Is it too cold outside to run my AC?

HeatingHelp

Is it too cold outside to run my AC?

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TWrich

This thread seems extremely professional, well done! Great back and forth. Thanks.

unclejohn

I installed a furnace and A/C in Dec a few years back and got a call in early June to check the A/c it would cool a while and then not so good. Check it and found that the metal plate at the top of the A coil had blown off and was laying inside the evap cab. All the air was blowing straight up through the top of the coil. That was a first for me.

GBart

1 mismatched units, 3 ton outdoor 4 ton indoor, ok if blower dialed in correctly, 2 - 2 stage condenser, indoor section has to be configured to match in board during installation, unit is rated for 70*F outdoor, below 82*F outdoor the unit should remain in 1st stage, low ambient control kit recommended

GBart

outdoor manual - http://www.utcccs-cdn.com/hvac/docs/1011/Public/04/42101600100_ICP_10443.pdf

indoor manual - http://icpindexing.toddsit.com/documents/086477/49621510300.pdf

again, speculation is nice but the factory manuals are the Bible for any given unit

Leonard

I know my 20 k window AC evaporator ices up after a while when it's <70 outside. But it's likely a midge low on R-22, I picked it up used 28 years ago at a yard sale. Only cleaned it and replaced worn switch. Some Vornado?? unit.

stonebutson

One thing nobody is mentioning is that cold crank case. While it’s sitting in the cold the refrigerant is puddling up in the crank case. When it’s turned on in fifty or sixty degree weather all the oil foams up and gets pumped out into the system. The compressor is now running with no lubricant and the evaporator is coated with oil and reducing an already low superheat because there probably isn’t a load on the system anyway. We just want to play with our new toys or schedule tune ups because there’s nothing better to do. If it isn’t set up for low ambient running ( case heater and fan control) - DON’T RUN IT

Leonard

Seen large HVAC on commercial restaurant building, has a crank case heater (always on) to warm the pump.

RONCASTLE

a/c manufactures will supply the minimum ambient operating temp. ( OUTDOOR ) in the spec sheet for the unit, at least Carrier does.

ChrisJ

Leonard said:

Seen large HVAC on commercial restaurant building, has a crank case heater (always on) to warm the pump.

You need more than crankcase heat.
I run a crankcase heater and a condenser fan controller on mine to keep the head pressure up. It's just a cheesy SCR controller but it gets the job done. The system behaves the same whether it's 40 degrees out or 90 degrees out.

Solid_Fuel_Man

I have been recently adding VFD's to condenser fans. We run pressure transducers on the LL to a simple Johnson controller which makes a 2-10vdc output which I use to throttle the VFD. These are in multiple fan condensers used at 50F and up. We've had lots of problems with one fan running, pulling the other(s) backwards and burning up the SCR controllers.

Getting rid of the single phase motors and running 3 phase motors has also greatly increased longevity I've found.

These are mostly on medium temp Agricultural storage warehouses. Been working very well so far.

jacobsond

Looks like another old thread. Anyway what really stood out to me was the wait a week for a TXV. If your the installing company shouldn't you have had one on the truck. Lo ambulant and loads create a special condition for techs. There are ways around,but a check back when the weather is above 75 is always best.

CanadaKeith

Old post yes but I'm glad it got brought forward. As a home inspector , we use the guideline of don't run the AC unless it has been 16C,60F or better for previous 24 hours. In general I try to not be the first person starting up a unit for the season. However, I could never find support for that temperature in any literature. Based on what the pros are saying it seems that rule has some merit.

Jack Getkin

This project appears to be a perfect example of a "failure to communicate". The contractor/installer must thoroughly understand the customer's needs and expectations and then communicate how the system to be provided will meet the needs. It appears as though some type of low ambient temperature control may be required in order for the system to function as desired by the end user. This should have been determined when quoting the system. Addressing it at this type is very likely going to result in a dissatisfied customer. We all need to remember we are the experts and, as such, the burden of communicating what is recommended & required rests with us. The business owner likely needs to take ownership of this and devote a little time to their customer to help them better understand what was provided along with any gaps in communication between the business and the customer.

Handyman 242

Many great comments. First issue is that the charge should be weighted in; getting the correct charge does not depend on outdoor temperature and will always be correct. Second issue which has already been stated is that other accessories should have been sold with the job to clean the air in the house. I run my AC fan in the winter to clean the air in my house (I have radiant heat) using a good media filter and a whole house mold, virus and bacteria killer.
The owner of the business gets an F for salesmanship and a D for knowing AC installation practices. I see many contractors installing systems between Oct and April and then having to go back and recheck the charge when it gets warm outside as they did not weigh it in originally. What is the lost revenue of going back on call backs and not getting additional accounts when the warm weather hits. These contractors will always be marginally successful, have higher overheard and profit starved.

ChrisJ

Handyman 242 said:

Many great comments. First issue is that the charge should be weighted in; getting the correct charge does not depend on outdoor temperature and will always be correct. Second issue which has already been stated is that other accessories should have been sold with the job to clean the air in the house. I run my AC fan in the winter to clean the air in my house (I have radiant heat) using a good media filter and a whole house mold, virus and bacteria killer.

The owner of the business gets an F for salesmanship and a D for knowing AC installation practices. I see many contractors installing systems between Oct and April and then having to go back and recheck the charge when it gets warm outside as they did not weigh it in originally. What is the lost revenue of going back on call backs and not getting additional accounts when the warm weather hits. These contractors will always be marginally successful, have higher overheard and profit starved.

So you feel weighing in a charge on a semi-accurate scale and never checking superheat or subcooling is acceptable?

Solid_Fuel_Man

Weighing in a charge? Um?

Superheat and subcooling are what determines a proper charge. It is then recorded on the unit for the next guy.

A charge is always weighed so I know how much refrigerant to bill the customer for.

Its things like this that sound very similar to when you take your car in for a malfunction, and tell the counter guy that all that needs to be done "is plug in the computer" and it'll tell you what's wrong with my car.....

ratio

To be fair, with some units the only way to correctly charge them is by weight, although a consumer-grade split is unlikely to fall into that category.

If you weigh in the lineset adder, you should be close enough that the unit'll work; from my experience with retrofits the ductwork'll be bad enough that you'd never notice the charge is off.

My biggest concern with weighing in the charge is that I have no way of verifying the factory charge.

Twister994

I have bad allergies too. I don’t know the specific temp but Freon what’s in the ac and helps it cool can freeze in cold
Weather. To me the 65 doesn’t sound cold
Enough to freeze it but maybe it is. No matter what ac you get and how good your installer is it’s not gonna run at any temp you want no matter how cold. About the only thing I could recommend is an in room unit for your bedroom that you could install yourself. Since it’s in the room the Freon will be at the same temp as the room inside your house and should allow you to run it at just about any temp. But as far as central or regular window units there definitely always will be a certain temp
You can’t run it below.

ChrisJ

> @Twister994 said:
> I have bad allergies too. I don’t know the specific temp but Freon what’s in the ac and helps it cool can freeze in cold
> Weather. To me the 65 doesn’t sound cold
> Enough to freeze it but maybe it is. No matter what ac you get and how good your installer is it’s not gonna run at any temp you want no matter how cold. About the only thing I could recommend is an in room unit for your bedroom that you could install yourself. Since it’s in the room the Freon will be at the same temp as the room inside your house and should allow you to run it at just about any temp. But as far as central or regular window units there definitely always will be a certain temp
> You can’t run it below.

R410a freezes at -247F.

With all due respect everything you said was wrong. Please do not give advice on this.

njtommy

We run dx and chilled water systems all year round. Doesn’t matter how cold it is we need to run them for Data rooms, MRI machines, and about probably a dozen other reasons. Just like we run boilers in the summer. Because we can and we make people comfortable.
Fan speed, head master controls and crank case heaters where all made for a reason. Interms of charging the system in the winter we block the condenser off as much as possible to drive out head pressure up to a normal operating pressure then continue to charge and adjust txv based on our subcool and super heat. We will then hook up the fan speed controller. After we feel the charge is correct.

Kvac13

Sound like it’s low on Freon or overcharged. Also a bad txv if installed. That machine will go off on low/hi pressure. They aren’t impossible but harder to charge when temps are below 60.

fbartol21

With regard to allergies the installer should have discussed options during the sales appointment. If so, he could have offered a better air filter and an event based air cleaning thermostat. Both are available from Aprilaire. I always used the model 8476 but today there are other options including Wi-Fi. You don't need cooling on for air filtration.

Lance

All good thoughts to learn about. I am a Master HVACR tech. First off we all know a heat pump is an A/C unit also. Yet it runs defrost (cooling mode) in the cold temps. So we know most all units are capable. And yes with a low outdoor ambient temp kit which modulates the outdoor fan means we can easily cool a hot room when its 30F outside. But in the home we rarely add it. IN todays new equipment, the old cap tube orifice is not used, and we have TXV or EEV which are also protecting compressor from liquid flood back. Even so on a cool day with a hot house, the ac load is low and the unit will not usually run long enough to cause any damage as the house t-stat will satisfy. I have charged A/C units in the rain in sleet in snow and heat. Knowledge is power to service all systems. What we cannot do in the cold is see how the system will perform on the hot design day it was sized for, including air performance, humidity control. But I guarantee you the installer lacked the skills or was untrained, or was not wanting or unable to respond to their clients request. I was factory trained at several factory schools. Anybody here of the "Snowball" compressor Trane ran in the subzero chamber? And now there is a Snowball 2.

hvacr

Any time you are operating an ac unit in inverted conditions (condenser pressures = or < evaporator pressure) it is considered a refrigeration application possibly requiring condenser pressure controls to maintain refrigerant flow. I would not recommend fan cycling, simplest is variable speed control for the condenser fan if you want to operate in inverted conditions.

The expansion valve requires a minimum differential to maintain suction superheat, scroll compressors also need differential pressures to maintain scroll seals.

Testing the system at higher ambient conditions may not indicate any issues. Based on heat exchanger approaches a minimum differential in air temperatures is required.

Vegas

i worked on many refrigeration systems and had to add low ambient controls to false load the condenser. it all worked when you read the instructions..