or fiber board and the return air/filter connection at the furnace.